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Chesil Beach -Introduction Page
Chesil Beach - Pebbles
Chesil Beach - Magnetite Pebbles (lodestone) from a Shipwreck
Chesil Beach - Storms and Floods
Chesil Beach - Geology Bibliography
Isle of Portland - General
Isle of Portland - Portland Bill
Isle of Portland - Withies Croft Quarry
Isle of Portland - Bibliography
Safety and Risk Assessment
Safety and Risk Assessment
Generally the cliffs of the Fleet Lagoon are very low, so there is no serious danger of injury from rock-falls. Low tide is essential for geological studies but there is no great risk of being cut off by the tide (except perhaps in unusual storm conditions). There is some minor risk of slipping on clay and slippery rocks on the shore, and possibly becoming stuck in mud. There can be a variety of debris, including old pieces of iron and occasional some broken glass. At Tidmoor Point there is a rifle firing range and it is obvious that under no circumstances should you proceed to that locality if there are warning flags flying or the sound of firing taking place. During all geological fieldwork it is recommended that you take a a mobile phone with you for emergencies.
For more information on geological risks see the Safety Webpage. A description in the present webpage of a geological locality does not imply that it is safe to approach the place, or that there is permission to do so, even if it has been studied in detail in the past. Field leaders should make their own assessments of risk appropriate to terrain, weather conditions on the day and tide on the day, and the ability and fitness of the field party.
(It would be useful to have at hand the Ordnance Survey Map OL15 Purbeck and South Dorset, 1:50,000 and also the British Geological Survey Map - West Fleet and Weymouth, 341 and part of 342, 1:50,000.)
Please note that the description of a locality on the Fleet Shore within this webpage does not necessarily imply that there is access to that locality or that it is desirable from a conservation point of view that people should visit it. The webpage is simply providing geological data, and in some cases the use of the webpage may reduce the need to visit certain places.
The Fleet Lagoon shores are good in places for the individual explorer and would please the lone walker-geologist. They are much less suitable for parties. Most of the Fleet Lagoon is not good for coach (bus) access. Coaches can be parked, however, at the Chesil Beach centre and from there the southeastern end of the lagoon is easily reached by a short walk over Ferry Bridge. Cars provide more choice of localities but parking is not always easy. Some places on the Fleet shores can be reached by parking a car at a specific place and then walking along footpaths to a particular geological exposure. The Dorset Coastal Path provides walking access to the southern Fleet shore. The northwestern part of the Fleet is more difficult; it is part of a large private estate, the Strangeways Estate, and there are no convenient paths to the localities there. Herbury requires permission from the farmer. Additional difficulties can arise because much of it is a nature reserve and the bird life should not be disturbed. At Tidmoor Point there is a small firing range which for obvious reasons cannot be passed at certain times.
This does not mean that the Fleet Lagoon cannot be used for studying the strata. It should be considered as a more difficult region than the main cliff sections, with smaller exposures, but with important information and fossil-content for the specialist. Before proceding, one should check that the tide will be low and one should carefully examine the Ordnance Survey map so as to find a place to leave the car (there is not much parking near the Fleet, except at Ferry Bridge). Then, in addition, choose an alternative to be held in reserve. If the plans involve meeting anyone, then be sure to have mobile phones for communication in case of access or parking problems.
It may be useful to have a Fleet programme with a "plan B". If everything goes wrong with the original itinerary then just abandon it and proceed to the Chesil Beach centre, Portland, Osmington Mills or Bridport instead!
For a general introduction to the Fleet Lagoon particularly regarding its natural history see: Moxam , D. An Account of the Natural History of Ferrybridge. By Don Moxom, Warden of the Chesil Bank and the Fleet Nature Reserve. See also the various publications in Carr, Seaward and Sterling (2000). Other works are given in the select bibliography at the end of this webpage.
Strata of the Fleet Lagoon
Strata of the Fleet Lagoon
The shore of the Fleet Lagoon crosses obliquely the Weymouth Anticline, a broad fold in Jurassic strata. The low cliffs and slumped banks provided fair exposures of Middle Jurassic Cornbrash, through Forest Marble, Fuller's Earth, Oxford Clay, Corallian and some Kimmeridge Clay. A special significance is that because the shore transects the core of the anticline it is revealing Middle Jurassic strata such as the Cornbrash which is difficult to see elsewhere. The Fleet is quite notable for fossiliferous localities, but, however, these were much better in the past when less-collected and, perhaps, in some cases, more eroded. There may be some disappointment to the visitor who has read old books on the area and expects to find large numbers of ammonites, but interesting faunas are present in places and there are also sedimentological features of interest.
From Ferry Bridge northwestward
From Ferry Bridge northwestward
From Ferry Bridge it is easy to walk along the shore at low tide. There is a footpaths for most the way along the cliff top and this may be convenient for returning. After passing the oyster farm and restaurant collapsing banks of clay and reeds rather than true cliffs are first encountered.
The exposures are poor but a dark grey clay from the base of the Kimmeridge succession is seen and on the shore are examples of the flat oyster Deltoideum delta that have been washed out it. Ammonites of the genus Pictonia occur in this area.
After a short distance there is a change in the cliff from the grey Kimmeridge clay to lighter-coloured Ringstead Waxy Clay of the top Corallian. On the beach fossil remains of the twisted worm tube Cycloserpula intestinalis is common. If the low-dipping strata in the exposures are pieced together a similar succession to that at Ringstead can be worked out. It is clearly better to visit the Fleet Corallian localities after seeing the clearer and larger cliffs around Osmington Mills, between Bowleaze Cove and Ringstead.
Ferrybridge is the outlet of the Fleet Lagoon. In storms it has to discharge large quantities of washover and infiltration water from the Chesil Beach. A small scale example of this process occurred on the 10th March 2008.
A deep depression over southern England with westerly winds in the English Channel caused a moderate storm surge coinciding with a high spring tide. The effects were not extreme but there was localised sea-flooding around the English Channel, particularly at a caravan park on Selsey Bill. There was flooding of the Sandbanks road, and with the ferry at the south end out of action, the end of the peninsula was temporarily cut off from the mainland.
Effects of the storm could be seen at Ferrybridge, where the road crosses a bridge southward to the Isle of Portland. The storm had caused seawater to overwash and infiltrate into the Chesil Beach. This added floodwater to the Fleet Lagoon and raised the level. The head of water then flooded out at Ferrybridge, almost reaching the level of the road. It flooded the Ferrybridge car park.
Adrian Bicker, who was photographing the storm effects wrote to me that:
"The height of the water in the Fleet surprised me as the tide should have been falling for 2+ hours. Then I remembered a previous visit to the Fleet at Abbotsbury, where I watched sea water running out of the shingle along the back of the beach and flowing into the Fleet. The higher the tide on the outside of the beach, the greater the volume of sea water entering the Fleet - along its whole length!"
This near-flooding happened with a moderately bad storm. Sooner or later an extreme hurricane like that of 1824 will occur again, although, of course, it might be in the distant future. When the sea comes over the Chesil Beach on a large scale, as it did then, the bridge may hardly be visible. There was a huge amount of water to flow out at Ferrybridge, although there was no obstructing bridge at that time. On November 23rd 1824 the Fleet water was standing 22 feet, 8 inches (6.9 metres) on the alluvial meadows of the Decoy near Abbotsbury ( Arkell, 1947). It is not known when this will next happen, but the situation at Ferrybridge and Wyke Regis during such an event should be given advance consideration.
Camp Road, Wyke Regis (SY 652772)
Camp Road, Wyke Regis (SY 652772)
The Fleet shore here can be reached by following Camp Road 1.4 km southwest from Wyke Church (SY 662778). At the Fleet shore (at SY 652772), the Nothe Grits are seen west of the Coastguard Station (SY 648776) and the Bencliff Grit where Camp Road meets the shore. There are good exposures of the Osmington Oolite (seen to a thickness of at least 16m) for 500m to the southeast (see photograph). This is towards Pirates' Cove.
This part of the Fleet can be reached by parking a car at Lanehouse (west of Weymouth) and walking down on a public footpath through a holiday camp to the shore. Alternatively it can be easily reached by using the coast path from Ferry Bridge. The uppermost parts of the Oxford Clay, including the Red Nodule Beds occur around here with the ammonite Cardioceras and giant incurved oyster Gryphaea dilatata. The South West Coast Path provides a right of way on the Fleet cliff top above all the Oxford Clay localities of this area. Faunas were listed by Arkell (1947) in the Memoir.
Furzedown (SY 646784)
Furzedown (SY 646784)
This is a minor headland southwest of the holiday camp and just to the northwest of Lynch Cove. It is the next promontory southeast of Tidmoor Point, which is easily found on the map because of the presence of the Rifle Range. Furzedown is almost the northwest limit that can be safely reached when firing is taking place.
