Lambeth Group
Encyclopedia
The Lambeth Group is a stratigraphic group
, a set of geological rock strata in the London
and Hampshire Basin
s of southern England
. 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
age (lower Eocene
). It is found throughout the London Basin with a thickness between 10m and 30m and the Hampshire Basin
with a thickness between 50m and less than 25m. Surface outcrops are present only on the outskirts of these, however, that the Lambeth Group underlies some 25% of London at a depth of less than 30m means the formation is of great engineering interest for tunnelling and foundations.
and A. Brongniart. It was called the Mottled Clay by J. Prestwich 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, however, has in turn been recently deprecated in 1994 in favour of the Lambeth Group by the British Geological Survey
in order to conform with new standards and to allow scope for more detailed subdivisions.
In Dorset
the Reading Formation appears on the coast at Studland Bay and at other points inland. The Hertfordshire puddingstone
is a well-known rock from near the base of the formation; it is a flint
pebbly conglomerate in a siliceous matrix. The fossils, estuarine, freshwater and marine, include Corbicula
cuneiformis, C. tellinella, Ostrea
bellovacina, Viva parus lentus, Planorbis
hemistoma, Melania (Melanatria) inquinata, Neritina
globulus, and the remains of turtle
s, crocodile
s, shark
s, birds (Gastornis
) and the mammal Coryphodon
. Bricks, tiles and coarse pottery and occasionally firebricks have been made from the clay beds in this formation.
basin the Lambeth Group usually rests on the Thanet Sand Formation, but they are found on the Chalk Group near Bromley
, Charlton
, Hungerford
, Hertford
, Reading
, etc. It is usually covered by the Harwich Formation, the oldest formation of the Thames Group.
Group (stratigraphy)
A group in stratigraphy is a lithostratigraphic unit, a part of the geologic record or rock column that consists of defined rock strata. Groups are divided into formations and are sometimes themselves grouped into "supergroups"....
, a set of geological rock strata in the London
London Basin
The London Basin is an elongated, roughly triangular sedimentary basin approximately long which underlies London and a large area of south east England, south eastern East Anglia and the adjacent North Sea...
and Hampshire Basin
Hampshire Basin
The Hampshire Basin is a geological basin of Paleogene age in southern England, underlying parts of Hampshire, the Isle of Wight, Dorset, and Sussex...
s of southern England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
. 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
Ypresian
In the geologic timescale the Ypresian is the oldest age or lowest stratigraphic stage of the Eocene. It spans the time between and , is preceded by the Thanetian age and is followed by the Eocene Lutetian age....
age (lower Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
). It is found throughout the London Basin with a thickness between 10m and 30m and the Hampshire Basin
Hampshire Basin
The Hampshire Basin is a geological basin of Paleogene age in southern England, underlying parts of Hampshire, the Isle of Wight, Dorset, and Sussex...
with a thickness between 50m and less than 25m. Surface outcrops are present only on the outskirts of these, however, that the Lambeth Group underlies some 25% of London at a depth of less than 30m means the formation is of great 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 CuvierGeorges Cuvier
Georges Chrétien Léopold Dagobert Cuvier or Jean Léopold Nicolas Frédéric Cuvier , known as Georges Cuvier, was a French naturalist and zoologist...
and A. Brongniart. It was called the Mottled Clay by J. Prestwich 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, however, has in turn been recently deprecated in 1994 in favour of the Lambeth Group by the British Geological Survey
British Geological Survey
The British Geological Survey 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 headquarters are in Keyworth, Nottinghamshire, but other centres...
in order to conform with new standards and to allow scope for more detailed subdivisions.
Subdivision
The Lambeth Group consists of three formations:- The Reading Formation, a series of lenticular mottled clayClayClay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
s and sands, here and there with pebbly beds and masses of fine sand converted into sandstoneSandstoneSandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
. These beds are generally unfossilFossilFossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
iferous. They are found in the north and west portions of the London Basin and in the Hampshire Basin. - The Woolwich Formation, grey clays and pale sands, often full of estuarineEstuaryAn estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....
shells and in places with a well-marked oysterOysterThe word oyster is used as a common name for a number of distinct groups of bivalve molluscs which live in marine or brackish habitats. The valves are highly calcified....
bed. At the base of the shell-bearing clays in southeast London there are pebble beds and ligniticLigniteLignite, often referred to as brown coal, or Rosebud coal by Northern Pacific Railroad,is a soft brown fuel with characteristics that put it somewhere between coal and peat...
layers. The Woolwich Formation occurs in west KentKentKent is a county in southeast England, and is one of the home counties. It borders East Sussex, Surrey and Greater London and has a defined boundary with Essex in the middle of the Thames Estuary. The ceremonial county boundaries of Kent include the shire county of Kent and the unitary borough of...
, the east borders of SurreySurreySurrey is a county in the South East of England and is one of the Home Counties. The county borders Greater London, Kent, East Sussex, West Sussex, Hampshire and Berkshire. The historic county town is Guildford. Surrey County Council sits at Kingston upon Thames, although this has been part of...
