In addition to the guides, there are bibliographies of the geological literature with internet links. The guides are linked to literature references in the bibliographies. This set of webpages was commenced in 1997 and is intended for geologists, geomorphologists, fossil collectors, university students and school students, walkers, naturalists and anyone interested in the magnificent coasts of southern England. The guides are intended to be permanent, reference resources on the geology of the south coast. Use is very heavy, and they comprise one of the most visited geological websites in the world.

A prerequisite for a geological visit to Bridport, Eype, Burton Bradstock, Charmouth, Beaminster or adjacent areas is the British Geological Survey map, Sheet 327. So too is the new memoir - British Geological Survey Memoir (2011), Geology of South Dorset. (Note that it includes Charmouth and east of Charmouth, including St. Gabriels Mouth and Golden Cap, but not Lyme Regis).

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British Geological Survey (BGS). (Compiler Wood, M.A.) 2011. Geology of South Dorset and South-East Devon and its World Heritage Coast.

Special Memoir for 1:50,000 geological sheets 328 Dorchester, 342 West Fleet and Weymouth and 342/343 Swanage and parts of sheets 326/340 Sidmouth, 327 Bridport, 329 Bournemouth and 330 Newton Abbott. Compile by M.A. Woods. By Barton, C.M., Woods, M.A., Bristow, C.R., Newell, A.J., Westhead, R.K., Evans, D.J., Kirby G.A., and Warrington, G. Contributors: Biostratigraphy - J.B. Riding; Stratigraphy - E.C. Freshney; Economic Geology - D.E. Highley and G.K. Lott; Engineering Geology - A. Forster and A. Gibson. British Geological Survey, Keyworth, Nottingham, 2011. 161 pp. This is the new version of the Geological Survey Memoir for the Dorset Coast etc. and replaces Arkell (1947) and the earlier memoir by Strahan (1898). It covers a wider area than these old memoirs, though, and includes all of "Jurassic Coast", UNESCO World Heritage Coast. It is a key reference work. Available from BGS Online Bookshop at 24 pounds stirling (in Jan. 2012).

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Geological Map of Central and East Dorset

This old map from Damon (1884) provides only summary information on the geology of the East Dorset coast and the Weymouth area. See recent work by the British Geological Survey for updates on the positions of faults and outcrop patterns and the subdivision of units.

English Channel - General, Geological Maps

Location and Geological Maps - Isle of Purbeck

The British Geological Survey map, 1:50,000, Solid and Drift, 2000 Edition, Swanage Sheet, 343 and part of 342, is well worth purchasing. It can be obtained from the British Geological Survey website and is very inexpensive, costing only 12 pounds sterling. The map shown above is the new edition of the year 2000. It is different in some respects from older editions.

Location map for the Isle of Purbeck in general and a map with coastal locations and simplified geology for the area around Kimmeridge and Gad Cliff.

The left hand geological map is from Woodward (1907). The middle and right-hand ones are from an old hand-painted geological map of the area from Braye (1890).These provide an old introduction to the geology and general topography of the area. It is recommended that you obtain the current geological map of the British Geological Survey (formerly the Institute of Geological Sciences), Geological Map - Swanage, Sheet 343 and part of 342. Solid and Drift Edition. 1:50,000. Go to the British Geological Survey website, maps section to order online.

There is an accompanying explanatory memoir by Arkell (1947), although now somewhat out-of-date. The present map - sheet 343 and 342 is broadly similar to the maps here but the details of the faults are corrected. The main feature is that the Cretaceous Chalk forms an east-west trending ridge, the Purbeck Hills. The most suitable topographic map for the area is the Ordnance Survey, Outdoor Leisure Sheet 15, Purbeck and South Dorset. Scale 1:25,000.

Here the Geology of the Isle of Purbeck is shown on part of a map modified from Damon (1884). Modern changes in the geological mapping of the area have only been of detail. Some place names have changed since Victorian times. The full map is also available above.

