Alabaster, C.J. 1974. Some Copper, Lead and Manganese minerals from Merehead Quarry, East Mendip. Proceedings of the Bristol Naturalists Society.
Al-Jasser, S.H. and Hawkins, A.B. 1979. Geotechnical Properties Of The Carboniferous Limestone of The Bristol Area; The Influence Of Petrography And Chemistry. International Society for Rock Mechanics. 4th ISRM Congress, Montreux, Switzerland. 1979. Authors: S.H. Al-Jassar (Geology Department, University of Bristol) and A.B. Hawkins (Geology Department, University of Bristol). [The paper can be purchased online]
The Carboniferous Limestone consists of eight lithologies: shelly, crinoidal, oolitic, micritic, dolomite and impure limestones, siliceous sandstone and mudstone. Samples of these rock types, apart from the mudstone, have been collected, sectioned, described in detail, the nine major elements determined, and the insoluble residue analysed by X-ray diffraction. Among the tests performed were unconfined compressive strength and modulus of elasticity measured parallel, vertical and oblique to the bedding: triaxial tests: two cycles of loading and unloading, taken to failure: point load tests on various sized samples: Schmidt hammer tests parallel and vertical to the bedding, in the field and laboratory. A relationship can be shown to exist between the geotechnical properties and these with the petrography and chemistry of the rocks.
[Example extract:] 2. Background Geology.
The dominantly marine 1000 m thick Carboniferous Limestone succession, deposited about 340 m years ago, is underlain in the Bristol area by the continental Devonian (Old Red Sandstone) and overlain by the deltaic and fresh-water sequences of the Millstone Grit and Coal Measures. The basal beds, the Lower Limestone Shale Group, are a diachronous littoral sediment consisting of heavily overconsolidated mudstones (shales), limestones and occasional sandstones. The overlying Black Rock and Clifton Down Groups consist dominantly of calcareous strata except for the Clifton Down Mudstone which follows a break in sequence (known locally as the Mid-Avonian Break) and the calcareous/arenaceous/ argillaceous sediments of the Lower Cromhall Sandstone. In the overlying Hotwells Group the arenaceous and argillaceous sediments increase in thickness until they pass, without a stratigraphic break, into the Millstone Grit (known locally as the Quartzitic Sandstone Group). During the Variscan (Hercynian, Armorican, Permo-Carboniferous) Orogeny the area suffered two periods of compressional stress, the first dominantly westwards, causing north to south trending folds best developed north of Bristol, and the later northwards producing east to west structures such as the Mendip Hills south of Bristol. As a result of these stresses the rocks of the area were tilted and in places even overfolded; in many places there are major thrust fault movements and locally within the limestones the formation of stylolites.
Atkinson, T.C. 1977. Diffuse flow and conduit flow in limestone terrain in the Mendip Hills, Somerset (Great Britain). Journal of Hydrology, vol. 35, nos. 1-2, pp. 93-110. School of Environmental Sciences, University of East Anglia.
The hydrogeology of the karstic Carboniferous Limestone is described. Water tracing has established recharge areas for fifteen major springs and water budgets confirm the size of the areas found. Groundwater flow occurs in two modes: turbulent conduit flow and diffuse Darcian flow in fine fractures. Recharge is 50 percent quickflow via caves and closed depressions and 50 percent slower percolation. Active storage in the diffuse component (S = 0.92 percent) is 30 times greater than in phreatic conduits. Diffuse hydraulic conductivity is 0.89m per day and an average of 60–80 percent of groundwater is transmitted by conduits in this maturely karsted and steeply dipping aquifer.
Atkinson, T.C., Smart, P.L. and Atkinson, J.N. 1884. Uranium-Series dating of speleothems from Mendip Caves: 1. Rhino Rift, Charterhouse-on-Mendip. NGR ST4847.5557. Altitude 210m. Length 320m. Vertical Range 144m.
Proceedings of the University of Bristol Speleological Society, 1984, vol. 17, part 1, pp. 55-69. Available in full online as a pdf file.
The morphology and deposits of Rhino Rift are described. The cave is an 'invasion vadose cave' formed when the local saturation level was 75-90 m. O.D. Ten U-series dates on four speleothems show that a boulder and cobble infill at the bottom of the known cave accumulated sometime after c. 45,000 years ago, whereas poorly sorted gravels blocking the cave passages were laid down before about 11,000 years ago. The cave itself was formed before 75,000 years ago, probably during isotope stage 5 or 6. The implications for the geology of the Mendip region are discussed.
Fig. 15 shows and extended section, redrawn after Stanton. Fig. shows details of sectioned speleothems. Table 1 gives speleothem age data. On pp. 66-67, the relationship to Cheddar Gorge caves is briefly discussed.
Avon RIGS Group. 2012. Outcrop. The blog of the Avon RIGS Group - promoting geology in the West Country. Outcrop, Monday 19th March 2012. Available online.
Extract: A recent success story for RIGS has been Barnhill Quarry in Chipping Sodbury. The quarry was operational from the late 19th century until the mid-1960s with the Carboniferous limestone being exploited for aggregates and building stone. Extraction of the rock led to the revealing of some magnificent exposures in the quarry walls, including stromatolites, limestone pavement, ripple bedding, dolomitic wadi deposits, thrust planes and an well-defined unconformity between Triassic shales and Carboniferous limestone. Part of the site was assigned SSSI status in 1966, with subsequent audits awarding RIGS designation to the whole quarry.
[Go to the website referred to above for photographs of stromatolites. The Cheddar Gorge stromatolite in the basal part of the Clifton Down Limestone is probably similar to these, but very poorly exposed by comparison with these splendid examples in Barnhill Quarry.]
Exposures at Barnhill Quarry, Chipping Sodbury. Left: Fossil stromatolites in Carboniferous Limestone [see this!!]. Right: Ripple bedding in Lower Cromhall Sandstone. Photo credit: WYG Environment, Barnhill Quarry Geoconservation Assessment.
Baker, E.A. and Balch, H.E. 1907. The Netherworld of Mendip. Exploration in the Great Caverns of Somerset, Yorkshire, Derbyshire and Elsewhere. Clifton, J. Baker and Son, London, Simpkin, Marshall, Hamilton, Kent and Co. 1907. 172 pp. By Ernest A. Baker, M.A. (Lond.), Author of "Moors, Crags and Caves of the High Peak" etc., joint-author of "The Voice of the Mountains", and by Herbert E. Balch. [This is an old, hard-cover, book with many photographs, but with content on various caving subjects, not just of Cheddar Gorge. It is not very technical with regard to the Gorge, although it does discuss several cave systems. It deals also with Wookey Hole etc.]
The objects of this work are twofold: to described the actual incidents of various interesting episodes in the modern sport of cave exploring, and to give an account of the scientific results of underground investigations in the Mendip region of Somerset. Speleology is the latest of the sporting sciences: like orology [mountain research] and Arctic exploration, it has two sides, sport and adventure being the lure to some, while others are chiefly attracted by the new light thrown by these researches on geology, the hydrology, and the natural history of the subterranean regions explored. The chapters dealing with the scientific results are by H. E. Balch, who has been working on the geology of the Mendips, more especially amongst the caves, for upward of twenty years: the accounts of actual experiences, in which the sporting side is predominant, are by E.A. Baker, who described the recent exploration of the Derbyshire caves in his Moors, Crags and Caves of the High Peak, 1903." .... [continues]
Balch, H.E. 1926. The Caves of Mendip. London, Folk Press Ltd.
Balch, H.E. 1935. Mendip - Cheddar, its Gorge and Caves. Wells. Clare and Son, Ltd. Balch, H.E. 1947. Mendip: Cheddar, its Gorge and Caves. Bristol. Wright, 2nd Edition. [also a 1941 edition]
Bamber, A.E. 1924. The Avonian of the Western Mendips from the Cheddar Valley Railway to the Sea, West of Brean Down. Proceedings of the Bristol Naturalists' Society, vol. 6, part 1, 75-91. By Miss Agnes Elizabeth Bamber, M.Sc, F.G.S. [Also an abstract is given in the Quarterly Journal of the Geological Society, vol. 80., pp. 182-3.]
1. Introduction; (a) Previous Work; (b) Geographical Extent.
2. Geological, Structure and Physical Features.
3. Description of the Zones; (a) Surface Extent and Lithological Characters; (b) Faunal Lists and Notes.
4. Description of the Best Exposures.
5. List of the Chief Exposures.
6. Comparison of the Avonian of the Western Mendips with; (a) The Avon Section; (b) Burrington Combe.
[This paper has much good faunal and zonal information and discusses various exposures. It is not specifically on Cheddar Gorge.]
"(b) Geographical Extent.
The area is 9 miles long in an E. to W. direction, and has a maximum width of "2J" [the computer text is erroneous here - is this 27, 22 or 21 or what?] miles in a N. and S. direction. It forms the western portion of the Mendip uplift. It includes five isolated Carboniferous inliers, which passing from west to east are as follows:
(1) Brean Down.
(3) Bleadon Hill.
(4) Banwell Hill.
(5) Wavering Down.
Along the northern side of our region are the villages of Banwell, Hutton and Uphill, and on the southern side those of Bleadon, Loxton, Compton Bishop and Cross. On the E., in the Triassic ... [continues].]
Bamber, A.E. 1924. The Avonian of the Western Mendips, from the Cheddar Valley Railway to the Sea, West of Brean Down. The Avonian of the Western Mendips, from the Cheddar Valley Railway to the Sea, West of Brean Down.
Quarterly Journal of the Geological Society, vol. 80, pp. 182-183. January 1924. [this is probably just an abstract - it is only one page. The full paper is in the Proceedings of the Bristol Naturalists' Society. See above, and is available as text online.]
In this paper a comparison is made between the Avonian of the Western Mendips and (a) the Avon Section and (b) the Burrington Combe section. The outcrops of the Carboniferous Limestone zones, classified according to the notation of the late Dr. A. Vaughan, have been mapped. Levels from K2 to S1 are exposed in the area. The lithological and palaeontological characters of the zones are described. Considerable faulting and folding occurs, more especially in the west of the region.
Bamber, A.E. 1924. Some episodes in the geological history of the south of England. Quarterly Journal of the Geological Society, vol. 98.
Barrington, N. and Stanton, W. 1977. Mendip: The Complete Caves and a View of the Hills. Cheddar Valley Press. 236pp. Sturdy, paperback book of large pocket size and quite thick. By Nicholas Barrington and William Stanton. Published by Barton Productions in conjunction with Cheddar Valley Press, Cliff Street, Cheddar, Somerset. ISBN 0 9501459 2 0, Printed in England by Dawson and Goodall, Ltd. Bath. Third Revised Edition, 1977. The caves are listed alphabetically with accounts ranging from a short summary to several pages of description. Each cave has a reference number. There are a large number of caves in Cheddar Gorge and the subject is not simple to deal with. There is a descriptive section on: Evolution of the Mendip Landscape, on pages 215 to 225. There are many photographs, mostly not good quality as prints, but very interesting. There are some older, historic photographs on pages 184-192. The book includes a small simple map of Cheddar Gorge with more than 40 numbered caves. There does not seem to be any large, good quality map of Cheddar Gorge. The book, or at least the third, revised edition is non-metric. Although, it is, of course, written for the caver, it provides useful information to the geologist. It is, well-worth purchasing for its important descriptive data and history, in addition to the photographs.
Barron, A.J.M, Sheppard, T. H., Gallois, R.W., Hobbs, P.R.M. and Smith, N.J.P. BGS, British Geological Survey, 2015. Geology of the Bath area: Carboniferous. This provides a summary of the geology of the Bath area, covered by the British Geological Survey. 1:50k geological map sheet 265. Earthwise, an online publication by the British Geological Survey (BGS). Available online at Geology of the Bath Area - Summary.
Selected extract regarding the Clifton Down Mudstone and stromatolites: "The sharp, erosional contact between the Gully Oolite and the overlying Clifton Down Mudstone Formation (CDM) is exposed in the extensively quarried inlier [7105-7315] at Wick (Kellaway and Welch, 1993). The basal part of the Clifton Down Mudstone Formation here comprises up to 3.5?m of brecciated and conglomeratic limestone with clasts of Gully Oolite and greenish grey mudstone, overlain by some 13?m of interbedded calcareous and non-calcareous mudstone that is typical of the Clifton Down Mudstone. At Wick, this facies is interrupted by a prominent 8.5?m - thick succession of hard, grey crinoidal and ooidal limestone, representing the Goblin Combe Oolite Formation (GCO). Above this, a further 18?m of lime mudstone and dolomitic limestone are regarded as the upper leaf of the Clifton Down Mudstone Formation. Stromatolitic algae are common in the Clifton Down Mudstone, but otherwise these rocks are poorly fossiliferous, and probably represent subtidal to peritidal deposits developed in a lagoon."
Belka, Zdzislaw [Zdzislaw Belka] 1987. The development and decline of the Dinantian carbonate platform: an example from the Moravia-Silesia Basin. In the book: European Dinantian Environments, Chapter: The development and decline of the Dinantian carbonate platform: an example from the Moravia-Silesia Basin., Publisher: John Wiley & Sons. Chichester, Editors: A.E. Adams, J. Miller, V.P. Wright, pp.177-188
Bell, F.G. 2013. Fundamentals of Engineering Geology. 656pp. [see p. 570 - Carbonate Sedimentary Rocks].
Bhatt, J. 1975. Evidence of evaporite deposition in the Lower Carboniferous Main Limestone Series of South Wales, U.K. Sedimentary Geology, vol. 13, issue 1, March 1975, pp. 65-70.
Petrographic examination of the dolomitized Main Limestone Series cropping out in the south, east and northeast corners of the South Wales Coalfield Basin shows evidence of the earlier presence of evaporite minerals. However, it is believed that lack of extensive evaporite deposits in these rocks may be due to the active diagenetic dissolution and oncoming humid coal conditions of post Main Limestone time. The evaporite minerals in the Main Limestone rocks seem to be overwhelmingly early diagenetic in origin in the light of the following observations: (1) calcite or dolomite pseudomorphs after gypsum crystals associated with a fine pelmicrite matrix; (2) association of such pseudomorphs with oolitic pelsparite; and (3) evaporite solution breccia texture.
Brandon, A. 1968. The geology of Carboniferous Strata (Visean-Namurian) in parts of Counties Leitrim and Cavan, Irish Republic. Unpublished Ph.D. thesis, Southampton University. By Dr. Alan Brandon.
BGS - British Geological Survey . 2010? The Rocks of Mendip. Go to website: The Rocks of Mendip.
"Silurian rocks (444 to 416 million years ago) The Silurian rocks of the Mendips are formally known as the Coalbrookdale Formation, and occur as a narrow elongated outcrop in the core of the eroded anticlinal fold that forms Beacon Hill, north-east of Shepton Mallet. The rocks comprise a sequence of fissile mudstones ('Wenlock Shales') around 600 m thick overlain by an interbedded succession of tuffs, agglomerates and andesite lava flows. A vent agglomerate represents a section through an ancient volcanic fissure, fortuitously exposed at the surface because of the almost vertical dip of the strata. Volcanic rocks are rare in the Silurian, and the Mendips are one of the few places in the UK where they can be observed." [continues.. good website!]
BGS (British Geological Survey). BGS website: Torr Works and Asham Wood.
BGS (British Geological Survey). BGS website:
History - East Mendip Quarries.
By 1957, Foster Yeoman, having largely completed the upgrading of Dulcote Quarry, near Wells, took over Merehead from Limmer with 150 acres of reserves at a cost of only 15 000 pounds. .... By 1967, output had increased to a quarter of a million tonnes annually. New, larger gyratory crushers were installed in 1969, the Norberg being one of the largest in Europe. These raised output rapidly to 3 million tonnes in 1971 and 5 million tonnes in 1973 (with potential capacity of 7 million tonnes a year), making the quarry the largest single producer of aggregates in Europe. ..
The quarry itself was working through steeply dipping beds 20 degrees to 40 degrees (occasionally with cavities) forming the southern limb of Beacon Hill Pericline. The western border of the quarry is parallel to the Downhead - East Cranmore road immediately to the west of which is the major Downhead Fault which marks the termination of the Carboniferous Limestone in this direction.
British Geological Survey. (BGS) 2015. etc.
The Fossils of Mendip Webpage freely available.
British Geological Survey. 1969 etc. [ Geological Sheet ST 45 (Solid and Drift Edition) Cheddar, Scale 1: 25,000, [Institute of Geological Science] British Geological Survey. Classical Areas of British Geology Series. 1959; 1969. [About 2 and a half inches to one mile.] There is a new edition of 1983. Six Inch Sheets are also available from BGS.
British Geological Survey [Institute of Geological Sciences, on the 1963 editions]. Sheet 280, Wells. Solid and Drift. One Inch Series, or newer, updated metric equivalent if available. This map includes Banwell, Axbridge, Cheddar Gorge, Chewton Mendip, Wells, Shepton Mallet and Chetwood. [Incidently, I have used the 1963 edition for checking Independent Mapping work by students in 1978 and 1982 [Guilor, Cockcroft, Houghton, Jones, Constable, and Francis (now Professor Jane Francis)]
British Geological Survey. Geological Sheet - Bristol District, Special Sheet, (Solid and Drift Edition). Parts of BGS Geological Maps - sheets 250, 251, 264, 265, 280 and 281. (These specific sheets may also be relevant, if available).
Bromhead, E.N. 2013. Reflections on the residual strength of clay soils with special reference to bedding-controlled landslides. Quarterly Journal of Engineering Geology and Hydrology. vol. 46, pp. 132-155. By Edward Nicholas Bromhead. [Significance - the Landslip Quarry, Landslide is at a hard-rock SPH - Slip Prone Horizon. - IMW]
This Glossop Lecture is about landslides and their slip surfaces at residual strength in clays. Particularly in southern England, but also elsewhere, landslides in infrastructure cuttings and many natural slopes are commonly found to be slowly moving compound landslides with a component of their basal shear surfaces following a particular bed (or 'slide-prone horizon') [SPH - ie. shear planes, see also Barton, M.(Prof. Max Barton) 2015 - 'Landslides and stratigraphy in the coastal outcrop of the Barton clay'. There are SPH - one at the C-D boundary and the other at F1-F2, below the Chama Bed]. A selection of both historical and modern case records of this type of landslide are presented briefly. The geotechnical conditions that give rise to this occurrence are discussed, and the dominant factor relates to the dip of the strata, which must be of low inclination for the landslide mass to remain in place over the critical clay bed in the geological sequence after sliding has been initiated. Observations of the slip surfaces in the field lead to the conclusion that the bedding-controlled elements of this type of landslide develop along thin, slide-prone or slide-susceptible, horizons in the bedding. The question of what caused the formation of those horizons in the first place is answered by putting forward two hypotheses to explain why bedding-controlled slip surfaces form where they do, and considering the evidence for or against each of them. The conclusion is reached that despite the attractiveness of the concept that these slip surfaces form by a progressive failure mechanism at the junction of two materials with dissimilar properties, the alternative concept that they occur where there is a bed of slightly enhanced smectite content better fits the observations. The mechanisms for such local changes in clay mineralogy are linked to inputs of volcanic ash at the time of deposition. Definitive proof of concept is, however, lacking, but taking into account how clay sediments are deposited in sedimentary basins, this paper makes suggestions for future lines of enquiry. Even now, nearly a half-century after Skempton’s seminal Rankine Lecture that introduced the concept of residual strength of clays to the wider geotechnical profession, the corpus of data is rather limited. Some of the datasets are shown to exhibit remarkable similarities, and the implications of this tend to support the preferred explanation of the origin of slide-prone horizons.
Brown, D. 1999. Somerset v. Hitler. Secret Operations in the Mendips 1939-1945. , Countryside Books, Newbury, Berkshire. 256pp. By Donald Brown.
