THE THREE MAIN LYME REGIS WEB PAGES
Lyme Regis - Seafront and Town
Lyme Regis East to Charmouth (this webpage) - MAIN EASTERN LYME REGIS CLIFFS
Lyme Regis - West, Monmouth Beach, Chippel Bay, Seven Rock Point - MAIN WESTERN LYME REGIS CLIFFS

.

.

(For more on this landslide, and a map, go to the: Spittles Landslide section.)

Taken normal sensible precautions; this website does not recommend that you follow any particular route, take any risks and does not suggest that you follow any specific programme. No responsibility is taken for any visit or field trip.

GENERAL-INTRODUCTION:

Safety and Risk Assessment - Addendum - Rock Fall Accident Risk

On the 18th June 2015, a woman was walking on the beach at Llantwit Major, South Wales. She was at the foot of a vertical Blue Lias cliff, very similar to the vertical Blue Lias cliffs at East Cliff, Lyme Regis (at the end of the new eastern Sea Wall and promenade) and to the west of Monmouth Beach. Apparently she was struck by a falling rock from the Blue Lias. The cliffs of this Lower Jurassic unit are vertical and consist of fractured and alternating limestone and shales, both at Lyme Regis and at Llantwit Major. The initial report on the accident in South Wales can be found online as follows:

"Woman, 23, dies in Llantwit Major beach rock fall" BBC New Online 19th June 205, South-East Wales Region. Also reported in newspapers of this date.

In spite of the presence of vertical Blue Lias cliffs at Lyme Regis there have been very few, if any, fatal accidents there. There is no suggestion whatsoever, being made here that people should not go to the coastal cliffs. What number should go is relevant. The vertical Blue Lias cliffs of Lyme Regis were not very easy to reach in the past and a walk over irregular rocks was needed to get to them. The East Cliff was not easily accessible and needed low tide. These factors reduced the number of people going to the vertical cliffs to a small number of serious enthusiasts. The East Cliff is still inaccessible at high tide. However, at low tide there is now, via the new eastern sea wall and promenade, a very easy access almost directly from a major car park (Charmouth Road) to a vertical and fractured, Blue Lias cliff. It remains to be seen as to whether this has increased the risk of accidents. Obviously people should stay out on the ledges as far as is reasonably possible and not get near the vertical cliff any more than necessary (hopefully there will be sensible caution without the imposition of severe restrictions).

.

GENERAL-INTRODUCTION

Access and Car Parking

The road down to the sea front and through the centre of Lyme Regis is rather steep and narrow. The main car park is at Charmouth Road, up on the northeastern slopes above the town. There is both car and coach parking here and it is only a short walk down to the town centre and beach. [There is now (in 2015) a path and steps down from the Charmouth Road Car Park to the new eastern sea wall and promenade.] Very large coaches cannot pass through the centre of Lyme Regis, because the turning needed is too sharp. There is another car and coach park at Holmbush which at the top of a steep hill above the Cobb. Cars, but not coaches, can also park down at Monmouth Beach (at higher car parking fees).

At Charmouth there is car parking at the sea front near the Heritage Centre. There is a also a car and coach park a short distance north and nearer to the village centre. It is only a short walk from here to the beach. The coast path at the back of Black Ven can be accessed from the seafront and also from the roads up the hill to the west of Lyme Regis, including Higher Sea Lane, the Old Lyme Road etc., but there is no parking up there.

INTRODUCTION:

Location and Geological Maps

Simplified geology and location maps and a general cliff section are provided below. In addition there are provided here some detailed maps from the work of the renown Liassic specialist, Dr W.D. Lang who published numerous papers on the Lias of this area in the early part of the 20th century. He was also a notable palaeontologist of the Natural History Museum, London. He later lived near the cliffs at Charmouth. The maps shown here are of more interest in the context of the original papers, and reference to Lang's original publications is strongly recommended.

.

For a geological visit to the Lyme Regis or Charmouth area obtain the British Geological Survey maps, Sheet 327, Bridport. It is also essential to have access to the new memoir - British Geological Survey Memoir (2011), Geology of South Dorset. This is highly recommended, and it should be the main reference for correct stratigraphical terminology.

.

INTRODUCTION:

Aerial Photographs:

For aerial photographs of the Lyme Regis area go to: The Channel Coastal Observatory , National Oceanography Centre, Southampton. There are numerous, orth-rectified aerial photographs taken at low tide on various occasions. They cover all the south coast of England and elsewhere. They are of very high resolution. In addition there is much technical data, such as Lidar, available. First go to the online site above, then register with the CCO online and receive an id and a password. Subsequently you can download the aerial photographs and other coastal data that you may need. Note that the photographs initially are in ECW format and need an appropriate viewer, which can convert them to jpg should that be necessary. Examples shown on this website have already been converted to jpg. The general geologist may only need some of the aerial photographs, such as those shown here; coastal and geomorphological specialists can obtain much more technical data for research studies.

The aerial photographs above are courtesy of and copyright of The Channel Coastal Observatory , National Oceanography Centre, Southampton. They show the coast of Black Ven between Lyme Regis and Charmouth, at different scales and resolutions. They provide an example of the type of images available, although they have been reduced and none are at the full original scale. The major features shown are the landslides and mudslides of Black Ven and the coastal exposures of the Blue Lias, with its althernating limestones and shales. In the upper part of Black Ven the Upper Greensand is present. It contains much chert and is oxidised to a brown colour. The green of unweathered glauconite is not seen in the aerial photographs. A particular feature of interest is the presence of boulder arcs or the former terminations of mudslides which have been subjected to coast erosion.

The aerial photographs immediately above show the outcrops on the shore of the Blue Lias limestones and shales. Identification of beds is reliant on the classic and well-known work of Dr. W. D. Lang (1914; 1924).

Many other aerial photographs of Black Ven in particular are available in various publications. The famous landslide locality has attracted much attention.

For an excellent aerial photograph of Black Ven in August (1969) see Plate 3 (page 7) of Conway (1974). This well-illustrated report of the British Geological Survey shows the two great mudslides which existed then and since now been degraded. They are the origin of the two large boulder arcs near Canary Ledge. More aerial photographs of Black Ven are available in a website:
The Black Ven Landslide: an Application of Digital Photography. By Jim Chandler of Loughborough University.

---

.
2. STRATIGRAPHY:

The Lower Jurassic System of West Dorset.

The simplified outcrop map above shows the distribution of Jurassic strata at the surface on the British land areas. The offshore outcrops, such as in the North Sea and the English Channel are not shown here. Jurassic also underlies extensive areas in southeastern England, as in the Weald of Kent and Sussex. Lyme Regis is shown at the southwestern end of the Yorkshire to Dorset outcrop.

Tables and diagrams above give some simplified and introductory scheme to the lithological sequence of the Lower and Middle Jurassic strata. One diagram gives the traditional zonal scheme of the Lower Jurassic with lithological equivalents, based on House (1993) and Cope (1980) .

The Blue Lias is the lowest unit discussed here. This consists of thin alternating shales, marls and argillaceous limestones at the bottom of this Jurassic succession. The Blue Lias is 32m thick, and includes all the Hettangian Stage - Psiloceras planorbis, Alsatities liasicus, Schlotheimia angulata plus the lower part of Sinemurian Stage - Arietites bucklandi, Arnioceras semicostatum . These limestones and shales overlie " Rhaetic " strata (Penarth Group) which is a lagoonal facies of Upper Triassic age (and in turn overlies Triassic red-bed, desert facies). The Blue Lias represents the first normal marine sediments resulting from the transgression of the sea over the deserts and lagoons of parts of the great supercontinent Pagaea. The marine fauna increases upwards in abundance and diversity as the sea opens and deepens and then ammonites and ichthyosaurs and plesiosaurs live in the fairly warm water of moderate depth above the muddy sea-floor.

Marine mud facies of the Shales-with-Beef, an oil source-rock, and the Black Ven Marls follow. The Shales with Beef are 25m thick and belong to the zone of Coenisites turneri . These are important fossiliferous units. The Belemnite Marls lie above and are present in the middle part of the cliff of Black Ven. Cretaceous strata lie unconformably above. To see higher parts of the Jurassic ( Stonebarrow , Golden Cap and Seaton etc), it is necessary to travel further east, where the Cretaceous unconformity (the Albian or Late Cimmerian (Kimmerian) unconformity) has not cut down to quite such a low level.

2. STRATIGRAPHY continued:

Jurassic Palaeogeography

A large map is provided above showing the position of the shelf seas of Europe in the Jurassic. Because this is a very generalised and not for a specific time in the period it should not be used as a precise marker of palaeolatitudes. It does indicate the area of extensional tectonics and basin development at the northeastern end of the Atlantic at that time. Not only was the formation of rifted basins responsible for much accumulation of clay, limestone and sandstone sequences of the Jurassic. In addition, the breakup of the old supercontinent Pangaea led to an increase in the number of spreading centres in the oceans (Lemon, 1993). This resulted in a consequent displacement of seawater from the oceans producing a rise in sea-level. Both the rifting and this process caused the transgression of Jurassic marine deposits over Permo-Triassic, desert red-beds.

Also above is a simplified palaeogeographic map showing the generalised distribution of sea and land in the British area during Early Jurassic times. The southern part of the Atlantic Ocean was opening to the southwest, but the North Atlantic was not open at this time. Shallow shelf seas with some locally deeper basins occupied much of the British region. This map is to set the scene in broad terms and the details varied at different times within the Early Jurassic. The southwest peninsula was probably the landmass from which the tree remains in the Lias of the Lyme Regis and Charmouth areas have come. There is uncertainty about whether Wales was completely submerged or whether there was land in the area. Because of a general later tendency for Britain to tilt eastward towards the North Sea basin, the London-Brabant (or London-Belgium) Uplands are now below sea-level and buried under younger sediments. As this area of Palaeozoic, hard-rock hills has gone down with the tilt so the Palaeozoic area of the Welsh mountains has come up in the west. The London-Brabant uplands are mostly at about 500m depth in the London area but rise to within 50m of sea-level in North Buckinghamshire.

The Lower Jurassic (Liassic) sea was continuous between the Dorset coast, where the strata are now very well-exposed, through the Midlands to the Yorkshire coast, which is also notable for excellent exposures. There are smaller Lower Jurassic outcrops elsewhere, particularly in South Wales and in northwest Scotland (Skye etc.)

2. STRATIGRAPHY continued:

Lias - Depositional Conditions

The Blue Lias differs from most other parts of the Lias of Dorset in containing much carbonate. Lignite is common at certain horizons and this indicates that the forested land was not far away. This is supported by the occurrence of Pterodactyls in the Lias (Lang, 1914). The sequence is not thin compared to other localities and deposition was clearly at a fair rate. For more on depositional rates, though, see the literature on cyclicity (e.g. House, 1985, and Weedon et al., 1999).

2. STRATIGRAPHY continued:

The Cliff Section

In these cliffs east of Lyme Regis to Charmouth there are very good section of the Lower Jurassic Lias, mostly clays and shales with some carbonate beds. Church Cliffs, immediately northeast of Lyme Regis. Members of a oil company field trip are seen assembling at Gun Cliff, at the seafront just east of the centre of Lyme Regis. It was not very different in April 1889, except that the sea-wall had not been built then: - "Proceeding ..through the town to the Gun Cliff, the Members passed Mrs. Dollin's famous fossil shop, the door of which stood inviting open. A hurried glance was taken at the many specimens presented to view, and a promise made to return to this emporium... "

Image above: Beyond here, eastward, the Blue Lias Formation, the cyclical basal unit of the Lias Group, is exposed at Church Cliffs. As mentioned above, at low tide and in favourable conditions it is possible to walk eastward to Charmouth continuing from Church Cliffs to the area of the Spittles and along the foot of Black Ven. This high land-slipped and boggy cliff has mudslides (mudflows) which project into the sea at the base. The beds in the cliffs above contain many fossils including ammonites and specimens can be brought down in the landslides and be washed out on the beach. The older mudslides can usually be crossed by a path, and beyond near to Charmouth there is a good, clean, accessible cliff exposure again. This continues to the old cement factory at Charmouth, now a cafe, a fossil shop and a heritage centre. There is a car park here and a road back to the village of Charmouth.

The cliffs, here, are famous because here Mary Anning found vertebrate remains about 200 years ago and here, too, in the early days of palaeontology, Hawkins quarried the cliffs for "sea dragons", the remains of ichthosaurs and plesiosaurs (Hawkins, 1834).