This location map is very useful for the names of coastal features on the cliffs of the southeast Isle of Purbeck. It is based Crewe (1977) but with climbing regulations and other items removed. It includes both standard topographical names, climbers names for localities and names from Anderson. For full detail see Crewe (1977) or Coe (undated).

This simplified geological and location map of the Lulworth Cove area is based on Townson (1975b) with some modifications based on the British Geological Survey map of Swanage (sheet 343 and part of 342). For more information please see the Lulworth Cove Guide .

Left: Simplified geological map of the Isle of Portland based on House (1993), the Ordnance Survey and Geological Survey maps and other sources. Note that quarrying has in some areas resulted in the removal of the Purbeck strata and a change in the geology of the area. Several quarries and areas of landslides are shown. PHH - Portland Heights Hotel with fossil trees and ammonites on display in the garden. PC area of celestite and the Portland Alabaster in the Soft Cockle Member of the Purbeck Formation. For detailed information please refer to the Ordnance Survey Map 1:50,000 Dorchester Sheet No. 194 or, better, the 1: 25,000 or 1:10,000. For geology please see the British Geological Survey 1:50,000 Weymouth Sheet 342 or for the adjacent sea-floor the 1:250,000 Portland Sheet 50N 04W, New Series including the Continental Shelf.

Right: 1884 geological map of the Isle of Portland, showing the Purbeck Formation extending further north, before the northern quarries had removed so much of this formation and the underlying Portland Stone.

Portland Area - Offshore Geology

The geology of the seafloor around Portland was investigated by Donovan and Stride (1961) by an acoustic survey supported by coring, the observations of divers and sample collection. This map is based on their work with some minor modifications (the geology of the offshore area is also shown on the British Geological Survey 1:250,000 Sheet 50N 04W, solid geology).

This simplified map provides the introductory geological setting and location information for the west Dorset coast. The eastern part of this map shows the uplands of Chalk The unconformity marks a descent to lower clay country in the central area of the map. Isolated hills here are capped with weathered Cretaceous Upper Greensand (often oxidised brown or yellow) with much chert. These units lie unconformably on fossiliferous grey Liassic (Lower Jurassic) marine clays. West of Lyme Regis there is a more extensive plateau of Upper Greensand with, here, some Chalk. In the far west, just over the Devon border, the uppermost Triassic strata, including the lagoonal " Rhaetic " strata (Penarth Group) appear.

Field guides are provided at present for the locality boxed in yellow on the map: Lyme Regis (this one); West Bay or Bridport Harbour and the Chesil Beach

General location and geological map for the Lyme Regis area. Detailed maps of Lang for the coast adjacent to Lyme Regis are also provided below.

Further Information on Maps

It is recommended purchasing the current geological maps of the British Geological Survey, BGS (formerly the Institute of Geological Sciences). These give more detail and are more accurate, particularly with regard to faults. See Geological Maps - Bournemouth, Sheet 329, Solid and Drift Edition, 1:50,000; Swanage, Sheet 343 and part of 342. Solid and Drift Edition. 1:50,000; Weymouth, Sheet 342; Fleet, Sheet 341 (mostly sea uncoloured!), Bridport, Sheet 327.for Lyme Regis, Sheet 326. For maps at scale 1:250,000 which include offshore as well as onshore geology see Portland, Sheet 50N 04W, which covers most of Dorset, and the adjacent map to the east - Wight 50N 02W (this extends from east of St Alban's Head and includes Swanage and Bournemouth). The 1:50,000 maps are the best coloured maps generally available, although 6 inch or 1:10,000 unpublished field maps exist at the British Geological Survey, BGS and can be used for reference.