When invasion threatened in 1940, Somerset's Mendip Hills were beset by land, air and sea. Defenders looked south for invaders and bombers while along the seaboard, convoys crept in, under under the protection of the Mendip Sea Watch, carrying war materials to sustain a desperate defence. In the face of these dangers, Mendip contained - and concealed - more wartime activity than even its own people suspected. Most of those people were engaged in their own unending war-work on the land, beating the even greater danger of starvation by blockade. This books gathers together their memories of how they faced that war. Even if some memories are incomplete, or inexactly recalled, or perhaps polished by time, they are all valid. They represent the experience of every community. Set into a factual historical context, they recall and illustrate life in those perilous years. Most of the Mendip story takes place on the high ground between Frome and Steep Holm, but a few episodes spread over into adjacent areas." [Introduction by the author - Donald Brown in 1999.]
Browne, M.A.E., Dean, M.T., Hall, I.H.S., Adams, A.d., Monro, S.K. and Chisholm, J.I. 1999. A lithostratigraphical framework for the Carboniferous rocks of the Midland Valley of Scotland. Version 2. British Geological Survey Research Report, No. RR/99/07. [reference temporarily held here re. the TWeed Borehole]
The lithostratigraphy of the Carboniferous rocks of the Midland Valley of Scotland has been reviewed. The Inverclyde, Strathclyde, Clackmannan and Coal Measures sedimentary groups can be recognised throughout the region, as can the component formations of the two higher groups. Formations in the two lower groups are recognisable only within sub-basins. Names now regarded as redundant are Tyninghame, Balcomie, Lugton Limestone, Dalry Sandstone, Caaf Water Limestone and Monkcastle formations. Tyninghame Formation is incorporated within the Ballagan Formation on the basis of a broader definition of the latter. The Balcomie, Lugton Limestone, Dalry Sandstone, Caaf Water Limestone and Monkcastle formations are now regarded as synonymous with the Clyde Sandstone, Lower Limestone, Limestone Coal, Upper Limestone and Passage formations respectively. The Kilbirnie Mudstone Formation is reduced to a member within the Limestone Coal Formation. The Troon Volcanic and Ayrshire Bauxitic Clay formations are reduced to members within the Passage Formation. Newly introduced lithostratigraphical names are the Bathgate Group and the formations within it, namely the Salsburgh Volcanic, Bathgate Hills Volcanic and Kinghorn Volcanic formations. Group status is required for this series of volcanic rocks because they markedly transgress the Strathclyde and Clackmannan sedimentary group boundaries. A rationalisation of the nomenclature applied to the main lithostratigraphical marker horizons in the Lower Limestone Formation has been undertaken, standardising on those of the Glasgow area. The base of the Coal Measures is placed at the base of the Lowstone Marine Band, its local correlative or at a plane of disconformity. The base of the Upper Coal Measures is taken in the Glasgow and Ayrshire areas at the base of the Aegiranum Marine Band, where it is locally known as Skipsey's Marine Band. In Fife and Lothian, however, the Aegiranum Marine Band has been tentatively re-correlated upwards in the succession with the 'Buckhaven Planolites Band' and Montague Bridge Marine Band respectively.
[Extract p.8 re Ballagan Formation palaeoenvironment:
"The oldest Carboniferous (Courceyan to Chadian) rocks (Inverclyde Group: Kinnesswood, Ballagan and Clyde Sandstone formations) were laid down whilst the climate was semi-arid and are characterised by the presence of carbonate beds and nodules and the absence of carbonaceous rocks, especially coal. Because of the semi-arid climate, the sandstone-dominated Kinnesswood and Clyde Sandstone formations contain calcareous and dolomitic pedogenic horizons (cornstones) formed on stable alluvial plains, whilst the mudstone-dominated Ballagan Formation is characterised by ferroan dolomite beds (cementstones) and evaporites (mainly gypsum preserved) laid down in alluvial plains and marginal marine flats subject to periodic desiccation and fluctuating salinity. The open sea lay to the south of the MVS with the more marine faunas in the 'cementstones' being found in the Solway Firth Basin. Initial access of the seawaters is shown as being from the east (Cope et al., 1992, maps C2, C3). Sandy alluvial fans are a feature of the Ballagan Formation along the southern edge of the Midland Valley of Scotland.".....
"The Ballagan Formation is characterised by generally grey mudstones and siltstones, with nodules and beds of ferroan dolomite (cementstone), the beds are generally less than 0.3 m thick. Gypsum, and to a much lesser extent anhydrite, and pseudomorphs after halite occur. Desiccation cracks are common and the rocks frequently show evidence of brecciation during diagenesis. Both these features are associated with reddening of the strata. Where present, the restricted fauna is characterised by the bivalve Modiolus latus, but ostracods are more abundant. Thin sandstones are present in many areas, and thick localised sandstones are also now included in the formation.
Name: The name Ballagan Formation was first used by Browne (1980) to replace the traditional term Ballagan Beds (or Series), which referred (though without formal definition) to the mudstone-cementstone sequence at Ballagan Glen (Young 1867a, b). The name is now defined to acknowledge the presence of sandstones, which locally may be thick, so that the term encompasses the strata in the Lothians that were earlier (Chisholm et al., 1989) called Tyninghame Formation.
The Ballagan Formation is well exposed in the Ballagan Glen [NS 5731 8022], but the (partial) type section is defined here just south of Perth in the East Dron Borehole [NO 1360 1572] (BGS Reg. No. NO 11 NW/24) from the bedrock surface at 15.26 m to 224.80 m. ..."
Bush, G.E. 1926. The Avonian Succession of Spring Garden and Vallis Vale, Frome, Somerset. Proceedings of Bristol Naturalists' Society. Annual Report and Proceedings, Vol. 6, (4) pp. 250-259.
Bush, G.E. 1930. Carboniferous Limestone (Avonian) succession in the Woodspring Promontory, Weston-super-Mare. Proceedings of the Bristol Naturalists' Society, vol. 7, pp. 138-141.
Carter, L. 2014. [by Linda Carter]. Cheddar Gorge and Caves. 58 pp. illustrated and including a reference list. Paperback. Somerset Archaeological and Natural History Society. This can be purchased at the Cheddar Gorge shops for 4.99 pounds only.
Chadwick, R. A. 1986. Extension tectonics in the Wessex Basin, southern England. Journal of the Geological Society, vol. 143, pp. 465-488.
The Permian to Cretaceous tectonic evolution of the Wessex Basin was controlled by horizontal tensional and vertical isostatic forces within the lithosphere. The gross morphologies of its constituent structures were governed by the location of Variscan thrust and wrench faults in the upper and middle crust, which suffered extensional reactivation in tensional stress fields oriented approximately NW-SE. Several episodes of crustal extension can be resolved, in early Permian, early Triassic, early Jurassic and late Jurassic/early Cretaceous times. These were characterized by the rapid subsidence of fault-bounded basins and commonly, by erosion of adjacent upfaulted blocks. Superimposed upon the fault-controlled subsidence, dominant during periods of fault quiescence, and becoming increasingly important with time, a component of regional subsidence is considered to have a thermal origin. This suggests that crustal extension was accompanied by some form of, not necessarily uniform, lithospheric thinning. Subsidence analyses assuming local Airey isostasy give cumulative crustal extension factors of 20–28% beneath the grabens. A more reasonable assumption of regional Airey compensation indicates basinwide crustal extension of 13–17%. which is consistent with BIRPS offshore deep seismic reflection data.
Chapman, M.B. 1912. IV. The chemical examination of the Carboniferous Limestone of the Avon Gorge. Geological Magazine, Decade 5, November 1912, Vol. 9, issue 11. 498-503. By Miss Mildred B. Chapman.
In view of the attention which has been drawn of recent years to the mode of origin of the purer limestones, I have been led to prosec?te some inquiries under this head on the Carboniferous Limestones of the Avon Gorge, near Bristol. I have paid greatest attention to the chemical composition of the rocks, particularly the proportion of insoluble residue remaining after treatment with hydrochloric acid; at the same time I have not wholly neglected the fossil contents, although for information on this point I have mainly relied on other observers.
Coleman, A.M. and Balchin, W.G.V. 1960. The origin and development of surface depressions in the Mendip Hills. Proceedings of the Geologists' Association, vol. 70, part 4, pp. 291-309.
Cossey, P.J., Adams, A.E., Purnell, M.A., Whiteley, M.J., Whyte, M.A. and Wright, V.P. 2004. British Lower Carboniferous Stratigraphy, Geological Conservation Review Series, No. 29, Joint Nature Conservation Committee, Peterborough, 617 pp.
Dixon, E.E.L. 1907. Geology of the South Wales Coalfield: part 7, The Country around Swansea. Memoirs of the Geological Survey, 1907.
Dixon, E.E.L and Vaughan, A. 1911. [E.E.L. Dixon and Arthur Vaughan] The Carboniferous Succession in Gower (Glamorganshire), with notes on its Fauna and Conditions of Deposition. Quarterly Journal of the Geological Society of London, vol. 67, pp. 477-571. [By Ernest Edward Leslie Dixon, B.Sc., A.R.C.Sc. F.G.S. and Arthur Vaughan, M.A., D.Sc., F.G.S. Read 9th March 2010. E.E.E. Dixon, British Geological Survey geologist; Dr. Arthur Vaughan, received the Lyell Medal of the Geological Society in 1910; died at the age of 47].
"The object with which the Avonian rocks of Gower (figs 1 and 2) described in the present paper were examined was primarily the comparison of their faunal sequence with that of Bristol and other parts of the South-Western Province. In this connection valuable pioneer work on parts of the sequence had already been done by Dr. W.B. Gubbin; and it was desired that our knowledge should be extended to the whole development, as also to the relationship of the zones that are based on brachiopods and corals with the representatives of the Pendleside Series which had been recognised in Gower by Dr. Wheelton Hind. ...."
[See this paper regarding the Modiola Phases, including Table III - The Modiola Phases - Calcareous Lagoon Phases - Represented in Gower. These are discussed further in the website of mine on Cheddar Gorge - go to:
Donovan, D.T. 1955. The Pleistocene deposits at Gough's Cave, Cheddar, including an account of recent excavations. Proceedings of the University of Bristol Spelaeological Society, vol. 7, part 2, pp. 76-104.
Donovan, D.T. 1969. Written discussion to paper taken as read (Ford and Stanton]: 6th September, 1968: [see: Ford D.C. and Stanton, W.I., 1969.] Proceedings of the Geologists' Association, 1969, vol. 80, pp. 379-380.
[Extract from the last part of the one page discussion:
"Regarding the regional chronology, I believe that extreme caution is necessary. When the erosional benches along the southern flanks of the Mendips are described (pp. 409-411) no mention is made of their origin. On pages 423-5 the benches are correlated, tentatively, with the Mediterranean Pleistocene sea-levels. Do the authors believe these benches to be marine erosion platforms? This seems a difficult interpretation in view of the altitudinal range of features in some groups - for example, the Warren Hill Bench is based on only four features ranging in height from 220 to 270 ft. O.D. In any case, are not the successive lower levels of water outlet from the limestone, demonstrated by the authors, likely to have been determined by the extent of removal of the soft Mesozoic rocks which once filled the Somerset levels?"
[Part of the reply by Ford on p. 380:]
"As regards the erosional benches on the southern flank of the Mendip Hills, those at 70ft (21m.) and 120-140ft (37-43m.) ('Axe Bench') are quite likely to be of marine origin. It is agreed that the higher remnants are poor evidence. They should only be taken to indicate that exhumation of the flank was most probably intermittent. The regional correlation must certainly be approached with the caution that Professor Donovan recommends. It was only with reluctance that the tentative chronology (Table III, p. 425, of our paper), was inserted by the undersigned - who now considers it a grave error to have used the Mediterranean eustatic fram at all. What is impressive in central Mendip is the rhythmic succession of erosional and depositional phases of comparable scales, within the caverns, and their apparent relation to valley-deepening events at the surface. In truth, our pre-Wurm chronology is scarely more than an emphasis of this rhythm. The older cave-fills lack fossil fauna and other characteristics of visible size, but contain several distinct stalagmite horizons. Our research group at McMaster University has some hopes of dating the stalagmite by radiometric means. This may put the chronological speculation on an altogether firmer footing."
Falcon-Lang, H. 1999. The Early Carboniferous (Courceyan–Arundian) climate of the British Isles: evidence from growth rings in fossil woods. Geological Magazine, vol. 136, no. 2, pp. 177-187. By Howard Falcon-Lang. Published March 1999.
Abstract: The British Isles lay at a palaeolatitude of 4 degrees S during the Early Carboniferous (Courceyan–Arundian) period. This paper examines fossil gymnosperm wood from ten localities in western Ireland and southern Scotland in order to analyse palaeoclimate. Fifty-two percent of the 77 fossil wood specimens studied exhibit growth rings that possess subtle, discontinuous ring boundaries and ring increments of narrow but variable width. These growth rings are qualitatively and quantitatively analysed, and are shown to bear a close similarity to growth rings in modern araucarian conifer woods; these araucarian growth rings are formed in response to tropical rainfall seasonality linked to monsoonal circulation. The findings of this study therefore support earlier palaeoclimatic interpretations, based on sedimentological evidence, which suggest that the British Isles experienced a monsoonal climate during the Early Carboniferous (Courceyan–Arundian) period.
Farrant, A.R. 1991. The Gough's Cave System: Exploration since 1985 and a reappraisal of the geomorphology. Proceedings of the Bristol Spelaeological Society. 1991, vol. 19, part 1, pp. 3-17.
Available online in full with photographs and maps:
The Gough's Cave System: Exploration since 1985 and a reappraisal of the geomorphology. NGR 46706391. Altitude 32m. AOD. Surveyed length: 2300 m.
The recent explorations in Gough's Cave are described including the discovery of [the main river passage, the alternative dry route into Lloyd Hall and the passages at the top of the Fonts. The cave is a complex resurgence system, developed on several levels along a minor drag fold, whose axial trend is 120 degrees, parallel to the strike. Strong north/south jointing is well-developed, and has a strong influence on cave development. A modified scheme of evolution is presented, which is contrasted with that of previous authors who suggest that there was only one input to the system via the Boulder Chamber. Recent digging in the cave and the exploration of the River Cave show that this is not the case and at least three other inlets existed including Damocles Rift, Mukin' Progress and the River Cave. Four major still-stands of the water table deduced from passage morphology arc proposed, the highest at or above 105 m AOD in Great Oones Hole/Long Hole, one at 70-75 m (Damocles Rift/Sand Chamber level), another one at c. 45 m (Boulder Chamber/Western Creep level) and the present water table at 23 m AOD in the River Cave. These are related to the evolution of the cave system. The modern active conduit exhibits strong structural control, forming a series of deep phreatic loops parallel to the dip and a horizontal water table passage along the strike.
[continues with main text and illustrations - very thorough and clear]
Ford, D.C. 1965. The origin of limestone caverns: a model from the central Mendip Hills, England. Bulletin of the National Speleological Society of America. Vol. 27, pp. 109-132. By Derek C. Ford of McMaster University, Hamilton, Ontario, Canada.
Ford, D.C. and Stanton, W.I. 1969. The geomorphology of the central Mendip hills. Proceedings of the Geologists' Association, vol. 79, pp. 401-427. [A full copy of the paper can be purchased from the Geologists' Association. See details online.]
The Hills, consisting mainly of cavernous Carboniferous Limestone, form a gently rolling plateau surface at 800 to 850 ft. (245–260 m.) O. D. Several monadnocks of Old Red Sandstone stand up to 200 ft. (60 m.) higher. The steep south flank of the plateau extends nearly down to sea-level and is basically a Triassic feature exhumed from beneath soft Mesozoic strata. The plateau, on the other hand, is thought to be largely a subaerial erosion surface of late Pliocene date.
Six erosion benches are recognised on the south flank between 670 ft. (205 m.) and 70 ft. (21 m.) O.D. They reflect the intermittently falling Pleistocene sea-level, and may be correlated with Zenner's eustatic levels from the Calabrian to the Main Monastirian [although see Donovan's discussion on this, and Ford's reply - the matter is questioned.]. A more irregular bench in the east is a structural feature developed at the base of the Lower Lias Clay.
A system of dry valleys similar in pattern to normal river systems is entrenched into the plateau. The original drainage pattern on the plateau surface was directed southwest or south, probably superimposed from a Miocene dome of Chalk. Entrenchment at the start of the present erosion cycle soon brought adjustment to the Palaeozoic structure. The Cheddar proto-system, closest to the Bristol Channel, had base-level advantage and beheaded most of the others.
The valleys debouch through gorges cut in the south flank. The size of the gorges varies according to the size of their fossil catchments. Changes of gradient in the thalwegs are due to a succession of knickpoints receding from the south flank baselevels. Valleys and gorges were incised by surface streams; the upper parts in the late Pliocene and early Pleistocene before drainage had gone underground, the lower parts when streams returned to the surface on Ice Age permafrost.
Underground drainage gravitated toward the lowest limestone outcrops. The two main springs are located at the mouths of the two main gorges, Cheddar and Ebbor. Ancient water tables traced in the dry springhead caves can be correlated with the erosion benches.
Most of the hundreds of closed depressions or dolines on the limestone plateau were created by solution working down from the surface. Also on the plateau are eighteen internally draining karst basins up to 50 ft. (15 m.) deep and 300 acres (1.2 km.2) in area. They developed at various stages of the Pleistocene by desiccation of headwater valleys. The older examples have a complex history and supported lakes on permafrost during glacial periods. Most show one or more overspill channels.
[See also discussion by Donovan, and reply by Ford, referred to above]
Ford, T.D. 2002. Dolomitization of the Carboniferous Limestone of the Peak District: a Review. Mercian Geologist. East Midlands Geological Society. By Trevor D. Ford.
Abstract. Large areas of the Carboniferous Limestone of the southern Peak District have been dolomitized, particularly the more coarse-grained calcarenitic facies. After a summary of the physical features of dolomitized limestone, its stratigraphic distribution and relationship to mineralization, the evidence points to a late Carboniferous date of dolomitization. Possible sources of the magnesium are from buried shales in adjacent basins, effectively as an early flush of hydrothermal fluids, from altered mafic minerals in volcanic rocks or both. It is proposed that a magnesium-rich fluid moved ahead of the hydrothermal mineral fluids and was exhausted before the mineral veins were infilled.
Friedman, G.M. 1966. Occurrence and origin of Quaternary dolomite of Salt Flat, West Texas. Journal of Sedimentary Research, March, 1966. vol. 36, No.1, pp.263-267. By Gerald M. Friedman.
Salt Flat graben is an intermontane basin in Hudspeth and Culbertson Counties, western Texas. The basin is filled with Quaternary sediments that include dolomite distributed among evaporite minerals. Carbon-14 dating indicates an age of 20,300+ or -825 years for one dolomite. Dolomite occurs at stratigraphically persistent levels associated with discontinuous lenses of native sulfur, gypsum, halite, and calcite. Dolomite was formed during periods of intense evaporation.
[This is one of the very few places where there is modern development of dolomite. See also the Coorong.]
Gallois, R. W. 2007. The formation of the hot springs at Bath Spa, U.K. Geological Magazine, Vol. 144, pp. 741-747. By Dr. Ramues Gallois of Exeter, formerly of the British Geological Survey. Available online in full, and with colour illustrations, as a pdf file. [interesting, easily accessible, reading with a good reference list]
The hot springs that emerge at 46ºC in the centre of Bath Spa, Somerset are unique in the UK. The four other thermal springs in Britain are also sourced in the Carboniferous Limestone, but they emerge at significantly lower temperatures (20° to 28ºC). Bath is situated in a region of low geothermal gradient (c 20°C/km depth) in a geological setting that seems an unlikely place for hot springs. Why then are these the only hot springs in Britain, and why are they confined to such a small (20 x 80 m) area? The explanation presented here involves a sequenceof geological events involving Triassic dissolution and Pleistocene permafrost that is unique to central Bath.