2. STRATIGRAPHY continued:

Strata and Cross Section in Black Ven

Viewed from a distance the most notable aspects of Black Ven are greyish Liassic clays forming the main part, with brown oxidised Cretaceous, Gault and Upper Greensand strata at the top. This uppermost part should mainly be green and glauconitic, like the Upper Greensand elsewhere. High on a cliff with oxidising meteoric waters running through it, within the vadose zone, the ferrous component of the iron in the glauconite has been oxidised (effectively rusted) to a brownish yellow colour. Further down in the section the pale grey coloured Belemnite Marls are conspicuous. Springs above them result in rivulets of water down the face of the cliff of these marls. Lower down much of the cliff is obscured by mud-slides.

---

3. BLUE LIAS FOSSILS continued: (Just a few examples)

[NB: The giant ammonites of the Blue Lias have been referred to in the past as species of "Coroniceras" or as species of "Arietites". This website does not make any claim to be a taxonomic study and it has been written at various dates and modified at various times and labelled photographs have been added at various dates. It should not be relied on with regard to which is the currently correct generic name; this is not really likely to cause any confusion.]

.

.

.

The large ammonite Coroniceras bucklandi or Arietities bucklandi can hardly be missed during a visit at low tide to the shore in front of the cliffs east of Lyme Regis (although better seen to the West at Chippel Bay). It is most conspicuous in the Top Tape (bed no. 29). It is present in the lowest zone - Arietites bucklandi of the Sinemurian and is the first giant ammonite to occur in the British Jurassic succession. A prepared specimen is on display at the end of the new (2015) eastern sea wall, and this also shown above.

Other giant ammonites in the Jurassic include Gravesia in the Kimmeridge Clay and Titanites in the Portland Stone. Gravesia in Dorset has lived in rather similar environmental conditions (argillaceous sea floor) to those of the Sinemurian Blue Lias.

Gryphaea arcuata

In an argillaceous limestone of the Blue Lias at the foot of Church Cliffs examples can be found of the "Devil's Toenail". This is Gryphaea arcuata Lamarck, once more commonly know as Gryphaea incurva, an oyster-like bivalve adapted to the muddy conditions of the Liassic sea-floor. These shells are seen at the top of a stone band and have been cut through by some sea erosion of the ledge. This small but robust mollusc, Gryphaea was an epifaunal (i.e. non-burrowing), suspension feeder (feeding on minute suspended animal life etc) that in adult life lived reclining on the sediment surface. Notice how the larger valve is downwards resting on what was once soft mud. The shell is now of calcite and probably always was, rather than aragonite. It is thicker in the umbo region. Note that the shells are in place here and would be classified as a life-assemblage. The sea-floor was presumably below storm wave-base. The presence of a benthic fauna here shows that at the time of deposition of this bed the sea-floor was not anoxic (it is something that the association with bituminous shale might have suggested). The genus Gryphaea had a range from late Triassic to late Jurassic, but this species was typical of the Lower Lias and is very widespread.

For more on Lyme Regis fossils please see the Liassic Fossils webpage.

---

Pentacrinites (Pentacrinus, Isocrinus) (See also Liassic Fossils webpage).

In certain beds of the Blue Lias succession, Lang (1924) has recorded ossicles of the crinoid - Pentacrinites (Isocrinus or Pentacrinus in the old literature). Beds mentioned as containing the remains of this benthic organism include: 22d (Mongrel Shales), 30a (Third Quick Shales), 32g (middle of the Gumption Shales, with Isocrinus (Pentacrinus) tuberculatus Miller, 41 (B92) Second Bed (a limestone). Of this listed occurrences only one, that in the Second Bed, refers to a limestone, although one without ammonites listed. The photograph above shows abundant coarse-ribbed ammonites (i.e. like Coroniceras). Note that of the above occurrences, Bed 30a (basal Third Quick Shales) is immediately above the Top Tape (29 or B80). Therefore it is quite likely that the photograph shows the top surface of the Top Tape, although this is not proven.

It is interesting to note that Pentacrinites often occurs with Gryphaea arcuata, although the oyster is more widespread than the crinoid. The co-occurrence is presumably the result of sea-floor conditions favourable for benthic faunas.

---

---

4 LOCATION:

Starting from Lyme Regis

Lyme Regis is a small and old town that lies on the coast in a clay valley between two spurs of Chalk and Upper Greensand (see map below). The valley is drained by the River Lim (or "Lime") from which Lyme Regis derives a part of its name. From about the year 900 Lyme became a town of some importance in the reign of Henry III, when it was known as "Nether-lym supra mare", in distinction from Up-lym (Uplyme). In the reign of Edward I the manor came to the crown and, as the King's demesne (manorial estate), the "Regis" was added and the town assumed its present name Woodward, 1889. The town and the river valley is in a syncline of Liassic clays (Shales-with-Beef and Black Ven Marls) with cliffs of the harder Blue Lias limestones and shales on either side. Lyme Regis is in a small bay between Church Cliffs on the east and Chippel Bay cliffs on the west. This bay corresponds to the area where the soft Liassic clays come down almost to sea-level. With the clays under the town there are many, serious problems with landslipping and some destruction of property has taken place.

Lyme Regis was once a industrial place, a port with much sea-fishing and a place where there was quarrying of the cliffs for limestone for cement. When major fossil discoveries were made about 200 years ago the town became famous for these. Now it is a small tourist place, still with an antique and historic atmosphere. It is characterised by narrow streets and many fossil shops.

Looking east across the centre of Lyme Regis, in the evening, from the Red Lion Hotel is St. Michael's Church which has a graveyard containing the body of the famous fossil collector Mary Anning and some of her family. The cliff area which we are going to see is to the southeast and is named after this church. High above the town of Lyme Regis to the northeast the top of Black Ven is visible, with the yellow, weathered Upper Greensand forming an upper scarp. We will discuss the route eastward along beach at the foot of this cliff.

Here is a view looking down a little further to the right of the church, with the first drops of rain falling from a storm approaching from the north. You can start at low tide or a falling tide from the old seafront area here at the centre of Lyme Regis, - Gun Cliff, where the small stream enters the sea. The little tower of the Guildhall is visible above the house roofs. The house (fish bar) seaward of the the Rock Point Inn is now protected by sea-defences. In this area there are interesting fossil shops and a museum.

More information on Lyme Regis geology is in the Lyme Regis, West Webpage.
For fossils please see the Liassic Fossils Webpage.
Publications on the area are in the Lyme Regis Bibliography Webpage.

.

4. LOCATION continued:
BROAD LEDGE

(Southeastern Lyme Regis)

.

The aerial photograph above shows the geological structure at low tide in the area from Broad Ledge, just southeast of the town of Lyme Regis, to the Church Cliffs area. However, note that this is an older composite aerial photograph, prepared in 2006, and since then (in 2015) a new sea-wall and promenade has been built here. [Aerial photographs including the new structure are not yet available, but, obviously, the geology is the same.]

.

Broad Ledge is a large, low-tide, outcrop of a stone band in the Blue Lias. About 500 years ago in the early days of Lyme Regis this would have been at least half a metre higher in relation to sea level. There has been much sea erosion in addition to rising sea-level, so it was probably an old promontory of the town, much resembling Broad Bench at Kimmeridge Bay.

The structure is a broad and gently anticline. The ledge is mostly composed of the Third Quick of the bucklandi part of the succession (Lang, 1924). Note that this is the "Broad Ledge" of the Ordnance Survey maps and of Lang and well-known as such. [It is not, however, the "Broad Ledge" of Wright (1860), which is actually Table Ledge (53), much higher in the succession (semicostatum Biozone).]

The Third Quick was described by (Lang, 1924). It can recorded briefly as follows:

Third Quick. Argillaceous limestone or "cementstone", probably microsparite. Lang bed no. 31 (equivalent to De la Beche (1826) bed no. B.82 and Woodward (1906) bed no. S.35). Thickness 0.3 metres approximately (1 foot). Persistant limestone full of Liogryphaea (i.e. the well-known, shallow-water, pterioid bivalve Gryphaea arcuata, the "Devil's Toenail" etc)

Broad Ledge does not give a very good exposure of this bed, even though the surface area is quite extensive. The ledge has barnacles and Patella, the limpet on much of it. The lowest part is covered in seaweed. At high tide most of it is covered by water.

At the edges of the ledge the Third Quick Shales are exposed (Lang bed 30, De la Beche B.81, Woodward S. 35). Faunal records (Lang, 1924) include Coroniceras cf schloenbachi, Ostrea irregularis and Gryphaea arcuata and Gryphaea sp.

It is interesting to observe that the limestone of Broad Ledge is undercut by bioerosion. Boring molluscs have penetrated the underlying shale but not the argillaceous limestone. "Tables" are a result of this undercutting Better examples were once developed from another bed on the foreshore opposite the town of Lyme Regis. The Shales-with-Beef bed "Table Ledge" (Lang bed 53) takes its name from such a table; because of quarrying and sea-defences tables of Table Ledge are not visible now.

At the edges of Broad Ledge there are rock pools. A notable inhabitant of these is the Snakelocks sea anemone, Anemonia viridis. This contains symbiotic algae, zooxanthellae, and thus requires good light conditions in the sea. It is quite conspicuous and the tentacles are green with purple tips. It possesses stinging cells and can produce a rash on the skin so it should be left untouched.

4. LOCATION continued:

CHURCH CLIFFS AND EAST CLIFF - General

This picture shows Lyme Regis town as seen from the Cobb. Notice St. Michael's Church near the centre. On the right hand side of the photograph is a sea wall (running roughly west to east) with a grass slope above it. Church Cliffs are in the embayment behind this small point or headland and continue into the dark cliffs at the foot of Black Ven (far right). Church Cliffs cut back to the churchyard of St. Michael's Church from which they take their name.

Above is an older photograph (2004) of Church Cliffs, with an old sea wall extending SSW-NNE and protecting the eastern part of the town. This sea wall is not shown on the old map below.

.

.

These eastern cliffs of Blue Lias have long been noted as a site of major coast erosion, which is, of course, the reason for the presence of the sea wall. New sea defences are to be constructed (and they are unlikely to be popular with geologists). Further to the northeast, towards Black Ven, there are no sea defences and fortunately there is still an excellent section in the upper part of the Blue Lias (bucklandi Zone).

De Luc observed that in 1805 the 'cape' on which the church at Lyme Regis stands was crumbling away into a series of steps, and he was then told that a large area of land, including some gardens, had been lost on this site. The cliff collapsed in broad strips, which had become detached by fissures and had successively slidden down the slope to the bottom. He suggested various protective measures, none of which was adopted.

4. LOCATION continued:

Church Cliffs and East Cliff in 1890 and 1900

Mr. Horace Woodward, F.G.S., on the shore here on 19th April 1889, explains the erosion of these cliffs -
"The Members [of the Geologists' Association] now descended to the beach below Church Cliffs, near the edge of which stands the parish church, whose churchyard has been to some extent curtailed. Attention was now directed to the great destruction of the cliffs at various points along the coast, caused mainly by gradual crumbling and landslips, while the sea has cleared away the fallen masses. George Roberts mentions that in 30 years, between 1803 and 1834, ninety feet in breadth of the Church Cliffs were lost, while a lane that led to Charmouth has for the most part slipped away to sea. But in this case man has not been free from blame, for Roberts mentioned that "thousands of tons of limestone, the very ledges around our shore," have been shipped off, and he feelingly remarks that "a ledge, within a few feet of the eastern jetty, has actually been broken up, and the Table-rock and Horse-pond, names familiar to the natives of Lyme, and which bring fond recollections and associations of youth, are no more."

4. LOCATION continued:

Church Cliffs and East Cliff continued

The Blue Lias sequence at Church Cliffs is still accessible at the northeastern end, but only providing the tide is low. It consists of alternating argillaceous limestones and shales with ammonites, bivalves, brachiopods and other fossils. The sequence above the Brick Ledges (see details below for position of this) is well-exposed. The most conspicuous bed, high in the cliff, is Table Ledge which marks the top of the Blue Lias. A sloping profile of Shales-with-Beef lies above and a little further east is the Spittles area where the bitumous shale burnt as the Lyme Volcano in 1908, a subject discussed further below. Although there has been extensive natural erosion there has also been much quarrying of the cliff here of the argillaceous limestone for cement manufacture. This was still continuing as late as 1913 according to Lang (1914). He commented on bed 25, the Top Copper, which is present at the foot of Church Cliffs:
"Calcite and iron pyrites veins are characteristic of this limestone. Large slabs of it were exposed close to the cliff on the north-eastern slope of Church Cliffs anticline (1913); but the quarrymen were busy breaking up the ledges, and probably this has suffered with the rest."