Here the Oxford Clay of the lowest Oxfordian Mariae Zone crops out very poorly at the foot of slumped cliffs. The pyritic ammonite fauna has the more rotund Quenstedtoceras, Q. mariae, and also early cardioceratids (developing a weak keel) (House, 1993). This unpromising exposure is the type section for the Furzedown Clays
Arkell (1947) discussed the Furzedown exposure in more detail. His comments were as follows:
"The Mariae Zone (Furzedown Clay) crops out on the north-west side of the next promontory southwards, west of Furzedown. Here the ammonites are almost as abundant but belong to far fewer species. They are in the same state of preservation as those at Tidmoor Point. With them are Nuculae, Pentacrinus ossicles, and numerous rather small Gryphaeae, mainly G. lituola Lamarck, with dwarfed G. dilatata J. Sowerby." Examples of the small Gryphaeae are shown below; notice the pen for scale.
LIST OF CEPHALOPODA FROM FURZEDOWN (Arkell's Collection)
Quenstedtoceras (Pavloviceras) mariae (d'Orbigny) (abundant)
Quenstedtoceras (Pavloviceras) omphaloides (J. Sowerby)
Cardioceras (Scarburgiceras) scarburgense (Young and Bird)
Cardioceras praecordatum Douville
Hecticoceras cf. matheyi de Loriol
Taramelliceras (Proscaphites) richei (de Loriol)
Perisphinctes (Properisphinctes) bernensis de Loriol
Peltoceras spp., many fragments of small nuclei
Belemnopsis (Hibolites) hastata (Blainville) (abundant)
? Rhopaloteuthis sauvanausa (d'Orbigny)
Arkell commented that this is the fauna of the typical Lower Oxfordian Stage of the Jura Mountains, Normandy, the Boulonnais, and Buckinghamshire. It has been termed in France the Marnes a [Marls with] Creniceras renggeri (Maire, 1908; 1928) . The Weymouth district furnished the type-specimen of Creniceras renggeri , figured by Sowerby, but it had not been rediscovered at the time of Arkell's (1947) memoir. This small ammonite is an oppeliid, a smooth-shelled (leiostracous) form with subdued ornamentation. It belongs to the Superfamily Haplocerataceae, which often show sexual dimorphism (a small shell and a large shell version - in modern teuthids the larger is the female). The species is notable for a crenulate venter [outer edge]. The original specimen may have come from Greenhill Gardens or Radipole Backwater or brickyard; there are places where there are no longer any sections.
In 1963 Palframan suggested that C. renggeri was a microconch [small shell version] of Taramelliceras richei [a larger ammonite] which Arkell had already reported to be present at the Fleet Lagoon. More recently, C. renggeri, has been rediscovered there, and at Ham Cliff, by Chapman (1995). He found it at 475m to the southwest of "Furzedown Farm" at map reference SY 6463 7846, and due east of the slipway on the southeast corner of Tidmoor Point. Chapman concluded that in the Weymouth area the dimorphic pair [i.e. macroconch - large and microconch - small] Taramelliceras richei/Creniceras renggeri occur in the Upper Oxford Clay as a constituent part of the middle and upper Scarburgense Subzone fauna. Since the macroconch form Taramelliceras richei has been recorded, albeit rarely, from the Praecordatum Subzone at both Ham Cliff and at the Fleet, C. renggeri probably has a similar range in the Mariae Zone of the Oxfordian.
[explanatory note: The Quenstedtoceras mariae Zone is the lowest zone of the Oxfordian Stage. Oxford Clay below this, i.e. the Quenstedtoceras lamberti Zone etc, belongs to the Callovian Stage of the Middle Jurassic. The reader should note that the Lower and Middle Oxford Clay are in the Callovian and only the Upper Oxford Clay is in the Oxfordian. The Callovian/Oxfordian boundary crops out between Furzedown and Tidmoor Point.]
East Fleet and Butterstreet Cove (SY 635799)
East Fleet and Butterstreet Cove (SY 635799)
This is a famous location for a "tidal wave" coming over the beach and up the valley in the 1824 hurricane (see the Chesil Beach storm webpage .
"The sea began to break over the beach at 5 a.m., the water came up as fast as a horse could gallop. James watched as long as he dared, and then, terrified, ran for his life to Chickerell..." (Le Pard, 1999).
The "tidal wave" hit the "Moonfleet" church - "James Bowring ... was standing near the gate of the cattle pound when he saw, rushing up the valley, the tidal wave, driven by the hurricane and bearing on its crest a whole haystack, and debris from the fields below. They ran for their lives to Chickerell, and when they returned they found that five houses had been swept away and the church was in ruins (Barnes, 1898 quoted by (Le Pard, 1999).). Of Fleet Church now only the Chancel remained (Mackenzie, 1995).
Thus, the original lower village of Fleet, normally sheltered by the Chesil Bank, was devastated by wave resembling a tsunami. Just why there was a sudden appearnce of giant wave which came over the Chesil Beach and the Fleet Lagoon is not clear. A notice in the small church states that there was 30 feet (9 metres) of water there. The church is round about 4m above sea-level, although I have no accurate figures; this suggests, if the figures are correct, a total water depth above sea-level of about 14m. If you walk to the church you can easily see how once the great wave had crossed the lagoon it would have been focussed into this small valley.
On the north shore of Butterstreet Cove, walking westward from the area of East Fleet Church, the Upper Cornbrash can be seen exposed in low cliffs. The zonal ammonite Macrocephalites has been found here. Fractured Cornbrash limestone is the reservoir rock for the Kimmeridge No.1 oil well.
Herbury (SY 611810)
Herbury (SY 611810)
Herbury or Herbyleigh (Davies, 1956) is a locality where the oldest strata at the surface in the Weymouth Anticline is seen. The fold plunges eastward and thus nothing lower than the Oxford Clay is seen in Weymouth Bay. Here on the Fleet the deeper level of the Fuller's Earth is exposed and it is notable, here, for the presence of the Boueti Bed, at the base of the Forest Marble. This can also be seen at West Cliff or Watton Cliff, Bridport. Strata from beneath this bed, the uppermost Fuller's Earth is exposed near the north-west tip of Herbury. The fauna includes the brachiopods Goniorhynchia boueti, Cyrtorhynchia, Avonothyris, Digonella, Dictyothyris and many bivalves and microfossils (House, 1993) Ammonites and echinoids are rare. House considered it to be almost collected out. However, the fauna may be found all along the considerable outcrop inland, especially in fields under plough (see detailed map in House 1961 ). Full faunal lists were given by Richardson (1909) and Fowler (1957) and microfossils have been studied by Sylvester-Bradley (1948) and Cifelli (1959).
(House, 1993) drew attention to the fact that the bed may be traced to just north of the Mendips. The similarity over so wide an area suggests a pause in sedimentation enabling suspension-feeding brachiopods to flourish. The small faults at Herbury have been said to be contemporary with deposition (Lake 1986a) because the successions differ across the faults.
There are no good quarries in the Forest Marble but many of the stone walls of the lowlands are of shelly flags from the upper division which may be collected from fields under plough. There are good exposures in the low cliffs of Herbury and on the foreshore to near Moonfleet Hotel (SY 617805). Near the southern end of Herbury the Digona Bed crops out. This level overlies the main flaggy division and the cream and grey marls have common Digonella digona, Avonothyris, Dictyothyris, Rhynchonelloidea, and ossicles of the crinoid, Apiocrinites occur. There are also with well-preserved bivalves.
Herbury was investigated as a possible site for a nuclear power station and shallow boreholes were put down (at one stage some such boreholes samples from the Fleet margin were to go to Southampton University). The proposal was rejected. Some limited information is provided in the footnote below.
"The Central Electricity Generating Board has announced plans (Dorset, the County Magazine, issue 83) for the construction of a nuclear power station at one of five sites in the south west, the two Dorset sites being at Winfrith and Herbury. .................
We believe that the projected rate of demand for electricity is greatly exaggerated, particularly due to the prohibitive cost of electricity when produced by nuclear means............
Winfrith is the only inland nuclear site in England and this has already caused problems of water supply and liquid waste disposal. The construction of a reactor on this site would necessitate the building of cooling towers 300 feet high, which would be an ugly scar on the Dorset landscape. The reactor would be worryingly close to the Poole-Bournemouth conurbation.
In Herbury, on the Fleet, the CEGB has chosen one of the most senseless sites imaginable on the British coastline. The reason for coastal sites is the easy access to supplies of sea-water for cooling purposes, but this is one of the very few locations in Britain where a shallow lagoon separates the main land mass from the sea. Chesil Bank and the Fleet place a natural barrier between the proposed nuclear reactor and its coolant....[continues]
lan Hatwell and Trevor Dykes , East Dorset Ecology Party"
[Letter in: Dorset, the County Magazine, Issue 85, p.19, undated but about 1980.]