"Introduction [small extract from the beginning]:
There are only five occurrences of thermal springs in the UK, of which only at Bath Spa exceeds the 30 degee C defined by White (1957) as the lowest temperature at which a spring should be called hot. The springs at Hotwells (Bristol), Taff's Well (Cardiff) and Buxton and Matlock Spa (Peak District) emerge at 20 to 23 degrees. All five thermal springs are sourced in Carboniferous Limestonee in similar geological settings. At each locality the geological structure allows meteoric water to descend to sufficient depth for it to be heated by the geothermal gradient and return to the surface without a significant fall in temperature. ....... the hot-spring water has been geothermally heated at temperatures that require burial depths of at least 2500m. (Edmunds et al. 2002)." [continues with - Geological Setting]
Garwood, E.J. 1913. The Lower Carboniferous succession in the north-west of England. Quarterly Journal of the Geological Society, vol. 68, pp. 449-586.
Geological Conservation Review. 2015. See: Cossey, P.J., Adams, A.E., Purnell, M.A., Whiteley, M.J., Whyte, M.A. & Wright, V.P. 2004. British Lower Carboniferous Stratigraphy, Geological Conservation Review Series, No. 29, Joint Nature Conservation Committee, Peterborough, 617 pp.
George - Professor Thomas Neville George, FRS. 1904-1980.
Generally known as Professor Neville George. President of the Geological Society of London. Awarded the Lyell Medal in 1963. He was born in Swansea and had South Wales geological interests, amongst others. He was Professor of Geology at Glasgow University.
George, T.N. 1952. Tournaisian facies in Britain. Report of the International Geological Congress, 18, Great Britain, part 10, pp. 31-41.
George, T.N. 1954. Pre-Seminulan Main Limestone of the Avonian series in Breconshire. Quarterly Journal of the Geological Society of London, vol. 110, pp. 282-322.
George, T.N. 1958. Lower Carboniferous Palaeogeography of the British Isles. Proceedings of the Yorkshire Geological Society, vol. 31, pp. 227-318.
George, T.N. 1972. [T. Neville George]. The Classification of Avonian Limestones. President's Anniversary Address for 1970, Geological Society of London. Journal of the Geological Society of London, vol. 128, pp; 221-256. The paper here is very good and was a classic paper of the time, although the terminology of the Lower Carboniferous is different now. It deals with the Carboniferous Limestone from South Wales to the Mendip Hills and includes much petrographic and facies data. It is very good and still relevant but the reader needs to have some familiarity with older terminology of "S2 and C2S1" "zones" etc. Amongst other matters, he found traces of evaporites in the Lower Carboniferous of the southern UK. ]
In systematised stratigraphical classification 'Avonian' is a term junior to 'Dinantian'; but its present ignorance of the precise correlation equivalents of Dinantian assises ["assises" - two or more beds of strata united by fossils of the same characteristic species or genera] and Avonian zones the term is conveniently retained for the Lower Carboniferous rocks, most of them typical 'Carboniferous Limestone', of the British South-Western Province, where there is also ignorance of the precise horizons of the Fammennian-Dinantian junction and the Dinantian-Namurian junction. At the same time, the Avonian assemblage zones have significance only in the carbonate rocks of the northern part of the Province; they are not applicable to the Lower Culm of the southern part, and they are applicable only with uncertainty to other Lower Carboniferous provinces in Britain. 'Avonian' is of only temporary and local validity: it is not the name of a standard series.
Avonian rocks are mainly shelf limestones of a variety of kinds. They display marked lateral and sequential changes that reflect the influence of many factors, of which contemporary earth-movement, with consequence migration of facies belts and the occurrence of sharp lithological breaks and non-sequences, was of major importance. The fossiliferous members of the series reflect subtly variant biotopes that throw light on a multiplicity of shelf environments whose characteristics and distribution have strong analogies, in association of organisms and in community balance, with near-shore shelf sediments of many of the warmer present-day aeas; and recurrent inorganic limestones (mainly calcite muds and oolites) demonstrate the general shallowness of the shelf seas over very wide areas. Detailed palaeogeographical reconstruction is possible for many of the rock groups over much of the ground.
A sedimentological classification of the rocks is not readily accommodated by a usual system of parameters inherited from the classification of detrital terrigenes. Nearly all the limestone endogenic, their calcareous constituents almost never the product of hinterland erosion or prolonged transport even when the 'clasts' within them are abraded fragments. Grain size in such sediments is commonly an accident of origin, not a reliable sign of the restlessness of the environment of deposition; a spirifer shell is much larger than the individual crinoid plates in the bed in which it lies; a stromatolite algal sheet is the welded product of growing algal nodules, and conversely an algal nodule may show partial disintegration into 'amorphouse' algal mud; a coral bush is the enclosing frame of the shells it houses and of the organic debris caught in its mesh, and at the same time it is itself embedded in a bank of the same kind of shells or in the wrappings of the same kinds of debris; drewite mudstone, a faecal pellet, an oolith, reflect related features in carbonate formation.
'Micrite' also has many ambiguities; it may be an accumulate virtually in situ; it may be detritus transported some distance, or fragmented and redistributed locally; it may he mainly of monogenetic provenance, in its shelly or its algal or its evaporitic constituents, and then be coarse-grained or fine-grained, apparently well-sorted, through immediate environmental 'accident', or it may be equally 'accidentally' unsorted or ill-sorted in grain size as an 'internal' product of a mixed biotope; it may be diagenetic, 'contemporaneosu' or 'penecontemporaneous' or 'subsequent'.
In a naive petrographic system mechanically applied, classification can result in the imposition of mutually incommensurable or incompatible criteria in attempts to distinguish between petrological kinds resistant to the system: rocks similar on the arbitary criteria (for instance of grain size) may little mutual affinity; rocks very different on the criteria may be closely allied. Principles in the classification of limestones, as they are illustrated in Avonian rocks need to be self-consistant and comprehensive: they cannot be adequately of use in description unless they are also genetic. [end of abstract].
George, T.N. 1978. Mid-Dinantian (Chadian) limestones in Gower. Philosophical Transactions of the Royal Society, Series B., vol. 282, pp. 411-462.
Ghummed, M.A. 1982. Petrology and Geochemistry of the Carbonates, Ballagan Formation, N.W. Midland Valley, Scotland. Ph.D. Thesis, Glasgow University, 275 pp. By Dr. Milad Ali Ghummed. University of Glasgow Library. Instantly online as title and abstract only, and from this page the full pdf (18Mb) can be downloaded:
Petrology and Geochemistry of the Carbonates, Ballagan Formation, N.W. Midland Valley, Scotland.
The pdf file is available from the above, free online: pdf-file -
This study investigates the nodular and stratified carbonate beds 1n the Ballagan Formation, in the Western Midland Valley of Scotland. The Ballagan Formation, which also includes lutltes and quartz arenites, lies stratigraphically between the Upper Old Red Sandstone end the Spout of Ballagan Sandstone: it constitutes the lower-most part of the Calciferous Sandstone Measures. Microscopic examination of thin sections showed that the carbonates comprise mainly three microfacies which are subdivided on the basis of fabric and crystal-size. Microfacies A is the finest-grained and from it the other two have diagenetically evolved; through neomorphism (Microfacies B), and metasomatism and segregation (Microfacies C). Microfacies B has resulted from multiple neomorphic stages as indicated by crystal-size variation. As a, .result of neomorphism, clay has concentrated In .the intercrystalline boundaries, leaving the new crystals slightly clearer than their precursors. Microfacies C has developed in two ways: (1) metasomatism and (2) segregation. Calcitization of dolomitic beds and segregatIon of calcite in an original argillaceous sediment, both produced Microfacies C. The controlling factors over these processes are unknown. Shrinkage cracks, cavity-cement, and veinlets are common features in both stratified and nodular carbonates. Poorly preserved laminations are uncommon in the untreated rock specimen, but are common in thin section. Whilst it is difficult to prove an algal origin for these structures, they morphologically resemble algal laminations. Calculation of mineral proportions from chemical analyses by X-ray fluorescence show that about 86 percent of the carbonate beds contain more than 50 percent of the mineral dolomite, therefore, they are generally dolomites by definition, with minor limestone occurrences. Terrigeneous material content is composed mainly of clay minerals; illite, chlorite, and montmorillonite with common quartz. Gypsum is a minor lithology in the rock assemblages. Electron microprobe analysis has shown that crystals of both Microfacies A and B are composed mainly of dolomite, the crystals of the first contain more clay than those of the latter. Crystals of Microfacies C are composed of calcite. Probing of veinlets confirmed a wide range of mineral compositions. From a consideration of the fineness, bed-thickness, structures, faunas, composition, rock-association and lateral facies relationships, these beds are thought to have formed in a lagoonal environment. On the seaward the lagoon was probably bounded by sand bars; on the landward by caliche pavements and alluvium. The best analogous environment is seen in the Coorong, 5. Australia, where fine dolomitic beds are laid down during the wet season and desiccated during the dry.
[With good thin-section photomicrographs and much geochemical data. A good work on Carboniferous dolomite of penecontemporaneous origin and associated with evaporites. Relevant to some other Carboniferous dolomites (and also of relevance, beyond the Mendip region discussed here, to the Tweed Borehole Carboniferous research project, re Romer's Gap.)]
Goodman, S. 1987. The relationship between light hydrocarbons and carbonate petrology - a study from the Mendip Hills. Geological Journal, Volume 22, Issue 4, pages 371 - 382, October/December 1987.
Anomalously high values of light hydrocarbons (C1 - C4) have been detected in carbonate rocks hosting base metal mineralization, and have a potential use in mineral exploration. Development of an exploration method based on such anomalies requires an understanding of the controls on the hydrocarbon content of the rocks, other than by mineralization, i.e. the hydrocarbons present in background areas. This study uses gas chromatography to investigate the light hydrocarbons present in rocks from such a background area, the Carboniferous Limestone of the Mendip Hills, in order to determine the extent to which different carbonate lithologies affect the quantity and nature of hydrocarbons present. It appears that the lithological effects are minimal when compared to the anomalous values from mineralized areas. The limited effects are due to variations in the depositional and diagenetic regimes of the original sediments.
Green , G.W. and Welch, F.B.A. 1964. The Geology of the Country around Wells and Cheddar. Memoirs of the Geological Survey of Great Britain, No. 280. (Explanation of One-Inch Geological Sheet 280, New Series). With contributions by G.A. Kellaway, D.R.A. Ponsford, M. Brooks, and M. Mitchell. Department of Scientific and Industrial Research, London, Her Majesty's Stationery Office. 225pp.
Green, G.W. 1992. British Regional Geology: Bristol and Gloucester Region. Third Edition, based on previous editions by G.A. Kellaway, F.B.A. Welch and R. Crookall. London, Her Majesty's Stationery Office. 188 pp. [a good edition, larger than most British Regional Geology books; this is more in the style of a memoir of the BGS].
Gregg, J.M., Shelton, K.L., Johnson, A.W., Somerville, I.D. and Wright, W.R. 2001. Dolomitization of the Waulsortian Limestone (Lower Carboniferous) in the Irish Midlands. Sedimentology, vol. 48, Issue 4, pp. 745-766. By Jay M. Gregg, Kevin L. Shelton, Aaron W. Johnson, Ian D. Somerville and Wayne R. Wright.
The Waulsortian Limestone (Lower Carboniferous) of the southern Irish Midlands is dolomitized pervasively over a much larger region than previous studies have documented. This study indicates a complex, multistage, multiple fluid history for regional dolomitization. Partially and completely dolomitized sections of Waulsortian Limestones are characterized by finely crystalline (0.01 - 0.3 mm) planar dolomite. Planar replacive dolomite is commonly followed by coarse ( = 0.5 mm) nonplanar replacive dolomite, and pervasive void-filling saddle dolomite cement is frequently associated with Zn -Pb mineralization. Planar dolomite has average d 18O and d 13C values (parts per thousand PDB) of -4.8 and 3.9 respectively. These are lower oxygen and slightly higher carbon isotope values than averages for marine limestones in the Waulsortian (d 18 O = - 2.2, d 13C = 3.7). Mean C and O isotope values of planar replacive dolomite are also distinct from those of nonplanar and saddle dolomite cement (- 7.0 and 3.3; - 7.4 and 2.4 respectively). Fluid inclusions indicate a complex history involving at least three chemically and thermally distinct fluids during dolomite cementation. The petrography and geochemistry of planar dolomites are consistent with an early diagenetic origin, possibly in equilibrium with modified Carboniferous sea water. Where the Waulsortian was exposed to hydrothermal fluids (70 - 280 degrees C), planar dolomite underwent a neomorphic recrystallization to a coarser crystalline, planar and nonplanar dolomite characterized by lower d 18 O values. Void-filling dolomite cement is isotopically similar to nonplanar, replacive dolomite and reflects a similar origin from hydrothermal fluids. This history of multiple stages of dolomitization is significantly more complex than earlier models proposed for the Irish Midlands and provides a framework upon which to test competing models of regional vs. localized fluid flow.
Hallam. A. and O'Hara, M.J. 1962. Aragonitic Fossils in the Lower Carboniferous of Scotland. Nature, vol. 195, pp. 273-274. 21st July 1962. Grant Institute of Geology, University of Edinburgh. Although many invertebrates form skeletons partly or wholly of aragonite, this normally inverts to calcite within a geologically negligible period of time, a few tens of thousands of years at the most (1). Indeed, more than 50 per cent of the aragonite laid down by some of the marine invertebrates studied by Lowenstam (2) inverted to calcite within a year. As the geothermal gradient lies completely within the stability field of calcite it has been maintained that aragonite within buried sediments could exist only in peculiar local conditions of high hydrostatic pressure and moderate temperature (3). Aragonite in rocks of a respectable age may therefore be presumed rare, and any record of such an occurrence is of interest both because of the problems posed by the preservation of this metastable mineral and the desirability of obtaining unaltered shells for palæo-ecological studies. .... continues [Summarised reference list of the above note: 1. Revelle, R., and Fairbridge, R. W., 1957. Geological Society of America, Memoir. 67, 1, 239. - 2. Lowenstam, H. A.,1954. Journal of Geology., vol. 62, 284. - 3. Graf, D. L., 1960. Illinois Geol. Survey, Circular 297, Pt. 1. 4. Currie, E. D., 1954. Transactions of the Royal Society of Edinburgh., vol. 62, 527. 5. Stehli, F. G., 1956. Science, 123, 1031.}
Hancock , N.J. 1982. Stratigraphy, palaeogeography and structure of the East Mendips Silurian inlier. Proceedings of the Geologists' Association, London, vol. 93 (3), 247-261.
Abstract: Sedimentary way-up criteria in the 'Wenlock shales' of the East Mendips inlier show that these beds, previously believed to overlie Silurian andesitic lavas and tuffs unconformably, are inverted and underlie the volcanics, probably conformably. A regressive sequence of brachiopod communities occurs in the shale and overlying tuffs. This regression is dated as probably M. riccartonensis zone (Lower Wenlock) by Eocoelia angelina, suggesting that the volcanics are also Wenlock. The regression is not contemporaneous with the widespread late Wenlock shallowing of Wales and the Welsh Borderland, and is probably related to the volcanism. Remapping of the inlier shows that although the Silurian beds are situated in the core of the East Mendips anticline, they exhibit no anticlinal structure within themselves. This, taken together with the discrepant Old Red Sandstone thicknesses north and south of the inlier, demonstrates that the southern boundary of Silurian rocks constitutes and overthrust and not an angular unconformity as hitherto believed. An exposed volcanic neck forms one possible source for the numerous Wenlock bentonites in Wales and the Welsh Borderland.
Hobson, D.M. and Sanderson, D.J. 1983. Variscan deformation in southwest England. In Hancock, P.L. (editor), The Variscan Belt in the British Isles. Publisher - Highler, Bristol, pp. 108-121. [re: Tectonic deformation of the Carboniferous strata]
Hepworth, J.V. and Stride, A.H. 1950. A sequence from the Old Red Sandstone to Lower Carboniferous, near Burrington, Somerset. Proceedings of the Bristol Nat. Society, vol. 28, pp. 135-138.
Hird, K., Tucker, M.E. and Waters, R. Petrology, geochemistry and origin of Dinantian dolomites from southeast Wales. In Adams, A.E., Miller, J. and Wright, V.P. (editors). European Dinantian Environments. Special Publication of the Geological Journal, New York, Wiley, no. 12, pp. 359-377.
Hitzman, M.W., Allan J.R. and Beaty, D.W., 1998. Regional dolomitization of the Waulsortian limestone in southeastern Ireland: evidence of large scale fluid flow driven by the Hercynian orogeny. Geology, 26, 547-550.
Harrison, D.J., Buckley, D.K. and Marks, R.J. 1992. Limestone Resources and Hydrogeology of the Mendip Hills. British Geological Survey, Keyworth, Nottingham, Technical Report, WA/92/19.
Hobbs, S.L. 1988. Recharge, Flow and Storage in the Unsaturated Zone of the Mendip Limestone Aquifer. Unpublished Ph.D. Thesis, University of Bristol. [not seen].
Holt, N.M, Garcia-Veigas, J., Lowenstein, T.K., Giles, P.S. and Williams-Stroud, S. 2014. The major-ion composition of Carboniferous seawater. Geochimica et Cosmochimica Acta. Vol. 134, pp. 317-314. By: Nora M. Holt, Javier Garcia-Veigas, Tim K. Lowenstein, Peter S. Giles, Sherilyn Williams-Stroud; June 2014.
The major-ion chemistry (Na +, Mg2 +, Ca2 +, K +, SO4 2 -, and Cl -) of Carboniferous seawater was determined from chemical analyses of fluid inclusions in marine halites, using the cryo scanning electron microscopy (Cryo-SEM) X-ray energy-dispersive spectrometry (EDS) technique. Fluid inclusions in halite from the Mississippian Windsor and Mabou Groups, Shubenacadie Basin, Nova Scotia, Canada (Asbian and Pendleian Substages, 335.5 - 330 Ma), and from the Pennsylvanian Paradox Formation, Utah, USA, (Desmoinesian Stage 309 - 305 Ma) contain Na + - Mg2K +- Ca2 +- Cl - brines, with no measurable SO4 2 -, which shows that the Carboniferous ocean was a "CaCl 2 sea", relatively enriched in Ca2 + and low in SO4 2 - with equivalents Ca2 + > SO4 2 - + HCO 3 -. d 34 S values from anhydrite in the Mississippian Shubenacadie Basin (13.2 - 14.0 permille) and the Pennsylvanian Paradox Formation (11.2 - 12.6 permille) support seawater sources. Br in halite from the Shubenacadie Basin (53 - 111 ppm) and the Paradox Basin (68 - 147 ppm) also indicate seawater parentages.
Carboniferous seawater, modeled from fluid inclusions, contained ~ 22 mmol Ca2 + / kg H2O (Mississippian) and ~ 24 mmol Ca2+ / kg H2O (Pennsylvanian). Estimated sulfate concentrations are ~ 14 mmol SO42 - /kg H2O (Mississippian), and ~ 12 mmol SO4 2 - /kg H2O (Pennsylvanian). Calculated Mg2 + / Ca2 + ratios are 2.5 (Mississippian) and 2.3 (Pennsylvanian), with an estimated range of 2.0 - 3.2.
The fluid inclusion record of seawater chemistry shows a long period of CaCl 2 seas in the Paleozoic, from the Early Cambrian through the Carboniferous, when seawater was enriched in Ca 2 + and relatively depleted in SO4 2 -.
**** During this ~ 200 Myr interval [Early Cambrian to Carboniferous], Ca2 + decreased and SO4 2 - increased, but did not cross the Ca2+ - SO4 2- chemical divide to become a MgSO4 [magnesium sulphate] sea (when SO4 2- in seawater became greater than Ca2+) until the latest Pennsylvanian or earliest Permian (~309 - 295 Ma). Seawater remained a MgSO 4 [magnesium sulphate] sea during the Permian and Triassic, for ~100 Myr.