The bedding in the good cliff exposure at the end of the Church Cliffs sea wall is horizontal. It marks the crest of an anticline because the Second Quick, above, dips west in Long Ledge and east in Snags Ledge. See Lang's map above for the details. This fold, the Church Cliff Anticline, causes the lower limestones to form a ring-like outcrop on the shore about 300m northeast of the church. Lower beds of the Blue Lias down to the Brick Ledges are brought up in the core of the anticline in the cliffs, but are much obscured by shingle and debris.

The exposures are excellent at the northeastern end of Church Cliffs and beyond to the Spittles, in favourable tide and cliff conditions one can walk eastward to see progressively higher horizons. Where the steep cliff gives way to the slumped slopes of Black Ven, the top of the Blue Lias descends to the shore. Here Table Ledge, the highest bed in the Blue Lias is present in faulted condition at Black Ven Rocks. Details at the foot of Black Ven, however, can be obscured quite badly by the toes of mudslides.

Some further information is given about the tidal hazard of Church Cliffs. As noted above, with regard to safety, this eastern route along the foot of the cliffs from Lyme Regis should not be undertaken without good knowledge of the tides on that day, and providing that the sea is not rough. Rising tide and wave action can at times make this traverse very dangerous. Photographs above show the low tide conditions in calm weather; this can be very different on other days. Legg (1999, p. 125) gives an account of an incident at "Black Beach". It is not certain that this refers to the beach shown but it seems very likely both from the description and because this is the main stretch of coast near Lyme with serious tidal problems.

At 6.52 pm on 11 September 1984 the lifeboat station at Lyme Regis was informed that some people, apparently picnicing, had been cut off by the tide at Black Beach groynes and there were bodies in the water. The wind was northwesterly force three or four with a slight sea. High water was due in two hours. The lifeboat was launched but the groynes were causing the sea to break in waves of eight to ten feet high. Three persons and a dog were stranded at the head of the groyne on stone steps beneath the sea-wall, and could not move because of the depth of the water below them and the height of the sea-wall above them. Two men and a woman were rescued. A dog was pulled up the wall on the leash by a policeman. The bodies of a man and a woman were recovered from the sea. The helmsman of the lifeboat, John Hodder, subsequently received the Royal National Lifeboat Institution's bravery award and crewmen received letters of appreciation. For a more complete account of this tragic accident see Legg (1999) .

This stretch of coast will be in different conditions at different times and on different days. Thus tide, timing, weather, sea-conditions and exit routes need to be assessed on the particular occasion of a visit. If the conditions are unfavourable here then the western coast of Lyme Regis, or Charmouth - Stonebarrow warrant consideration as alternatives. Note that high tide and bad weather may sometimes, though, drive geologists too close to unstable cliffs at any of these places, and individual assessments of the hazards need to be made on the day.

4.LOCATION continued:
WESTERN, LYME REGIS END:

Church Cliffs and East Cliff - Blue Lias Succession

[BLUE LIAS LOG OF STONE BEDS]

This log of the sequence and particularly the stone beds within the Blue Lias at Lyme Regis is based, with modifications on the classic work of Dr. William D. Lang, D.Sc., F.G.S. in 1914 and 1924. Photographs shown here can be related to the log. It should help recognition of the named (and numbered) beds of the Blue Lias and to enable specific fossil horizons to be located. It is not intended to give full and precise sedimentological details, merely to be some basic guidance for use in the field. The "shale" units are generalised, not distinguishing between blocky, conchoidal marl (calcareous mudstone) and bituminous shale. Nevertheless, because there are so many beds, it is necessary first to recognise some of the main argillaceous limestones, before commencing detailed work. The notes on beds and the fossil listing in the diagram should help in this respect.

The listing by Lang, used here, was not the original. Wright (1860) published a vertical section a listing of Blue Lias beds with details is in the old memoir of Woodward and Ussher (1911). Lang's work is an improvement on this, particularly with regard to ammonite zones. For the diagram given in the present webpage the strata have not been remeasured but there is some partial updating from House (1985; 1993). Further corrections and improvements will be made on the basis of fieldwork when time permits.

The limestone names originate from the quarrying for cement during the 19th Century and beginning of the 20th Century. There was a cement factory at Charmouth (now a cafe, shop and heritage centre) and another at Monmouth Beach, west of Lyme Regis from 1850 to 1914 (Thomas, 1993). The limestones in the cliff were found to be a useful base for hydraulic cement (quick drying in marine conditions). The origin of the names of some of the quarried beds, such as Third Quick, Venty, Rattle, Top Copper and Iron Ledge can be guessed at. Others such as Glass Bottle are not so obvious (but "a cave has been discovered on the cliffs to the west of the town with some broken fragments of old French brandy bottles" - Anon., undated). Skulls refers to nodular, irregular, concretionary beds, to some extent resembling Chalk flint nodules in shape. Table Ledge presumably takes its name from the "Table Rock" that was original present on the shore at the eastern jetty of Lyme Regis (the synclinal structure takes the top of the Blue Lias down to near beach level at the Esplanade). Unfortunately, this shoreline feature (Roberts, 1834) was broken up long ago by coastal quarry workers (Woodward and Ussher, 1911).

The thicknesses given in Lang (1914) are approximate. The paper is on the Charmouth side of Lyme Regis so the thickness presumably apply to Church Cliff and East Cliff. His 1924 paper gives more precise figures but they sometimes differ appreciably from the earlier estimates. Lateral changes are probably largely responsible and the details are unlikely to be the same at Monmouth Beach and Church Cliffs. In any case, some beds are impersistent. The zonal schemes of Lang have been modified. Used here are the zones as given in House (1993).

For some of the fossils listed in the log please go to the Lias fossils webpage. From time to time more fossils will be added to that page. There have been some changes of names since the publications of Lang. To some extent the list has been updated, but not necessarily completely so. Note that Coroniceras bucklandi is now Arietites bucklandi (in the very early literature it was Ammonites bucklandi); in some cases a particular oyster Ostrea may be now Liostrea; the bivalve formerly reported as Gryphaea incurva J. Sowerby is now Gryphaea arcuata Lamarck; records of Lima refer to Plagiostoma; some species of what was formerly just listed as Rhynchonella may belong to Calcirhynchia (e.g. Calcirhynchia calcarea S.S. Buckman)

Note that although also found further down in the sequence, most ichthyosaur and plesiosaurs in the Blue Lias have come from the Sinemurian bucklandi zone, that is within the upper part of the Blue Lias.

Labelled photographs showing the upper part of the Blue Lias at the western part of Black Ven are provided above. These have the traditional bed names added and this should facilitate recognition of the major units.

4. LOCATION continued:
WESTERN, LYME REGIS END:

Church Cliffs and East Cliff - Blue Lias Cyclicity

As shown in the cliff photographs above, the Blue Lias seems to show a cyclical pattern of marls, bituminous shales and limestone. Here is a small sequence in more detail, as shown in a photograph taken at Church Cliff or East Cliff in 2011. This shows the very base of a cycle - represented by the top of a limestone bed, then a thin calcareous mudstone or marl, then highly-laminated bituminous shale, then a thin transition up into less bituminous marl (or mudstone), and then nodular argillaceous limestone (cementstone).

An idealised scheme for the cyclicity in these beds i given above. The details have been much discussed in the past. Only the broad outline is given here, based on the work of Hallam (1960) and Sellwood, Durkin and Kennedy (1970) with some modifications. See these papers for more details. Some features of the photographs which follow can be related to particular parts of this cyclical scheme. You may wish to examine the images carefully to see whether the sedimentological and faunal details tie in with the diagrammatic scheme.

The topic of apparent cyclicity in the Blue Lias is much complicated than appears and there have been quite a number of recent papers on the topic.

In particular, read Sheppard, Houghton and Swan (2006). This paper deals with the sequence in South Wales, rather than Lyme Regis, but is very informative and has a good discussion of previous literature. These authors found that statistical analysis showed no evidence of cyclicity. They concluded that the beds of lime mud in the Blue Lias of Nash Point were the consequences of episodic storm action on a hemipelagic shelf, and that diagenetic differentiation was 'steered' by this episodicity and not by orbital control.

Uncompacted ammonites ( probably Arietites) in a limestone bed. The lack of compaction is due to early cementation, a common feature of many limestone beds and septarian nodules.

Details of erosion by the sea of the centre of an uncompacted ammonite are shown above. The eccentric Reverend William Buckland placed an ammonite like this over his head and rode away from the Lyme Regis cliffs on his horse.

Major evidence for a primary cyclicity, as opposed to a purely diagenetic, are ichnofossils. Shown here are the large, branching, decapod burrows - Thalassinoides and the smaller, fine tubular, branching tunnels of sipunculoids - Chondrites. This slab has presumably been inverted and the base of the bed is visible. The burrows in this case place limestone in marl, most of which has been eroded away. Notice that some Chondrites burrows cut across Thalassinoides burrows. Small white, hollow shells of the rhynchonelled brachiopods are present. These are Calcirhynchia calcarea.

The cyclicity in the Blue Lias has been studied by time-series analysis of the sediments by (Weedon et al., 1999). Those authors concluded that the dominant cyclicity British Rhaetian to Sinemurian was of Milankovitch orbital-obliquity type. These cyclical changes in the Earth's orbit take place every 38ka (thousand years). It should be noted, however, that that interpretation depends largely on the accuracy of absolute dating and of correlation for the Lower Jurassic. It therefore needs to be considered with caution until confirmed by the use of more fixed dated horizons. Taking it for the moment as correct, then it is interesting in the field to think of the time involved from the deposition of one limestone to the deposition of the next as approximate 38 thousand years. This provides some sort of time-frame to discuss sedimentation (and should it be wrong then the next most likely cyclity is the 20ka orbital precession type).

The large ammonites - mostly Arietites bucklandi, formerly known as Coroniceras, occur particularly in the upper part of a particular cementstone bed, No. 29, the Top Tape. The ammonites are not compacted but are in "solid" condition in the stone bed, but in the adjacent shales ammonites are compressed. In the same bed there are large Thalassinoides burrows, probably made by shrimp-like crustaceans, are shown together with much smaller, branching, feeding burrows of Chondrites. Notice the small white shells of brachiopods (Calcirhynchia calcarea but listed in the old literature as Rhynchonella calcicosta ). The paired valves, have resisted compaction and are partly hollow and partly contain white calcite. They occur particularly in the area of the Mongrel from Under Copper, through Iron Ledge, Specketty, Mongrel to Top Copper Shales. This is the lower part of the bucklandi Zone of the lower Sinemurian Stage.

The early diagenetic stage of development of the Blue Lias stone bands involved septarian-type nodular cementation. In this common phenomenon there is growth of the nodule by continued growth of the individual calcite crystals of which it is composed. This mainly happens in the peripheral part. This peripheral expansion causes fossils to be expanded like this Plagiostoma, in one of the stone bands at the foot of Church Cliffs (for more see the webpage: Lyme Regis - Westward). The expansion in this case has been somewhere near 10 percent. See the old paper of Todd on this subject, and the more recent work of Bellamy . Surprisingly, desiccation or water-loss underground has sometimes been put forward as an explanation of septarian nodule cracking. Desiccation under water (i.e. below the water-table) and from the inside out is not only extremely improbable but it certainly does not explain "explosion of fossils". The peripheral expansion theory explains all the commonly observed features..

4. LOCATION continued:
WESTERN, LYME REGIS END:

Church Cliffs and East Cliff - Nautiloid

Shown above is a typical nautiloid is in a cementstone block loose on the beach at the foot of Church Cliffs. It is not a good specimen and has lost details of the shell. This is the normal condition in which remains of these cephalopods are found. The block will only have been subject to limited wear and rounding whilst on the beach. The matrix is sand and it has not been battered much by pebbles. The shell stands in relief above or below the level of the surface of the stone band. It is uncompressed and the chambers have been filled with carbonate sediment. For illustrations of cleaned, prepared, fossil forms see the Nautilus section in the Lias fossils webpage.

For information on living nautiloids see: Chambered Nautilus. See also: The Nautilus Report.