Langton Hive Point (near Langton Herring)
Langton Hive Point (near Langton Herring)
Langton Hive Point is easily reached by parking the car at Langton Herring and walking down Coastguard Road to the shore. Here you will find a remarkable bed of small oysters in a whitish marl. They consist of Praeexogyra hebridica var. elongata. This is the Elongata Bed, a bank or lumachelle, which occurs near the base of the Middle Jurassic Frome Clay (the Upper Fuller's Earth in the old literature). It is above the Wattonensis Beds and attains some 5 metres thickness here. This is the best place to see it, although it is also present in Watton Cliff or West Cliff, Bridport. The oysters are encrusted with minute attached formaminiferans including. Nubeculinella and Radulopecten according to House (1993). This oyster bed is of interest in that the Frome Clay is a reservoir horizon at Wytch Farm Oil Field, but the porosity of this calcareous bed just here seems very low.
Rodden Hive Point (SY 599821)
Rodden Hive Point (SY 599821)
The Fuller's Earth is exposed here. House (1993) stated that the oldest beds are near Rodden Hive Point and are clays with mudstones with the bivalves Nucula and Myophorella and crushed ammonites, especially Procerites ( Arkell, 1947 , House 1957) often with attached worm tubes and bryozoa. These are thought to be equivalent to the Wattonensis Beds but the brachiopod Wattonithyris has not been recorded. The Wattonensis Beds were proved to be 32m below the Hebridica Beds in the Sea Barn Farm Borehole with 185m of Fuller's Earth below down to the Inferior Oolite.
Shipmoor Point (SY 576836)
Shipmoor Point (SY 576836)
Shipmoor Point is shown on the map above at the northwestern end of the Fleet Lagoon. This is the best local exposure of the Cornbrash but it is unfortunately difficult of access and permission is required from the Strangways Estate. The following notes are based on House (1993) simply to report what is there. There will be no good reason for most geologists to go there; it is close to protected area of the swannery of Abbotsbury and best avoided. There is no public footpath to this locality.
The photograph above, taken from the Chesil Beach, shows Chester's Hill and Shipmoor Point is at the extremity of this. The picture does not show the main exposure but just the slopes without cliff development where this Middle Jurassic mudstone under the hard Cornbrash limestone. At the point there are 6.5m of strata exposed, including the very fossiliferous Lower Cornbrash (2m) with the zonal guide brachiopods Cererithyris intermedia below and Obovithyris obovata above. Other brachiopods include Kallirhynchia yaxleyensis and the bivalves Meleagrinella echinata, Pleuromya, Pholadomya, Ctenostreon and others. The more massive limestones of the Upper Cornbrash follow and yield the brachiopods Rhynchonelloidella cerealis, Microthyridina siddingtonensis and the large burrowing bivalve Pholadomya deltoidea. The ammonite Clydoniceras is expected from the Lower Cornbrash and Macrocephalites from the Upper Cornbrash. See also Arkell (1947) for further information on Shipmoor Point.
A similar section to that at Shipmoor Point is seen at Berry Knap (SY 586830) 1.1 km to the southeast where the Cornbrash dips 15 degrees to the north. The rich fauna ofthe Cornbrash is readily collected wherever the level is under plough, as often immediately north of the Langton Herring road (around SY 621824) where Forest Marble rubble strews the field to the south and the boundary runs along the road. According to House (1993) the Upper Cornbrash has yielded Macrocephalites on the Fleet shore in Butterstreet Cove near Fleet (SY 630791-634791) which is easy of access by the footpath to the shore past the isolated church. Faunas of the Lower Cornbrash can sometimes be found farther west. In the Sea Barn Farm Borehole 18.2m of Cornbrash was proved.
Abbotsbury - The Peat with Beaver Remains
Abbotsbury - The Peat with Beaver Remains
Boulders of peat on the beach at Abbotsbury, are also considered here. These peat blocks are much larger than the peat fragments seen at the Portland end. They have been found just southeast of the old tank defences. Blocks of two metres or more in length have been thrown up on the top of the beach, as shown in the photographs above, taken on 18.10.2000. The blocks were probably eroded from peat beds beneath the beach by the lower part of waves in storms of the winter 1999/2000. The peat is argillaceous, light brown where it is clayey and dark brown to black where there is plant material. Some of this seems to be small logs or twigs. The material has since degraded largely by drying out and distintegrated to some extent. Notice how this argillaceous peat has shrunk and broken into small polygonal cracks.
Beaver bones have been found in this by David Harvey during the year 2000. There is no doubt that this peat represents marshy peaty sediments from the Fleet Lagoon over which the Chesil Beach has been driven back. Beavers were presumably once common inhabitants of the Fleet Lagoon, at least at the this northwestern end where the salinity is lower.
Harvey (undated) has provided further information about the beaver bones in the peat. Dorset Coast Forum (undated) commented that the peat revealed that the site of the Fleet lagoon had formerly been a freshwater Alder marsh. Peat on the Chesil Beach at Abbotsbury (but not the beaver sample) had been dated at 6100 +/- 120 BP.
Thus a regression at about 6000 BP seems to have caused a freshwater marsh phase in the area. This requires consideration in relation to more peat and apparently older estuarine, shelly clay, found at Bexington West and discussed below.
Blocks of Cerastoderma Clay from beneath the Chesil Beach at West Bexington
Blocks of Cerastoderma Clay from beneath the Chesil Beach at West Bexington
Whittaker (2000) reported that shelly clays with peats had been washed up at West Bexington after prolonged swell conditions in 1992. They indicated that brackish to near-marine conditions existed 4.5km. to the northwest of the present day Fleet, probably between 4000 and 5000 years BP. The extent of the "Proto-Fleet" at this time was conjectured.
More recently blocks of the shelly clays have appeared again at West Bexington. Peter Chapman, an Engineering Geologist at Bridport, kindly informed by email on the 16th February 2009 that some unusual blocks of shelly clay and peat had been washed up on the beach. I had already planned to travel to West Bexington, and thus I went there and took the photographs shown above.
I am grateful to Peter Chapman, of Brody Forbes Partnership (Consulting Engineers based at West Bay) for drawing attention to these blocks. Examples are shown above. They are thrown up on the beach like the Beaver Peat of Abbotsbury, discussed above. They mostly consist of laminated estuarine clay that is quite firm. With the clay is some peat, with woody remains up to several centimetres in diameter (but flattened). The clay has cyclical thin bands or layers of Hydrobia shells at intervals of a few centimetres. Both with the Hydrobia and in the intervening clay Cerastoderma (Cardium - the common Cockle) shells are abundant. These are often paired and in place and then represent a life assemblage (biocenosis).
The blocks are also present to the southeast of West Bexington. It is particularly interesting that they continue to Cogden and are present northwest until the cliff line is reached. At Cogden, near Cliff End, they appear to contain more or larger Littorina littorea.
Cerastoderma, or Cockle, shells are abundant in a dark grey clay. This clay is laminated with laminae of Hydrobia and small Littorina at intervals of a few centimetres. These are shown below.
Hydrobia lamellae in the Cerastoderma Clay
At regular intervals of a few centimetres within the Cerastoderma Clay there are laminae of Hydrobia and small Littorina shells. These seem to be of estuarine, mud-flat origin.
The small modern gastropod, particularly Hydrobia ulvae (the Laver Spire Snail), is a very common mollusc in estuaries It grazes on algae on mud surfaces when the tide is in. When the tide goes out it burrows into the mud. It can reach densities of 20,000 to 80,000 gastropods per square metre of mud in some places. Large numbers of the shells of this gastropod are washed up on the harbour side of Hurst Beach, especially in the lagoons between recurves near Hurst Castle.
Pebbles, like those of the present Chesil Beach but blackened occur embedded in the Cerastoderma Clay. The pebbles are only slightly smaller than those on the beach at present. The blackening, is the familiar effects of pyrite that occurs when pebbles are buried in reduced mud in estuaries. It is not know, though, whether the pebbles are penecontemporeous with the estuarine mud or whether, and more likely, they represent the base of a later transgressing Chesil Beach. In either case their occurrence is more easily explained by the Cerastoderma Clay overlying the peat.
The Cerastoderma Clay - Environment of Deposition
There are two common species of Cerastoderma in the region at the present day. Cerastoderma edule is the Estuarine Cockle. It occurs in the Ferrybridge mudflats. Cerastoderma glaucum, the Lagoon Cockle is found in the Fleet beyond the Narrows. The differences between the two species are small and I have not determined whether the West Bexington specimens are of C. edule or C. glaucum. The latter can be tolerant of quite low salinities, down to about 5 parts per thousand. The associated Littorea littorea can survive salinities down to about 10 parts per thousand. Hydrobia occurs as more than one species and can be tolerant of various salinities. Thus, firm conclusions cannot, as yet be drawn regarding the salinity of the old lagoon or estuary beneath the West Bexington area.