Fluid inclusions also record a long interval, from the Early Cambrian to the Middle Devonian, when seawater had low Mg2+ /Ca2+ ratios (< 2) that coincide with calcite seas.
**** The Mg2+ /Ca2+ ratio of seawater rose from 0.9 in the Middle Devonian, to 2.5 in the Middle/Late Mississippian, 2.3 in the Middle Pennsylvanian, and 3.5 in the Early Permian.
The transition from calcite seas to aragonite seas, established from the mineralogy of oolites and early marine cements, occurred in the Late Mississippian. Fluid inclusions show that seawater Mg2 + /Ca2 + ratios rose above 2 by the Middle to Late Mississippian coinciding exactly with the shift to aragonite seas. Aragonite seas existed for ~ 100 Myr, from the Late Mississippian until the Late Triassic/Early Jurassic.
Hopson, C. A and Melson, W.G. 1990. Compositional Trends and Eruptive Cycles at Mount St. Helens. Geoscience Canada, vol. 17, no. 3, pp. 131-141. By Clifford A. Hopson, William G. Melson
Available online as a pdf file:
Hopson and Melson, Compositional Trends and Eruptive Cycles at Mount St. Helens.
The 40,000-year eruptive history of Mount St. Helens reveals an overall compositional trend from rhyodacite to andesite, with basalt at ~1.9 and ~1.6 ka. A cyclic eruption pattern is superimposed on this trend. Cycles comprised a repose interval, when compositional and thermal gradients developed in the underlying magma body, followed by an eruption interval in which progressive tapping of magma beheaded these gradients. Recovery of gradients varied with duration of the ensuing repose period. Eruption sequences follow the pattern: (1) eruptive progression from Plinian eruptions to dome growth accompanied by pyroclastic flows and tephra, followed (in some cases) by lava flows punctuated by pyroclastic outbursts; (2) a mineralogic progression from hydrous Fe-Mg phenocrysts (hb, cm, bi) toward pyroxenes; (3) a magmatic compositional progression from rhyodacite or dacite to andesite. Progressions 1 and 2 stem mainly from volatile gradients in the magma reservoir whereas progression 3 (and to some extent 2) reflects gradients of melt composition and crystal content. Three eruption cycles within the last 4,000 years follow this pattern. Earlier cycles are probable but only dimly perceived, mainly from the partial record of tephras and pyroclastic flows.
Hussein, M. 1986. Evaporite deposition and source rock evaluation of a Holocene-Pleistocene continental sabkha (Salt Flat Playa) in West Texas. [This is important location for modern dolomite formation - and thus a rare locality. This good study may be relevant to the Carboniferous dolomite and evaporite sequence of the Tweed Borehole, Berwick-upon-Tweed, northern England, where there are alternating subaqueous and subaerial deposits.] Ph.D. Thesis, 1986. University of Texas at Dallas. By Dr. Mahbub Hussain.
Abstract. The Salt Flat sabkha (dry playa) in West Texas - New Mexico is located within Salt Basin Graben, an intermontane basin at the foothills of the Guadalupe-Delaware Mountains. Major facies in this sabkha comples are : bajada, sand flat and mud flat sabkaha. The Bajada is a wedge of poorly-sorted, coarse grained alluvial sediment at the base of the Guadalupe Mountains and adjoining foothills. The sand flat is a dune complex of cross-bedded quartz and gypsum sands underlain by a Pleistocene lacustrine sequence. Sabkha flat sediments are mainly laminated varve-like sequences of alternating millimeter-scale dark and light laminae. In addition to the millimeter-scale laminated texture, the entire sequence is characterized by a superimposed coloration of light and dark layers some centimeters in thickness. The sabkha flat sediments are a suite of evaporite and carbonate minerals of both primary and diagenetic origin. Dolomite and gypsum comprise over 70 percent of the sediment; the rest is halite, cacite, aragonite, and minor amounts of quartz. The nature and distribution of minerals in different units, coupled with radiocarbon dates : suggest that lighter gypsum-rich couplets were originally deposited during more saline evaporative phases of the brine lake water body. Freshening during more humid times in the Late Pleistocene diluted the surficial brine, enhanced density stratification of the water body and created anoxic bottom conditions favoring carbonate deposition. Lake sediments were originally deposited under subaqueous conditions; a change in climate created more arid depositional setting reflected in Holocene deposition in the lake. The change in climate to more arid conditions had two effects on the playa. First, it converted the playa from a large perennial water body to a deflation lake. Second, it moved the water surface down into the sediment column where it became a water table. Lowering of the water table moved the laminated evaporite from a subaqueous setting into the capillary and vadose zones and converted the Holocene playa flats into regional discharge zones for basinward-flowing subsurface water. Pore brines evaporating from the capillary zone and flowing through the phreatic zone of the mud flat play an important role in the diagenetic alteration of the sediment matrix. The nature, and abundance of the organic matter in the sabkha flat sediments, as well as overall depositional setting, indicate that shallow-water continental sabkha sediments, if preserved, may be a potential hydrocarbon source rock. End of Abstract.
Irwin, D.J. 1986. Gough's Old Cave - Its History.
Proceedings of the University of Bristol Spelaeol. Society, vol. 17 (3). pp. 250-266. Available online as a pdf file.
Gough's Old Cave - Its History.
Abstract: During the latter half of lite 19th century Gough's Old Cave was variously known as The Great Stalactite Cavern, The New Great Stalactite Cavern and Gough's Stalactite and Stalagmite Cavern. The cave was probably shown to visitors from about the late 18th century. It was certainly open for public viewing by 1869 and was then run by John Weeks. The well-known legend of the Jack and Nancy Beauchamp - Gough partnership is now questioned due to the emergence of new documentary evidence. The extensions made in the cave by Gough between 1877 and 1889 are described, together with accounts of visits by travellers and scientific organizations. Rivalry existed between Gough and the Cox brothers, rising to its peak in the late 1880s. The important extensions made in Gough's New Cave between 1892 and 1898 eclipsed the 'Old' cave, which was finally closed to the public in the early 20th century. This paper has been based on contemporary' accounts as far as possible, including newspapers, official documents and travel guides.
Jacobi, R.M. 1985. The history and literature of Pleistocene discoveries at Gough's Cave, Cheddar, Somerset. Proceedings of the University of Bristol Speleological Society, vol. 17. part 2, pp. 102-115.
Abstract: Finds have been, made in Gough's (New) Cave for over a century. Many were accidental intrusions into the routine development of the Cave's tourist potentials. Documentation is correspondingly piecemeal, and has generated numerous ambiguities. Of international importance are discoveries made during excavations in the entrance area of the Cave between 1927 and 1931.
KeepCheddarGorgeous - website.
Keep Cheddar Gorgeous. A conservation website with links to other website on associated subject matter.
Kellaway, G.A. 1996. Discovery of the Avon-Solent Fracture Zone and its relationship to Bath hot springs. Environmental Geology, vol. 28, pp. 34-39.
Kellaway G.A. and Welch, F.B.A. 1948. British Regional Geology: Bristol and Gloucester District. 2nd Edition, London, HMSO, i-iv and 91pp.
Kellaway, G A and Welch, F. B. A. 1955. The Upper Old Red Sandstone and Lower Carboniferous rocks of the Bristol and the Mendips compared with those of Chepstow and the Forest of Dean. Bulletin of the Geological Survey of Great Britain, No.9, pp. 1-21.
Kellaway, G A and Welch, F.B.A. 1993. Geology of the Bristol district. Memoir of the British Geological Survey. Special Sheet [England and Wales], 1:63,360. London, Her Majesty's Stationery Office. 199pp. Contributors: Ivimey-Cook, H.C., Mitchell, M., Owens, B., Rushton, A.W.A., Warrington, G. and White, D.E., with petrography by R. Dearnley. ISBN 0 11 884466 0. Large paperback book, with a photograph of part of Cheddar Gorge on the front . This memoir relate not just to the narrow confines of the Bristol geological survey sheet 264 (1:50,000) but includes a larger area from north of Chipping Sodbury to south of Cheddar. It also includes Avonmouth, Portishead and the Bristol and Somerset Coalfield. It is a thorough report with many monochrome maps, diagrams and cross-sections etc. There are some wide, colour photographs. It has a reference list containing about 317 references.
Kirkham, A. 1976. Palaeoecology and diagenesis of the Clifton Down Limestone Group (Carboniferous Limestone) of the Bristol District. Ph.D. Thesis, Bristol University (from a reference listing). But given by Kirkham (2005) as: Kirkham, A. 1977. Facies variation and diagenesis of the Upper Arundian - Holkerian (Lower Carboniferous)sediments of the Bristol Area. Ph.D. Thesis, Bristol University, England. [See also Kirkham, 1998 and 2004, re dolomite and evaporites in the Arabian Gulf - references in Kirkham, 2005, details below.]
Kirkham, A. 2004. Patterned dolomites: Microbial origins and clues to vanished evaporites in the Arab Formation, Upper Jurassic, Arabian Gulf. In C.J.R. Braithwaite, G. Rizzi, and J. Darke (Editors), The Geometry and Petrogenesis of Dolomite Hydrocarbon Reservoirs. Geological Society, London, Special Publication v. 235, p. 301-308.
Kirkham, A. 2005. Thrombolitic-Ortonella reefs and their bacterial diagenesis, Upper Visean, Clifton Down Limestone, Bristol area, Southwest England. Proceedings of the Geologists' Association, vol. 116, no. 3-4, pp. 221-223. By Dr. Anthony Kirkham.
Abstract: Thrombolites, cryptalgal structures, occur in the Upper Visean (Mississippian) Clifton Down Limestone, mainly in the Concretionary Beds at the top of formation in the Bristol area. Both flocculently clotted and digitate thrombolites occur. Internally both forms comprise spherulitic mosaics and Ortonella thalli. Penecontemporaneous encrustations of fibrous cements, formed by exposed and juxtaposed and highly eccentric spherulites, were replaced by fascicular-optic calcite. Similar encrustations of fascicular-optic calcite also occur on brachiopods and coral debris. Calcite-precipitating bacteria influenced the growth of these distinctive spherulites and cements. Antipathetic relationships between the spherulitic mosaics and Ortonella thalli within the thrombolites represent alternating marine and fresh-water conditions respectively. The encrustations were prone to endolithic microbial borings and the spherulitic thrombolites were often penecontemporaneously eroded. The evidence, therefore, suggests that the spherules and cements were very early diagenetic. Occasionally the thrombolites and encrustations were interlayered with stromatolites. The matrices of the clots typically comprise wackestone that contains calcispheres, foraminifera and ostracods,and are preferentially burrowed. Between the clots, the matrices were sometimes flushed to create open galleries which were prone to geopetal sediment fills. Brachiopods and encrusting serpulids also occur within the thrombolites. Such benthic assemblages and their muddy carbonate matrices suggest relatively low-energy, subtidal, marine depositional environments, but the previously open galleries plus the thrombolites' susceptibilities to erosion and their association with well-laminated stromatolites and oolitic sediments suggest washing in higher energy, shallow-water settting in which relatively small sea-level falls could lead to exposure and establishment of fresh or brackish-water influences. Their early lithification and positive erosional morphologies clearly defined the thrombolites as biostromes, which at least in gross terms, appears to be correlative over tens of kilometres within the Concretionary Beds especially. End of abstract.
Lewis, D.N., Donovan, S.K. and Sawford, P. 2003. Fossil echinoderms from the Carboniferous Limestone sea defence blocks at Barton-on-Sea, Hampshire, southern England. Proceedings of the Geologists' Association , 114, 307-317.
Abstract: The sea defence/coastal protection works at Barton-on-Sea, Hampshire include blocks of Carboniferous Limestone (Clifton Down Limestone Formation, Dinantian, Holkerian) from the Foster Yeoman 'Torr Works' Quarry at Merehead, East Cranmore, Shepton Mallet, Somerset. A rich fauna of echinoderms, corals, bryozoans, trilobites, brachiopods and gastropods is present in these blocks. The echinoderms include plates of the tests of the echinoids Palaechinus sp., Archaeocidaris sp. and an indeterminate echinoid: calyces of the crinoids platycrinitid sp., Actinocrinus sp. aff. A. rotundatus Wright, monobathrid sp. indet., camerate sp. indet. and Taxocrinus sp.; and numerous ossicles, including Cyclothyris (col.) sp. and Pentagonocyclicus (col.) spp. Camerates were important members of early Carboniferous crinoid faunas, although the absence of cladids is notable. Examination of any fossils contained within coastal protection blocks is an important source of information when the place of origin of the blocks is known but is unavailable for study purposes. [by David N. Lewis, Natural History Museum, London, Stephen K. Donovan, Nationaal Natuurhistorisch Museum, Leiden, and Paul Sawford, Ruislip Road, Northolt, Middlesex.]
Llewellyn, P.G., Backhouse, J. and Hoskin, I.R. 1969. Lower - Middle Tournasian Miospores from the Hathern Anhydrite Series, Carboniferous Limestone, Leicestershire. Proceedings of the Geologists' Association, vol. 80?, pp. 85-92.
Llewellyn, P.G. and Stabbins, R. 1970. The Hathern Anhydrite Series, Lower Carboniferous, Leicestershire, England, Instit. of Mining and Mineralogy, vol. 79, pp. B 1-B 15.
The full abstract is not available here, only a brief comment on the substance of the paper. The authors described Tournasian (Courceyan) bedded and nodular anhydrite in a borehole. It was interbedded with dolomite, mudstone and massive to nodular limestone. (Similar anhydrite is in the Long Eaton Borehole). Go to British Geological Survey publications for more information; the Hathern Anhydrite has been described in Carney, J N, Ambrose, K and Brandon, A. 2001. Geology of the country between Burton, Loughborough and Derby (141). Incidently, compare to the Tweed Borehole which is in Tournasian anhydrite and dolomite. Further comment from Rayner - On the south side of the Widmerpool Gulf the Hathern Borehole, see Llewellyn below, penetrated 206 m. of limestones low in the sequence underlain by anhydrite and overstepped by Namurian.
Llewellyn P. G., Mahmoud S. A. and Stabbins R., 1968. Nodular anhydrite in Carboniferous limestone, west Cumberland. Institution of Mining and Metallurgy, Transactions, Section B: Applied Earth Science, vol. 77(735): B18-B25.
Logan, B.W. 1961. Cryptozoan and associated stromatolites from the Recent, Shark Bay, Western Australia. Journal of Geology, vol. 69, 517-533.
Logan, B.W., Read, J.F., Hagan, G.M., Hoffman, D., Brown, R.G., Woods, P.J. and Gebelein, C.D. 1974. Evolution and diagenesis of Quaternary carbonate sequences, Shark Bay, Western Australia. American Association of Petroleum Geologists, Memoir 22, 358 pp.
Logan, B.W., Rezak, R. and Ginsburg, R.N. 1964. Classification and environmental significance of algal stromatolites. Journal of Geology, vol. 72, pp. 68-83.
MacQuown, W.C. and Bloxam, T.W. 1972. Depositional History of Carboniferous (Middle Visean) Limestones from Bristol and Parts of South Wales. American Association of Petroleum Geologist's Bulletin, AAPG, vol. 56 (1972), pp. 2392-2414. Authors W.C. MacQuon, Jr. and T.W. Bloxham.
The mid-Visean Clifton Down Limestone and parts of adjacent formations on the Gower Peninsula of southern Wales can be subdivided into informal lithologic units with dominant microfacies that reflect both minor cyclic deposition and the effect of terrigenous influx toward the type locality at Bristol, England. These units also contain distinctive biotic and geochemical constituents that support paleoenvironmental interpretations. Carbonate sediments were deposited on a shallow subsiding shelf under poorly oxygenated conditions, in a warm humid environment subject to variable physical energy, as indicated by the presence of abundant algae, relatively dark color, a relatively thick carbonate sequence without evaporites, and microfacies ranging from low-energy fine pelmicrites to high-energy coarse oointrasparudites. The seemingly complex sequence of lithologic units can be explained by postulating concurrent local regression, including seaward oolitic sand barrier migration and regional transgression, including slow basin subsidence. The oolitic barrier is thought to have been formed by waves and related longshore currents on a slope break above a structural hinge line between a shallow shelf and a slightly deeper geosynclinal basin in the present Bristol Channel area. Restriction of the shallow shelf between the barrier and St. George's Land, about 30 miles north, created a back-barrier, tidal-flat environment. Subtidal, intertidal, and questionable minor supratidal subenvironments are indicated by tidal-channel ooliths, angular intraclasts, and algal-mat fragments possibly derived from mudbanks, some of which may have been subaerially exposed. Distal prodeltaic facies, with varying terrestrial influx through time, are thought to have resulted from the lateral swinging or intermittent progradation in a known delta complex north and east of Bristol, beyond the area of the present study.
Mullan, G.J. and Moody, A.A.D. 2014. An account and survey of Great Oone's Hole, Cheddar Gorge, Somerset. Proceedings of the University of Bristol Speleological Society, vol. 26, pt. 2, pp. 117-130 (available in full online). The history and archaeology of Great Oone's Hole in Cheddar Gorge are described, and a new survey is presented. The results of a previously unpublished investigation carried out in 1976-7 are discussed. It is concluded that the deposits have been too badly disturbed previously to merit further investigation. [end of abstract].
Introduction: Great Oone' Hole is situated high on the southern side of Cheddar Gorge, between Gough's Cave and Cooper's Hole [at the coach park]. It is one of the few Mendip caves that can be described as having been 'always open' but despite this it seems to have had a relatively obscure history and to be rather less well-known that some of its neighbours. The account was inspired by two things; the resurvey of the cave as part of a project being carried out to build a comprehensive 3D model of all the caves in the Cheddar catchment and the discovery in the Society's Library of a log book detailing a trial excavation in the entrance area of the cave carried out in 1976-7 but never published. [continues with "Oones, Great and Otherwise"].
Murray, J.W. and Wright, C.A. 1971. The Carboniferous Limestone of Chipping Sodbury and Wick. Geological Journal, vol. 7, pp. 255-270. Abstract:
The rock types and successions encountered at two localities have been described and interpretated with reference to modern analogues. In the Clifton Down Limestone a cycle of sedimentation is recognised passing from intertidal algal mats, through lagoons, barrier and open shelf deposits and back through the same sequence to intertidal algal mats.
The Carboniferous Limestone forms an arcuate rim to the Bristol Coalfield syncline (Fig. 1). On the eastern limb of the fold the rocks dip 30-40 degrees W. They form a straight outcrop which passes beneath the Mesozoic unconformity to the south. Arnold's Quarry, Chipping Sodbury (Grid Ref. ST 725825), is situated close to this point. Five miles to the south lies the Wick Rocks inlier in which there is the extensive Wotton Bros. Quarry (Grid Ref. ST 710730). The two quarries expose rocks of similar age (Visean, Lower Carboniferous). Arnolds Quarry is of particular interest because of excellent bedding plane exposure in addition to the more-or-less continuous bed-by-bed exposure. The aims of this paper are first to record in detail the successions at the two localities, second to describe the lithology of the rocks using modern nomenclature, third to interpret the environment of accumulation, and fourth to compare this with other interpretations.
2. Previous Work.
The earliest description of the two areas were those of Buckland and Conybeare (1824 p. 215) and Morgan (1889). More detailed accounts of the Wick inlier were given by Reynolds (1912) and Smith (1930), the latter emphasising the abnormally large thickness of the succession. Vaughan (1905) stressed the great similarity between the palaeontological sequences at Sodbury and at 'Wick Rocks' (236). The detailed palaeontological sequence for Sodbury was based on the railway cutting and the "two large town-quarries" now incorporated in Arnold's Quarry. Detailed descriptions were later made by Reynolds (1923), Tuck (1925), and Coysh (1927). .........
[selected extract on stromatolites, from p. 257]
[Lower Carboniferous stromatolites of Chipping Sodbury]
(1) Stromatolites. Two main growth forms are present. a gently folded structue which superficially resembles ripple marks (= laterally linked hemisphaeroids in the terminology of Longan et al. 1964) and columnar structures (= verticaly stacked hemisphaeroids of Logan et al. 1964).