4. LOCATION continued:
WESTERN, LYME REGIS END:

Church Cliffs and East Cliff - Beach Pebbles and Sand

Boulders on the beach at Church Cliffs and elsewhere further east towards Charmouth consist mostly of slabby, light-grey, Liassic limestone and with some more spherical or ovoid "Cowstone". The latter is brownish-green, carbonate-cemented, Upper Greensand, often with some fossils, which has fallen from the Cretaceous of the top of Black Ven etc. (Lang, 1914). It is greener and grittier than the smooth grey limestone. Where shingle is present the larger pebbles are of Lias limestone and the smaller material of Upper Greensand chert, which although very hard, is splintery enough to break up readily under the action of the waves. Many medium-sized Chalk flints also occur. The photograph, taken near the western end of Church Cliffs at low tide, shows particularly interesting components, hard liver-coloured, quartzites from the Triassic, Budleigh Salterton Pebble Bed in Devon, where locally they are known as "popples" (Note also the brown Fucus etc., the brown stipe and holdfast of Laminaria near the pen and the green Ulva seaweed, torn off the Lias limestone ledges by storms.) These distinctive, resistant rocks have arrived, already well-rounded and usually of flattened, ovoid shape. Their presence at Charmouth has already been recorded by (Lang, 1914). In the past they have travelled further east by long-shore drift (see Bray, 1992) and are abundant in the Chesil Beach. He noted that with them are dove-grey Devonian limestone pebbles with dark-red veins. Much of the material has probably been naturally transported, but he warned that fisherman have in the past ballasted their boats with pebbles and moved material along the coast.

This mention, here, of beach gravel is only in general terms. A very thorough, quantitative study of beach material and its source and transport has been made by Bray (1992), and reference should be made that publication for more details, particularly of supply by coastal erosion.

Beach sand is capricious in its appearance and distribution. Table Ledge beneath Black Ven has been at times covered by sand and at times the indurated marl has been clearly exposed (Lang, 1914). Mud-slides may also cover it. There is always some sand at low tide beneath Charmouth beach proper, and generally a fair amount east of the river mouth, where the shingle is small. The sand, however, diminishes in quantity further east and the shingle becomes larger. Lang commented that there is a steep pebble beach beneath Westhay Water, that becomes still steeper with larger pebbles at St. Gabriel's Mouth, making landing from a boat difficult except in the calmest weather.

4. LOCATION continued:
WESTERN, LYME REGIS END:

Church Cliffs and East Cliff - The Saurian Shales

[Note: Unfortunately, sea defence works, both the older and the new have been built over part of the exposure of the Saurian Shales, in the Church Cliffs area, just east of Lyme Regis. Ichthyosaur remains can be found elsewhere from time to time, but this is one good exposure that has partially, at least, gone to concrete.]

.

(For more illustrations and details of ichthyosaurs go to Ichthyosaurs, Introduction section of the Lias Fossil Webpage . For plesiosaurs go to the Plesiosaur section.)

The Saurian Shales and adjacent strata belong to the Zone of Arnioceras semicostatum (turneri Zone in the old literature). They are of special interest because of their reptilian, fish and invertebrate fossil content.

Lang (1924) reported the Fish Bed Shales as 0.76m thich (2ft, 6ins), the Saurian Shales as 2.92m (9ft, 7ins), and the Table Ledge as 0.3m (1 foot). These are the units which make up the semicostatus Zone, and it is a thin zonal unit compared to other in the Lower Lias (Wright (1860) gave greater figures which may be inaccurate. He listed the combined Fish Bed Shales, Fish Bed and Saurian Shales as 18 feet, and the Table Ledge (his "Broad Ledge") as 3ft, 6ins.)

Wright did not list the fish, but recorded from the semicostatum Zone the other fossils (partly in the old names, but updated where obvious) as below:

Ichthyosaurus platyodon, (in the Natural History Museum, London)
Ichthyosaurus intermedius, (in the Warwick Museum)
Ichthyosaurus communis, (in the Natural History Museum, London)

"Ammonites" turneri,
Arnioceras semicostatum,
"Ammonites" bonnardi,

Turbo,

Lima punctata,
Plagiostoma gigantea, ("Lima gigantea")
Lima pectinoides,
Cardinia ovalis,
Ostrea,
Avicula,
Pecten textorius,
Pecten glaber,
Astarte consobrina,
Crenatula,
Plicatula,
Gervillia lanceolata,
Gryphaea obliqua,

Cidaris edwardsii,

Pentacrinus tuberculatus.

(In addition - Fish)

Most of the fossil fish from the Blue Lias come from the Fish Bed and the Fish Bed Shales near the top of the Blue Lias, and just below the Saurian Bed.

For a listing of fossil fish from the Lower Lias at Lyme Regis, although not necessarily from this bed, see the Fossil Fish section of the Liassic fossils webpage.

A brief reference to fish was made by Horace Woodward (1889) in an account of a field excursion to Lyme Regis:

"Remains of Fishes are also abundant, although their horizons are not so well known. They include species of Acrodus ("fossil leeches"), Hybodus, Eugnathus, Lepidotus, Aechmodus, and Pholidophorus, many of which occur in the zone of Ammonites obtusus.

4. LOCATION continued:

Church Cliffs and East Cliff - Coastal Protection Scheme - New Sea Wall (in 2015)

.

.

.

.

.

.

.

4. LOCATION continued:

Church Cliffs and East Cliff - Coastal Protection Scheme - History

West Dorset District Council has applied to DEFRA for funding to investigate the construction of sea defences at Church Cliff. The following is from information released in 2005.

See:

West Dorset District Council 2005. 26/07/05: Funding good news for Lyme Regis. (with aerial photograph). Dorsetforyou Website )
With coast protection and land stabilisation work under full steam in Lyme Regis, funding has already been secured to start planning the next phase of work to protect the town. The Department for Environment, Food & Rural Affairs (DEFRA) has approved 1 million pounds funding for preliminary design work at the eastern end of the town in East Cliff and Church Cliff. DEFRA will pay 65 percent of the costs with West Dorset District Council meeting the rest of the costs. District council Leader Robert Gould says: "I'm delighted that DEFRA have agreed to support costs to start planning the next phase of work in Lyme Regis. This money will allow us to see if a scheme is feasible in future years. That includes producing design options, consulting with local people as well as other groups and, not least, securing more funding to actually implement the scheme. In the region of 170 properties plus road and amenity land are at risk from coastal erosion and landslides in the eastern part of the town. The preliminary design work will critically evaluate earlier studies plus update ground, geological and environmental models to assess change. It will prepare options to protect the coast, property as well as the natural environment - which makes the area so attractive to locals and visitors alike. Initial steps will be to commission collection of new data with a high and low level fly past taking detailed photographic images of the coastline from the air. It also includes a laser scan of the beach, cliffs and landslip areas - similar to a supermarket bar code reader collecting a detailed picture of the ground profile. The preliminary design will be led by West Dorset District Council's engineers based at offices on the Cobb in Lyme Regis. Regular updates will be available from the council's coastal scheme information centre on the seafront and this website.

Since that date a geological survey has been undertaken by Dr. Ramues Gallois.

Coastal Forum Meeting re: Church Cliffs

A Coastal Forum Meeting was held on the 8th June 2006 (The minutes are available on the internet).

An important point in this document is that ground investigations and monitoring had indicated surface movement of 9.5m in the East Cliff area directly below Charmouth Road car park during the last 10 years (see image above). [On the 7th May 2008 there was a major landslide a short distance to the northeast of this area at the Spittles, and this is discussed elsewhere on this webpage. Is there therefore some risk now of a similar landslide taking place below the Charmouth Road car park?]

The minutes contains information on the proposed Phase IV of the Lyme Regis sea defence works. Surveys had been undertaken of the existing sea wall and compared with those previously taken in 1984 and 1996. Surveys had been undertaken of the foreshore, cliffs and properties in the East Cliff and Timber Hill areas. High Point Rendel had been appointed at lead consultants for Phase IV. Monitoring data had been collated. The geomorphology data had been updated and compared to 10 years ago. The exposure in the Ware Cliff, Church Cliff and East Cliff area had been logged. The foreshore had been profiled using a laser scanning technique.

Work to be undertaken during the coming months is listed: Evaluate monitoring instruments and investigations data. Update environmental and ecology studiesj. Undertake further investigations. Develop a consultation process. Validate the ground model. Landslide and stability analysis. Outline design of possible solutions.

The Outline Programme:
1. First stage review complete
2. commence preliminary design work
3. present possible options - late 2006
4. develop preferred options
5. planning application - late 2007
6. application for construction funding
Issues to face:
1. English Nature - Natural England
2. DEFRA - Environment Agency

.

4. LOCATION continued:
WESTERN, LYME REGIS END:

Spittles Area, Northeast of East Cliff

The "Lyme Volcano" (Burning Cliff)

Further east, towards the eastern end of the Spittles, the bituminous shale in the cliff was on fire from spontaneous combustion in 1908. This was the "Lyme Volcano" or the "Burning Cliff". This fire took place in a landslip debris on a terrace in the Shales-with-Beef above the cliffs of Blue Lias. (For more information see the Lyme Burning Cliff webpage.)

Although organic matter may not be as abundant as in the Kimmeridge Clay, it is in sufficient quantities here for spontaneous oil-shale fires. The fire in in 1908 took place in a mound of fallen debris on the Shales-with-Beef at the eastern end of Church Cliffs, on a terrace above the first lower cliffs, the sea-cliffs. This is the site of the major landslide of the 7th May 2008, discussed below.

The cliff fire was started by the exothermic reaction of the oxidation of pyrite, and burning for months became known as the 'Lyme Volcano' (Woodward, 1908 ; Jukes-Browne, 1908; Lang, 1909 ). Clouds of smoke with foul sulphurous fumes were produced and the shales were burnt to the appearance of red tiles. An interesting photograph of this is published in Ensom (1998, p. 22). Similar fires occurred at Charmouth in 1751 and Golden Cap in 1890. Steaming cliffs but no visible fires were reported at Charmouth in late 1987 and early 1988 (Ensom, 1998). Pulverised limestone, iron pyrites mixed in clay and buried for a year or two has been shown to ignite (Damon, 1884).

The Lyme Volcano or Burning Cliff became a tourist attraction. It was said that when the 'volcano' showed signs of subsiding it was stimulated by paraffin (Woodward, 1908; Lang, 1909). See Burning Cliffs webpage for details and references). There was a similar fire at Charmouth in 1751.

The upper photograph was taken back in the 1970s or 1980s; unfortunately, the exact date is unknown. The location is above Church Cliffs near their eastern end. The view is of Black Ven on a misty day. A substantial mudslide has descended to the beach. The remains of this, eroded back by the sea, seem to be visible in the right-hand photograph taken in 2001.

The lower photograph above, a modern one from the beach, shows the Blue Lias dipping eastward in the cliffs. Eastwards the higher parts of the Blue Lias come closer to the beach. Here we see various named argillaceous limestones such as Glass Bottle and Venty that were probably used for cement at the Charmouth cement factory on the beach. Notice at the right hand side of the photograph the debris that has slid down from Black Ven has formed an apron at the base that consists of mud with clasts of chert and limestone.

The beach debris is largely chert derived from the Cretaceous, Upper Greensand Chert Beds that cap Black Ven. This buff-coloured form of chert (impure chalcedonic silica) contains sponge spicules and sand grains. It is not as fine-grained, as uniform or as dark-coloured as flint and often contains sand grains. It is relatively angular because it has not travelled far, just down the cliff.

4. LOCATION continued:
WESTERN, LYME REGIS END:

The Spittles Area, continued

Major Landslide of 7th May 2008

Adjacent to the site of the Lyme Volcano, a major landslide, about 400 metres in length, took place at about 10pm on the 7th May 2008. The cliff fall was observed by the local Fire and Rescue Service crews carrying out an exercise on the beach. The tide was high and no-one was close to the cliff fall. It produced a rumbling noise so loud that it could be heard in Lyme Regis. The fall seems to have been a very rapid collapse, with no advance warning. A strong smell from released gases was noted by observers (Morris, 2008).

Shale from the Shales with Beef, and the top shaly horizons of the Blue Lias (the F. Bed and S. Shales) slid on a low-angle shear plane over the cliff of the Blue Lias limestone and shales. The Grey Ledge and Glass Bottle seem to have formed the top of the "waterfall" over which the shale fell (the slip-plane may be a little higher at the southwest end - possibly near Table Ledge). Colluvium also came down together with brown debris from a rubbish tip (Morris, 2008). Burnt debris from the cliff fire, the Lyme Volcano, has not been identified yet, but may be present in the rubble.