, the borders of east Kent, in south EssexEssexEssex is a ceremonial and non-metropolitan county in the East region of England, and one of the home counties. It is located to the northeast of Greater London. It borders with Cambridgeshire and Suffolk to the north, Hertfordshire to the west, Kent to the South and London to the south west...
and at NewhavenNewhaven, East SussexNewhaven is a town in the Lewes District of East Sussex in England. It lies at the mouth of the River Ouse, on the English Channel coast, and is a ferry port for services to France.-Origins:...
in SussexSussexSussex , from the Old English Sūþsēaxe , is an historic county in South East England corresponding roughly in area to the ancient Kingdom of Sussex. It is bounded on the north by Surrey, east by Kent, south by the English Channel, and west by Hampshire, and is divided for local government into West...
. - The Upnor Formation, consisting of light-colored false-bedded sands with marine fossils occurs in east Kent. Where it rests on the Thanet beds it is an argillaceous greensand with rounded flintFlintFlint is a hard, sedimentary cryptocrystalline form of the mineral quartz, categorized as a variety of chert. It occurs chiefly as nodules and masses in sedimentary rocks, such as chalks and limestones. Inside the nodule, flint is usually dark grey, black, green, white, or brown in colour, and...
pebbles; where it rests on the chalkChalkChalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates shed from micro-organisms called coccolithophores....
it is more clayey and the flints are less rounded and are green-coated.
In Dorset
Dorset
Dorset , is a county in South West England on the English Channel coast. The county town is Dorchester which is situated in the south. The Hampshire towns of Bournemouth and Christchurch joined the county with the reorganisation of local government in 1974...
the Reading Formation appears on the coast at Studland Bay and at other points inland. The Hertfordshire puddingstone
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 county of Hertfordshire but small amounts occur throughout the London Basin. Despite a...
is a well-known rock from near the base of the formation; it is a flint
Flint
Flint is a hard, sedimentary cryptocrystalline form of the mineral quartz, categorized as a variety of chert. It occurs chiefly as nodules and masses in sedimentary rocks, such as chalks and limestones. Inside the nodule, flint is usually dark grey, black, green, white, or brown in colour, and...
pebbly conglomerate in a siliceous matrix. The fossils, estuarine, freshwater and marine, include Corbicula
Corbicula
Corbicula is a genus of freshwater and brackish water clams, aquatic bivalve mollusks in the family Corbiculidae, the basket clams.The genus name is derived from Latin corbis "basket", referring to the shape and ribs of the shell....
cuneiformis, C. tellinella, Ostrea
Ostrea
Ostrea is a genus of oyster in the family Ostreidae. Evidence of a number of species of this genus in the geological fossil record demonstrates the ancient nature of this genus, and also gives testimony to the species that co-existed with members of the Ostrea genus...
bellovacina, Viva parus lentus, Planorbis
Planorbis
Planorbis is a genus of freshwater air-breathing 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.- Description :...
hemistoma, Melania (Melanatria) inquinata, Neritina
Neritina
Neritina is a genus of small aquatic snails with an operculum, marine, brackish water, and sometimes freshwater gastropod mollusks in the family Neritidae, the nerites.Neritina is the type genus of the tribe Neritinini.- Species :...
globulus, and the remains of turtle
Turtle
Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...
s, crocodile
Crocodile
A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all extant members of the order Crocodilia: i.e...
s, shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....
s, birds (Gastornis
Gastornis
Gastornis is an extinct genus of large flightless bird that lived during the late Paleocene and Eocene epochs of the Cenozoic. It was named in 1855, after Gaston Planté, who had discovered the first fossils in Argile Plastique formation deposits at Meudon near Paris...
) and the mammal Coryphodon
Coryphodon
Coryphodon is an extinct genus of mammal. It was widespread in North America between 59 and 51 million years ago. It is regarded as the ancestor of the genus Hypercoryphodon of Mid Eocene Mongolia....
. Bricks, tiles and coarse pottery and occasionally firebricks have been made from the clay beds in this formation.
Stratigraphic relationship
Except in the HampshireHampshire
Hampshire is a county on the southern coast of England in the United Kingdom. The county town of Hampshire is Winchester, a historic cathedral city that was once the capital of England. Hampshire is notable for housing the original birthplaces of the Royal Navy, British Army, and Royal Air Force...
basin the Lambeth Group usually rests on the Thanet Sand Formation, but they are found on the Chalk Group near Bromley
Bromley
Bromley is a large suburban town in south east London, England and the administrative headquarters of the London Borough of Bromley. It was historically a market town, and prior to 1963 was in the county of Kent and formed the administrative centre of the Municipal Borough of Bromley...
, Charlton
Charlton, London
Charlton is a district of south London, England, and part of the London Borough of Greenwich. It is located east-southeast of Charing Cross. Charlton next Woolwich was an ancient parish in the county of Kent, which became part of the metropolitan area of London in 1855. It is home to Charlton...
, Hungerford
Hungerford
Hungerford is a market town and civil parish in Berkshire, England, 9 miles west of Newbury. It covers an area of and, according to the 2001 census, has a population of 5,559 .- Geography :...
, Hertford
Hertford
Hertford is the county town of Hertfordshire, England, and is also a civil parish in the East Hertfordshire district of the county. Forming a civil parish, the 2001 census put the population of Hertford at about 24,180. Recent estimates are that it is now around 28,000...
, Reading
Reading, Berkshire
Reading is a large town and unitary authority area in England. It is located in the Thames Valley at the confluence of the River Thames and River Kennet, and on both the Great Western Main Line railway and the M4 motorway, some west of London....
, etc. It is usually covered by the Harwich Formation, the oldest formation of the Thames Group.