In addition there are various geological maps published in papers and books. See particularly House, M. 1993, Geology of the Dorset Coast. Geologists' Association Guide. A Geological Map of the English Channel, Carte Geologique de la Manche, including the Dorset Coast has been published by the Bureau de Recherches Geologique et Minieres and Service Geologique National of France. There are other more detailed sea-floor maps available, of which that of Donovan and Stride (1961) is well-known and referred to in some of these field guides ( see for example the Portland Bibliography )

Barton and Hordle Cliff, Hampshire - Eocene Soft clays and sands with abundant marine, lagoonal and lacustrine molluscan fossils are being actively eroded on the landslipped east Dorset and Hampshire coast. Sharks' teeth occur and , crocodile, turtle, mammal, snake and other bones have been found. There are more than 500 species of fossil shells in the Barton Clay. This is in an early stage and is to be expanded shortly

Chesil BeachThe greatest shingle beach in northwest Europe is composed of remarkably well-sorted, resistant pebbles of mainly flint and chert. The pebbles increase in size towards the Isle of Portland in a consistent manner that has caused much discussion over the last two centuries. Pebbles of Triassic quartzite have derived in the past from the coast of Devon, even though now there is no direct route for them to travel by longshore drift because headlands project into fairly deep water. Behind the beach is the unusual brackish Fleet Lagoon. Incidently, the beach is famous, as the site of numerous historic shipwrecks. The Chesil Beach is connected to the Isle of Portland, described separately.

Durlston Bay, Purbeck Type-Section - Cretaceous. This classic section near Swanage in eastern Dorset shows the thickest well-exposed sequence of lagoonal Purbeck strata in England, with almost 250 numbered and described beds. It contains horizons with mammals, pterosaurs, crocodiles, turtles, fish, insects, isopods, ferns, ostracods, charophytes, ferns, numerous molluscs and the occasional dinosaur footprint. Thin-bedded limestones and marls are dominant but there is also gypsum and dolomite. The Jurassic-Cretaceous boundary is near the base of this sequence. The Building Stones and the Purbeck Marble, a gastropod limestone have long been quarried. A bibiography is provided.

The Durlston Bay subsections are listed here:
Durlston Bay - Introduction and Upper Purbeck Formation
Including the Purbeck Marble, a Viviparus biomicrite limestone, and the Purbeck Ledges of Broken Shell Limestone at Peveril Point.
Durlston Bay, - Middle Purbeck Formation and the Purbeck Building Stones
This includes the Cinder Bed (a lagoonal oyster bed), the Mammal Bed, Mr Beckles' Mammal Pit, freshwater fossils, crocodiles and dinosaurs (and their footprints), the Purbeck Building Stone and Purbeck quarrying.
Durlston Bay, Lower Purbeck
This includes the gypsum and insect beds and the Broken Beds of the basal Purbeck Formation at Durlston Head. These are a breccia that was originally evaporitic and still contains celestite (strontium sulphate) as a relic of the evaporites.
Durlston Bay, Purbeck Bibliography
This includes references used in the above sections and an extensive list of Lower Cretaceous, Purbeck Formation and Durlston Bay literature.

Isle of Portland, Dorset, Upper Jurassic The famous rocky peninusula with Upper Jurassic oolitic limestone, the Portland Stone, used for the rebuilding of London after the Great Fire in 1666. The fascinating "island" has numerous cliff sections, quarries, some caves, giant ammonites, fossil trees and a Pleistocene raised beach. The quarries and cliffs expose the Portland Stone with the basal Purbeck Formation above. That has fossil trees replaced by silica and still rooted in a carbonaceous soil with pebbles, the Great Dirt Bed. Stromatolites cover the trees. Fossil insects are common in the Purbeck Formation. The raised beaches, of round about 100,000 years old, contain numerous low-tide mollusc shells. Special features of Portland are the Basal Shell Bed of the Portland Stone, celestite and Portland Alabaster in the Purbeck Formation, and the remarkable rotational and topple landslides around the coast. The large-scale quarrying of Portland Stone by convicts to build the great breakwaters of Portland Harbour has left an interesting maze of old quarries.