The new cliff fall is located at about the same site as the 1908 landslide that caused the "Lyme Volcano". Lang noted in 1914 that even at that date there was still some debris falling from this old landslide -
"the rest is covered with talus, reinforced by matter falling from beneath the burning cliff in 1908".

The weather at the date of the landslide was relatively dry, but previously had been very wet. Arber (1941) has drawn attention to the comments of Jukes-Browne (1908). He observed that "the Lias is mostly likely to founder when a rainy period is succeeded by a spell of dry weather, during which water evaporates from fissures and is drawn out of the shales and clays, which consequently contract and move downwards, finally breaking clean away from the cliff-face behind. One such fall, in 1908, was associated with the phenomenon of a "Volcano", due to the spontaneous combustion of pyrite (Jukes-Browne, 1908; Lang, 1914).

Debris from the old rubbish tip on the cliffs near the Spittles has descended to the beach with the large blocks of shale. It is mostly fairly old, since the rubbish dates back to shortly after the cliff fire of 1908 and has probably not been in much use recently. Glass bottles are particularly conspicuous and many of these have been broken by the cliff fall. They are likely to be drifted northeastward toward Charmouth, but abrasion from sand on the beach will gradually round the fractured edges and reduce the risk of accident from them. Some car chasis are present but in bad rusted condition. Sooner or later the debris will eroded, washed into the sea and will eventually be lost in the beach sediments.

4. LOCATION continued:
WESTERN, LYME REGIS END oontinued:
Spittles Area, Northeast of Church Cliffs, continued:

Jukes-Browne's Discussion of Landslides in the Church Cliffs to Spittles Area

There is much similarity between the landslide of the 7th May 2008 and the landslide of the 10th June 1908, which is shown on the map of Jukes-Browne (1908) above. Both are at the same place and both took place in dry weather. Jukes-Browne's account may reasonably apply in many respects to the May 2008 fall. The only difference is that in 1908 the ledges were still being quarried. An important and dangerous conclusion is that major falls take place in the Church Cliffs to Spittles area suddenly and without any warning at all!

Here is part of the account by Jukes-Browne (1908).

The landslip took place about 1.15p.m. on June 10th [1908]. As above stated, Mr. Cameron was on the cliffs about an hour before it happened and he did not notice any sign of impending change. No new fissures had appeared, and no movement was taking place, while boats were busy as usual taking stone from the limestone beds at the foot of the cliff.

Eye-witnesses stated that three minutes after the last stone-boat had left, a portion of the cliff suddenly gave way, and the large mass, weighing many thousand tons, fell forward on to the beach with a loud rustling and rumbling noise, which was plainly heard in the town, while a cloud of sulphurous smoke issued from the burning mound. Othe slips and falls occurred either simultaneously of soon afterwards, and when Mr. Cameron arrived on the spot he found several changes had taken place.

The movements were not all at one spot, but had occurred at several places along a tract which was 500 yards in length. The main mass of the cliff which had fallen onto the shore was not more than 230 yards long, and this forms a long slope of debris which at high water projects into the sea and forms a promontory (see map). The terrace, or plateau, north-west of this fall was much fissured, and a large mass of black shale had fallen from the slope above and behind, forming a long ridge near the burning mound, which was itself split by a fissure.

A little later on the same day large falls took place from cliffs on the seaward side of this plateau, one of these included the seaward part or peak of the split burning mound (see Plate 3). About 50 yards east of the mound, and rather lower down a mass of clay and shale, from 50 to 60 yards long, moved forward over the more solid limestone beds, but did not fall onto the beach. No other extensive slip has yet occurred although the whole cliff between this point and Lyme Church is in unstable condition.

The causes which have specially conduced to the landslip and the falls from this portion of the cliff appear to be two, the abstraction of limestone from the shore below, and the soakage of water into the cracks which form on the slopes.

Although there is no actual quarrying on the cliff itself, yet the beds of limestone, or ledges (as the workmen call them) which crop out on the shore below are quarried with pick and bar and the stone thus obtained is taken away to the cement works in boat loads. These ledges are followed up to the foot of the cliffs, and the removal of stone must weaken the foundation of the cliff, and must also enable the waves at high water to break with greater force against it for the tide here comes up to the base of the cliffs.

This harmful practice of getting stone from the shore ought to have been forbidden long ago. Stone was formerly taken from below Church Cliffs; but this has been disallowed for many years, and the Lyme people will do well to put a stop to it everywhere.

The second contributing cause is the land flowing off the slopes above. This partly issues from springs a little above the contour of 300 feet, and partly runs a surface water after heavy rain. Above tiers of cliff and broken ground which lies below the road to Charmouth, Timber Hill rises to a height of 530 feet above the sea. After rain much water flows off the slopes of the hill, and Mr. Cameron informs me that the there are two lines of water-flow on its southern side.

One of these watercourses comes down the fields a little east of the house called Fairfield, and the water which runs along in wet weather cascades over the cliff by the old Gasworks. Another waterway runs in a parallel line about 330 yards to the eastward and loses itself in cracks and fissures on the Lias cliff above the very place where the great fall has taken place.

There can be no doubt that the soakage of water into these cracks and fissures, and its percolation downward along joints and divisional planes of the Lias, would loosen the cohesion of the parts near the border of the cliffs. Again when a period of wet weather is followed by a spell of dry and sunny weather the water lying in the fissures is gradually evaporated, and much moisture is drawn out of the Lias clays and shales, resulting in a contraction of the tracts below and between such fissures, with a consequent tendency to move in the direction of least resistance. This is, of course, seaward, just as roofing slates placed on a gentle slope will gradually move down it in consequence of alternating contraction and expansion caused by differences in temperature.

There must come a time when the tension is strong enough to overcome the cohesion of some fissured mass to the rock at the back of it, and then a fall of cliff or a landslip takes place. The movement of on slip is likely to loosen other unstable masses, and even the vibration caused by a slip or fall is enough to start adjoining masses on a downward journey; so that one fall is often followed sooner or later, by other falls. ....

[an earthquake or seismic shock theory is then eliminated]

It is important to remember that this landslip took place during dry weather. April had been a wet month, but the later part of May and the beginning of June were dry and sunny so that I think we may infer the final cause of detachment was contraction, owing to the evaporation of moisture and drying of the minerals which form the cliff.

[end of extract]

Note by the present author:

I have seen a dry weather cliff collapse of Lias clay in Stonebarrow Hill in the 1960s. I was leading a field trip in summer on a hot day in June, and heading eastward from Charmouth. Several members of the party scrambled up onto the cliffs of shale to collect ammonites. I stayed, speaking to someone, out on the beach which was wide because it was low tide. Suddenly and without any warning a stretch of cliff about 100 metres long collapsed throwing up a cloud of dust. This was alarming but, fortunately, when the dust cleared we could see this had happened just beyond, and eastward of, the people on the cliff. They were extremely lucky to be completely unharmed. After that no-one approached the cliffs. I am quite convinced that shrinkage of the clay by drying in warm weather can cause cliff falls of Lower Liassic strata, and that no warning indications take place. This is rare but potentially very dangerous! I suspect that Jukes-Browne (1908) may have been right when he wrote that:
"on the west side of Lyme the slips take place in the Lias itself: and if records of former slips had been kept, it would probably be found that most of them occurred during spells of dry weather."

LOCATIONS, CENTRAL, BLACK VEN:

Black Ven - Middle-Slope -
Belemnite Marl Cliff

.

1889 - "The Members now reached the foot of Black Ven, and having obtained the services of a local guide, they commenced to ascend the cliff. The hill rises to a height of 450 feet in places, and constant slips and changes in the cliffs render guidance advisable; indeed, the path proved treacherous in places, and some Members sank ankle deep in Lias mud. On attaining the level of the Belemnite beds only the more adventurous (including several ladies) clambered up higher to make aquaintance with the Gault, which here rests directly on the Lias." - (Woodward, 1889).

---

The third precipice of Black Ven is formed by the pale grey, cyclical, Belemnite Marls. They are clearly visible in the photograph because of the lighter colour in relation to the underlying Black Ven Marls, the faintly-banded, steep, pale-grey cliff which they produce and the water trickling down them from the Cretaceous strata above. They are capped by a thin limestone, the Belemnite Stone (with Passaloteuthis and Hastites), where this is not overstepped by the Cretaceous Gault. Although water runs down over them, the Belemnite Marls are actually more permeable than the Black Ven Marls so that springs break out at the belemnite beds. This causes the terrace at their foot to be very boggy. These fossiliferous strata are better seen further east at Stonebarrow and in the sea-cliffs below Golden Cap.

Belemnites are very abundant and on rare occasions the ink sacks have been preserved and the sepia used for drawings (Buckland, 1836). Small pyritised ammonites, near Acanthopleuroceras valdani, are common according to Davies (1935; 1956). For full details of ammonites see Lang et al (1928). They include Tropidoceras, Apoderoceras, Platypleuroceras and Beaniceras. The Belemnite Stone Bed, apart from many belemnites and ammonites has bivalves and some rhynchonellid brachiopods.

Although they had been mentioned earlier (e.g. De La Beche, 1824) the earliest thorough investigation of these strata was by Day (1863). He first named the beds the "Belemnite Beds", defined their boundaries and subdivided them on a lithological basis. He defined the Belemnite Beds as lying above the beds containing Echioceras raricostatum and including as the upper limit the Belemnite Stone. A later classic paper listing very extensive faunal details, Lang, Spath, Cox and Muir-Wood (1928).

Note that above the Belemnite Marls a wedge of the lower part of the Green Ammonite Beds, truncated by the unconformity beneath the Gault is present in the eastern part of Black Ven. It includes the nodules containing Androgynoceras lataecosta, infilled with greenish calcite, the "green ammonites" that give these clays their name.

.

LOCATION continued:
TOP BLACK VEN - CRETACEOUS:

(Note that these upper cliffs are not easily accessible from the beach or the foot of Black Ven. There quicksands or muds, and impenetrable vegetation. Furthermore, the coastal footpath to the cliffs at the top is now closed)

.

Notice, how, even in dry summer conditions, water is seeping out of the permeable Upper Greensand debris on this hill top. This water supply favours landsliding. The Belemnite Marl Member of the Lower Lias forms the almost vertical cliff underneath. This is completely impermeable. The top of the Upper Greensand in the cliff just here has been affected by Pleistocene cryoturbation.

.

Cretaceous sandy clay, sands and chert beds overstep the Lower Lias clays at a height of 98m above sea-level. The strata are Albian in age. They are generally known in simple lithological terms as the Gault and Upper Greensand, most of the sequence here being sand (Downes, 1885).

They commence with a thin basal Gault pebble bed, in which water-worn Liassic fossils occur. followed by 12m of loam and loamy sand. This is the so-called "Gault", although it is more sandy than normal. It contains a variety of fossils including the bivalves Pecten orbicularis, Lima parallela and Inoceramus concentricus. The serpulid (worm tube) Serpula concava occurs.

.

.

The "Upper Greensand" which follows has three divisions, the Cowstones below, followed by the Foxmould and the Chert Beds. The Cowstones are hard, tough sandstone concretions lying in three bands in 6m of grey sand. They contain Upper Gault fossils. Then come 21m or more of grey, yellow and brown sand, the Foxmould. This is shown in a photograph above. In the top yellow cliffs at and near Timber Hill much of the originally green glauconitic sand is weathered to yellowish brown Foxmould sand and is leached. This sand is easily seen at a distance in the top cliffs. It is not easily approached from the Lyme Regis side because of the collapse of the road and the footpath and the growth of vegetation on the debris.

.

Above the Foxmould are the "Chert Beds", now known as the Whitecliff Chert Member of the Upper Greensand Formation (see Woods et al., 2011, fig. 31 on p. 88 etc) . These are leached and decalcified so that the fractured and angular chert is loose. At the top some of the cherty material may be colluvium or hillwash.

Fragments of Mortoniceras show that both the Foxmould and the Chert Beds above are of Upper Gault age. Exogyra conica and Neitheia quadricostata are commoner fossils and are often found with the shell replaced by beekite, a rosette-like form of chalcedony (Davies, 1935; 1956).

.

.

LOCATIONS, CENTRAL, BLACK VEN:

Black Ven -
Landslides and Mudslides - Additional Aspects

.

.

.

.