UK Marine (undated) have given information about salinity of the present Fleet Lagoon. They commented:
".. at Abbotsbury, tidal variation is not seen in the trace for salinity, with levels for approximately 12 days at around 24 ppt, dropping to around 12 ppt on 25.10.98, and increasing to 15-18 ppt for the last 2 days of the record."
"At Chickerell, tidal influence can clearly be seen, with variations in salinity from around 34 to 35.5 ppt."
Thus, from this data it can be seen that the salinity for whole existing Fleet Lagoon is appropriate for at least Cerastoderma glaucum. Unless the cockle in the clay at West Bexington can be shown to be Cerastoderma edule (probably unlikely) then the salinity conditions for the former lagoon or estuary in which the Cerastoderma Clay at West Bexington and Cogden was deposited need have been no higher than those in the Fleet at present.
The Peat - Description
The peat appears to be older than the Cerastoderma Clay. The peat show an eroded surface in contact with the clay. Furthermore pieces of peat occur in the clay. More study is needed, though.
As mentioned above, peat has previously been found at Abbotsbury. Harvey (undated) has found beaver bones in the peat. Dorset Coast Forum (undated) commented that the peat revealed that the site of the Fleet lagoon had formerly been a freshwater Alder marsh. Peat on the Chesil Beach at Abbotsbury (but not the beaver sample) had been dated at 6100 +/- 120 BP. If the peat at West Bexington is of about the same age as this (merely speculation at the moment), then the estuary or saline lagoon was developed after about 6100 BP.
Fossils from the Peat Blocks - Holliday et al.
For more information see:
, A., Brokenshire, A., Christian, R. and Smith, D. 2009. West Bexington, West Dorset - Peat Blocks and Fossils. Newsletter of the Dorset Group of the Geologists' Association. Online at:
West Bexington, West Dorset - Peat Blocks and Fossils. . Text by Alan Holiday and Adrian Brokenshire; photos by Alan Holiday, Robert Christian and Doreen Smith.
This article provides some history of the occurrence of the blocks. It includes good photographs of the fauna and reports the discovery of:
Pupilla muscorum (land snail)
Red Deer - rear part of skull
Beaver - skull
Plant remains, resembling Eel-Grass.
Discussion - Whittaker's "Proto-Fleet"
The shelly clay has originated in the estuary or saline lagoon that was originally at the back of the shingle beach. The salinity was brackish, at least, and above freshwater, but it did not have to be very high for the presence of Cerastoderma, Littorina littorea and Hydrobia.
The possibilities for discussion are that the deposit is that of a former estuary at West Bexington and Cogden, or that it is the remains of an former extended Fleet Lagoon. There are no significant cliffs at the back until Cliff End, the northwestern end of Cogden is reached. However, there are small relic lagoons at the back of the Chesil Beach in the West Bexington and Cogden area. Some are filled with reeds (Phragmites).
The extent of the stretch of blocks from West Bexington to the northwestern end of Cogden. The fact that the blocks are slightly different at Cogden, and the fact that they disappear immediately the cliff is reached, all indicate a buried estuarine lagoonal deposit from West Bexington (at least) to Cliff End.
Thus there was formerly an estuary or an extended Fleet Lagoon here. The exact age is not known but the peat might correspond to the 6100 BP peat of Abbotsbury. If this is the case then the Cerastoderma clay may be a record at West Bexington of an estuary or former Fleet Lagoon after 6100 BP. More detailed studies of the fauna and, in particular, some carbon-dating is needed.
Provisionally, at the moment, the Cerastoderma Clay seems to be a post-Neolithic, marine transgressive deposit over low coastal peat and forest. It was probably associated with the development of a much larger Fleet Lagoon, the predecessor to the existing Fleet.
The Memoir of Arkell (1947) and the field guide of the late Professor Michael House have been important sources of information. Both studied the shores of the Fleet in detail and provided a large source of new data. Michael House mapped this area in the early 1960s. I am particularly grateful to David Harvey for information about the beaver bones, and for very useful discussion during field work. Peter Chapman has been very helpful in recording and discussing the West Bexington beach blocks, and I am very grateful to him.
References and Bibliography
Please see also the separate Chesil Beach Geological Bibliography.
Anonymous . 1993. Note re grant to Fleet Study Group for exploratory boreholes. Geologists' Association, Circular , 901:7.
Arkell , W.J. 1947 . The Geology of the Country around Weymouth, Swanage, Corfe and Lulworth. Memoir of the Geological Survey, 386 pp.
Bird , E.F.C. 1971. A 17th century attempt to drain the Fleet. Dorset, the County Magazine, no. 17.
, E.C.F. 1972. The physiography of the Fleet. Proceedings of Dorset Natural History and Archaeological Society, for 1971, published 1972, volume 93, 119-124.
Brookfield , M.E. 1973a. The Palaeoenvironment of the Abbotsbury Ironstone (Upper Jurassic) of Dorset. Palaeontology, vol. 16, part 2, pp. 261-274. Abstract: The Abbotsbury Ironstone represents a rare sandy facies of the Lower Kimmeridgian in Britain. Palaeoecological studies show that it consists of of three facies deposited in an offshore beach or barrier bar environment. The main control on the fauna is thought to be the degree of water agitation.
Brookfield, M. E. 1973b. Palaeogeography of the Upper Oxfordian and Lower Kimmeridgian (Jurassic) in Britain. Palaeogeography, Palaeoclimatology, Palaeoecology, 14, 137-167. Abstract: A series of maps with descriptive notes illustrate the palaeogeographic changes in the British Isles during the Upper Oxfordian and Lower Kimmeridgian. The division between the stages marks no sharp faunal or sedimentological change, as hitherto assumed. The passage is a gradual change from shallow water carbonates, through delta-influenced conditions to open shelf environments, spanning the top three zones of the Oxfordian and lower three zones of the Kimmeridgian. The common stratigraphic sequences in all basins indicate a common overall control on sedimentation. The relative importance of sea-level changes, climate and tectonic movement cannot be separated and may be interconnected.
Brookfield, M.E. 1973c. The life and death of Torquirhynchia inconstans (Brachiopoda, Upper Jurassic) in England. Palaeogeography, Palaeoclimatology, Palaeoecology, 13, 241-259. Abstract: Torquirhynchia inconstans, a rhynchonellid brachiopod, shows a curious asymmetric commissure. This is interpreted as an adaption to life in tidal environments. Types of preservation, growth line, and size frequency analysis indicate that the population analyzed consists of dominantly mature individuals, which by analogy with recent brachiopod populations is a primary feature of the original population, and not due to selective destruction, selective transport, or selective predation of smaller individuals. The possible functions of the asymmetry of Torquirhynchia inconstans are considered, and it is concluded that the brachiopod was adapted to life in tidal environments, a conclusion supported by sedimentological evidence. Asymmetric brachiopods are considered to have developed from colonies of partly asymmetric, variable brachiopods by selection of extreme variants.
Brookfield, M.E. 1973d. The Palaeoenvironments of the Upper Oxfordian - Lower Kimmeridgian Sediments in Dorset, England. Unpublished Ph.D. Thesis, Reading University, 550 pp.
Brookfield, M.E. 1978. The lithostratigraphy of the upper Oxfordian and lower Kimmeridgian Beds of south Dorset, England. Proceedings of the Geologists' Association, 89, 1-32. Carr, A.P., Seaward, D.R. and Sterling P.H. (editors) 2000. The Fleet Lagoon and Chesil Beach; Proceedings of the Third Symposium of the Fleet Study Group (revised edition).Published by Chesil Bank and the Fleet Nature Reserve in partnership with Dorset County Council at County Hall, Dorchester, Dorset, in 2000. 112 pp, papeback, ISBN 0952402204. Has been on sale at the Chesil Beach Centre.
Carr, A.P. 1981. Chesil Beach: aspects of its structure, stability and the processes acting upon it. Pp. 9-14 in: Ladle M. (ed.) The Fleet and Chesil Beach. A Scientific Account Compiled by the Fleet Study Group: Structure and Biology of a Unique Coastal Feature. 74pp. ISBN No. 0 85216 288X. Printed by Dorset County Council. August, 1981. [14 papers about the Fleet and Chesil Beach deriving from a one day seminar held at the Dorset County Museum. Reproduced typescript with diagrams. Preface by A.T. Swindall, County Planning Officer, County Hall, Dorchester, Dorset. Editor: M. Ladle, The River Laboratory, East Stoke, Wareham, Dorset.]