Portland Quarry - Withies Croft Wall
This late 19th Century quarry face is the subject of detailed study. It includes a succession of oolitic Portland Stone with lagoonal Purbeck limestones above. The Purbeck sequence includes palaeosols (soils) with silicified coniferous trees, and stromatolites and ostracod beds.

Kimmeridge, Dorset, England - Upper Jurassic and oil source rock - Introduction and Fossils . The Kimmeridge Clay is famous both as a richly fossiliferous marine Jurassic clay formation and as the main source rock for the North Sea oil. The cliff sections in Dorset provide excellent and classic exposures of these ammonite-rich shales. Oil shale occurs in the central part. The Kimmeridge area is discussed here in a number of separate websites, each of which is being progressively expanded:

Kimmeridge - Introduction
Kimmeridge Bay
Kimmeridge - Hen Cliff, Yellow Ledge and Cuddle Kimmeridge - Blackstone, Oil Shale at Clavell's Hard
Kimmeridge - Burning Beach, Burning Cliffs
Kimmeridge - Rope Lake Head to Freshwater Steps
Kimmeridge - Egmont Bight to Chapman's Pool
Kimmeridge - West to Gad Cliff
Kimmeridge - Fossils
Kimmeridge - Bibliography - Start
Kimmeridge - Bibliography Continued

Lulworth Cove, Dorset, Jurassic-Cretaceous . Lulworth Cove and the nearby localities of Stair Hole (shown here), the Fossil Forest, Durdle Door etc are some of the famous and most-visited geological sites in Britain. There is an excellently exposed Jurassic-Cretaceous succession with major folding in a monocline that marks the northern margin of the English Channel Inversion. Purbeck lagoonal strata are very well-exposed. The remains of a subtropical forested island has been preserved at the Fossil Forest, with its soils, pebbles, trees, caliche and stromatolites. The evaporites which covered it and were involved in its preservation were subsequently brecciated, partly replaced by limestone, and now form the remarkable Broken Beds. The Lulworth coast is a special place for geomorphological features. The cove is almost circular, with a narrow breach in the Portland Stone ridge. Stair Hole, Dungy Head and Durdle Door show features relating to the further development of this coast of near-vertical Mesozoic limestones, clays and sandstones. At Lulworth Cove there is a Heritage Centre . Lulworth is where most people start their study of the Dorset coast geology.

Individual sites for the Lulworth area follow:
Lulworth - Dungy Head, Jurassic-Cretaceous
Lulworth - Durdle Door, Jurassic-Cretaceous
Lulworth, Fossil Forest, End-Jurassic
Lulworth, Dorset - Stair Hole, Jurassic-Cretaceous

Lyme Regis, Dorset, Blue Lias, Lower Jurassic This is the classic and extremely well-known locality for the highly fossiliferous marine Lower Jurassic or Lias. It is zoned on ammonites. The ichthyosaurs and plesiosaur remains from here are famous and early specimens were discovered by the renown Mary Anning at the beginning of the 19th Century. This field guide deals at present mainly with the cyclical shales, marls and cementstones (argillaceous limestones) of the Blue Lias in the cliffs west of Lyme Regis. It will be expanded with additional information on other parts of the Lias and on the " Rhaetic " strata beneath.

Mupe Bay, Dorset, Jurassic-CretaceousA beautiful bay mostly in Purbeck and Wealden strata with northern cliffs of Chalk. It is east of Lulworth Cove. The site is in early and will be expanded in the near future.

