The Lambeth Group is a

stratigraphic group In geology, a group is a lithostratigraphic unit consisting of a series of related formations that have been classified together to form a group. Formations are the fundamental unit of stratigraphy. Groups may sometimes be combined into super ...

, a set of geological

rock strata In geology and related fields, a stratum ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as ei ...

in the

London London is the capital and largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary down to the North Sea, and has been a majo ...

and

Hampshire Basin The Hampshire Basin is a geological basin of Palaeogene age in southern England, underlying parts of Hampshire, the Isle of Wight, Dorset, and Sussex. Like the London Basin to the northeast, it is filled with sands and clays of Paleocene and yo ...

s of southern

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

. It comprises a complex of vertically and laterally varying gravels, sands, silts and clays deposited between 56-55 million years before present during the

Ypresian In the geologic timescale the Ypresian is the oldest age (geology), age or lowest stage (stratigraphy), stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by th ...

age Age or AGE may refer to: Time and its effects * Age, the amount of time someone or something has been alive or has existed ** East Asian age reckoning, an Asian system of marking age starting at 1 * Ageing or aging, the process of becoming older ...

(lower

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

). It is found throughout the London Basin with a thickness between 10m and 30m and the

with a thickness between 50m and less than 25m. Although this sequence only crops out in these basins, the fact that it underlies 25% of London at a depth of less than 30m means the formation is of engineering interest for tunnelling and foundations.

History

The formation was first known as the Plastic Clay by T. Webster in 1816 after the Argile plastique of

Georges Cuvier Jean Léopold Nicolas Frédéric, Baron Cuvier (; 23 August 1769 – 13 May 1832), known as Georges Cuvier, was a French natural history, naturalist and zoology, zoologist, sometimes referred to as the "founding father of paleontology". Cuvier ...

and A. Brongniart. It was called the Mottled Clay by

Joseph Prestwich Sir Joseph Prestwich, FRS (12 March 1812 – 23 June 1896) was a British geologist and businessman, known as an expert on the Tertiary Period and for having confirmed the findings of Boucher de Perthes of ancient flint tools in the Somme valle ...

in 1846, but in 1853 he proposed the name Woolwich-and-Reading Beds to emphasise the differing local aspects of the series. This name received widespread usage, but it was in turn deprecated in 1994 in favour of the ''Lambeth Group'' by the

British Geological Survey The British Geological Survey (BGS) is a partly publicly funded body which aims to advance geoscientific knowledge of the United Kingdom landmass and its continental shelf by means of systematic surveying, monitoring and research. The BGS h ...

, to conform with new standards and to allow scope for more detailed subdivisions.

Subdivision

The Lambeth Group consists of three formations: *The

Reading Formation The Reading Formation is a geologic formation in southern England. It dates to the Paleocene period, and is part of the Lambeth Group. It overlies the London Basin and is below the Harwich Formation. The formation is composed of "a series of lent ...

: a series of lenticular mottled

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...

s and sands, here and there with pebbly beds and masses of fine sand converted into

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

. These beds are generally un

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

iferous. They are found in the north of the London Basin, mid-west of the Thames Basin and in the Hampshire Basin. *The

Woolwich Formation The Woolwich Formation is a Formation (geology), geological formation in southeast England. It preserves fossils dating back to the Paleogene Period (geology), period. See also * List of fossiliferous stratigraphic units in England References ...

: grey clays and pale sands, often

estuarine An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...

shells comprise a great deal, in places including a well-marked

oyster Oyster is the common name for a number of different families of salt-water bivalve molluscs that live in marine or brackish habitats. In some species, the valves are highly calcified, and many are somewhat irregular in shape. Many, but not al ...

bed (strata). It overspills borders of west

Kent Kent is a county in South East England and one of the home counties. It borders Greater London to the north-west, Surrey to the west and East Sussex to the south-west, and Essex to the north across the estuary of the River Thames; it faces ...

, is found in edges of east Kent, in south

Essex Essex () is a county in the East of England. One of the home counties, it borders Suffolk and Cambridgeshire to the north, the North Sea to the east, Hertfordshire to the west, Kent across the estuary of the River Thames to the south, and G ...

and at Newhaven,

Sussex Sussex (), from the Old English (), is a historic county in South East England that was formerly an independent medieval Anglo-Saxon kingdom. It is bounded to the west by Hampshire, north by Surrey, northeast by Kent, south by the English ...

. At the base of the shell-rich clayer lay in southeast London are pebble beds and lignitic layers. *The

Upnor Formation The Upnor Formation is a geological formation found in the London Basin of southeastern England.false-bedded sands with marine fossils occurs in east Kent. Where it rests on the Thanet beds it is an argillaceous greensand with rounded

flint Flint, occasionally flintstone, is a sedimentary cryptocrystalline form of the mineral quartz, categorized as the variety of chert that occurs in chalk or marly limestone. Flint was widely used historically to make stone tools and start fir ...

pebbles; where it rests on the

chalk Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor. Chalk ...

it is more clayey and the flints are less rounded and are green-coated. In

Dorset Dorset ( ; archaically: Dorsetshire , ) is a county in South West England on the English Channel coast. The ceremonial county comprises the unitary authority areas of Bournemouth, Christchurch and Poole and Dorset (unitary authority), Dors ...