An important aspect of the Lyme Regis to Charmouth coast section is the occurrence of landslide features on Black Ven. This cliff contains one of the largest systems of landslides in Europe ((Koh, 1992).

See particularly:

Chandler, J.H. 2005?. Evolution of the Black Ven Landslide. - website by Jim Chandler of Loughborough University, produced in connection with Charmouth Heritage Coast Centre. This provides access to many excellent aerial photographs of Black Ven.

For maps of the locality see Ordnance Survey Sheet 1:50,000 sheet 193, 1:25,000 sheet SY29/39, and also various larger scale maps and aerial photographs of the Ordnance Survey. The Geological Survey map is the 1:50,000 sheet 326. For a detailed map of the geomorphological features and a cross-section see the short publication of Conway (1974).

The abundance of landsliding here is because of a combination of rapid coast erosion, a high cliff (almost 175m), and the occurrence of permeable Upper Greensand chert beds above impermeable Gault Clay and Liassic clays. At the top of the cliff water runs through the Cretaceous sands, lubricating slides. The dip is 2 to 3 degrees in a southeast to east-southeast direction in the Jurassic strata and this gentle seaward dip further facilitates sliding. The plane of unconformity at the base of the Cretaceous dips at angles of 1 to 2 degrees in a south to southwest direction, so this is also in a seaward direction. The result of all this is a retreating cliff at the foot with landslides and mudslides forming treacherous ground on the dark cliffs above.

.

LOCATIONS, CENTRAL, BLACK VEN:

Black Ven -
The Terraces and Their Cliffs [updated in July 2015]

.

[NB. The reader is not advised to go up these cliffs. A route up may be found, so as to avoid soft mud or steep cliffs; however, when descending even a short distance the route used to ascend may not be easily recognised. In wet or stormy conditions this could accidently lead the geologist into either soft mud or a near-vertical cliff. It could be hazardous, and in any case, part of the area is a nature reserve. The higher part of Black Ven is now extremely difficult because of dense and thorney vegetation. It was much more easily accessed in years past. It was not difficult 50 years ago; there was much less vegetation then in the rather cooler climate.]

.

.

.

.

.

.

.

.

LOCATIONS, CENTRAL, BLACK VEN:

Black Ven -
Coastal Retreat Rates

The instability at Black Ven has a long history and has long been studied (Arber, 1941; Brunsden, 1969). It comprises rotational slides, topples, rock falls and slumps of Upper Greensand rock and mudslides, mudflows and sandflows (see Koh, 1992 for more detail).

The original coast road from Charmouth to Lyme Regis was destroyed by landslips in the eighteenth century. A cart track running parallel to the road 100m further inland disappeared in 1965. Cliff reatreat of the order of 5 metres per annum to 30m per annum is typical during occasional phases of major activity, according to Koh, 1992. There are spells of lesser retreat in between.

The Cretaceous Chert Beds and Foxmould form a steep, yellow, upper cliff at the rear and above the Black Ven mudslides. At the top of this cliff (Timber Hill - golf course) vertical cracks develop in the oxidised, yellow, permeable, sand with broken chert. The cliff edge then recedes as blocks calve away and collapse. This process resembles that in the cliff top at Highcliffe and Barton on the Hampshire Dorset border where Pleistocene gravels over clay behave in a similar way. As result of this cliff-top slumping the coastal footpath was interrupted by several metres of cliff crest recession in 1986. A slice was taken out of the Lyme Regis golf course. This type of progressive slumping from nearly-vertical fissures leaves a steep, yellow cliff at the top of Black Ven.

Seepage at the base of the Cretaceous chert beds, where there is iron oxide (limonite) cementation from downward moving water, has cut gullies into the underlying Foxmould sands, which slurries to form outwash (Bird, 1995) . The debris makes its way down the cliff producing in places a yellow stain over underlying Liassic strata like the Belemnite Marls.

The undercliff of Liassic clays subsides irregularly and piecemeal, sometimes with local rotational movements that create back-tilted blocks between muddy pools and swampy hollow. Very large, rotational collapse movements like those in the landslip west of Lyme Regis and on the West Weare Cliffs of the Isle of Portland are not developed, though.

Mudslides ("mudflows" or "mud glaciers") are well-developed here at times. They descend to the foot of Black Ven, where the toe is eroded by the sea. A terminal moraine of rocks is left, forming a boulder arc. Various fossils can washed out of these mudslides, and the shore is well-worth examining here.

Mudslide movement is erratic and depends on rainfall in particular years. Some shown above may be old and reactivated from time to time; there was for example major seaward movement of mud in 1983. There have been further landslides on Black Ven in the wet winter of 1994-95 ( (Bird, 1995). A beach of angular gravel widens towards the promontory of slumped clay, which has acted as a groyne, intercepting drifting beach material.

LOCATIONS, CENTRAL, BLACK VEN:

Black Ven -
Coastal Retreat Rates

Bray (1986; 1992) carried out an analysis of aerial photographs and old maps and made a recent field survey to determine coastal retreat rates. He did this for both backscar and sea cliff retreat over an 87 year period. The retreat rate is highly variable, with variation of up to 5m per year. Long term rates were calculated as follows:

Black Ven - 0.71m per annum,
Stonebarrow - 0.04m per annum,
Coast between Lyme Regis and West Bay, generally - 0.3 to 0.4m per annum.

Whereas these figures give a good indication of the present rate, Bray (1986; 1992) also managed to obtain data on coastal retreat at Golden Cap over the past 5,000 years. A sea-floor sampling programme (conducted jointly with Dorset County Council) revealed boulder arcs extending 3km to 4km offshore from Golden Cap. The boulder arcs are remnants of ancient coastal landslides which indicate the amount of cliff recession since sea-level approached its present elevation 4,000 to 5000 years ago. Bray calculated that the coastal retreat based on the offshore boulder arcs as follows:

Average for Golden Cap for 5,000 years - 0.6m to 1.0m per annum

Thus the figures for the past are not very different, and the present circumstances are fairly representative. Bray's work has also shown that the West Dorset cliffs have supplied by coastal landsliding 22 to 29 million tonnes (1 cubic metre equals 1.6 tonnes) over the past 4000 to 5000 years. He considered it unlikely that it was unlikely to have been the formative process of Chesil Beach because it had probably formed by 7000 BP but had nourished and enlarged the beach. It is therefore interesting to compare the beach material of Lyme Regis and Charmouth, with its Upper Greensand cherts, its flint and its scattered Budleigh pebbles, with the Chesil Beach deposits.

LOCATIONS, - WEST OF CHARMOUTH (EASTERN BLACK VEN):

Black Ven to Charmouth Cliff - Shales-with-Beef

.

.

.

East of the last mudslide of Black Ven for about half a kilometre there is a cliff of Lias shale and a beach of boulders. The cliff exposure is of the Shales-with-Beef of the Lower Lias. These are bituminous, black, marine shales with fibrous calcite (beef) and cone-in-cone in places. The beach here is of boulders some of which are grey carbonate concretions from the Lias, and other are of carbonate-cemented sandstone from the Upper Greensand (Cowstones etc). There are also many irregular lumps of chert which is also from the Upper Greensand. At low tide the Bar Ledges (lowest part of the Shales-with-Beef) are visible here. When the tide is mid to high then it is necessary here to walk from boulder to boulder on the upper beach. This is difficult because the irregularity of the boulders and care has to be taken not to place a foot wrongly and then fall on the rocks.

.

.

.

.

.

.

The Shales-with-Beef are a relatively bituminous and shaley part of the Lower Lias, occurring just above the Blue Lias with its obvious cementstones. They probably represent the most organic-rich part of the Lower Lias, and it is at this horizon that the oil-shale fire, the "Lyme Volcano" took place. The Shales-with-Beef are close to Charmouth and the Charmouth Heritage Coast Visitor Centre and are therefore very easy to visit from Charmouth. If walking to them from Lyme Regis, it is necessary to check on tide conditions and as to whether there are any obstructions caused by mudslides. The upper limit of the Shales-with-Beef is the birchi Nodular and Tabular, an obvious line of cementstone and nodules in the cliff.

The lower part of these strat are also exposed on the shore at low tide as the Bar Ledges, which are also shown in the photograph above. The Bar Ledges are an accessible, although rather seaweed-covered, lower part of the Shales-with-Beef. Lang (1914; 1932) has mapped and described these and given a brief summary of the faunas. Note that they are not necessarily like the reefs of cementstone that occur in the Blue Lias. Hard, bituminous shales and particular shale horizons with much beef may form reefs.

Beef or "beef" is familiar in the geological literature of Dorset and the Isle of Wight. It is an old quarry-workers' name, because of its appearance when occurring as thin seams with vertical fibres of calcite. The "Shales-with-Beef" of the Lower Lias and the "Chief Beef Beds" of the Durlston Formation, Purbeck Group are most well-known. Both are organic-rich units with aragonitic fossils, the Lower Jurassic, Shales-with-Beef being fully marine, whereas the Lower Cretaceous, Chief Beef Beds are of lagoonal origin in an environment of varies, often brackish, salinity. "Cone-in-cone" is a variation on beef, and characterised by a peculiar conical structure. Beef also occurs in the Vectis Formation (Lower Cretaceous) of the Isle of Wight, and small quantities are present in the Jurassic, Kimmeridge Clay. It is not found in the Eocene clays of the region and not known in the post-Inversion strata above the Late Cimmerian Unconformity.

Tarr (1933) described beef as the result of leaching of calcium carbonate of a fine porous marl by a groundwater solution and subsequent redeposition. He noted that in a horizontal layer, there has been growth from both directions, but it took place faster on the upper side because the dominant movement of water was downward. This simple hypothesis is probably not the real explanation, but the observation of upward and downward growth is interesting; see the photographs in the adjacent part of this webpage.

.

The petrography of the Shales-with-Beef is of interest, because this unit is a potential oil source rock. Thin layers of fibrous calcite known as "Beef" occur in the shales at intervals. This type of fibrous calcite has been formed by burial diagenesis, usually from aragonite in the presence of organic matter. It is a late burial product, normally with fibres orientated towards the direction of maximum stress. The largest crystals occur where the compressive stress is greatest, as at Lulworth Cove. It sometimes contains cone-in-cone. Beef also occurs in the most organic rich part of the Purbeck Formation (El-Shahat and West, 1983) and in other formations. It is probably one indicator of potential oil source-rocks.

.

A key paper on the beef of the Shales-with-Beef of Lyme Regis and Charmouth is that of Marshall (1982) (James D. Marshall at the time at the Department of Geology, Leicester University). This paper provides clear and informative data and discussion regarding isotopic composition, morphology and Fe content etc.

.

The Shales-with-Beef have thin layers of beef not only in the shales but also around the outside of the birchi nodules. These beds are the most organic-rich part of the Lias, a formation with maximum TOC of about 8% Hallam (1960). The Shales-with-Beef have some similarities to the Kimmeridge Clay. Dolomite beds occur. These include the laminated dolostone referred to by Lang as bed 72(a) and the Lower Cement Bed which is Lang's Bed 80 (Bellamy, 1980).

LOCATIONS, WEST OF CHARMOUTH:

Black Ven to Charmouth Cliffs-
The Expanding Birchi Nodules of the Shales-with-Beef

The Shales-with-Beef (Lang, W.D., Spath, L.F. and Richardson, W.A. 1923) extend up to a band of large calcareous nodules or concretions, the birchi Nodules (or birchi Nodular), followed by a tabular limestone, the birchi Tabular. Both of these have yielded well-preserved specimens of the ammonite Microderoceras birchi, although these will be difficult to find now that there are so many professional collectors who scour the cliffs and ledges. This particular ammonite has been known as the "tortoise ammonite" or "white ammonite" because of the white calcite which often fills the chambers (Davies, 1935; 1956). The birchi Nodular or birchi Nodules and birchi Tabular forms the lowest terrace on the high slumping cliff of Black Ven ("ven" is a local form of fen and alludes to the boggy terraces of the cliff). They descend to sea-level at the mouth of the Char; there were once referred to as cementstones and used for cement. The old building on the beach at Charmouth, now a cafe and Charmouth Heritage Coast Centre, was originally a cement mill.

Birchi Nodular and Tabular in the Cliff

.

.

.

Birchi Nodules in Entirety

.

.

.

Birchi Nodules - Calcite - Dolomite Phases

.

The relationship of the non-expanding, septarian, calcite phase to the surrounding, expanding ferroan dolomite phase is best seen in sea-washed specimens, loose on the beach. These rarely contain the outer beef layer.