Carr, A.P. 1981. Chesil Beach: aspects of its structure, stability and the processes acting upon it. Pp. 9-14. In: Ladie, M. (Editor) 1981. The Fleet and Chesil Beach: Structure and Biology of a Unique Coastal Features. 74 pp. ISBN 0 85216 288X. A scientific account compiled by the Fleet Study Group. Double-spaced typescript, A4 paperback with monochrome diagrams on sale at low cost at the Chesil Beach Centre, and available for reference in the Tophill Library, Easton, Portland.
Carr, A.P. and Blackley, M.W.L. 1973. Investigations bearing on the age and development of Chesil Beach, Dorset and the associated area. Transactions of the Institute of British Geographers, 58, 99-111.
Carr, A.P. and Blackley, M.W.L. 1974. Ideas on the origin and development of Chesil Beach, Dorset. Proceedings of the Dorset Natural History and Archaeological Society (for 1973), 95, 9-17.
Carr, A.P., Seaward, D.R. and Sterling P.H. (editors) 2000. The Fleet Lagoon and Chesil Beach; Proceedings of the Third Symposium of the Fleet Study Group (revised edition).Published by Chesil Bank and the Fleet Nature Reserve in partnership with Dorset County Council at County Hall, Dorchester, Dorset, in 2000. 112 pp, papeback, ISBN 0952402204. Has been on sale at the Chesil Beach Centre.
1. The role of the Fleet Study Group - J. FitzPatrick - 7.
2. The Fleet, Dorset, in relation to other coastal lagoons - R.S.K. Barnes - 9.
3. The role of the Ilchester Estates - E.W.S. Green - 13.
4. The Fleet - an introduction to the physical environment - G.G. Poole - 15.
5. Chesil Beach: recent changes in a longer term context - A.P. Carr - 23.
6. Cored material from the Fleet: some initial inferences - E.D.K. Coombe - 31.
7. Fleet water temperatures - D.R. Seaward - 41.
8. The evolution of the Fleet during the last c. 5000 years, based on the evidence of the Foraminifera and Ostracoda - J.E. Whittaker - 45.
9. A preliminary report on diatom samples collected from the Fleet in Dorset - B. Hardey - 57.
10. Zostera and Ruppia in the Fleet - N.T.H. Holmes - 67.
11. Flowering plants of the shores of the Fleet - S.M. Eden - 75.
12. A preliminary survey of the Rotifera of the Fleet - A. Saunders-Davies - 77.
13. Invertebrate faunal studies in the Fleet - C. Pickering, M. Ladle & M. Sheader - 79.
14. Oysters: their variation in time and space - J. Winder - 83.
15. Pacific oyster spatfall monitoring in the Fleet Lagoon as part of the )NCC survey of non-native marine species - N.C. Eno - 85.
16. Opportunities, practice and problems of oyster culture in the Fleet - N. Copperthwaite - 89.
17. Monitoring oyster farming in the Fleet: benthic infauna - K.). Collins & V. Byfield - 93.
18. Factors affecting the numbers of waterfowl on the Fleet (1983-1993) - J.Fair - 101.
19. Management of the Fleet and Chesil Beach: a review of activities and issues - D.Elton - 105.
20. The Bridging of the Fleet at Smallmouth - J.C.Wagner & M.Wagner - 109.
21. The Dorset Coast - M.Turnbull - 111.
Some further information on the Carr paper:
Carr, A.P. 2000. Chesil Beach: recent changes in a longer-term context. Pp. 23-30 in Carr, A.P., Seaward, D.R. and Sterling P.H. (editors) 2000. The Fleet Lagoon and Chesil Beach; Proceedings of the Third Symposium of the Fleet Study Group (revised edition). Extract of the start: This paper briefly reviews evidence for the evolution of Chesil Beach on a geological timescale; thereafter it looks at significant descriptions by 16th to 18th century topographers, historians and cartographers and, finally, attempts to relate both these sets of data into the context of more recent change. Apart from the summary of the wave refraction data (Holmes, unpub.) and parts of both Table 1 and Figures 1 (site map) and 2, no new information is published here. For a general review of work on Chesil Beach and a comprehensive list of references up till that date, readers are recommended to go to Carr and Blackley (1974). More detailed information on the -specific aspects discussed here will be found in the various sources quoted especially Carr (1983a) and Carr and Seaward (1991, 1992).
Geological timescale : There seems little doubt that at earlier stages in geological history the hills to the landward side of the Fleet lagoon were exposed to marine action. Indeed, boreholes carried out for the CEGB indicate a cobble storm beach underlying the relatively recent (in a geological sense), unconsolidated, deposits of the Fleet. It is difficult to give a date to this (or these) event(s). (There may have been more than one because sea level is thought to have been at approximately its present relative height on several occasions during the Quaternary period.) An immediate problem is that if there were 'protoChesils' which finally became destroyed what happened to the bulk of the pebbles of which they were composed? It seems improbable that attrition rates of flints and cherts were sufficiently great to destroy the bulk of the constituents... [continues]
Central Electricity Generating Board . 1968. Investigation of prospective nuclear power station sites: Portland Harbour and Tidmoor Point: part 1. Hydrographic Survey. [See also Hatwell and Dykes objection to a nuclear power station on the shores of the Fleet. They, however, referred to Herbury rather than Tidmoor Point. There was also a geological site investigation by the CEGB regarding the land behind the Fleet Lagoon.]
Chapman , N. 1996 (for 1995). The rediscovery of Creniceras renggeri (Oppel) in the Upper Oxford Clay near Weymouth, Nigel Chapman. Proceedings of Dorset Natural History and Archaeological Society, vol. 117, pp. 153-4. Extract - para 1: In the list of fossil ammonites recorded by Arkell (1947, p. 32) from the Mariae Zone westsouthwest of Furzedown Farm on the Fleet shore (SY 6463 7846) one notable absentee was Creniceras renggeri (Oppel). But Arkell did record Taramelliceras richei (de Loriol) at the locality, and this form was subsequently shown to be the macroconch dimorph of Cr. renggeri by Palframan (1966). Similarly Cr. renggeri was not listed from the Ham Cliff Anticline, northeast of Weymouth (SY 7150 8181). This note reports the presence of Cr. renggeri at both localities: Sowerby (1823, pI. 321) states that Weymouth is the type area for the species, but the precise source is not known: it could be either of two localities mentioned above or perhaps Greenhill or on the shore close to the old Weymouth Brickpit (SY 673 795) at the southwest end of Radipole Lake where a Mariae zone fauna is reported by Woodward (in Strahan 1889, p. 20).
Chesil Bank and Fleet Nature Reserve . 1991 onwards. Fleet News and Newsletter.
Chesil Bank and Fleet Nature Reserve. undated (but available in 2005). Chesil Bank and the Fleet Nature Reserve: Facts and Figures. Brochure 13 pp. The Royal Manor of Portland Chesil Beach Centre, Portland Beach Road, Portland, Dorset, DT4 9XE. tel. 01305-760579, fax. 01305-759692.
Coombe , E.D.K. 2000. Cored material from the Fleet: some initial inferences. Pp. 31 to 40 in: Carr, A.P., Seaward, D.R. and Sterling P.H. (editors) 2000. The Fleet Lagoon and Chesil Beach; Proceedings of the Third Symposium of the Fleet Study Group (revised edition). Published by Chesil Bank and the Fleet Nature Reserve in partnership with Dorset County Council at County Hall, Dorchester, Dorset, in 2000. 112 pp, papeback, ISBN 0952402204.
Abstract: Recent research into the Fleet sediments has been prompted by the unique geomorphological relationship of the lagoon with Chesil Beach. The sediments which floor the Fleet represent a sediment trap implying an infill from the Portland Harbour area, and not from the west ahead of an advancing Chesil (Poole, 1966). Of 25 planned, some 23 boreholes were sunk (1990 to 1993) to a maximum depth of -5.62 m OD, and 21 cores analysed for their stratigraphical composition. This includes petrology, mineralogy, geochemistry, magnetic susceptibility, using modern techniques of laser granulometry, scanning electron microscopy, EDAX analyses, mineral magnetic analyses (molspin magnetometer and pulse magnetiser), calcimetry, and wet and dry bulk densities. Two cores (4 and 6) have been analysed in greater detail, on which some radiocarbon dating of peat and other remains has been done, together with the classification, and analyses of ostracods and diatoms. A pollen analysis has yet to completed. Further radiocarbon dating of cores over the longitudinal cross section is also planned which should confirm the believed diachronous nature of the sedimentary deposition. Stratigraphic horizons in the lateral and longitudinal cross sections have been tentatively constructed and are offered herewith. From these, inferences are drawn regarding sedimentary infill and evolutionary history of the Fleet Lagoon, and of Chesil Beach itself.
Damon , R.F., 1884. Geology of Weymouth, Portland and the Coast of Dorsetshire from Swanage to Bridport-on- the-Sea: with Natural History and Archaeological Notes. 2nd ed., R.F.Damon, Weymouth, 250 pp.