The gently folded stromatolites are commonly abround 9 cm thick and are rarely more than 30 cm thick. The cores of the 'folds' are sometimes filled with a white calcite mosaic. This presumably represents a cavity infilling. Typically these stromatolites are bound to the upper surfaces of the underlying sediment (usually micrite or oosparite). They are invariably overlain by a thin shale [why is this?].
Stromatolites of this kind closely resemble the 'crinkle' growth form described from the algal mats of the Trucial Coast of Arabia (Kendall and Skipwith 19169 a, b). These are intertidal algal mats which develop in the protection of barrier islands in the large lagoon, Khor al Bazam. Similar algal mats are known from other Trucial Coast lagoons and from around Qatar (Illing, Well and Taylor 1965). If this analogy is correct, the gently folded stromatolitesd of the Carboniferous can be interpreted as indicative of intertidal conditions on a protected shoreline. Further, it is known that the formation of a algal mat represents the final phase of infilling of the lagoons along the Trucial Coast (see Evans, Schmidt, Bush and Nelson 1969). The area the becomes supratidal. Only a thin veneer of sediment forms in this situation. It is contributed either as marine sediment washed in by storms or as wind blown dust.
The columnar growth form is confined to one bed at Chipping Sodbury. This bed is 73 cm thick and the columns are around 3 cm in diameter. They are closely spaced but do not touch.
Modern analogues of such stromatolites have been described by Logan (1961) from Shark Bay, Australia. The examples come from the lower part of the intertidal zone at the heads of the bay. However, they are much greater in diameter in relation to height than are the Carboniferous forms.
It is of interest that the earliest workers (e.g. Vaughan 1905) referred to the stromatolites as 'Concretionary Beds' and were uncertain of their origin. Garwood (1913) described them under the name Spongiostroma and recognised their algal origin although he believed incorrectly that they secreted their calcareous structure rather than as now believed trapped calcareous material. However, in 1906 Vaughan compared the Concretionary Beds with the Cotham Marble. He considered that the origin of the structure had not been satisfactorily explained. He wrote: "It seems probable that such beds could only be laid down under water undisturbed by waves and charged with abundant carbonate carbonate of lime, and it seems a fair deduction that the remarkable occurrence of these beds marks a datum level of absolute time, almost comparable in exactitude with that marked by a continuous lava sheet." The final acceptance of these structures as stromatolites of algal origin dates from the the excellent review of the subject by Anderson (1950).
[end of stromatolite section in this paper; it continues with "Oolitic rocks"]
[Note with regard to the Cheddar Gorge sequence, the Clifton Down Limestone Formation has stromatolites or microbial [algal] mats at least two horizons. The basal part of the Clifton Down Limestone Formation at Cheddar Gorge contains LLH stromatolites (i.e. microbial mats) at the Horseshoe Bend. They occur at a higher horizon at Cooper's Hole Cave. IMW]
Nagy , Z.R., Somerville, I.D., Gregg, J.M, Becker, S.D. and Shelton, K.L. 2005. Lower Carboniferous peritidal carbonates and associated evaporites adjacent to the Leinster Massif, southeast Irish Midlands. Geological Journal, vol. 40, Issue 2, pp. 173-192. By Zsolt R. Nagy, Ian D. Somerville, Jay M. Gregg, Stephen P. Becker, and Kevin L. Shelton.
Analysis of a 275 m-thick section in the Milford Borehole, GSI-91-25, from County Carlow, Ireland, has revealed an unusual sequence of shallow subtidal, peritidal and sabkha facies in rocks of mid?-late Chadian to late Holkerian (Viséan, Lower Carboniferous) age. Sedimentation occurred on an inner ramp setting, adjacent to the Leinster Massif. The lower part of the sequence (late Chadian age) above the basal subtidal bioclastic unit is dominated by oolite sand facies associations. These include a lower regressive dolomitized, oolitic peloidal mobile shoal, and an upper, probably transgressive, backshoal oolite sand. A 68 m-thick, well-developed peritidal sequence is present between the oolitic intervals. These rocks consist of alternating stromatolitic fenestral mudstone, dolomite and organic shale, with evaporite pseudomorphs and subaerial exposure horizons containing pedogenic features. In the succeeding Arundian–Holkerian strata, transgressive–regressive carbonate units are recognized. These comprise high-energy, backshoal subtidal cycles of argillaceous skeletal packstones, bioclastic grainstones with minor oolites and algal wackestones to grainstones and infrequent algal stromatolite horizons.
The study recognizes for the first time the peritidal and sabkha deposits in Chadian rocks adjacent to the Leinster Massif in the eastern Irish Midlands. These strata appear to be coeval with similar evaporite-bearing rocks in County Wexford that are developed on the southern margin of this landmass, and similar depositional facies exist further to the east in the South Wales Platform, south of St. George's Land, and in Belgium, south of the Brabant Massif.
The presence of evaporites in the peritidal facies suggests that dense brines may have formed adjacent to the Leinster Massif. These fluids may have been involved in regional dolomitization of Chadian and possibly underlying Courceyan strata. They may also have been a source of high salinity fluids associated with nearby base-metal sulphide deposits.
Pickering, A. [Andrew Pickering] and Foster, N. [Nicola Foster]. Cheddar through Time. Book. (also E-book available through Amazon for 4 pounds, 99 pence.) Paperback, by Andrew Pickering and Nicola Foster. 31st August 2011.
Pirlet, H. 1968. La sedimentation rhythmic et la stratigraphic du Visean superieur V3b, V3c inferieur dans les synclinorium de Namur and de Dinant. Mem. Acad. r. Belg. Cl. Sc. [Memoirs of the Royal Academy of Belgium] 4th, vol. 17, pp. 1-98.
Ponsford, D.R.A. 1970. Silurian volcanic rocks of the Mendip Hills, Somerset. Geological Magazine, vol. .
Available online: Ponsford, 1970, Silurian volcanic rocks.
The recent paper by Dr. P.C. van de Kamp on the above topic (Geol. Mag., 106, 1969, 542-553) is of considerable interest. The author claims that the main rock is rhyodacite whereas all previous publications and our own researches have suggested that the main lava flows are of andesitic composition. The main reason for the new opinion would seem to be aa high quartz content in the rocks based on chemical analyses and it is pertinent to enquire whether this could be due to secondary enrichment.
[.. continues ...]
A further interesting point in connection with the Silurian volcanic rocks of the Mendips concerns the origin of the rounded lava masses found in the tuff beds and referred to by Dr van de Kemp as "abundant bombs in ash matrix". Since their first discovery by Reynolds (1907) they have been called conglomerates but I agree that they should be termed agglomerates. However, like Reynolds, I could not accept that they are bombs and could offer no alternative until a a recent paper by Dr Doris Reynolds (1969) which has supplied, in my opinion, the true explanation, namely gas-fluidization whereby tuff fragments, moved by gas under pressure, becomes an erosive agent in the volcanic vent. The agglomerate was reported to occur in strength 0.8Km. (half a mile) east of Moons Hill and interpreted by Reynolds (1907) as marking the site of a vent. His ideas would now seem to be confirmed but many details remain to be resolved. [references follow]
Ramsbottom, W.H.C. 1973. Transgressions and regressions in the Dinantian: a new synthesis of Dinantian stratigraphy. Proceedings of the Yorkshire Geological Society, vol. 39, pp. 567-607.
In the area between the Southern Uplands of Scotland and the Mendip Hills the Dinantian succession below the D1 Zone is shown to comprise four major cycles each characterized by transgressive and regressive phases recognized by changes in lithology and fauna. The transgressive phases on the shelf areas are represented by bioclastic limestones, and the regressive phases by oolitic limestones and calcite mudstones, the latter often dolomitized and containing stromatolites and interpreted as the early stages of evaporite deposition. Regressions are indicated also by the frequent presence of pebble-beds, breccias and non-sequences in the marginal areas of deposition, indicating that there was an actual lowering of sea level rather than a mere filling-up of the areas of deposition. Dolomitization of limestones underlying the regressive phases is a common feature, and it is suggested that this is a consequence of the evaporation induced by regressions and that it offers an explanation of the distribution of many of the dolomitic limestones of the Carboniferous Limestone. The major cycles are traced and correlated throughout the area. Each major cycle can be shown to include a number of minor transgressions and regressions when it is traced into the Northumberland Trough where minor cyclicity occurs throughout. Above the base of the D1 Zone this minor cyclicity becomes evident over the whole area. It is concluded that the major influence on Dinantian sedimentation (apart from any due to local tectonic effects) was repeated eustatic change in sea level, and in support it is shown that similar changes in sea level have taken place in extra-British areas. It is suggested that various stratigraphical breaks and unconformities, hitherto regarded as of tectonic origin, can be more easily explained by regressions. The recognition of these cycles provides an improved means of chronostratigraphical division of the Dinantian. Each major transgression brings with it distinctive faunas and a new scheme for the division of the Dinantian is proposed, which necessitates at least partial abandonment of the Vaughanian Zones, and their replacement by divisions based on the major cycles.
Ramsbottom, W.H.C. 1979. Rates of transgression and regression in the Carboniferous of NW Europe. Journal of the Geological Society, vol. 136, no. 2, pp. 147-153.
The Carboniferous in NW Europe shows more than 30 large transgressions (with intervening regressions) up to the middle part of Westphalian C. Marginal areas of deposition show stratigraphical breaks between each transgressive cycle. Each large transgression was not continuous but appears to have been pulsed, with each small transgressive pulse reaching further than its predecessor. The rates of transgression are assessed at several different levels in the Carboniferous. Many of the features found in NW Europe appear to have been of general occurrence.
Ramsey, A.T.S. 1987. Depositional environments in Dinantian limestones of Gower. In: Adams, A.E., Miller, J. and Wright, V.P., editors, European Dinantian Environments. Special Publication of the Geological Journal, No. 12, pp. 265-308, Wiley, New York.
[Doris Reynolds lived from 1 July 1899 to 10 October 1985. She was a geologist who spent much of her career in Scotland. She was an Honorary
Research Fellow at the University of Edinburgh. She married Professor Arthus Holmes in 1939.]
Reynolds, Doris L. 1954. Fluidization as a geological process, and its bearing on the problem of intrusive granites, American Journal of Science, 252 (1954), pp. 577-613. By Dr. Doris Reynolds.
Reynolds, Doris L. 1969. Fluidization as a volcanological agent. Proceedings of the Geological Society, London, No. 1655, pp. 110-115.
Reynolds, S.H. - Professor Sydney Hugh Reynold, M.A., Sc.D., F.G.S., Professor of Geology in the University of Bristol, in about 1920.
, Sidney H.
1907. A Silurian inlier in the eastern Mendips. Quarterly Journal of the Geological Society, London, Vol. 63, pp. 217-240. By Professor Sidney Hugh Reynolds, M.A. F.G.S. Read March 13th 1907.
The Mendip Hills consist of four periclinal upfolds of Carboniferous Limestone, arranged en echelon from north-west to south-east. Each pericline includes a core of Old Red Sandstone [Devonian], and the igneous rocks. It is with these that the present paper deals. The existence of igneous rocks in the Eastern Mendips was first noted by Charles Moore [Quarterly Journal of the Geological Society, 1867, vol. 23.] who described them as:
"a basaltic dyke of considerable thickness emerging from the beneath the Old Red Sandstone at East End near Stoke Lane" [the rocks are actually of andesite not basalt]
He considered that, from the general physical character of the Mendips, it was not improbable that the dyke might be co-extensive with their range. He not only attributed the upheaval of whole Mendip range to the intrusion of this igneous mass, but also considered that it was responsible for the remarkable inverted character of the Carboniferous beds at Luckington, where the Coal-Measures are worked under the Carboniferous Limestone.
John Morris refers to the rock at Stoke Lane, as
"a dyke of considerable thickness, emerging from beneath the Old Red Sandstone, occurring as bosses in the field, but, traced for some distance over the district, it is conglomeratic in places, and pronounced by Mr. D. Forbes to be dolerite"
The igneous rocks are not shown in Sander's map of the Bristol Coalfield (published in 1864), but appear in the map of the Geological Survey (1884), as a series of isolated patches extending from Downhead on the east to Beacon Plantation, southwest of Stoke Lane, on the west, a distance of about 3 miles. [....continues].
Reynolds, S.H. 1921. The Lithological Succession of the Carboniferous Limestone (Avonian) of the Avon Section at Clifton. Quarterly Journal of the Geological Society, vol. 77, pp. 213-245. By Professor Sidney Hugh Reynolds, M.A., Sc.D., F.G.S. Professor of Geology in the University of Bristol. (Read January 5th, 1921).
[Note that this is a good early paper for field photographs and also for photomicrographs. See Plates VIII to XIV. Stromatolites were observed and understood to be "algal limestones".
Plate VIII. Mitcheldeania Limestone, "Stick Bed" and Seminula Pisolite. Field photographs.
Plate IX. Field photograph of , "Spongiostroma" Limestone, Bored China-Stone, Algal Limestone [LLH (domed) stromatolites], and "Rubbly Limestone" [limestone breccia].
[to be continued]
1. Introduction and Previous Work.
2. Description of the Rocks.
2a - The Cleistopora Beds.
2b - The Zaphrentis Beds.
2c - The Syringothyris Beds.
2d - The Seminula Beds.
2e - The Dibunophyllum Beds.
3. Changes which have affected certain of the rocks.
4. Modiola Phases of the Avonian Section.
5. Summary and Conclusions.
6. Vertical Section of the Right Bank of the Avon.
[end of Contents]
Example extract from: Introduction and Previous Work.
"Although a very large amount of information concerning the lithology of the Carboniferous Limestone is now available, that of no section has hitherto been described in detail, and it seemed that a full account of the rocks of the classical Avon Section [in Avon Gorge, Bristol] might prove of value. The first full account of the composition or structure of one of the rocks of that section was W.W. Stoddart's description of the 'Bryozoa-Bed ('Microzoal Bed') in 1861 and 1865. In one of his papers on the Geology of the Bristol Coalfield he further gave a considerable amount of information concerning the Avon rocks.
Sorby in his Presidential Address to the Geological Society in 1879, briefly alluded to some of the oolites from the Avon Section, but it was not until Mr. R.B. Wethered turned his attention to the subject that any detailed work was done. Mr Wethered's investigations referred, on the one hand, to the chemical and mineralogical features, and on the other to the faunal and microscopics characters. His paper on 'Insoluble Residues obtained from the Carboniferous Limestone Series at Clifton dealt with the former subject while that 'On the occurrence of the Genus Girvanella in Oolitic Rocks and Remarks on Oolitic Structure contains a full desciption and analysis of the several oolite bands occurring in the Avon Section. A fairly full account of the microscopic structure of many rock-types is also to be found in his paper on 'The Building of Clifton Rocks'. G.F. Harris also described and figured an oolite from the Avon Section, the example being from 'near Clifton Bridge' and probably from D2." [continues]
[with regard to the stromatolites in the Cheddar Gorge section, note that in Fig 1 of Plate 9 there is a field photograph of stromatolites. They are labelled as "Spongiostroma Limestone". -- on p. 226, re S1 - "while the surface of certain layers rises into rounded elevations (Plate IX, fig. 1), which sections show to consist largely of Spongiostroma.". Also shown on Plate IX, Fig. 3 is the surface of a bed of stromatolites. This has the caption: "Algal limestone, Concretionary Beds, S2(d), Observatory Hill, Clifton."
[The mussel-like bivalve, Modiola is of interest because it characterises lagoonal facies, probably sometimes hypersaline, in the Carboniferous Limestone of the south of England and Wales. This euryhaline bivalve which also occurs in parts of the Tournasian evaporitic sequence from the Tweed Borehole, from near Berwick-on-Tweed and under investigation by the British Geological Survey and several researchers. There is a possible modern analogue. The modern mussel-like bivalve Brachidontes pharaonis has a salinity tolerance from 35 to 53 psu [practical salinity units]. Brachidontes lives in the waters of Qatar and theoretically could approach the gypsum-precipitating sabkhas.]
Reynolds, S.H. 1927. The Mendips. Geography, vol. 14, pp. 187-192.
Reynolds, S.H. and Vaughan, A. 1911. Faunal and lithological succession in the Carboniferous Limestone Series (Avonian) of Burrington Coombe (Somerset). Quarterly Journal of the Geological Society, vol. 67, pp. 342-392,
[concretion beds in Burrington Coombe - similar to Rhaetic Cotham Marble. - i.e compare to stromatolites in the basal Clifton Down Limestone at Cheddar. ]
Richardson, L. 1928. Wells and Springs of Somerset. Memoir of the Geological Survey.
Riding, R. and Wright, V.P. 1981. Paleosols and tidal flat/ lagoon sequences on a carbonate shelf. Journal of Sedimentary Petrology, vol. 51, pp. 1323-1339. Abstract, shortened and modified [full version is available online]. Carbonate shelf sequences in the Lower Carboniferous of southwest Britain contain thin peritidal intercalations within open shelf facies.
Analysis of ....... the Caswell Bay Mudstone, at Miskin, South Wales, shows it to contain a lower paleosol and an upper tidal-flat/lagoon sequence. These are separated and bounded by erosion surfaces directly related to the origin of the units they underlie. The complete sequence, using letters for rock units and numbers for disconformities, is: a. oolite [inner shelf shoal], 1. irregular disconformity [subaerial/subsoil surface], b. oolite breccia-conglomerate in clay matrix [regolith with clay introduced as windblown or overbank material], c. mottled micrites [calcrete], 2. planar disconformity [back-barrie shoreface], d. peloid micrites, e. laminated micrites, f. paper shales and thin limestones [all shallow subtidal lagoon-low intertidal flat sediments], 3. planar disconformity [barrier shoreface], g. bioclastic limestone [inner shelf open marine sands and gravels]. Units b to f total 6 metres in thickness and constitute the Caswell Bay Mudstone. They comprise a couplet of terrestrial and back-barrier sediments preserved during a transgression, ....... Breaks 1-3 represent a subaerial surface plus two barrier-associated erosion surfaces. These three breaks are here termed a triple disconformity. The subaerial surface is the major break of the three and the back-barrier shorezone surface marks the base of the transgressive sequence. The uppermost break, the barrier shoreface, is a relatively minor intra-sequential erosion plane. ... Paleosol-tidal flat/lagoon couplets and triple disconformities should be widespread features of transgressive barrier-island carbonate shoreline sequences...
Scott, W.B. 1986. Nodular carbonates in the Lower Carboniferous, Cementstone Group of the Tweed Embayment, Berwickshire: evidence for a former sulphate evaporite facies. Scottish Journal of Geology, v. 22, 325-345,
Sheridan, D.J.R., Hubbard, W.F. and Oldroyd, R.W. 1967. Tournasian strata in Northern Ireland. Scientific Proceedings of the Royal Dublin Society, vol. 3, pp. 33-37.