.

.

.

.

.

Birchi Nodules - the Calcite Beef Phase

.

.

.

.

.

.

Birchi Nodules - Relationship to Burial History Diagenesis

.

.

The expanding, calcite-dolostone nodules (of the bituminous Lower Liassic, Shales-with-Beef), with calcite in the centre, shown above are fallen material, seen loose on the beach. They clearly show how the outer, darker-grey, ferroan dolomite has grown expansively, as it sometimes does in the Fermentation Zone. In this case the inner calcite nodule has been pulled apart in fissures extending to its periphery. A feather structure developed in one case shows that the diagenesis was not continuous, but had interrupted phases of dolomite growth. See Bellamy (1980) for explanation and further details of dolomite and dolostone expansion and expansive growth.

.

.

The birchi Nodules are quite remarkable concretions, providing important evidence of the sequence of burial diagenesis, as described by (Bellamy, 1980). The examples shown here is not in situ but has been washed out onto the beach (this particular concretion is also shown in Bellamy's fig. 231, p. 133). The early core is usually of limestone which has been engulfed in later, burial dolomite. On the outside is an envelope or cortex of "beef", fibrous calcite formed under later and more substantial burial in the presence of organic matter. Although this specimen was photographed in about 1979, other good examples can be seen at Charmouth at present.

Similar nodules occur in the Kimmeridge Clay at Black Head near Osmington Mills. The Upper Jurassic Kimmeridge Clay is very similar to the Lower Lias clays, in many respects.

.

.

The location where the birchi Nodular is accessible is in the cliffs at the Raffeys reentrant and in nodules washed out onto the beach near Charmouth sea-front. Bellamy (1980) described these unusual septarian nodules as the "birchi Nodular compound carbonate bodies". He provided more detail and his thesis is worth consulting. Early-formed magnesium-rich microspar limestone nodules are surrounded by ferroan dolomite and enclosed within an outer envelope of non-ferroan calcite beef. There is differential compaction of the laminae within the dolomite around the earlier-formed calcite nodules. Laminae within the calcite nodules are planar. Uncompacted bioclasts and diffuse lenses of organic matter occur in the inner, finely crystalline calcite nodules. The surrounding dolomite has well-defined kerogen laminae. The diffuse organic matter has thus been converted to laminated kerogen at the change in carbonate diagenesis from calcite to dolomite (see Bellamy, p. 132 et seq. and figs. 231 and 232 for more information). The dolomite formation is probably related to the dolomite development under burial in the fermentation or methanogenesis zone, as in the Kimmeridge Clay, with regard to which it has been more discussed. The exterior beef usually has calcite c-axes are orientated at right angles to maximum stress. The Sr content of the burial beef can be about 400 ppm contrasting with about 800 ppm for the early, Mg-rich microspar calcite of the core. See (Bellamy,1980) for more information on the mineralogy, geochemistry and petrography of these nodules. The beef is discussed in more detail below.

Prior to the the work of Bellamy, the chemistry of the birchi nodular had been studied by (Raiswell, 1971). However, as Bellamy pointed out, he failed to mention the development of either dolomite or beef and it is possible that he collected where these outer carbonate phases are absent or from another horizon in the Shales-with-Beef or Black Ven Marls. More discussion on septarian nodule formation will be found in Astin (1986) and Astin and Scotchman (1988). Their study of Kimmeridgian septarian nodules by oxygen isotopes showed that the concretion grew during early burial, with septarian veins (carbonate veins filling the cracks) forming from about 30 m depth onwards. Later septarian veins formed between about 200 and 500 m during a second burial. This relatively early septarian cracking under burial at upto 500m is compatible with the first stage as shown in the diagram above. Astin and Scotchman considered that synchronous formation of septarian fractures and fibrous calcite matrix suggested to these authors that the Kimmeridge Clay became overpressured during the later stages of both burials.

It is of interest that Lang in 1955b and 1956 drew attention to a curiosity regarding birchi nodules: "In a paper on Mudflows (Proceedings of Dorset Natural History and Archaeological Society, Vol. 75 for 1953, p. 155) a birchi nodule was described with its beef 'jacket' striated as if scratched by a glacier, but probably by internal 'moraine', as the block rested or moved slowly at or near the bottom of a mud-flow. A second specimen, though wave-worn, was found on Charmouth beach, some 100 yards [91m] W. of the big groyne, and had probably been washed by wave action from the snout of the big mud-flow in the 'breakaway' locally known as Raffey. The top of the slab measured 87 by 19 inches [2.21m by 0.48m]."

It is also worth noting that sphalerite occurs in the birchi nodules (Bellamy, 1980). This mineral also occurs in small quantities in septarian nodules in the Oxford Clay of Weymouth and probably elsewhere.

LOCATIONS, EASTERN, NEAR CHARMOUTH

Black Ven to Charmouth
Shales-with-Beef - the Beef or Fibrous Calcite

Details of isotope geochemistry of carbonates in the Lias has been given by Campos and Hallam (1979). Their work indicates that the Blue stone bands are of early origin. The birchi nodules have a later history. The isotope geochemistry of the beef has been discussed by Marshall (1982). it has been formed under deeper burial than the Blue Lias stone bands and probably most of the concretions. Aragonitic bioclasts as a source material for the calcium carbonate of beef has been discussed by El-Shahat and West (1983). Beef normally occurs in strata with a significant organic carbon content.

LOCATIONS, EASTERN PART, NEAR CHARMOUTH:

Black Ven to Charmouth
Shales-with-Beef - Source Rock for Oil and Gas

Of importance is the fact that the Lower Lias, and particularly the Shales-with-Beef, have a high organic content and have been buried to more than 3 km under southeastern Dorset and offshore to the southeast. Where the sedimentary sequence is thick they have become thermally mature. This is the main source of oil for the Wytch Farm Oilfield and was probably generated by late Cretaceous times when burial depths were already sufficient.

Incidently, a minor but strange feature of the Shales-with-Beef is the occurrence of minute disks of barite (barytes) or barium sulphate in bed 71e (Lang, et al. 1923) .

.

[END OF SECTION ON BIRCH NODULES AND BIRCHI TABULAR]

.

LOCATIONS, EASTERN, NEAR CHARMOUTH:

Black Ven to Charmouth -
Black Ven Marls

.

.

.

The middle clay precipice on Black Ven consists of the Black Ven Marls (Charmouth Mudstone Formation of the Lias Group). Some details are shown in the logs above (including an interesting old log of Wright, 1878-1886), although they are primarily intended for the discussion on the dinosaurs, which follows. The Black Ven Marls commence above the birchi Nodules. The cliff continues up to the stellare Nodules and the Coinstone pyritic limestone, still within the Black Ven Marls, but which forms another terrace. The harder bands in the Black Ven Marls are of interest in that they mostly have been cemented early and preserved uncompressed ammonites. There is a Lower Cement Bed 12m above the birchi Nodules and the Pavior or Upper Cement Bed another 4.6m higher. Above are paper shales (bituminous shales) with Asteroceras obtusum and lines of nodules, the Flatstones and Woodstone. The Flatstone has a good insect fauna (Whalley, 1985), including beetles, grasshoppers, water-bugs, dragonflies, and also occasional conifer plant remains. All this supports the ideas of nearby land and it was likely that Cornubia, southwest England, was above sea-level at this time, and probably some areas nearer to Charmouth. Dinosaur remains, some of which at least come from this bed are referred to below. Thus the browsing reptiles of the forest are also known.

There is an impersistent Pentacrinite Bed, with the magnificently preserved crinoid Pentacrinus fossilis (Simms, 1986), known in the past as Pentacrinus briareus. Note that crinoid remains also occur in the Blue Lias. There is an impersistent limestone with the ammonite Promicroceras planicosta and a mudstone with some nodules containing sphalerite has been reported (Davies, 1935; 1956). The stellare Nodules are septarian and can contain the common ammonite Asteroceras stellare in uncrushed condition. This ammonite is large with ribs that are generally radial unlike the inclined ribs in the related but smaller Asteroceras obtusum. The Asteroceras ammonites are sometimes cut through and polished to show internal structure (Coram, 1989). This bed descends with the gentle easterly dip to the shore, 1.25 km east of Charmouth at the Mumbles Reef (House, 1993). The second terrace on Black Ven is formed by the clays above the stellare Nodules. The lymense Bed, a pyritic horizon with beef and well ammonites occurs above the stellare Nodules and further up is Watch Ammonite Stone, a limestone with ammonites of Echioceras raricostatum type and finally at the top of the Black Ven Marls there is a thin pyritic limestone known as Hummocky. The higher part of the Black Ven Marls are very pyritic, and the pyrite was once collected for manufacture of sulphuric acid. Shortly after deposition the organic-rich sea-floor muds were highly reducing, with sulphide ions produced by bacteria in the sulphate-reduction zone. This part of the sequence is poorly exposed in Black Ven because this second terrace is below the third precipice from which fall much talus.

LOCATIONS, EASTERN, NEAR CHARMOUTH:

Black Ven Marls
Dinosaur - Scelidosaurus harrisonii Owen

[For other reconstructions of the animal in life see the webpage: Scelidosaurus - Scelidosaurus harrisonii]

In the year 1858 James Harrison of Charmouth was quarrying the cliffs, presumably for the manufacture of cement. He found a few fragmentary fossils of limb-bones and sent them for examination to the very well-known, Professor Richard Owen of the British Museum (Natural History), London. Owen commented in 1861 that these came from the "upper member of the Lower Lias" at Charmouth. It is not clear in exactly which bed these were discovered.

Later, Owen (1861-1881) explained that
" the continued attention paid by James Harrison, Esq., to the organic remains discovered during quarrying operations on the face of the cliff of Lower Lias at Charmouth, Dorsetshire, with liberal encouragement to the workmen, has procured for the original discoverer of the first indication of the Scelidosaur the materials for the present account of an almost complete skeleton of that extinct reptile. Following in the track opened out by the discovery of the skull described in the preceding Monograph, about twelve successive blocks of Lias were secured, with more or less evident indications of included bones, all of which, together with the skull, have been purchased for the British Museum. Subsequent complete exposure of the included organic remains has brought to light the entire vertebral column of the trunk and tail, to very near the termination of the latter..."

The horizon and locality of the original find by Harrison is just given as the upper part of the Lower Lias near Charmouth. He found the nearly complete skeleton possessing the imperfect cranium (specimen R. 111 of the Natural History Museum) in the Lias near Charmouth. The Natural History Museum purchased the bones in 1865. The length of the specimen is 3.4m.

It is of interest that sometime before 1959, as reported in Delair (1959), additional bones of a supposed immature individual were found in a Flatstone Nodule (Black Ven Marls - obtusum Zone) by Black Ven, near Charmouth by J.F. Jackson, Esq. These remains are also in the Natural History Museum. Thulborn (1977), however, considered these to be unrelated and to be the remains of a lightly built ornithopod adapted for cursorial locomotion. He was definate in stating that it is not a close relative of Scelidosaurus harrisonii.

Good information on Scelidosaurus harrisonii is given in the webpage:
Scelidosaurus - Scelidosaurus harrisonii. This webpage is a post by "dinomike" on Dec. 3rd, 2010.

The classification of Scelidosaurus harrisonii is summarised as:

Order: Ornithischia
Suborder: Thyreophora
Infraorder: Ankylosauria
Family: Scelidosauridae
Genus: Scelidosaurus
Species: Sceldidosaurus harrisonii

The good skeletal remains come the Charmouth and Lyme Regis area. In 1989, some fossil scutes identified as belonging to Scelidosaurus, were found in the Kayenta Formation (Glen Canyon Group) of northern Arizona. The assignment to Scelidosaurus has been disputed, though.

Description (After "dinomike" - see above):

A full-grown Scelidosaurus was rather small, compared to most other dinosaurs. Some vertebrate palaeontologists have estimated a length of 4 metres (13 ft) Scelidosaurus was quadrupedal, with the hindlimbs considerably longer than the forelimbs. It may have reared up on its hind legs to browse on foliage from trees, but its forefeet were as large as its hind feet, indicating a mostly quadrupedal posture. Scelidosaurus had four toes, with the innermost digit being the smallest. It has bony scutes in the skin. The dinosaur had very small leaf-shaped cheek teeth suitable for cropping vegetation. For information on the skull see Norman and Charig (1996)

Of particular interest is the report of the preservation of soft tissue in a specimen of Scelidosaurus byMartill et al. (2000). These fossil remains consist of eight caudal vertebrae in a cut slab of carbonate mudstone, which was judged to date from the late Hettangian to Sinemurian stages. An envelope of preserved soft tissue was visible around the vertebrae, and show the presence of an epidermal layer over the scutes. The authors concluded that the osteoderms of all basal armoured dinosaurs were covered in a tough, probably keratinous layer of skin.