the Reading Formation appears on the coast at

Studland Bay Studland is a village and civil parish on the Isle of Purbeck in Dorset, England. The village is located about north of the town of Swanage, over a steep chalk ridge, and south of the South East Dorset conurbation at Sandbanks, from which it is ...

and at other points inland. The

Hertfordshire puddingstone Hertfordshire puddingstone is a conglomerate sedimentary rock composed of rounded flint pebbles cemented together by a younger matrix of silica quartz. The distinctive rock is largely confined to the English counties of Buckinghamshire and Hert ...

is a distinctive rock from near the base of the formation; a

pebbly conglomerate in a siliceous matrix. The fossils, estuarine, freshwater and marine, include ''

Corbicula ''Corbicula'' is a genus of freshwater and brackish water clams, Aquatic animal, aquatic bivalve mollusks in the family Cyrenidae, the basket clams.Gofas, S. (2015). Cyrenidae Gray, 1847. In: MolluscaBase (2015). Accessed through: World Registe ...

cuneiformis'', ''C. tellinella'', ''

Ostrea ''Ostrea'' is a genus of edible oysters, marine bivalve mollusks in the family Ostreidae, the oysters. Fossil records This genus is very ancient. It is known in the fossil records from the Permian to the Quaternary (age range: from 259 to 0.0 ...

bellovacina'', '' Viva parus lentus'', ''

Planorbis ''Planorbis'' is a genus of air-breathing freshwater snails, aquatic pulmonate gastropod mollusks in the family Planorbidae, the ram's horn snails, or planorbids. All species in this genus have sinistral or left-coiling shells.Bouchet, P.; Rosen ...

hemistoma'', ''

Melania Melania is a feminine given name that derives from the Greek word (melania) meaning "black, dark". People named Melania include: * Melania the Elder (350–410), a Christian saint and an influential figure in the ascetic movement * Melania the ...

(Melanatria) inquinata'', '' Neritina globulus'', and the remains of

turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked tu ...

crocodile Crocodiles (family (biology), family Crocodylidae) or true crocodiles are large semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term crocodile is sometimes used even more loosely to inclu ...

shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimo ...

s, birds (''

Gastornis ''Gastornis'' is an extinct genus of large flightless birds that lived during the mid Paleocene to mid Eocene epochs of the Paleogene period. Fossils have been found in Europe, Asia and North America, with the remains from North America or ...

'') and the mammal ''

Coryphodon ''Coryphodon'' (from Greek κορῦφὴ, "point", and ὀδοὺς, "tooth", meaning ''peaked tooth'', referring to "the development of the angles of the ridges into points n the molars") is an extinct genus of pantodonts of the family Corypho ...

''. Bricks, tiles and coarse pottery and occasionally firebricks have been made from the clay beds in this formation.

Stratigraphic relationship

Except in the

Hampshire Hampshire (, ; abbreviated to Hants) is a ceremonial county, ceremonial and non-metropolitan county, non-metropolitan counties of England, county in western South East England on the coast of the English Channel. Home to two major English citi ...

Basin, the Lambeth Group usually rests on the

Thanet Formation The Thanet Formation is a Formation (geology), geological formation found in the London Basin of southeastern England.Montrose Group, but is found on the

Chalk Group The Chalk Group (often just called the Chalk) is the lithostratigraphic unit (a certain number of rock strata) which contains the Upper Cretaceous limestone succession in southern and eastern England. The same or similar rock sequences occur acr ...

near

Bromley Bromley is a large town in Greater London, England, within the London Borough of Bromley. It is south-east of Charing Cross, and had an estimated population of 87,889 as of 2011. Originally part of Kent, Bromley became a market town, char ...

, Charlton,

Hungerford Hungerford is a historic market town and civil parish in Berkshire, England, west of Newbury, east of Marlborough, northeast of Salisbury and 60 miles (97 km) west of London. The Kennet and Avon Canal passes through the town alongside the ...

Hertford Hertford ( ) is the county town of Hertfordshire, England, and is also a civil parish in the East Hertfordshire district of the county. The parish had a population of 26,783 at the 2011 census. The town grew around a ford on the River Lea, ne ...

and

Reading Reading is the process of taking in the sense or meaning of Letter (alphabet), letters, symbols, etc., especially by Visual perception, sight or Somatosensory system, touch. For educators and researchers, reading is a multifaceted process invo ...

. It is usually covered by the

Harwich Formation The Harwich Formation is a geological formation found in the London Basin of southeastern England. It is Ypresian (early Eocene) in age. It lies unconformably on the Lambeth Group over most of its extent, but may overlie either the Thanet Formatio ...

, the oldest

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondar ...

of the

Thames Group The Thames Group is an Eocene lithostratigraphic group (a sequence of rock strata) which is widespread in southeast England, especially in the Hampshire Basin from Dorset through Hampshire to West Sussex and in the Isle of Wight and in the London ...

Notes

References

* * * {{cite book , last=Jackson , first=A.A. , title=Bedrock geology UK south. An explanation of the bedrock geology map of England and Wales{{snd1:625,000 fifth edition , publisher=British Geological Survey , publication-place=Keyworth, Nottingham , year=2007 , isbn=978-0-85272-586-3 , oclc=243694452 , ref={{sfnref , British Geological Survey , 2007 Geologic formations of England Geological groups of the United Kingdom Paleocene Series of Europe Paleogene England Thanetian Stage Ypresian Stage Geology of Hampshire Geology of London