Osmington Mills, Dorset, England, Corallian, Upper Jurassic. The cliffs around Osmington Mills, east of Weymouth, provide fine sections through relatively shallow, marine Upper Jurassic strata - the Corallian Group of Upper Oxfordian age. The succession is a cyclical one of sands, clays and limestones. It is a sequence that is highly fossiliferous with many bivalves and with numerous trace fossils and varied sedimentary structures. The Osmington Oolite Formation, in addition to oosparites and oomicrites, includes an oncolite bed and sponge deposits. Ammonites, corals and fossil wood occur. The cliff sections are much used for student studies of sedimentology, palaeontology, trace fossils and for graphic logging exercises. Oil sands and an oil seep here started the search for oil in Dorset that ultimately led to the discovery of the great Wytch Farm Oilfield.

Sabkhas Sedimentology, Middle East and N. Africa . Although obviously not on Dorset, this provides sedimentogical comparisons for sabkha evaporites in the Purbeck Formation of Dorset (although the Purbeck evaporites were from a semi-arid rather than desert environment). This webpage is in early stages at present and will be expanded later.
Solent Shores, England, Tertiary-Pleistocene
This is mentioned here because it is just east of the Dorset region. The Solent estuaries around Southampton, Portsmouth, the New Forest and the Isle of Wight have been formed by the rise in sea-level about 10,000 years ago in the Flandrian Transgression. Eocene strata and gravels are exposed. This site is in a very early stage at present. Associated with this is a Bibliography on the Geology of the Solent . .
Studland and Swanage, Cretaceous-Tertiary
The origin of the remarkable sand-dune area of the South Haven Peninsula, Studland is discussed here. The Chalk cliffs of Ballard Down and Harry Rocks are described. The Ballard Down Fault is a major fault with a curved fault plane and many different theories have been put forward to explain it. Eocene beds above the Chalk are exposed at Studland. This site is being expanded at present.
West Bay, Bridport, Jurassic Oil Reservoir Sandstone The Lower Jurassic, Bridport Sands are excellently exposed in the cliffs east of Bridport Harbour or West Bay. They are shoal (and beach?) sandstones with levels of early cementation. Belemnites, ammonites and other fossils occur and the sandstones are much bioturbated. Large curved, wave-like sedimentary structures at the base of the cliff have been the subject of much discussion. This is the upper reservoir for the Wytch Farm oilfield and is a good example of a Jurassic marine sandstone oil reservoir, of the the type which occur in the North Sea.
Worbarrow Bay, Dorset, Jurassic-Cretaceous
The Purbeck section here contains gypsum, most of which is secondary and porphyrotopic. It also includes satin-spar and well-developed enterolithic veins. The cliff show dinosaur footprints and a thinner but similar succession of varied lagoonal limestones and shales to those at Durlston Bay. The Wealden is excellently exposed in beautifully coloured cliffs of marls, clays and sandstones with lignite. The Upper Greensand and Chalk is seen at the northern end of the Bay. This site is to be expanded shortly.

Geology of Dorset - an Introduction

The rocks of Dorset are mainly those of the Jurassic System, the outcrop of which stretches northward to the coast of Yorkshire. Some stratigraphical information on these strata is given in the tables above. Organic-rich shales in these are are important oil source rocks and various sandstones and limestones are oil reservoir rocks. At the base, the Lower Jurassic or Liassic strata are seen in west Dorset, dipping eastward beneath younger beds, while the Upper Jurassic is exposed in middle and east Dorset. Above these are Cretaceous clays, marls, greensand and chalk, with, in the east, near Poole and Bournemouth, some soft sediments of Tertiary age.

Exposed in the red Devon cliffs west of Dorset, and underlying the buff limestones and grey shales of Jurassic age, are the red Permian and Triassic breccias, marls, sandstones and pebble beds. Some of these beds are important reservoir rocks for oil and also for hot water for geothermal energy. The red strata originated in desert conditions when Britain was at the latitude of the present Sahara Desert about 250 million years ago. The equator slowly moved away to the south. Shallow seas in warm Mediterranean climatic conditions spread over the area. The first influx of water led to the formation of shallow lagoons, partly or completely land-locked. In these the grey shales and limestones of the Penarth Group or "Rhaetic" were deposited. They contrast with the underlying red beds, and can be seen in the cliffs at Pinhay Bay and nearby to the west of Lyme Regis, at the Devon/Dorset county boundary.