Davies , G.M. 1956. The Dorset Coast: A Geological Guide. Adam and Charles Black, London, 128pp.
Dorset Coast Forum . (with contribution from David Harvey). (undated). The Abbotsbury Beaver. Dorset Coast Forum, part of Dorset-for-You - dorsetforyou.com.
Extract: In 2000 the remains of a prehistoric Beaver were discovered at Abbotsbury, in a block of peat that had been washed up on the shore. Blocks of peat are often thrown onto Chesil Beach, Dorset, particularly in the Abbotsbury - West Bexington section. These contain numerous plant macrofossils, notably Alder and reed, though animal remains are considerably rarer, the only previous record seems to be that of a portion of a Deer skull found associated with a peat block in 1995. It is impossible to say if the large rolled molar of an unidentified species of elephant, found on the beach in 1823 was derived from the peat, but it seems unlikely.
Early in 2000 David Harvey of Bridport was examining peat blocks on Chesil beach at Abbotsbury, in the vicinity of the old tank traps (SY 568 839), when he found a group of bones, clearly derived from an eroded block of peat. The bones were given to the Chesil Beach Centre at Ferrybridge and subsequently identified by English Heritage as being those of European Beaver Castor fiber.
"The bones consist of an almost complete left scapula, a complete left clavicle and a fragment of the proximal half of a right ulna. The three bones are similar in size to those of an adult male beaver from Bergroitzer, Germany [AML specimen 1545, Faunal reference collection, Centre for Archaeology, Fort Cumberland, Portsmouth]."
While the date these remains is uncertain, other samples of peat that have been found on the beach have been dated to 6100 +/- 120 BP which may indicate their approximate age. ....
....... Although flooding caused by dams can result in trees being drowned, it has also been suggested that beavers historically helped the spread of Alder in Britain, by creating suitable habitat for these water-loving trees. This latter point is particularly interesting as the peats found on Abbotsbury beach often contain remains of Alder. This suggests that, at the end of the mesolithic and the beginning of the Neolithic, the Fleet, instead of being a narrow brackish lagoon, was a wide, freshwater marsh, which would almost certainly have been very rich in wildlife..." continues
[Go to the original website for more information. See also Harvey (undated), below]
Dorset County Council. 1980-1988. Various reports regarding the Ferrybridge replacement and other topics. Includes the Ferrybridge Hydrological Survey of 1987, with ma;ps and correspondence, the bathymetric survey of 1988, and Chesil Beach surveys of March 1987, February 1988 and July, 1988. Some should be listed under Dorset County Surveyor (Hutchinson, D.A.). See Archive List of the Fleet Study Group.
Fair , John and Moxam, Don. 1993. With photographs by Peyto Slater. Abbotsbury and the Swannery. The Dovecote Press Ltd., Stanbridge, Wimborne, Dorset, BH2 4JD. 87 pp. ISBN 1874336075 casebound, ISBN 1874336083 paperback. Price £9.95p. for the paperback version. By John Fair and Don Moxam.
"Abbotsbury's world famous Swannery was first mentioned six hundred years ago. It remains a fascinating and unique link with the way of life of the medieval monks who gave Abbotsbury its name. The illustrated story of the one of England's most beautiful villages. The Monastery and the Swannery. The Chesil Bank and the Fleet. The Duck Decoy and life in the reed and withy beds. The famous subtropical gardens."
"Gloriously illustrated by superb colour photographs" - this is true; the photographs by Peyto Slatter are of remarkably good quality!
Falkner , J.M. 1898. Moonfleet. By J. Meade Falkner. Fiction with some use of local history. A famous novel, an adventure story in the tradition of Treasure Island, based on the Dorset coast, particular the village of Fleet and the Fleet Lagoon, the "Fleet of the Mohunes". It makes reference to a storm overtopping the beach and to the church at Fleet which was wrecked in the 1824 hurricane.
Fisher, O. 1873. On the origin of the estuary of the Fleet in Dorsetshire. Geological Magazine, vol. 10, pp. 481, 573. By the Reverend Osmund Fisher of Cambridge University.
Fisher, O. 1874. On the origin of the estuary of the Fleet. Geological Magazine (letter) for 1874, p. 190.
Fortwengler , D. and Marchand, D. 1994. Nouvelles unites biochronologique de la Zone a Mariae (Oxfordian inferieur). Geobios, M.S. 17, 203-209.
Harvey , D. 200?. Report on beaver bones found in peat on the Chesil Beach at Abbotsbury. Reported in:
Dorset Coast Forum. (undated). The Abbotsbury Beaver. Dorset Coast Forum, part of Dorset-for-You - dorsetforyou.com.
"The remains were almost completely exposed when found and not easy to identify as being ancient at first due to so many seabird bones scavenged around the area. On closer examination though the remains were aged, this could not have been accomplished by remaining on the beach as the sea, weather (and tourists) would have destroyed them in a very short while, although sun drying may have split and curled the shoulder blade? The limb bone was loose (and lucky not to have been blown away on the wind) and when lifted an impression was left on the peat - similarly with the shoulder blade, although the underneath part had reduced to powder in part."
The bones were given to the Chesil Beach Centre at Ferrybridge and subsequently identified by English Heritage as being those of European Beaver Castor fiber.
"The bones consist of an almost complete left scapula, a complete left clavicle and a fragment of the proximal half of a right ulna. The three bones are similar in size to those of an adult male beaver from Bergroitzer, Germany [AML specimen 1545, Faunal reference collection, Centre for Archaeology, Fort Cumberland, Portsmouth]."
Hatwell , I. and Dykes, T. 1980? Reactor resistance. Dorset: the County Magazine, Issue 85 (undated, but post April 1979). [Brief objections from the East Dorset Ecology Party to a nuclear reactor at Winfrith or at Herbury on the Fleet Lagoon.] "The Central Electricity Generating Board has announced plans (Dorset, the County Magazine, issue 83) for the construction of a nuclear power station at one of five sites in the south west, the Dorset sites being Winfrith and Herbury... In Herbury, on the Fleet, the CEGB has chosen one of the most senseless sites imaginable on the British coastline. The reason for the coastal sites is the easy access to supplies of sea-water for cooling purposes, but this is one of the few locations in Britain where a shallow lagoon separates the main land mass from the sea. Chesil Bank and the Fleet place a natural barrier between the proposed nuclear reactor and its coolant.." [continues].
See also: Central Electricity Generating Board . 1968. Investigation of prospective nuclear power station sites: Portland Harbour and Tidmoor Point: part 1. Hydrographic Survey. [Note this refers to Tidmoor Point rather than Herbury. There was also a geological site investigation of the land behind the Fleet Lagoon by the CEGB involving shallow boreholes and the taking of samples. The details of this are not known although there was discussion about the samples at the Geology Department, Southampton University, at the time. I think that the Cornbrash and somewhere near Wyke Regis was discussed.]
Hayward , R.J. (undated, but probably 1982). The last years of FerryBridge. Dorset, the County Magazine, No. 94, pp. 35-39. The magazine is a combined special issue presented as the Portland Souvenir Magazine. With photographs, including and aerial photograph, and a print of the horse-drawn ferry boat that preceded the bridge. Extract of the start of the article: R. J. Hayward outlines the events which led up to the decision to replace Portland's vital and only road link with the mainland. The existing Fleet channel is to be filled and an alternative passage cut through the shingle spit about 200 yards to the south. Here a new bridge will have been constructed, to replace the badly corroded, sinking, Ferrybridge. The reason for the change of position is that it is much cheaper to build a bridge on dry land - in the few cases where this is possible - and then divert the water.
The wrought iron bridge linking Portland to the mainland at Ferrybridge, Wyke Regis, is being replaced. The bridge, opened in June 1896, is badly corroded and is also sinking slowly into the clay strata upon which it was built. At present the bridge carries between 15,000 and 16,000 vehicles a day, far more than it was designed to carry - and many of which are much heavier than the bridge designers of the 19th century anticipated. But this is not the real problem. That is the serious corrosion that has eaten into the bridge over the last few years. The bridge was last grit blasted down to bare metal and repainted in 1973-74... [continues]
This article is then followed by a short article by Rodney Legg also on the new bridge. Legg, R. 1982(?), New Bridge threatens Britain's rarest insect. Dorset, the County Magazine, No. 94, pp. 39-41. This includes a map on the scale of 1:2500 of the Ferrybridge and Small Mouth channel. Work on the new bridge began in 1980 with test drillings on the site of the proposed new bridge. Construction will be carried out in 1982. The County Council expect the old bridge to carry traffic until late 1983.