Shen, J-W and Qing, H. 2010. Mississippian (Early Carboniferous) stromatolite mounds in a fore-reef slope setting, Laibin, Guangxi, South China. International Journal of Earth Sciences, March 2010, Volume 99, Issue 2, pp. 443-458. By Jian-Wei Shen and Hairuo Qing
The Mississippian (Early Carboniferous) is generally a period of scarce carbonate buildups in South China. This study documents outcrops of stromatolite mounds at Mengcun and Helv villages, in Laibin City, Guangxi Province, South China. The stromatolite mounds contain various stromatolite morphologies including laminar, wavy-laminar, domal or hemispheroidal, bulbous, and flabellate-growth columns. Intramound rocks are brachiopod floatstone and dark thin-bedded laminated micrite limestone. Individual stromatolites at Mengcun village are generally 3–6 cm thick and morphologically represent relatively shallow-water laminar (planar and wavy-undulated stromatolites) and deeper-water domal, bulbous and columnar forms. Where mounds were formed, the stromatolites continued growing upward up to 60 cm thick. Thrombolitic fabrics also occur but are not common. Stromatolite microscopic structure shows the bulk of the lamination to consist of wavy microbialite and discrete thin micritic laminae. These mounds are intercalated in deep-water fore-reef talus breccia, packstone formed as a bioclastic debris flow and thin-bedded limestone containing common chert layers of the Tatang Formation (late Visean). Further evidence supporting the deep-water setting of the stromatolite mounds are: (1) a laterally thinning horizon of brachiopod floatstone containing deep-water, small, thin-shelled brachiopods, peloidal micritic sediments and low-diversity, mixed fauna (e.g., thin-shelled brachiopods, tube-like worms and algae) that have been interpreted as storm deposits, (2) common fore-reef talus breccias, (3) lack of sedimentary structures indicating current action, (4) preservation of lamination with sponge spicules, and (5) lack of bioturbation suggesting that the stromatolites grew in a relatively low energy, deep-water setting. The stromatolite mounds are the first described stromatolite mounds in Mississippian strata of South China and contain evidence that supports interpretations of (1) growth history of Mississippian microbial buildups and (2) environmental controls on stromatolite growth and lithification.
Sibley, T.F. 1905. The Carboniferous Limestone of Burrington Coombe. Proceedings of the Bristol Naturalists Society, vol. 4, part 1, pp. 14-21.
Sibley, T.F. 1906. The Carboniferous Limestone (Avonian) of the Mendips Area. Quarterly Journal of the Geological Society, vol. 62, pp. 324-380.
Simms, M.J. 1990. Triassic palaeokarst in Britain. Cave Science, vol. 17, No. 3, December 1990. Transactions of the British Cave Research Association. Available online as a pdf file. See the section on the Mendip Hills, p. 95 et seq.
` Smith, N.J.P. and Darling, W.G. 2012. Potential problems in the Bath and North East Somerset Council and surrounding area with respect to hydrocarbon and other exploration and production. 32 pages including maps and diagrams. Available free online.
Renewables and Energy Security,British Geological Survey [BGS], Commissioned Report CR/12/055. NERC. Keyworth, Nottingham.
The remit of the study was to provide:
1. A short review of methods of shale gas and coalbed methane working, and the potential problems that have been attributed to hydraulic fracturing that could give rise to detrimental effects in the B & NES [Bath and Northeast Somerset} area. These should include changes to the groundwater regime that might affect local water supplies and/or the hot springs; methane leakage at surface into water supplies (potable and the hot springs); and induced seismic events. Comment should be made on the potential risks associated with horizontal drilling if any.
2. A summary of the geological succession and structure with particular respect to possible shale gas and coalbed methane targets in the area and the hydrogeology of the hot springs. Reference could be made here to geothermal projects which may also use hydraulic fracturing.
3. An assessment of the possible risks from hydraulic fracturing that B & NES, adjacent councils and other regulatory bodies would need to consider.
4. Conclusions and recommendations.
Having identified the possible risks, what reassurances would B & NES and/or neighbouring councils require from developers to ensure that any proposed works would not have a detrimental effect on persons, facilities or infrastructure in their areas of governance, with particular reference to the hot springs. [end of remit - text continues]
Somerset Historic Environment Record 10397.
Great Oone's Hole, Cheddar Gorge, Cheddar.
An open hole, 300ft above the road. On the left bank of Cheddar Gorge 80m above the present valley floor and 15m below the plateau. A 4m wide entrance leads into a roomy tunnel c.150m long. Outside the entrance is a 5m wide platform.
(Ransacked, with no record of finds. However, there are finds in Weston-super-Mare museum which may have come from this site, including Upper Palaeolithic flints. There are fake paintings in this cave. Davies claims Upper Palaeolithic finds; Campbell accepts two pieces as possible. Partial excavations c.1902 and 1970s revealed Later Upper Palaeolithic flint artefacts and faunal material.)
Somerset County Council 2004. David Roche GeoConsulting. 2004. Geodiversity Audit of Active Aggregate Quarries Quarries in Somerset; Project Overview Report. Report No: 2410/10PO December 2004. Somerset County Council. Geodiversity Report Overview.pdf. Online and downloadable as a pdf file. See:
Project Overview Report - Somerset County Council www.somerset.gov.uk/easysiteweb/gatewaylink.aspx?alid=42607
Geodiversity encompasses the wide variety of geological features which make up the Earth and the processes which have formed these features throughout geological time. Active quarries provide some of the best and most extensive geological exposures available and they offer a unique opportunity for three dimensional observation as the geology continues to be revealed by continuing operations. This detailed information can provide a valuable insight to the geology in areas where surface exposure may be poor and interpretation of the hidden geological structure from surface features alone can be difficult. The project described continues the pilot study started in Devon in 2003 with the collection and recording of available information on the geodiversity revealed in seven active aggregate quarries in the East Mendip area of Somerset. Geodiversity audit reports with photographic detail have been prepared as a record for each quarry and these are summarised here in the context of geological history. The oldest rocks in Somerset are seen in aggregate quarries in the core of the Mendip ridge. They are volcanic andesite lavas with volcanic ashes and agglomerates and associated marine sediments containing fossils of the Silurian Period of geological time about 430 million years old. They were formed during a period of explosive volcanic activity in a shallow tropical sea. Little would be known about the early history of Mendip at this time if the rocks had not been exposed in the quarries. Unconformable on the volcanic rocks, the Old Red Sandstone conglomerates, sandstones and shales were deposited in seasonal floods in a largely desert or semi-arid environment. These late-Devonian rocks grade upwards without any break into Lower Carboniferous marine shales and limestones Some of the best continuous sections through the Carboniferous Limestone are seen in the large limestone aggregate quarries, some of which are amongst the biggest quarries in Europe. The full limestone succession is in the order of 1000m thick with many shell and coral fossils indicative of formation in shallow, clear water, tropical seas. These older rocks were sharply folded and faulted by pressure of a continental collision from the south in the Variscan Orogeny at the end of the Carboniferous and early Permian about 300 million years ago. The mountain terrain formed in the Variscan was then subject to intense erosion in the desert conditions of the Permian and Triassic in which the scree deposits of the 'Dolomitic Conglomerate' were formed around the edges of Mendip. Traces of late Triassic and Jurassic sediments are also preserved around the edges of Mendip resting unconformably on the older rocks, and in fissures in the Carboniferous Limestone which can be seen in several of the active quarries. Vertebrate bones have occasionally been found in the fissures, including very rare bones of ancestral mammals about 250 million years old. The main conclusion is that the geodiversity seen in active aggregate quarries constitutes a valuable educational and research resource of geological detail which can be integrated with the regional and global geological history. Using the experience of this project as a stimulus, the wider education and training opportunities of many disciplines related to the minerals industry need to be developed in partnership with others to raise the career profile in this essential and varied industrial sector.
Dr. William Iredale Stanton, mining geologist in Angola, hydrogeologist, speleologist and specialist on the caves of Mendip. He published various books and papers on the subject of Mendip caves and on other matters. See also Barrington. (Barrington, N. and Stanton, W. 1977. Mendip: The Complete Caves and a View of the Hills. Cheddar Valley Press. Paperback.). The late Dr Stanton was awarded his doctorate in geology and spent his career working in hydrogeology throughout the world including many parts of Africa and Portugal. He returned to Westbury-sub-Mendip upon his retirement where he was instrumental in local projects involving caving and wildlife and won an MBE in 1993. He and his wife died in 2009-2010 in sad circumstances (press reports online).
Stanton, W.I. (date?) Cheddar Caves. Book, published by Photo Precision Ltd. Paperback. [Is this a separate book or is it another reference to: Barrington, N. and Stanton, W. 1977. Mendip: The Complete Caves and a View of the Hills. Cheddar Valley Press. 236pp ?]
Stanton, W.I. 1966. The Impact of Limestone Quarrying on the Mendip Hills. University of Bristol Speleological Society Proceedings, 1966, pp. 54-62 (or 63?), with one plate, a map of the Mendips. Available in full online.
Introduction: The Mendip Hills in North Somerset are partly composed of Carboniferous Limestone, which is extensively quarried for various purposes. The rapid growth of the quarries is abhorrent to, and has caused conflict with, many sections of the community. This paper seeks to examine the problem from the viewpoints of the geologist, the lover of fine hill country, and the cave explorer, who has a special interest in limestone. A constructive approach, reconciling the various interests, is suggested..- In the accompanying map the geological data are drawn from Geological Survey publications, and data on quarry concessions and ownership from the maps of the Somerset County Council. The author visited all the quarries and mapped their extent in 1964 and 1965. Major caves and springs are defined as those with more than about 400 ft. of passage, and a mean flow of more than about 500,000 gallons daily, respectively. [continues with: Brief History of the Mendips and Their Possible Future:]
Stanton, W.I. 1977. Mendip Water. In Barrington, N. and Stanton, W.I. (Eds.) Mendip: The Complete Caves and a View of the Hills. Cheddar Valley Press, Cheddar, pp. 201-213.
Stanton, W.I. 1985. Cheddar Gorge and Gough's Cave. Proceedings of the University of Bristol Spelaeological Society, vol. 17, part 2, pp. 121-128. By Dr. W.I Stanton.
This paper is available online as a pdf file. Find by Google or other search engine - "Cheddar Gorge and Gough's Cave - UBSS" or search for "Stanton Mendip Cheddar Gorge" or for "Stanton Mendip UBSS".
[an aerial photograph by Aerofilms is shown at the start]
[Introductory text follows as an example. See particularly the figures which contain plans and section through the cave systems.]
"Cheddar Gorge is the classic example of a waterless limestone gorge with a tributary sysem of waterless limestone valleys. It is also one of Britain's greatest natural scenic attractions. Opening into it are several caves at different levels, whose origins are linked to the development of the gorge. The largest known cave is Gough's Cave, visited by half a million tourists each year. The Origin of Cheddar Gorge. Early speculation on the origin of Cheddar Gorge ranged from earthquake riftine to marine erosion. These ideas were replaced in the later nineteenth century by the cavern collapse hypothesis (Winwood and Woodward, 1891) which held that the "Cheddar Pass" had been created by roof collapse in a series of great caves. Balch (1947, pp. 65-7) summarized the arguments for collapse, citing the approach ravine to Wookey Hole Cave as an example of the process in action. Present day views on dry valley formation were heralded by Reynodls (1927) who argued that the smaller dry limestone gorge of Burrington Coombe, 4 km north of Cheddar, was eroded by a surface stream. This was possible because the ground was permanently frozen in the colder phases of the Pleistocene. Water from rain or snowmelt could not infiltrate underground as it does now, but ran off the Mendip plateau via the existing river system, eroding gorges where the flow was strong and the gradient steep. Coleman and Balchin (1960) introduced a different concept, regarding 'Cheddar Gorge as a simple youthful valley which has recently performed the typical youthful action of abandoning its surface course for an underground one'. Ford and Stanton (1969) combined earlier theories by arguing that Mendip dry valleys and gorges were excavated in two main stages. First when sea level was higher and the Mendips were hardly distinguishable as a range of hills the high water table in the limestone allowed permanent surface drainage in the principal valleys, as happens today in the far east of Mendip in, for example, the Nunney Brook. Later when sea level fell during the Early Pleistocene and the Mendips were rapidly exhumed from their enveloping soft post-Carboniferous strata, the water table dropped faster thatn the streams could wear down their beds. Swallets and caves formed, and the surface flow in the valleys became intermittent, finally ceasing except in great floods. In periglacial phases of the Pleistocene the ground froze, the swallets and percolation channels were blocked with ice and frozen mud, and summer meltwater torents reactivated the valley systems. The steepest gradients were at the valley mouth, which had been left 'hanging' by the exhumation process, and there the gorges developed. Cheddar Gorge, with its catchment area of 40 square kilometres (most of the Mendip Plateau), is by far the biggest. The smaller gorges, Ebbor and Burrington, have catchment areas of only about 3 square kilometres each.
[continues: with "Morphology of Cheddar Gorge" etc.]
Stanton, W.I. 1988. The Ancient Springs, Streams and Underground Watercourses of the City of Wells. Wiltshire Natural History and Archaeological Society. Annual Reports for 1987 and 1988, pp. 25-46. By the late Dr. W.I. Stanton. [Further information. This article has been extracted from pages 25-48 of the ninety-ninth and one hundredth Annual Reports for 1987 and 1988 to commemorate the centenary of the Wiltshire Natural History and Archaeological Society. Wells Museum, 8 Cathedral Green, Wells, Somerset, BA5 2UE. It includes a map showing 11 swallet holes connecting to St. Andrew's Well, Wells. The publication has not been seen by the present writer but it may be a booklet obtainable from the museum.]
Stanton, W.I. 1991. Hydrogeology of the Hot Springs of Bath. In Kellaway, G.A. (ed.). Hot Springs of Bath. Bath City Council, Bath, pp. 127-142.
Stehli, F.G. 1956. Shell Mineralogy in Palaeozoic Invertebrates. Science, vol. 123. pp. 1031-1032. Stehli reported a thin inner aragonite layer and thin outer calcite layer in an unidentified species of a Pennsylvanian (i.e. Upper Carboniferous) Bellerophon. Stehli found an inner aragonite layer and an outer calcite layer in Amphischapha.
This work of Stehli has been confirmed by a subsequent author. See then p. 78 of US Geological Survey, Professional Paper, 575D - Research 1967, Chapter D. Ellis L. Yochelson, John S. White and Mackenzie Gordon Jr. Aragonite and Calcite in Molluscs from the Pennsylvanian Kendrick Shale (of Jilson) in Kentucky. It is of interest to note that the Carboniferous ammonoid (goniatite) Gastrioceras, like the Jurassic ammonites, originally had a shell of aragonite. Of course diagenesis can result in the conversion of aragonite to calcite, so this may be found as the shell material in many cases at present.
Stephenson, M.H., Williams, M., Leng, M., Monaghan, A.A. 2004.
Aquatic plant microfossils of probable non-vascular origin from the Ballagan Formation (Lower Carboniferous), Midland Valley, Scotland.
Proceedings of the Yorkshire Geological Society, v. 55, pp. 145-158. 1st January 2004.
Seven previously undescribed palynomorphs, Brazilea sp. B, ?Carbaneuletes sp. A, ?Reduviasporonites sp. and Algal palynomorph spp. 1 to 4, some of which are closely similar to the spores and filaments of extant fresh or brackish water algae, are described and illustrated from the Lower Carboniferous Ballagan Formation of central Scotland. The palynomorphs occur in a succession yielding delta(18)O and delta(13)C values from carbonate that indicate a brackish water depositional origin. They occur in several sections with a low diversity ostracod fauna dominated by Beyrichiopsis, Cavellina, Knoxiella, Shemonaella and Sulcella species, but lacking typical fully marine forms such as Bairdia and Amphissites. In addition, the sequences contain Botryococcus and Circulisporites, which are fresh to brackish water indicators, but lack spinose acritarchs that indicate marine conditions. The palynomorphs, which lack trilete marks or other haptotypic features, are thus likely to be of aquatic algal origin, and were probably produced to allow algae growing in ephemeral ponds to survive periods of desiccation and to colonize successive waterbodies in an and coastal plain palaeoenvironment. The palynomorphs may be of value in further palaeoenvironmental studies as indicators of fresh to brackish conditions.
Stow , D.A.V. 2005. Sedimentary Rocks in the Field: A Colour Guide. By Dorrik A.V. Stow. Manson Publishing, 320pp. [This is an excellent book with numerous clear colour photographs, and is superb for recognition of sedimentary rock types and sedimentary structures.]
Van De Kemp, P.C. The Silurian rocks of the Mendip Hills, Somerset; and the Tortworth area, Gloucestershire, England. Geological Magazine, Vol. 106, No. 6, 1969, pp. 542-553, plates 28-29.
Van de Kemp, 1969. Silurian rocks of the Mendip Hills.
Field, petrograph and chemical studies on the Silurian volcanic rocks of the Mendip Hills show that there are probably 15 or more rock units in the series including andesite and rhyodacite lavas, rhyodacite tuffs, agglomerates, and a dolerite dyke. The predominant rock type is rhyodacite which may be as much as 80 percent of the volcanics. Volcanics of Silurian age from the Tortworth area, Gloucestershire, are of latite-andesite composition.
The Mendip rocks have been deuterically altered. Calcite-quartz-laumonite veins are common in fractures in these rocks. The agglomerates are particularly susceptible to weathering and some bombs are extensively altered to clays. Twelve rocks were chemically analysed for 36 elements each. no anomalous base metal concentrations were found in the volcanics although Pb, Zn, and Cu mineralisation is known in the are. K/Rb varies from 202 to 909 in these calc-alkaline rocks.
Vaughan, A. 1905. The palaeontological sequence in the Carboniferous Limestone of the Bristol Area. Quarterly Journal of the Geological Society, vol. 61, pp. 181-305.
Vaughan, A. 1906. The Carboniferous Limestone Series (Avonian) of the Avon Gorge. Proceedings of the Bristol Naturalists' Society, 4th Series, vol. 1, pp. 74-168.
Von der Borch, C.C. 1976. Stratigraphy and formation of the Holocene dolomitic carbonate deposits of the Coorong area, South Australia. Journal of Sedimentary Petrology, vol. 46, no. 4. By Christopher C. Von der Borch.
Von der Borch, C.C., Bolton, B. and Warren, J.K. 1977. Environmental setting and microstructure of subfossil lithified stromatolites associated with evaporites, Marion Lake, South Australia. Sedimentology, vol. 24, pp. 693-708.
A variety of finely lamined, subfossil, aragonitic stromatolites and oncolites occur on a regressive marginal flat surrounding Marion Lake, South Australia. These algal forms overlie a substrate of coarse, highly porous, moldic aragonitic limestone which passes progressively towards the lake centre through a zone of interstratified aragonite and gypsum and ultimately to pure crystalline gypsum. All of these facies overlie at least one upper Pleistocene marine unit. Detailed petrographic and stratigraphic studies, combined with comparative studies of related nearby lakes containing a variety of living cryptalgalaminites, provide a model for development of the Holocene sedimentary sequence. Marion Lake last became inundated by the sea around 6500 years ago during the Holocene transgression, when a protected marine environment was initiated. Lateral sediment accretion sealed marine passes into the resulting lagoon system soon after sea level stabilised, and a variety of gypsum and gypsum-carbonate-algal facies evolved. Pure gypsum was deposited in waters 2-3 m. deep in the central basin area concurrently with the formation of alternating gypsum and aragonite layers towards basin margins. Blue-green filamentous algae thrived in the shallower marginal areas and at least partly controlled carbonate deposition, which must have occurred during seasonal outflow of carbonate-rich ground water from the calcareous dune aquifer over denser gypsum-saturated water. These systems eventually migrated towards the centre of the lake to produce the relationships preserved today. The fresher waters also leached the gypsum from the marginal gypsum-carbonate facies. Collapse due to gypsum dissolution, along with aragonite crystallisation, combined to form a lake-marginal mega-polygon facies. Teepee structures formed around polygon margins, with optimum conditions for stromatolite development occurring on the teepee crests. The actual stromatolites which occur around Marion Lake are strongly indurated and involve a variety of morphologies, the most common of which are laterally linked hemispheroids. Stacked hemispheroids and oncolites are also relatively common, along with irregular forms, many of which encrust a variety of substrate irregularities. Vertical relief of the stromatolites varies from centimetres to tens of centimetres and all forms are characterised by extremely fine interlaminations of alternate light and dark grey laminae which typically occur several per millimetre. The microstructure comprises micritic aragonite crystals with fibrous habit associated with organic matter, and occasional zones of abundant algal filament molds which are generally normal to the laminae.
Von der Borch, C.C., Lock, D.E. and Schwebel, D. 1975. Ground-water formation of dolomite in the Coorong region of South Australia. Geology, pp. 283-285.