The specimen came from a collection of Professor John Challinor (1894-1990) and was used as a teaching aid at Portsmouth University. It has no label and no provencance data. The matrix is typical of that of nodules of the English Lias. Soft tissue preserved as kerogen is comparable to other vertebrate material from the Sinemurian of Charmouth. Palynological data suggests an Hettangian - Sinemurian age, but an exact horizon has not been fixed.

In the year 2000, the professional fossil collector David Sole discovered the partial remains of a Scelidosaurus, after a cliff fall at Black Ven, near Charmouth. This "Horned Scelidosaur" is extremely well-preserved in three-dimensional form. It has body armour and even evidence of its last meal. The 195 million year old dinosaur remains were further retrieved piece by piece over five years by David Sole.

LOCATIONS, EASTERN, NEAR CHARMOUTH:

Black Ven Marl Member
Dinosaur - Scellidosaurus harrisonii - stratigraphical occurrence

The position of the Stonebarrow Flatstones, referred to above with regard to insects, near the middle of the Black Ven Marls is well shown in a log of Hesselbo and Jenkyns (1995), Fig. 10, p. 117. They occur in Bed 83, the Obtusus Shales, which were described by Lang (1914) as a band of paper shales (i.e. bituminous shales) about 2.4m (8 feet) thick that project from the general surface of the cliff and are a conspicuous feature, even where the cliff is grassed over, since at such places they often project through the grass and can be traced from section to section. Lang referred to a layer of nodules which occurs in the shales where they reach the beach under Stonebarrow, and these are presumably the Stonebarrow Flatstones. Asteroceras obtusum is collected from these beds and Xipheroceras aff. dudressieri (d'Orbigny) has been found here. These shales run out to sea between Dover Ledge and the Mumbles Rocks (see the geological map in Lang (1932) . Perhaps this is a place to look for more dinosaurs.

These logs of parts of the Black Ven Marls are intended to help the understanding of just Scelidosaurus seems to occur only at one horizon. The left-hand graphic log is based, with modifications, on Lang and Spath (1926). It gives the main units within the Black Ven Marls and shows the approximate position from which the dinosaur remains were found. There are two levels of Flatstones so the exact position is not fixed. All the beds are necessarily laterally continuous and there some differences between the section on Black Ven and at the foot of Stonebarrow. The nodule horizons are emphasised here to fix positions relatively easily. See Lang and Spath for details of the ammonite faunas within this.

The right-hand diagram gives a different version of the Black Ven Marl succession. This is based on the work of Hesselbo and Jenkyns (1995) and provides ammonite zonal information and a metric scale.

The occurrence of several dinosaur remains in the Lower Jurassic, Liassic sequence in Dorset at only one specific horizon is a mystery. The Obtusum Zone in which it occurs is a specially interesting unit, though, and in the Mendip area is represented by the Obtusum Nodule Bed, which rests on various lower zones in different places and contains fossils derived from their denudation; it is, in fact, a remanie bed (Arkell, 1933). This shows that in places the Jurassic sea floor was land at this time, doubtless inhabited in suitable environments by Scelidosaurus . The level of the Jurassic sea-floor fluctuated with basins and swells developed and irregular phases on swells where the seafloor did not subside and shoals and exposed surfaces developed Sellwood and Jenkyns (1975). The Coinstone, some way above the Flatstones, is the result of such exposure on a swell. Subzones are missing here, although present in other places to the north, and a very low island or peninsula existed for perhaps a quarter of a million years. This was then submerged, perhaps quite rapidly. This is not the dinosaur horizon but it shows that there was a swell of some type at Charmouth, not too long in geological terms after the dinosaur deaths of the Flatstones lagerstatten (fossil bed) . It is, therefore, quite feasible that the emergence and submergence of the Coinstone type, occurred near here in Flatstone times. There is a mechanism of basement faults, and there is evidence (to be discussed later) of penecontemporaneous fault movement in the Lower Jurassic. Low land with dinosaurs, trees and insects could have been flooded, either relatively rapidly but quietly or by a tsunami. Fault-driven oscillation was the cause; dinosaur death the result.

LOCATIONS, EASTERN, NEAR CHARMOUTH:

Black Ven to Charmouth

LOCATIONS, EASTERN, CHARMOUTH:

Charmouth Sea Front

.

.

.

Charmouth seafront welcomes geological visitors with a Heritage Centre and a fossil shop. It is a good place for geological or palaeontological activity. Car parking is easy and coaches can be parked a short distance away. Generally, there is easy access by stony beaches to the clay cliffs either side.

.

A front of brown muddy seawater, moving slowly westward with the ebbing tide was seen from Charmouth (Higher Sea Lane) on the 13th March 2015. This mud might have come from the landslide at Evans Cliff (western end of Stonebarrow Hill, or Cain's Folly).

See the webpage:

.

Charmouth East to Stonebarrow Hill

LOCATIONS:

Charmouth -
Old Cement-Mill Charmouth

The building on the sea front, converted for the Heritage Centre and various purposes now, is the old cement-mill. Woodward and Ussher (1911) commented that:

"Some of the cement-stones in the cliff near Charmouth, especially the "two cement bands" [in the Black Ven Marls] have been employed in old times for making cement, and remains of a disused cement-mill still stands near the sea-shore.

The Lower Cement Bed (Lang's Bed 80) is, incidently, not a limestone (except locally where unreplaced) but an argillaceous dolomite, with about 84% weight percent dolomite mineral and about 2% calcite, according to (Bellamy, 1980). It is interesting to note that rather similar dolomites were quarried from the Kimmeridge Clay east of Kimmeridge for cement manufacture in the 19th Century.

.

APPENDIX 1: EASTERN, CHARMOUTH - HIGHER PART:

Devil's Bellows, Old Lyme Road etc, Charmouth

The backscarp of the landslide here has shown some cliff retreat in this area over past years and in recent years. (eg.Conway 1974) and Barton (1977).

Retreat of the cliff edge has certainly been taking place in various parts of the Black Ven area. It has long been very well-known as an active landsliding region and even significant stretches of roads have been lost (e.g. the western and main part the Old Lyme Road or Old Charmouth Road). Fairly recently, the original coastal footpath at the top of Black Ven has been closed and there has been a major diversion to the north (to the Charmouth - Lyme Regis road). The general stratal and structural aspects of the cliffs are well-known. The Lias is well-known but details of the Cretaceous strata are less well-established, particularly where they are affected by landsliding.

There is also the matter of dip. Here, the dip of Cretaceous strata is of particular interest because these strata both hold water and allow movement of water. In general there a low-angle, south or south-southwest dip of the Cretaceous strata in the Black Ven Landslide area (Conway, 1974, p. 2). This may influence intrastratal water-flow in the Cretaceous Foxmould sandstone. Some details of the cliff here are now illustrated and briefly discussed, but, as mentioned, without drawing major conclusions.

[Offline ]

.

APPENDIX 2: EASTERN, CHARMOUTH - SUBURBAN AREA:

HIGHER SEA LANE AREA

(east of Black Ven)

.

.

APPENDIX 2: THE HIGHER SEA LANE LANDSLIP (1970s)

[The Landslide Embayment at Raffey's Ledge, east of Black Ven]

.

.

.

.

.

.

At the Charmouth side of Black Ven, near Raffey's Ledge, there has been in the past (particularly the 1970s) a particular problem with cliff degradation features (a landslide embayment - a small mudslide) approaching housing (part of Higher Sea Lane etc) which has been built relatively close to the cliff. However, since then the cliff has stabilised here, but there has been some very minor activity in recent years (up to 2015). See the photograph above. There does not seem to be any immediate problem in relation to housing at present (in 2015), but the Raffey's area is worth occasional observation.

In the 1970s there was a dispute about whether fossil-hunting in the cliffs should take place in the Raffey's - Higher Sea Lane area. There was a Public Inquiry, which the writer attended. Fossil-collecting was not stopped.

See particularly the detailed work on the Raffey's Embayment by Denness et al., (1972; 1975) and also the general Black Ven work of Conway (1974) which is relevant to this.

For more information, particularly see Denness et al., (1972; 1975) and the maps and diagrams within the publications. A brief extract from the conclusions of the 1975 publication follow:

"This comprehensive investigation [Denness et al. 1975] of the Higher Sea Lane landslip has established the general and specific factors which affect cliff stability in the area and has outlined the stable and unstable parts of the cliff. The local instability is associated with reactivation of fossil mudflows which overlies the Lias clay at the point of maximum cliff recession. The basic problem is identified as the location of a secondary reservoir (Conway, 1974), i.e. the mudflows which supply water to the gently dipping Lias beds, and cause landslipping in a direction perpendicular to the original direction of movement. The Higher Sea Lane area is influenced by the location of a primary reservoir consisting of the Chert Beds [i.e. the Whitecliff Chert Member of the Upper Greensand] and the Foxmould [soft sandstone of the Upper Greensand] higher in the Black Ven landslip complex....." [continues].

It is not known to present author as to whether any of the remedial measures suggested took place. These involved reducing water content in the area partial regrading of the cliff [not observed] and installation of electrode monitoring sets. Not much has happened at the Higher Sea Landslip in the last 40 years though. The active movement there seemed to have stopped naturally. Elsewhere on the eastern side of side of Black ven, tension gashes and faulting of land has occurred [ref. Barton].

.

APPENDIX 3, NOTE ON HISTORY

Arriving at Lyme Regis

18th April, 1889. "The Members of the Geologists' Association assembled at the Waterloo Station in time for the 2.40 p.m. train on Thursday, and journeying as far as Axminster, arrived at eight o'clock, about an hour after the appointed time. A brake and an omnibus, each with three horses, awaited the party, and as "shades of night were falling fast", an immediate start was made. Proceeding into the little town of Axminster, and beneath an archway through the yard of the George Inn, the vehicles were driven at a rapid rate through the narrow street that leads into the Lyme road. It seemed like a revival of old coaching times, and as the foremost carriage was driven full gallop down the hill, the Director, Dr. Horace Woodward, mildy inquired if no brakes were used in these parts.
- "Yes, surely," answered the driver. - "You used no brake coming down that hill," said Woodward. - "That worn't a hill!" was the somewhat gruff reply.
Subsequent experience proved that there were many far steeper hills, and especially the final descent to the Three Cups Hotel at Lyme Regis, which the Members reached safely soon after nine o'clock."]
(based on Woodward, 1889)

.

ACKNOWLEDGEMENTS

I am particularly grateful to Dr Clive Needham and his colleagues from Agip UK for kindly providing several of the photographs on this webpage. Discussion with Ian Troth has been very helpful. The students and staff of the Civil Engineering Department of London South Bank University have generously participated in fieldwork and photography on these cliffs. I am particularly grateful to Dr Paul Sandford, Professor Mike Gunn and the geologist and technician Tony for their help and cooperation. I very much appreciate the kindness of Jane Evans for allowing me to reproduce an image of her postcard of the Lyme Volcano of 1908. I am very grateful to the Curator of Lyme Regis Museum, Paddy Howe, for helpful information and discussion, on the day after the Spittles Landslide of May, 2008.

More on Lyme Regis Cliffs:
See: Lyme Regis, West webpage.

For fossils see the Liassic Fossils webpage.

Copyright © 2019 Ian West, Tonya Loades and Joanna Bentley. All rights reserved. This is a purely academic website and images and text may not be copied for publication or for use on other webpages or for any commercial activity. A reasonable number of images and some text may be used for non-commercial academic purposes, including field trip handouts, lectures, student projects, dissertations etc, providing source is acknowledged.

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.

Webpage - written and produced by:

Ian West, M.Sc. Ph.D. F.G.S.

.

at his private address, Romsey, Hampshire, kindly supported by Southampton University,and web-hosted by courtesy of iSolutions of Southampton University. The website does not necessarily represent the views of Southampton University. The website is written privately from home in Romsey, unfunded and with no staff other than the author, but generously and freely published by Southampton University. Field trips shown in photographs do not necessarily have any connection with Southampton University and may have been private or have been run by various organisations.