Extract from p. 41: On 13 May 1980 the transportation sub-committee gave their go ahead in principal to this proposal. The immediate advantage of building a new bridge further south is that it could be built on dry land, thus cutting down the construction time. The idea is that, having built the bridge on land, you then excavate a channel under the bridge to join The Fleet with Portland Harbour. A further advantage is that plans for a controversial pipe bridge over The Fleet to carry sewage from Portland to the new sewage pumping station at Wyke Regis can now be shelved and the necessary pipes included in the structure of the new bridge. The existing tideway under the present Ferrybridge will be filled in. It is this that is causing most consternation to local conservation groups. They feel that moving the natural tideway would have a detrimental effect on the Fleet, which is already silting up at Littlesea. A team from the Hydraulic Research Station, Wallingford in Berkshire investigated the effects of moving the tideway and their results suggest that the proposed diversion through the new channel would have no adverse effects. The county council is sensitive to the environmental lobby and has stated that it is willing to finance research and surveys to ensure the conservation interests are safeguarded. Experts from the Fleet study group are also investigating the likely effects and the Nature Conservancy Council are considering what surveys to carry out to safeguard the biological and ecological aspects of the tideway change... [continues].
House , M.R. 1955. New records of the Red Nodule beds near Weymouth. Proceedings of the Dorset Natural History and Archaeological Society, 78 (for 1956), 64-70.
House, M.R. 1961. The structure of the Weymouth Anticline. Proceedings of the Geologists' Association, 71, 221-238.
House, M. E. 1989. Geology of the Dorset Coast. Geologists' Association Guide, 162pp. See new edition - 1993.
House, M.E. 1993 (and earlier edition in 1989) - Geology of the Dorset Coast. Geologists Association Guide No. 22. 2nd edition, 164 pages plus plates. ISBN 0 7073 0485 7.
Hunt, L. 1983. Bridge over shifted waters. Heavy Construction, November/December 1983. [Re Ferrybridge].
Kemp , J.P. undated. The Book of Weymouth and Portland. By John Kemp; drawings by McLean. ISBN 0 907683 32 0. Nigel J. Clarke Publications, 3 Russel House, Lyme Close, Lyme Regis, Dorset. 54pp. [Small paperback booklet. With the following pictures: p. 24 Smallmouth Ferry before 1839 with rope and horses; p. 50 of Portland Ferry House, 1800.]
Kemp, J.P. undated - 199?. The Book of the Chesil Beach. 22pp. Small paperback booklet with interesting general and historic information. Price 2 pounds, 50 pence, obtainable from the Chesil Beach Centre.
Kinahan, G.H. 1874. On the origin of the Lagoon, called the Fleet, Dorsetshire. Geological Magazine for 1874, p. 50. See also Letters, pp. 189, 239, 240.
Lake , S.D. 1986. Evidence for Bathonian and Portlandian synsedimentary fault movements in Dorset. Proceedings of the Dorset Natural History and Archaeological Society, 107 (for 1985), 191-192.
Legg , R. 1982(?) (on Ferrybridge and Small Mouth, Chesil Beach). See Hayward (1982).
Marchand , D., Courville, P., Bonnot, A., Rossi, J. & Scoufflaire, Q. 2002. Very Small Ammonites (Micromorphs) from Lower Oxfordian Marls (Mariae Zone). Gabhandlungen Der Geologischen Bundesanstalt - Band 57, Wien, February 2002, …ditions H. Summesberger, K. Histon & A. Daurer,475 pp.
Maire , V. 1908. Contribution a la connaisance de la faune des Marnes a Creniceras rengerri, dans la Franche-Comte septentrionale. Premiere partie, Le Callovien et l'Oxfordien inferieur a Authoison (Haut-Saone). Bull. Soc. grayloise d'Emul. 11, 143-163.
Maire, V. 1908. Contribution a la connaisance de la faune des Marnes a Creniceras rengerri, dans la Franche-Comte septentrionale. Etude sur les Oppeliides. Trav. Lab. geol. Fac. Sci. Lyon, fasc 12, 10, 60 pp., 3 pls.
Moxam , D. An Account of the Natural History of Ferrybridge. By Don Moxom, Warden of the Chesil Bank and the Fleet Nature Reserve. " Introduction: The Chesil Bank is one of the five largest shingle beaches in Britain, whilst the Fleet is the largest regular tidal lagoon in Britain. Growing within the Fleet are two species of eel-grass Zostera spp. and two species of Ruppia, and these support an invertebrate fauna that is now extinct in many parts of Europe. The eel-grass is food for the largest resident mute swan population in Britain. For these reasons and many more, the Fleet and Chesil Bank have been designated as a Site of Special Scientific Interest of the highest grade, equivalent to a National Nature Reserve...[continues]
Ordnance Survey . 2004. Explorer Map OL15 - Purbeck and South Dorset, 1:25,000 scale. [price in 2005 - £6-99p. This is recommended topographical Ordnance Survey (not Geological Survey) map for location purposes when undertaking geological studies on the Dorset coast from Bournemouth to Bridport. Unfortunately, it does not include Lyme Regis.]
[It is an essential map for locating footpaths and other routes to the shores of the Fleet Lagoon.]
Palframan , D.F.B. 1966. Variation and ontogeny of some Oxfordian ammonites: Taramelliceras richei (de Loriol) and Creniceras renggeri (Oppel), from Woodham, Buckinghamshire. Palaeontology, 9, 290-311.
Palmer , S. 1963. Prehistoric stone industries of the Fleet-area, Weymouth. Proceedings of the Dorset Natural History and Archaeological Society, vol. 85.
Palmer, S. 1967. Trial excavations in the Fleet-area, Weymouth. Proceedings of the Dorset Natural History and Archaeological Society for 1966, vol. 88, pp. 152-157. By Susann Palmer. [Excavations at Butterstreet Cove]
Robinson, E. and Whittaker, J.E. 1988. Restricted collecting around the Fleet, Dorset. The British Micropalaeontologist, No. 34.
Quereilhac , P. 2000. A propos de quelques ammonites recoltees dans l' Oxfordien du Poitou. Editions Ph. Quereilhac, Poitiers, p 27., pl XXI.
Sowerby , J. de C. 1823. Mineral Conchology, Vol. 5, London.
Strahan, A. 1898. The Geology of the Isle of Purbeck and Weymouth. Memoirs of the Geological Survey, England and Wales, 278pp. Extract, p. 203 et seq.:
" The Chesil Beach:
This great shingle-bank commences near Bridport, and extends a distance of 18 miles to the Isle of Portland, where it terminates abruptly against the cliffs south of Chiswell. For the first six miles of its course it keeps in contact with the coast, but then for eight miles maintains a beautifully even curve at a distance of 200 to 1,000 yards from the main land, enclosing between itself and the shore a shallow salt-water and brackish lagoon known as the Fleet. For the last two miles the beach strikes boldly out to sea to join itself on to Portland. It ranges in width from 170 yards at Abbotsbury to 200 yards at Portland, and in height from 22 feet 9 inches above high-water mark at Abbotsbury to 42 feet 9 inches at Chiswell. From Abbotsbury to Wyke it rises at the rate of 1 in 8,450 and from Wyke to Chiswell at the rate of 1 in 880. The shingle extends to a depth below Low-water Spring Tides of six fathoms at Abbotsbury, seven fathoms at Fleet, and eight fathoms at Portland, at which depth it gives way to sand. The stones of which the visible part of the beach consists increase in size from Abbotsbury to Portland, but those lying below Lowwater Mark diminish in size in the same direction. Borings have shown that the shingle rests on its landward side upon a floor of clay at a depth of three or four feet above Low-water Spring Tides. The clay is said to have been exposed on the seaward side after storms, but it was not met with in the borings. It seems, therefore, to form a shelf upon the edge of which the beach is built. It is usually spoken of as Kimmeridge Clay, but a short length only of the beach actually stands upon that formation. The main part of the beach above High-water Mark is composed of loose shingle, which is always being shifted according to the changes of the wind, but the shingle below this is held in a matrix of sand and grit which is almost, if not quite, watertight. The tide, therefore, gains access to the Fleet at its eastward end only, by the narrow opening known as Small Mouth, and the rise and fall at Abbotsbnry does not exceed a few inches and then only at Spring Tides, when a good deal of water leaks through the upper unconsolidated part of the bank. In exceptional storms, however, the sea seems to have gained access somewhat freely to the Fleet. Leland, writing in 1546, speaks of the south-eastern winds breaking through the bank, and Camden, in 1590, says the Chesil Beach" when the south wind rises, gives and commonly cleaves asunder." Whatever this expression may mean, it is recorded that on November the 23rd, 1824, the sea-water stood to a depth of 22 feet 8 inches on the alluvial meadows at the Decoy, near Abbotsbury, this result having been brought about not so much by the giving way as by the overtopping of the bank by waves at high tide. In this same year the sloop Ebenezer, of 100 tons, ran on the crest of a wave so high up the bank that she was subsequently launched into Portland Roads. This occurred about midway between Ferry Bridge and Chiswell.