The 90 by 200 km coastal plain os southeastern Australia provides a setting through which throughout Quaternary time was ideally suited for the sedimentation of dolomite and other carbonate minerals. Comparative studies between various present day sedimentary environments and cores taken from regions of active dolomite formation near the Coorong Lagoon have defined a typical Holocene regressive sedimentary cycle for the area. A basal restricted marine and lagoonal aragonite and Mg-calcite unit, approximately, 6,500 yr old, passes upwards into ephemeral lake units with carbonate minerals ranging from protodolomite plus Mg-calcite to ordered dolomite. Hydrologic data show that the present coastal zone is the main area where seaward-flowing shallow ground waters emerge from unconfined carbonate aquifers beneath the coastal plain. This fact, and the observation that modern dolomite ideally forms from ions provided by ground waters, whereas aragonite, Mg-calcite, and protodolomite assemblages form from a marine or mixed sea-water-ground-water reservoir. The observed Holocene cycle is therefore explained by progressive seaward movement of a sea-water-ground-water interface, due to a slight relative fall of sea level about 6,500 yr ago combined with lateral sediment accretion. That the bulk of the dolomite formation is presently occurring near the coast is explained by the fact that this is the site, near base level, of most ground water discharge and evaporation. Possible sources of Mg ions for the extensive formation of of dolomite throughout Quaternary time are Mg depletion of high Mg-calcite allochems in the carbonate aquifers and leaching of ash deposits around Quaternary volcanic centers near ground-water source areas.
Von der Borch, C.C. 1976. Stratigraphy of stromatolite occurrences in carbonate lakes of the Coorong lagoon area, South Australia. By Christopher C. von der Borch. In: Walter, M.R. 1976. Developments in Sedimentology, 20, Stromatolites. Elsevier Scientific Publishing Company, Amsterdam. Part 8, Recent Models for Interpreting Stromatolite Environments. [no abstract].
Geologically recent stromatolites have been described from several areas of modern carbonate sedimentation, the most notable of which is Shark Bay in Western Australia (Logan, 1961; Davies, 1970b). Other important areas include the Persian Gulf (Kendall and Skipwith, 1968; Kinsman et al., 1971), the Bahamas (Monty, 1967, 1972), Bermuda (Gebelein, 1969) and the Great Salt Lake, Utah (Carozzi, 1962). In addition to the above, a somewhat restricted but nevertheless interesting occurrences of stromatolites has been described from two ephemeral carbonate lakes associated with the Coorong Lagoon in South Australia (Walter et al. 1973). These stromatolites occur in carbonate muds composed of the minerals hydromagnesite, aragonite, dolomite and calcite (Alderman and Von der Borch, 1960, 1961: Skinner, 1963; Peterson and Von der Borch, 1965; Von der Borch, 1965). Small amounts of amorphous silica are associated with these carbonates. This assemblage has its analogues in the geological record, particularly in the Precambrian (e.g. the Skillogalee Dolomite Formation of South Australia, Preiss, 1973a) where silicified dolomite stromatolite-bearing rocks are relatively common. Because of this, an aid in recognising equivalent depositional environments in the ancient rock record, the sedimentological history and stratigraphy of the Coorong stromatolite association will be described in some detail. [ continues with - Geological Setting].
Von de Borch, C.C. and Lock, D. 1979. Geological significance of Coorong dolomites.
Sedimentology, 1979, vol. 26, pp. 813-824. Authors at School of Earth Science, Flinders Univesity of South Australia.
Microcrystalline dolomite and related carbonate minerals have been forming throughout the Quaternary in shallow ephemeral lakes on the coastal plain of the Coorong area in southern Australia. These Coorong dolomites differ significantly from sabkha-type dolomites. They form in areas where evaporation rates during summer months exceed groundwater inflow rates to a series of alkaline lakes. This results in the lakes becoming desiccated during summer months. Brines resulting from this drying phase are then refluxed out of the system into seaward-flowing groundwaters of an unconfined coastal aquifer. Dolomites and other fine-grained carbonates remain behind, whilst saline and sulphate evaporite minerals are flushed out of the system. Progressive restriction by sedimentation in and around the Holocene coastal dolomite lakes results in an upward-shallowing sedimentary cycle. Basal sediments which formed in a restricted marine environment pass upward to lacustrine dolomites or magnesites exhibiting desiccation and groundwater resurgence features such as mudcracks and tepees. The Upper Proterozoic Skillogalle Dolomite Formation, an early rift basin unit of the Adelaide Supergroup, contains dolomites which show many of the features characteristic of the peculiar groundwater hydrology which plays an important role in Coorong dolomite genesis. These features include aphanitic dolomites which lack relict saline or sulphate evaporite minerals. The Skillogallee Dolomite Formation in some areas overlies an earlier dolomitic unit, informally named the Callana Beds, typified by abundant pseudomorphs after sulphate minerals. Sabkha style dolomites characterising the Callanna Beds are replaced up-section by the Coorong-type dolomites of the Skillogallee Dolomite Formation. this implies the development of increasingly more active groundwater regime. The ultimate source and mode of concentration of the necessary Mg required to form both the modern and ancient dolomites remain imperfectly understood.
Von de Borch, C.C. and Schwebel, D. 1975. Ground-water formation of dolomite in the Coorong region of South Australia. Geology (Boulder), vol. 3, no. 5, pp. 283-285.
Wainwright (a company supplying aggregrate). 2008. Geology: Moons Hill and Stoke Quarries. Go to website: Wainwright: Geology: Moons Hill and Stoke Quarries.
Example extract follows, but see the full website with photographs.
The rocks extracted from Moons Hill and Stoke Quarries are volcanic in origin and were formed 425 million years ago during the Silurian period of geological time. They form part of a renowned feature of British geological history and have been the subject of much debate and research over the years. The volcanoes which produced the lavas, ashes and other rock types extended over a wide area of what is now south west England. Rocks of the same type and age can be found in Devon and Gloucestershire.
Volcanic lavas, described as Andesites, were extruded over a wide area forming beds up to 100 to 150 metres deep. During this period of volcanic activity, accumulations of volcanic ash also built up, sometimes overlying the lavas, sometimes interbedded with them. The fine-grained ashes are known as Tuffs and often contain blocks or cobbles of Andesite lavas; these formations are known as Agglomerates. Because of the presence of shale and mudstone below the volcanic rocks and sometimes interbedded with them, we know that this volcanic activity was taking place in a marine environment. The whole sequence of lavas, ashes and agglomerates can be readily identified and measured in the Quarry because the beds are now standing vertically on end like books on a bookshelf.
After being deposited in a semi-molten state in horizontal layers, the volcanic rocks cooled and solidified and were eventually buried by thousands of metres of sedimentary rocks including terrestrial sandstones and limestones formed in oceans and lagoons. Many millions of years later these rock beds were subjected to an intense period of structural uplift resulting in the formation of the Mendip anticlinal folds, in the core of which the most ancient formations can be found. The idealised cross section through Moon's Hill quarry shows how the volcanic rocks now lie in relation to the other formations.
At Moons Hill and Stoke Quarries we concentrate on producing aggregate from the Andesite beds, these being generally stronger and more durable than the Tuffs. The latter are however quite suitable for most specifications. The Andesite aggregates are regarded as roadstone of the highest quality.
Walter, M.R., Golubic, S. and Preiss, W.V. 1973. Recent stromatolites from hydromagnesite and aragonite depositing lakes near the Coorong Lagoon, South Australia. Journal of Sedimentary Petrology, vol. 43, pp. 1021-1030.
Wall , G.R.T. and Jenkyns, H.C. 2004. The age, origin and tectonic significance of Mesozoic sediment-filled fissures in the Mendip Hills (SW England): implications for extension models and Jurassic sea-level curve. Geological Magazine, July 2004, vol. 141, no. 4, pp. 471-504. By Gavin R. T. Wall (Oxford University) and Hugh C. Jenkyns (Esso Australia Ltd.)[copy of paper in IMW collection]
In the eastern Mendip Hills, on the northern margin of the Wessex Basin, SW England, the Carboniferous Limestone is cut by numerous fissures that are filled with Mesozoic sediments (sedimentary dykes, neptunian dykes). The fissures contain a record of Triassic-Lower Jurassic sediments that are only sparingly preserved in their normal stratigraphical position between the Carboniferous Limestone and the unconformably overlying Upper Inferior Oolite of Bajocian age. Detailed analysis of cross-cutting relationships, facies analysis, biostratigraphy, lithostratigraphy and strontium-isotope ages of relevant Mesozoic sediments has allowed the construction of an Upper Triassic-Lower Jurassic fissure-fill stratigraphy for the eastern Mendip area. Most fissures were clearly formed by rapid influx of unlithified sediment from the land surface or sea floor. Some smaller cavities, or larger cavities with restricted access to the unconformity, were apparently filled by sediment that trickled down into the fissure system. The vast majority of the Mendip fissures are interpreted as having formed as a response of the Carboniferous Limestone, north of major basin-bounding faults, to pulses of tectonic extension during Ladinian-Norian/Rhaetian, late Hettangian-early Sinemurian, late Sinemurian-early Pliensbachian, mid-Pliensbachian, late Pliensbachian and Bajocian times. Triassic-earliest Jurassic fissures have a broad spread of strike from E-W to NW-SE to N-S, accommodating extension in a roughly NE-SW direction. Younger Jurassic fissures show well-defined E-W and N-S trends with the former becoming dominant through time. Total extension of about 4.7 percent N-S and about 0.6 percent E-W was produced by the formation of Triassic-Jurassic fissures within the Carboniferous Limestone. Such patterns of extension are thought likely to be characteristic of the subsurface geology in much of southern England and Wales. Major implications of this study are that: (1) the presence of seismically unresolvable sediment-filled fissures in supposedly rigid fault blocks can lead to a significant underestimate of regional extension based on the restoration of motion on normal faults on seismic-reflection profiles, and (2) the isolation of pulses of tectonic activity with a temporal resolution of 105-106 years may provide a means of identifying a tectonic signal in relative sea-level curves derived from the Jurassic sedimentary record.
Keywords: extension, fissures, neptunian dykes, Mendip, Mendips, Triassic, Jurassic, Mesozoic, sea-level changes, Carboniferous, Holwell, Frome, Beacon Hill, pericline, Dolomitic Conglomerate.
Welch , F.B.A. 1929. The geological structure of the central Mendips. Quarterly Journal of the Geological Society, London, vol. 85, issue 1-4, pp. 45-76. Extract: "The area here termed the Central Mendips comprises that part of the Mendip Hills which lies between Cheddar and Shepton Mallet. This paper deals only with the Palaeozoic rocks, which occupy the greater part of the area, and appear in inliers among the Mesozoic rocks on the south."
Available online as a pdf from the Lyell Collection of the Geological Society, London.
Welch, F.B.A. 1933 (for 1932). Geological structure of the eastern Mendips. Quarterly Journal of the Geological Society, London, vol. 89 for 1932, pp. 14 - 52. Accessible as a pdf file from the Geological Society Lyell Collection. By Francis Brian Awburn Welch.
No abstract. Example extract from Introduction:
Geologically, the area consists of the Beacon Hill pericline, which is the most southerly situated of the four echeloned periclines constituting the Mendip Hills. This pericline forms an approximately east-and-west ridge which attains at its western end a maximum altitude of 974 feet O.D. Its ridgelike character, especially prominent in its western part, is due to the resistant nature of the rocks of which it is composed: namely, Carboniferous Limestone, 'Millstone Grit,' and a central core of Old Red Sandstone and Silurian rocks. Succeeding these hard beds on the north are the soft Coal Measure shales (Lower Coal Measures), whilst the low ground on the south is occupied by Mesozoic strata banked against the Palaeozoic massif.
West , I.M., Brandon, A. and Smith, M. 1968. A tidal flat evaporitic facies in the Visean of Ireland. Journal of Sedimentary Petrology, vol. 38, No. 4, pp. 1079-1093, Figs 1- 14, December 1968. By Ian M. West, Alan Brandon and Melvyn Smith, Department of Geology, The University of Southampton, England.
A slightly revised version of this paper is available as a webpage of this website. Please go to:
West, Brandon and Smith. A tidal flat evaporitic facies in the Visean of Ireland. (revised version online, 2010).
(To see a rather poor copy of the original, unrevised paper go to:
Appendix - Carboniferous Evaporites - Ireland - West, Brandon and Smith.)
A sequence of thinly bedded limestones, dolomites, shales and sandstones contains evaporitic beds in County Leitrim and Cavan, Republic of Ireland. This sequence constitutes the Aghagrania Formation (new name) of B2 to PIc age, (Upper Visean), with a type section east of Drumshanbo, County Leitrim. The evaporitic beds which have not previously been recorded from this horizon or locality, are mostly unfossiliferous laminated limestones and dolomites with macrocells [nodules of the usual calcium sulphate type, i.e. chickenwire] and with pseudomorphs after gypsum, anhydrite, and halite. This facies of the Aghagrania Formation also includes evaporitic breccias, and celestite and carbonate replacements of calcium sulphate. Blocks of gypsum in boulder clay, on the shore of Lough Allen, are probably derived from these beds. The evaporitic strata alternate with shales and limestones containing marine faunas, and with unfossiliferous sandstones. All the facies show evidence of shallow water deposition and were probably formed in an area of low relief subjected to transgressions and regressions of a shallow sea. The evaporitic beds may be compared to the dolomite and gypsum deposits of present day tidal flats and associated shallow lagoons. They also resemble certain other occurrences of ancient laminated dolomite and limestone beds which been recently described and attributed to a tidal flat origin.
Whittaker, A. and Green G.W. 1983. Geology of the Country around Weston-super-Mare. Memoirs of the Geological Survey of Great Britain, H.M.S.O. London. Memoir for 1:50,000 geological sheet 279, New Series, with parts of sheets 263 and 295. Contributors: Geophysics: J.D. Cornell, Offshore Geology: B.N. Fletcher, Palaeolology, D.T. Donovan, H.C. Ivimey-Cook, M. Mitchell, M.J. Reynolds, and G. Warrington. Institute of Geological Sciences, Natural Environment Research Council, London, Her Majesty's Stationery Office, 1983. 147pp. See Chapter 3, Carboniferous pp. 5-36, See particularly Fig. 4 on p. 25, Generalised horizontal section of the Carboniferous Limestone between the upper part of the Black Rock Limestone (Ivorian Stage) and the base of the Hotwells Limestone (Asbian Stage) showing the major lithological variations and their suggested relationships for the area between the western Mendip Hills, Weston-super-Mare and the Avon Gorge (Avon Gorge section, partly after A. Kirkham, 1976.)
Williams, G.D. and Chapman, T.J. 1986. The Bristol-Mendip foreland thrust belt. Journal of the Geological Society, London, vol. 143, pp. 63-73. 9 figs.
Abstract: The thrusts and associated fold structures of the Bristol-Mendip area are interpreted in terms of a thin skinned, piggy-back foreland thrust belt of Variscan age with dominant northward transport. Strike-normal balanced sections and compatible strike-parallel sections have been constructed to illustrate the 3-D geometry of the linked thrust system. North-south shortening of c. 20 km (40%) is calculated from deformed and restored strike-normal sections. A thick and extensive thrust wedge of pre-Old Red Sandstone basement in the west of the area is responsible for culminations expressed at the surface as the Mendip periclines. Uplifted culminations permit erosion to lower stratigraphic levels in the west and south of the area. Strike-parallel sections and a hanging wall cut-off map indicate that the majority of thrusts in the area are mainly oblique ramps rather than simple frontal and lateral ramps, or flats. The en-echelon pattern of the Mendip periclines may be related to the oblique NE climb of two of these thrusts. The angle of frontal ramp climb through the Dinantian stratigraphy is generally low, and this explains the presence of numerous klippen of Lower on Upper Carboniferous rocks, whilst suggesting that certain thrust sheets were much more extensive than present outcrops indicate. Early, pre-thrusting movement on basement lineaments in the Variscan foreland created uplifts, angular unconformities and a predominance of N-S structures in the north of the area.
Williams, M, Stephenson, M., Wilkinson, I.P., Lend, M.J. and Miller, C.G. 2005. Tournaisian - Early Visean ostracods from the Ballagan Formation, central Scotland, UK. By Mark Willims, Michael Stephenson, Ian P. Wilkinson, Melanie J. Leng and C. Giles, Miller. Journal of Micropalaeontology, vol. 24 (1): 77 - 94, May 2005.
Abstract: The Ballagan Formation (Late Tournaisian - Early Visean) of central Scotland yields an ostracod fauna of 14 species in ten genera, namely Beyrichiopsis, Cavellina, Glyptolichvinella, Glyptopleura, Knoxiella, Paraparchites, Sansabella, Shemonaella, Silenites and Sulcella. The ostracods, in combination with palynomorphs, are important biostratigraphical indices for correlating the rock sequences, where other means of correlation, especially goniatites, conodonts, foraminifera, brachiopods or corals are absent. Stratigraphical distribution of the ostracods, calibrated with well-established palynomorph biozones, identifies three informally defined intervals: a sub-CM palynomorph Biozone interval with poor ostracod assemblages including Shemonaella scotoburdigalensis; a succeeding interval within the CM palynomorph Biozone where Cavellina coela, Cavellina incurvescens, Sansabella amplectans and the new species Knoxiella monarchella and Paraparchites discus first appear; and, an upper interval, in the upper CM Biozone, marked by the appearance of Sulcella affiliata. At least locally in central Scotland, S. affiliata permits a level of resolution equivalent to a sub-zonal upper division of the CM Biozone. The fauna, flora, sedimentology and stable isotope composition (13 C and 18 O) of carbonate minerals in the Ballagan Formation suggest the ostracods inhabited brackish, hypersaline and ephemeral aquatic ecologies in a coastal floodplain setting.
Winwood, H.H. and Woodward, H.B. 1891. Excursion to the Mendip Hills. Proceedings of the Geologists' Association, vol. 11, pp. clxxi - ccxvi.
Wood, M.W. and Shaw, H.F. 1976. The geochemistry of celestites from the the Yate area near Bristol (U.K.). Chemical Geology, vol. 17, pp. 179-193.
Worthington, S.R.H. and Ford, D.C. 2009. Self-organised permeability in carbonate aquifers. Ground Water, Issue Paper. Ground Water, vol. 47, no. 3, pp. 326-336. Available Online.
Abstract: Advances over the past 40 years have resulted in a clear understanding of how dissolution processes in carbonate rocks enhance aquifer permeability. Laboratory experiments on dissolution rates of calcite and dolomite have established that there is a precipitous drop in dissolution rates as chemical equilibrium is approached. These results have been incorporated into numerical models, simulating the effects of dissolution over time and showing that it occurs along the entire length of pathways through carbonate aquifers. The pathways become enlarged and integrated over time, forming self-organized networks of channels that typically have apertures in the millimeter to centimeter range. The networks discharge at point-located springs. Recharge type is an important factor in determining channel size and distribution, resulting in a range of aquifer types, and this is well demonstrated by examples from England. Most carbonate aquifers have a large number of small channels, but in some cases large channels (i.e., enterable caves) can also develop. Rapid velocities found in ground water tracer tests, the high incidence of large-magnitude springs, and frequent microbial contamination of wells all support the model of self-organized channel development. A large majority of carbonate aquifers have such channel networks, where ground water velocities often exceed 100 m/d.
This paper briefly discusses on p. 330 the Carboniferous Limestone aquifer at Cheddar.
Worthington, S.R.H. 2007. Groundwater residence time in unconfined carbonate aquifers. Journal of Cave and Karst Studies, v. 69, no. 1, pp. 94-102. Paper available in full online.