The water deepened into shallow shelf seas of the Lias. They were of moderate depth and spread over a large part of England. The position of the coastline varied as did the depth of the sea, but Brittany, Cornwall, Wales and most of Ireland seem to have been land areas. There were islands in the Liassic sea in the neighbourhood of Cardiff and the Mendips. The land was of low relief, no longer a desert, and its rivers discharged quantities of mud into the sea. Hence the Jurassic rocks are mainly clays and shales, with occasional sands, limestones and ironstones, which were formed in shallower water. At times part of the sea-floor was raised to within reach of wave-action and suffered erosion instead of continuous deposition. This caused a local break or hiatus or non-sequence in the geological record.

The sea that covered the British area in Jurassic times was no land-locked basin. It communicated freely with the ocean and newly-evolved forms of life entered it freely. It is by the fossil remains of these organisms that we are able to date the rocks and correlate those of the same age in different areas, even if they are of different lithological types. Particularly notable was the development of many species of ammonites. These first appear in Dorset in the Blue Lias, the lowermost Jurassic shales with thin limestones, in Pinhay Bay. Obviously geographical factors affected the distribution of faunas then as now, and forms that abounded in a sandy bay might not occur on the muddy bottom further offshore, but after allowing for differences of facies there are still enough common elements in the fauna to allow correlation. Thus it has been possible by means of macrofossils to establish a very good chronological (chronostratigraphic) division of the sedimentary strata side by side with lithostratigraphic units such as the Bridport Sands Formation and the Inferior Oolite. Micropalaeontological studies have enabled microfossil zones to be tied in with the macrofossil zones. Other work has taken place on palaeomagnetism and on the recognition of cycles of sedimentation. For reference purposes, the zones are shown in the tables with follow but most emphasis here is on the easily-recognised lithological units, like the Blue Lias or the Portland Stone.

At the end of the Jurassic Period the sea shallowed. The Cretaceous strata includes lagoonal deposits of the Purbeck Formation with crocodiles, turtles, early mammals, insects, trees, isopods, and many low-salinity gastropods and bivalves. The gastropods are not unlike modern pond-snails. Wealden clastic sediments of fluvial origin follow, and then come the marine Lower Greensand, the Gault clay and the Upper Greensand. These are muddy and sandy deposits of shallow shelf seas. The major unit at the top of the Cretaceous is the Chalk, a product of a very clear and clean sea, that was formed at a time of high sea-level. The K/T Boundary (the Cretaceous/Tertiary boundary) is not well seen in Dorset because some of the uppermost Cretaceous strata are missing, so there is no information here on the great asteroid impact event. The Tertiary strata of eastern Dorset include deltaic sands and clays and notable for an interesting assemblage of warm temperate plant remains. Pipe clays and coarse grits occur.

The faunas of the Jurassic, Cretaceous and Tertiary strata are important for understanding the palaeoenvironments in which the organisms lived. The fossil can be compared to living organisms and provide much environmental evidence. The Dorset coast is famous for the large vertebrates, particularly of the marine reptiles - ichthyosaurs and plesiosaurs. Tree remains say much about conditions on the land. Bones of dinosaurs and pterosaurs (pterodactlys etc) are sometimes found. Sedimentological studies also provide valuable information on the palaeoenvironments; sedimentary structures tell about current directions and velocities; evaporites minerals are indications of former brine salinities and reveal information about the climate.

Dorset and Devon are special is providing excellent exposures of varied strata from Devonian to Eocene age, and in having a good fossil content and sedimentary structures. These guides, mainly through the use of numerous illustrations, shows the main stratal features to be seen at a number of impressive cliff sections on the Dorset, Hampshire and Devon coasts.