The deeply indented inner shore-line of the Fleet contrasts strongly wIth the monotonously even curve of the Chesil Beach. It has clearly never been exposed to the action of such a surf as breaks upon the bank, but presents rather the features characteristic of subaerial denudation, with but slight modification. Thus the effect of surf and tide upon such beds as here crop out would be to cut them all back impartially, the mass of the strata being soft clays, and the rock-bands insignificant. So far from this having been the case, the difference in hardness has been emphasised, and the Cornbrash and Corallian, the hard bands in the Forest Marble and some others form bold headlands, while such cliffs as exist are proportional in size to the miniature surf that arises within the Fleet. It thus has come about that the lagoon widens or contracts according to the nature of the strata cropping out in its northern shore. At Wyke it is contracted by the Corallian hills to a width not exceeding 200 yards,in the Oxford Clay outcrop it widens out to a maximum of 1,000 yards; the Cornbrash of Fleet hems it in again to a width of 250 yards, but in the soft Fuller's Earth outcrop it expands to lOO yards. Further north these outcrops are traversed in reverse order, and the Fleet after widening out in the Oxford Clay finally terminates at the Corallian escarpment west of Abbotsbury.
But though the Fleet, properly so called, ends here, similar features on a smaller scale extend towards the western part of the Chesil Bank at Burton Bradstock. Thus, half a mile east of Abbotsbury Coastguarst Station there is a slight hollow between the beach and the hill-slopes. At and near the Station a little cliff of Fuller's Earth dominates the shingle, but 600 yards westwards a hollow recommences, which develops westwards into a low waterlogged flat upwards of 300 yards in width. The hollow is occupied by a grey alluvial clay, washed down from the adjacent slopes of Fuller's Earth, and doubtless was a small " fleet" until an artificial opening was cut in the Chesil Bank at the site of Swyre White House. One mile further west a similar hollow, partly silted up and partly still occup,ied by water, is known as Burton Mere. But at Cliff End, 15 mIles from Chiswell, this feature of a hollow inside the Shingle Bank comes to an end, and thence for three miles the shingle is piled against the foot of a cliff of Oolitic clays and limestones. Speculations as to the origin of the Chesil Bank have given rise to a voluminous literature. One of the first and the most exhaustive papers was that of Mr. (Sir John) Coode in 1853 to which we are indepted for the measurements quoted above." ... [continues for three and half more pages]
UK Marine (undated). U.K. Marine Special Areas of Conservation (website). Additional observations of water quality within the Fleet.
Extract [on salinity]
"Continuous monitoring of dissolved oxygen, salinity and turbidity in Fleet waters at Abbotsbury and Chickerell over 15 days in October 1998.
Continuous monitors for dissolved oxygen (DO) concentrations were sited in the Abbotsbury embayment and in the channel off Chickerell Hive Point to gather data on summer diurnal variations in DO. These results have not been interpreted in EA 1998b. However, preliminary examination of the continuous monitor trace indicates that at Abbotsbury, tidal variation is not seen in the trace for salinity, with levels for approximately 12 days at around 24 ppt, dropping to around 12 ppt on 25.10.98, and increasing to 15-18 ppt for the last 2 days of the record. This drop in salinity corresponds approximately to a series of peaks in turbidity on 25.10.98, and is assumed to be due to a rainfall event. For dissolved oxygen, there does appear to be some diurnal variation, but the trace is not regular, varying between less than 80 percent and well over 100 percent. Around 25.10.98 and for the following two days, diurnal variation was barely discernible, with DO consistently around 80 percent saturation.
At Chickerell, tidal influence can clearly be seen, with variations in salinity from around 34 to 35.5 ppt presumably corresponding to tidal influx of higher salinity water. Dissolved oxygen at this site does not vary with the tidal cycle, but there does appear to be diurnal variation, with higher levels (greater than 100 percent saturation) during the middle of the day, and lower levels of 70-80 percent during the night. This variation is indicative of algal or plant photosynthesis increasing water oxygen concentrations during the day, with lower levels at night. Turbidity was fairly constant at a low level, with the exception of a few groups of peaks of up to 600 NTU (Nephelometric Turbidity Units). These groups of peaks corresponded to disruptions to the tidal and diurnal variations in salinity and DO. At the same time as some of the peaks in turbidity, salinity is reduced, and the diurnal variation in DO levels is less obvious. They may therefore be associated with rainfall events, however, there is no data on rainfall in the report (1998b)."
Waller , M.P. and Long, A.J. 2003. Holocene coastal evolution and sea-level change on the southern coast of England: a review. Journal of Quaternary Science, 18, 351 - 359. Special Issue: The Quaternary History of the English Channel. Issue Edited by P.L. Gibbard, J.P. Lautridou. John Wiley & Sons, Ltd. By Dr. Martyn P. Waller (Kingston) and Dr. Antony J. Long (Durham).
Abstract: Data collected recently from select areas within the eastern, central and western English Channel are used to reconstruct the Holocene evolution and sea-level history of the southern coast of England. Rapid sea-level rise in the early Holocene produced a ubiquitous vertical and lateral expansion in the marine influence. From ca. 6800 cal. (calendar) yr BP the rate of sea-level rise declined and a shift from minerogenic to organogenic sedimentation is also widely recorded. A further decline in the rate of sea-level rise occurred in the late Holocene, during which time the eastern and central English Channel experienced coastal inundation and a return to minerogenic sedimentation. Explanations for this apparent contradiction include the effects of this decline on the accumulation of minerotrophic peat and changes in sediment supply. Sea-level index points from the eastern Channel generally plot below those from the central and western Channel, indicating differential crustal movement, although sediment compaction and tidal range also may be responsible for apparent altitudinal variation between these areas. Despite an increase in the quantity and quality of the data available from this region over the past 20 yr these, and a number of other important issues, require further clarification. [Relevant to the history of the Chesil Beach and Fleet Lagoon.]
Whatley , R.C.and Ballent, S. 2004. A Review of the Mesozoic Ostracod Genus Lophocythere and Its Close Allies. Palaeontology, 47, no. 1, pp. 81-108. Abstract: The progonocytherid cytheracean ostracod genus Lophocythere and its immediate allies in the Jurassic are reviewed. All known species of 16 genera are considered. We consider that only eight of these genera (Acanthocythere, Afrocytheridea, Aulacocythere, Fuhrbergiella, Lophocythere, Neurocythere, Terquemula and Trichordis) remain valid; the eight rejected genera are Crucicythere, Cuvillierella, Dhrumaella, Infacythere, Nophrecythere, Paralophocythere, Pokornya and Tropacythere. [refers to a specimen from the Boueti Bed at Herbury, Dorset].
Whittaker, J. E. 2000. The evolution of the Fleet during the last c.5000 years, based on the evidence of the Foraminifera and Ostracoda. pp. 45-56 in: Carr, A.P., Seaward, D.R. and Sterling, P.H. (Editors) 2000. The Fleet Lagoon and Chesil Beach, Proceedings of the Third Symposium of the Fleet Study Group. Published by Chesil Bank and Fleet Nature Reserve in partnership with Dorset County Council at County Hall, Dorchester, Dorset, in 2000. 111pp. ISBN 0 952 4022 04.
Abstract: An analysis of the Foraminifera and Ostracoda from four shallow hand-cores penetrating to a maximum depth of -5.85 m OD. into the bed of the Fleet, Dorset, indicate important environmental changes have taken place in the water body during the last circa 5000 years. The sediments for the most part are lagoonal silts and clays with significant peat layers. However, in the three cores taken in West Fleet the base of each section is represented by sands containing a shallow marine assemblage not unlike that found in Weymouth Bay today. This is followed upwards in all the cores by evidence of salt marsh before the onset of the mainly brackish-marine lagoonal phase which continues to the present day. The Phragmites peats are thought to represent stillstands or falls in what was generally an otherwise rising Holocene sea level; the Fleet may have then become an entirely freshwater body cut off from access to the sea. High diversity shell bands occur on top of the peats, each indicating a marine pulse and a return to tidal, lagoonal conditions. The ostracods in particular evidence subtle changes in the ecology of the Fleet throughout its lagoonal phase. For much of its existence West Fleet appears to have been much more like a typical estuary than it is today, with extensive creek development and large intertidal areas at low water.
Shelly clays with pears washed up from under Chesil Beach at West Bexington, after prolonged swell conditions in 1992, indicate brackish to near-marine lagoonal conditions existed 4.5 km to the north-west of the present-day Fleet, probably between circa 4000 and 5000 years BP. The extent of the 'Proto-Fleet' at this time is conjectured.
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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 or other causes. Not all places 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.
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Ian West, M.Sc. Ph.D. F.G.S.