Abstract: Tracers have been widely used in unconfined carbonate aquifers to measure groundwater velocities and travel times. Injected tracers have largely been used to measure travel times from sinking streams to springs. Environmental tracers have largely been used to estimate overall residence times in an aquifer, and give times that are typically one hundred times longer than estimates from injected tracers. Use of both environmental and injected tracers has enabled residence times and storage volumes to be calculated for both diffuse and conduit components in a number of aquifers. With the addition of permeability data it is possible to calculate storage and flow components for the matrix, fracture and channel components. Results show that the matrix of the rock provides almost all storage, but has very long residence times, especially in older carbonates. Channels provide little storage, account for most of the flow, and have very short residence times. Fractures play an intermediate role between the matrix and channels and have low storage and moderate residence times. These same contrasts are found in many different aquifers and are likely to be found in all unconfined carbonate aquifers. Thus these aquifers are marked not so much by ranging from conduit flow to diffuse flow types, but rather in having triple porosity with contrasting flow and storage properties in the matrix, fractures and channels. The combination of environmental and injected tracers provides a powerful tool for elucidating these contrasting properties.
[Wright, V.P. - Paul Wright, Consultant carbonate specialist, author of many papers on carbonates and on Carboniferous stratigraphy. Cardiff, UK. Nautilus GTA.]
Wright, V.P. 1981. Algal Aragonite-encrusted Pisoids from a Lower Carboniferous Schizohaline Lagoon. Journal of Sedimentary Petrology, Vol. 51 (1981), No. 2. (June), pp. 479-489. [note: hypersaline setting]
Abstract: Pisoids from the Lower Carboniferous Llanelly Formation of South Wales contain both algal and fascicular-optic calcite laminae. The latter are here interpreted as a replacement product of aragonite and display characteristic calcitization textures. The original aragonite laminae formed in a hypersaline setting and are compared with Recent coniatoid deposits. The pisoids also show evidence of having grown periodically in a near normal marine setting as well as showing evidence of early solution probably by meteoric waters. The pisoids grew in a schizohaline lagoon formed as the initial phase of a marine incursion, during a period of fluctuating peritidal and arid floodplain deposition. The schizohalinity resulted from seasonal effects in a climate with a marked dry season.
Wright, V.P. 1982. The Recognition and Interpretation of Paleokarsts: Two Examples from the Lower Carboniferous of South Wales. Journal of Sedimentary Petrology, vol. 52, (1982), no. 1 (March), pp. 83-94. By V. Paul Wright.
Abstract: Criteria for the identification and interpretation of paleokarstic surfaces in ancient carbonate sequences are discussed and two examples of such surfaces are described from the Lower Carboniferous of South Wales. One type is compared to Kavornossen karren, a type of tropical karst well developed today on Puerto Rico. The second example, a mammillated paleokarstic surface of a type common in the Lower Carboniferous, is interpreted as a deckenkarren, formed beneath a vegetation cover and similar to the Makondo karsts of South Africa. Paleokarsts can provide information on the paleoclimates, paleohydrology, and vegetation cover existing at the time of their formation.
Wright, V.P. 1983. A rendzina from the Lower Carboniferous of South Wales. Sedimentology, vol. 33, pp. 221-241. Also, available in full in the E-book, : Wright, V.P. and Tucker, M.E. - Calcretes, Reprint Volume 2 of the IAS, International Association of Sedimentologists, and also in hard copy.
Abstract: A thin calcrete-crust horizon from the Lower Carboniferous Llanelly Formation of South Wales consists of two parts; an upper laminated unit and a lower peloidal unit. The former is interpreted as a subaerial stromatolite and the latter as an A horizon of a palaeosol. Comparisons are made with the A horizons of rendzinas and it is concluded that the calcrete-crust represents a complete rendzina profile. This fossil rendzina contains abundant evidence of a soil fauna in the form of fecal pellets and small burrows.
Example extract. "Geological Setting: The calcrete-crust horizon has been named the Darrenfelen Pedoderm (Wright, 1981a). A pedoderm is a mappable paleosol unit which has characteristics and stratigraphic relationships that permit its recognitions in the field (Brewer, Cook and Speight, 1970, p. 106). It has been found at five localities in the outcrop area of the Llanelly Formation [about the middle of the Lower Carboniferous, Carboniferous Limestone] in South Wales. This formation comprises part of the attentuated Lower Carboniferous succession in the northeast part of the South Wales coal field (Fig. 1A), which consists in the main of shallow, subtidal and peritidal limestones deposited on the northern (landward) edge of a carbonate shelf which covered much of South Wales (Wright, Raven and Burchette, 1981). The units comprising the sequence are shown in Fig. 1(B). The Llanelly Formation is composed of four distinct members (Fig. 1C); the Clydach Halt and Gilwern Clay members are floodplain deposits with sheet-flood, stream-flood and high sinuosity channel sandstones and conglomerates and claystones with calcrete profiles (Wright,1982). The Penllwyn Oolite Member is a thin oolitic unit separated from the underlying Cheltenham Limestone Member by an oncolitic grainstone, the Uraloporella Bed containing replaced aragonite cements and the problematical tubiform microfossil Uraloporella (Wright, 1981c). The Cheltenham Limestone Member consists of a series of peloidal limestones of lagoonal to supratidal facies-type deposited as a facies mosaic (Wright, 1981a), althought occasionally containing fining-upward shoaling units (Wright, 1981b). The calcrete crust described herein occurs 0.5 to 1 metre below the Uraloporella Bed and has been found at five localites; at the Graig quarry on the eastern side of Gilwern Hill near Abergavenny ..." [continues - for more details see Google Books - Wright Calcrete Rendzina IAS etc.]
Wright, V.P. 1986. Facies sequences on a carbonate ramp, the Carboniferous Limestone of South Wales. Sedimentology, vol. 33, pp. 221-241.
Abstract: During early Carboniferous times a major sea-level rise led to the development of an extensive carbonate ramp over what is now South Wales. Differential subsidence and sea-level changes resulted in distinctive facies sequences in the ramp succession and a model is offered which recognizes three distinct geomorpho-tectonic settings; inner, mid- and outer ramp. The inner ramp zone occurs in the more landward part of the province and was an area undergoing little or no subsidence. The sequence is dominated by oolitic grainstones and peritidal limestones representing shoal and back shoal environments. The peritidal units are transgressive deposits consisting of stacked asymmetrical shallowing-up cycles. The sequence contains many subaerial breaks and tectonic uplift resulted in base-level changes and fluvial incision. The mid-ramp zone sequence is intermediate in thickness between the inner and outer ramp successions and consists mainly of bioclastic limestones deposited below fairweather wave base. Sedimentation periodically exceeded sea-level rise and subsidence, and regressive (progradational) oolitic sand bodies developed, the thickest of which are stacked units with up to four individual sand bodies. Storm processes were of major importance in this setting. The outer ramp zone is represented by a thick sequence of muddy bioclastic limestones deposited below storm wave base and major Waulsortian reef-mounds also developed. None of the shallowing phases seen in the other ramp zones can be detected in this sequence. Subsidence and eustatic sea-level rise seem to have been the major controls on deposition but the recognition of eustatic sea-level falls is difficult. The detailed facies model for ramp carbonates presented here may be applicable elsewhere in the geological record.
Wright, V.P. 1987. The evolution of the early Carboniferous Limestone province in southwest Britain. Geological Magazine, vol. 124.
Sirs. Research into limestones has recently turned from detailed, small-scale analysis to looking at the evolution of carbonate sequences on a broad scale. Carbonate sediments today form in three main geomorphic settings: ramps, shelves and platforms (Ginsburg and James, 1974; Read, 1982; Tucker, 1985). The controls on the development of thick limestone sequences in each of these settings, such as tectonics-subsidence, eustatic sea-level changes and intrinsic sedimentary processes are becoming better understood (Kendall and Schlager, 1981; Schlager, 1981). Models have have been developed which enable analogous geomorphic provinces in the geological record (Read, 1982, 1985), and these large-scale models can be used to give new perspectives to many limestone successions and can reveal complex, evolutionary development stages hitherto unsuspected.
One of the largest carbonate sequences in Britain is represented by the Lower Carboniferous limestones of south Wales and the Bristol-Mendip area (Fig. 1). The sequences consist of a southward-thickening wedge of limestones and dololomites, over 1500 m. thick in southerly outcrops. The limestones overlie the fluvial Old Red Sandstone (Devonian) and are overlain by the deltaic-paralic Upper Carboniferous. The southern margin with the Cornubian Basin to the south is problematic because the transition is not exposed and major tectonic displacement has also occurred (Johnson, 1984). The limestone sequence has previously been interpreted as having been deposited on a carbonate shelf (Ramsbottom, 1970). Recent work has revealed a more complex history suggesting that the province passed through three stages, before finally achieving a typical shelf configuration. These stages can be recognised by interpreting and comparing broad facies sequences developed sequentially during the early Carboniferous. This is now possible because a number of recent studies have detailed the facies types in the sequence enabling the integration into an overall model.
Stage 1. During earliest Dinantian times (Hastarian [i.e. lowest substage of the Tournasian Stage] or early Courceyan) a major transgression, probably eustatic (Johnson, 1982) flooded the Old Red Sandstone alluvial planes of southwest Britain. The depositional unit represented by this stage is the Lower Limestone Shale Group (Cefn Bryn Shale Group of South Wales) which has been described in detail by Burchette (1986 and unpublished Ph.D. thesis of the University of Wales, 1977). Much of the unit consists of mudstones and shales interpreted as offshore muddy facies. There is evidence in the form of carbonate barrier facies of up to three minor regressive (progradational) phases during the deposition of the mudrocks but each was short-lived and the unit culminates in a very extensive mudrock deposition representing the maximum extent of the Carboniferous transgression (George, 1972).
Following the initial transgression carbonate production was swamped by siliclastic input. Such a stage is typically found following major sea-level rises and has been called the "start-up" phase by Kendall and Schlager (1981). This phase occurs because carbonate sediments are produced in situ and a period of time is required before the production rate reaches its potential.
Stage 2. This stage, from the late Hastarian to late Arundian, is marked by a predominance of carbonate sediments deposited as a markedly thickening wedge in which three zones can be recognised (Fig. 1). Along the northern landward edge of the limestone province, what is now the northern limb of the South Wales coalfield synclinorium, the sequence is thin, only 70m thick and consists of mainly oolitic and peritidal limestones with fluvial intercalations (Wright, 1986). Subaerial exposure surfaces and stratigraphic breaks are numerous and indicate periodic local uplift. Along the most southerly outcrops, in south Dyfed and the borehole in Cannington Park, the same sequence reaches over 1000m and consists of a relatively monotonous sequence of argillaceous, locally bituminous, bioclastic mudstones to packstones with Waulsortian reef mounds (Lees, 1982; Lees and Hennebert, 1982). Intermediate between these two sequences are those exposed in Gower and in the Vale of Glamorgan where bioclastic limestones dominate the sequence but with several shallowing events represented by oolitic grainstones. The bulk of the bioclastic limestones show evidence of having been deposited well below wave base and contain storm-event-beds (Wu, 1982). The oolites represent prograded oolite shoals with beach-shoreface deposits (Waters, 1984). Peritidal facies also occur but are volumentrically minor (Riding and Wright, 1981; Beus, 1984).
The differential subsidence of the ramp occurred during a major phase of lithospheric extension and it may have been related to half graben or graben structures (Leeder, 1986). It is possible that the ramp itself was behaving like a hangingwall dipslope bounded to the south by the submerged Bristol Channel Landmass and to the north by structures such as the Neath Disturbance and the Ritec Fault. ..... [missing word] uplift occurred along these ... structures in Carboniferous times and this uplift might be analogous to the footwall uplift. Alternatively the ramp may, like its class Quaternary equivalent of the southern Arabian Gulf have formed on the margin of a foreland basin, but it is more likely that the area developed into such a basin later in the Carboniferous.
Stage 3. The Holkerian succession exhibits a very different facies pattern. The palaeogeography during much of this stage was controlled by a major build-up of oolitic and pelleted limestones in the central zone discussed above, represented by the Hunts Bay Oolite in south Wales (George et al. 1976; Ramsay, 1986). Behind the oolitic complex a thick series of complex, open lagoonal, oolitic and peritidal carbonates was deposited, represented by the Dowlais Limestone of South Wales and Clifton Down Limestone of Avon and Somerset (Murray and Wright, 1971, Wright ..... [continues].
[end of extract here of - Wright 1987. Evolution - early Carboniferous Limestone province SW]
Wright, V.P. 1991. Palaeokarsts and palaeosols as indicators of palaeoclimate and porosity evolution: a case study from the Carboniferous of South Wales. Pp. 329-341 in Wright, V.P., Esteban, M. and Smart, P.L. 1991. Palaeokarsts and Palaeokarstic Reservoirs. Springer Verlage book, University of Reading Postgraduate Institute for Sedimentology. By V. Paul Wright and others.
A study of subaerial surfaces in the Carboniferous limestones of South Wales has revealed two palaeo-karst associations. The first consists of densely piped and rubbly solution horizons lacking features such as calcrete crusts, rhizoconcretions, and needle-fiber calcite but with meniscus cements and extensive phreatic blocky calcite cements. The palaeokarst morphology is comparable to some present-day humid karsts. The other association shows horizons of less well-deveoped karst which are associated with calcrete crusts, rhizoconcretions and needle-fibre calcite. Thick calcrete horizons also occur indicating formation under a semi-arid climate. These subaerial surfaces are associated with only minor early meteoric cementation.
These sets of features can be directly compared to the Quaternary eolianites of Yucatan. Here the Upper Pleistocene deposits, subaerially exposed under a more arid climate, while exhibiting little early cementation, do contain calcrete crusts, rhizoconcretions, and needle-fiber calcite. The Holocene equivalents, now exposed under the present more humid climate, exhibit extensive blocky sparry calcite cementation but lack calcrete crusts and their associated features.
The recognition of different suites of subaerial features not only allows the assessment of paleoclimates but also provides a means of predicting the degree of cementation concurrent with each subaerial phase. This may prove a useful tool in reservoir evaluation in carbonates. [end of abstract].
Wright, V.P., Esteban, M. and Smart, P.L. 1991. Palaeokarsts and Palaeokarstic Reservoirs. Book. University of Reading Postgraduate Institute for Sedimentology, Contribution No. 152. This book includes: Wright, V.P. 1991. Palaeokarsts and palaeosols as indicators of palaeoclimate and porosity evolution: a case study from the Carboniferous of South Wales. Pp. 329-341 in the above book.
Wright, V.P. and Faulkner, T. J. 1990. Sediment dynamics of early Carboniferous ramps: A proposal. Geological Journal, vol. 25, Issue 2, pp. 139-144. Abstract: In this paper we contend that the widespread development of carbonate ramps, in preference to carbonate shelves, during the early Carboniferous was a consequence of the different style of carbonate production during that period. Not only was the overall rate of biogenic production probably slightly lower than at most other times in the Phanerozoic but its distribution was also different. The marked differential carbonate productivities between shallow and deeper water, a key factor in forming accretionary shelf margins, was not as strongly developed during the early Carboniferous. Benthic biotas, especially reef builders, were partly impoverished following the late Devonian extinctions and were also affected by oceanographic and climatic changes taking place during the Tournaisian, including possible anoxic phases.
Wright, V.P. and Mayall, M. 1981. Organism - sediment interactions in stromatolites: and example in the upper Triassic of South West Britain. pp. 74-84 in Phanerozoic Stromatolites; Case Histories. Monty C. (editor) 249 pp. (publisher - Springer Verlag, Berling).
Wright, V.P., Woodcock, N.H. and Dickson, J.A.D. 2009. Fissure fills along faults: Variscan examples from Gower, South Wales. Geological Magazine. Volume 146, Issue 06, November 2009, pp 890-902.
Abstract: The extent to which persistent, rather than transient, fissures (wide planar voids) can exist along upper crustal faults is important in assessing fault permeability to mineral and hydrocarbon-bearing fluids. Variscan (late Carboniferous) faults cutting Dinantian (Lower Carboniferous) limestones on the Gower peninsula, South Wales, host clear evidence for fissures up to several metres wide. Evidence includes dendritic hematite growth and elongate calcite growth into open voids, spar ball and cockade breccia formation, laminated sediment infill and void-collapse breccias. Detailed mapping reveals cross-cutting geometries and brecciation of earlier fissure fills, showing that fissures were formed during, rather than after, active faulting. Fissures therefore probably formed by geometric mismatch between displaced fault walls, rather than by solution widening along inactive faults.
Yochelson, E.L., White, J.S. and Mackenzie, G. 1967. Aragonite and Calcite in Molluscs from the Pennsylvanian Kendrick Shale (of Jilson) in Kentucky. pp. D76 - D78. US Geological Survey Research 1967. Professional Paper, 575D - Research 1967, Chapter D. By Ellis L. Yochelson, John S. White and Mackenzie Gordon Jr. Work done in cooperation with the US National Museum.
Abstract: In X-Ray studies of a representative of each of 18 molluscan species to determine the mineral composition of the shell, three genera of cephalopods, nine genera of gastropods and three genera of pelecypods [bivales] show and outer layer of aragonite and calcite. One gastropod genus has an outer calcitic shell layer and an inner aragonite layer.
Extract: In general the two nautiloids examined (samples 29-34) confirm Stehli's observations [i.e. of an aragonite shell]. Our material has consistently shown aragonite to be the only material in both layers and septa; Stehli reported some calcite in the cameral deposits and aragonite exclusively in the shell. The ammonoid Gastrioceras examined by both Stehli and ourselves (samples 35 and 36) also has a shell of aragonite." [It is important to note that the Carboniferous ammonitoids or goniatites had, just like the Jurassic ammonites, a shell originally of aragonite. This is not surprising. Even aragonitic Jurassic ammonite, often have a shell diagenetically replaced by calcite.]
SOME LIMITED SUPPLEMENTARY NOTES ON CHEDDAR CAVES
Outline map of Gough's Cave, Cheddar. Figure 5.11 (of this webpage). Long Hole and Great Oone's Hole lie partly over the show cave section and are omitted for clarity (from surveys by Wessex Cave Club and Cave Diving Group).
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Individuals or group leader should take suitable observations and precautions regarding risk from road traffic, particularly in Cheddar Gorge, and industrial traffic in quarries. Not all places discussed in this website need be visited and the descriptions and photographs here can be used as an alternative to visiting. Individuals and leaders should take appropriate safety precautions, and in bad conditions be prepared to cancell part or all of the field trip if necessary. Permission should be sought for entry into private land and no damage should take place. Attention should be paid to weather warnings, local warnings and danger signs. No liability for death, injury, damage to, or loss of property in connection with a field trip is accepted by providing these websites of geological information. Discussion of geological and geomorphological features, coast erosion, coastal retreat, storm surges etc are given here for academic and educational purposes only. They are not intended for assessment of risk to property or to life. No liability is accepted if this website is used beyond its academic purposes in attempting to determine measures of risk to life or property.
Disclaimer: Geological fieldwork involves some level of risk, which can be reduced by knowledge, experience and appropriate safety precautions. Persons undertaking field work should assess the risk, as far as possible, in accordance with weather, conditions on the day and the type of persons involved. In providing field guides on the Internet no person is advised here to undertake geological field work in any way that might involve them in unreasonable risk from cliffs, ledges, rocks, sea, caves, unstable quarry faces or other causes. This web page is not a caving guide and it does not recommend entry into any caves, other than commercial show caves. Individuals or group leader should take suitable observations and precautions regarding risk from road traffic, particularly in Cheddar Gorge, and industrial traffic in quarries. Not all places discussed in this website need be visited and the descriptions and photographs here can be used as an alternative to visiting. Individuals and leaders should take appropriate safety precautions, and in bad conditions be prepared to cancell part or all of the field trip if necessary. Permission should be sought for entry into private land and no damage should take place. Attention should be paid to weather warnings, local warnings and danger signs. No liability for death, injury, damage to, or loss of property in connection with a field trip is accepted by providing these websites of geological information. Discussion of geological and geomorphological features, coast erosion, coastal retreat, storm surges etc are given here for academic and educational purposes only. They are not intended for assessment of risk to property or to life. No liability is accepted if this website is used beyond its academic purposes in attempting to determine measures of risk to life or property.
Webpage - written and produced by:
Ian West, M.Sc. Ph.D. F.G.S.