Ancestral Thames
   HOME

TheInfoList



OR:

The Ancestral Thames is the geologically ancient precursor to the present day
River Thames The River Thames ( ), known alternatively in parts as the The Isis, River Isis, is a river that flows through southern England including London. At , it is the longest river entirely in England and the Longest rivers of the United Kingdom, s ...
. The river has its origins in the emergence of Britain from a
Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...
sea over 60 million years ago. Parts of the river's course were profoundly modified by the Anglian (or Elsterian) glaciation some 450,000 years ago. The extensive terrace deposits laid down by the Ancestral Thames over the past two million years or so have provided a rich source of material for studies in
geology Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth ...
,
geomorphology Geomorphology () is the scientific study of the origin and evolution of topographic and bathymetric features generated by physical, chemical or biological processes operating at or near Earth's surface. Geomorphologists seek to understand wh ...
,
palaeontology Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure geo ...
and
archaeology Archaeology or archeology is the study of human activity through the recovery and analysis of material culture. The archaeological record consists of Artifact (archaeology), artifacts, architecture, biofact (archaeology), biofacts or ecofacts, ...
.


Cretaceous to Miocene periods

During the latter part of the Cretaceous period, around 80 million years ago, sea level is thought to have been over 150 metres higher than today. Much of the land which was later to form Britain was covered by sea. In this marine environment, thick deposits of
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. Ch ...
were laid down. From the early
Paleocene The Paleocene ( ), or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), ...
(from around 65 million years ago), much of what is now Britain emerged above sea level. The maximum uplift occurred in the north-west, with a regional tilt towards the east and south-east. The
North Sea The North Sea lies between Great Britain, Denmark, Norway, Germany, the Netherlands, Belgium, and France. A sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian Se ...
basin and the western
English Channel The English Channel, also known as the Channel, is an arm of the Atlantic Ocean that separates Southern England from northern France. It links to the southern part of the North Sea by the Strait of Dover at its northeastern end. It is the busi ...
basin also developed. The drainage of much of England was thus aligned to the south-east. As the land emerged from beneath the Cretaceous sea, precursors of some of today's major drainage systems of central, eastern and southern England developed. Thus, from the early
Tertiary Tertiary (from Latin, meaning 'third' or 'of the third degree/order..') may refer to: * Tertiary period, an obsolete geologic period spanning from 66 to 2.6 million years ago * Tertiary (chemistry), a term describing bonding patterns in organic ch ...
period a number of major consequent rivers flowed approximately NW-SE down the tilted emergent Chalk surface towards what later became southern England. One of those watercourses was a precursor of the River Thames. South-eastern England was low-lying and, from the late Palaeocene onwards (from about 55 million years ago), it was inundated periodically by marine transgressions from the east. Substantial deposits of marine,
lacustrine A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from t ...
and deltaic origin were laid down across the region. In particular, over 150 metres of
London Clay The London Clay Formation is a Sediment#Shores and shallow seas, marine formation (geology), geological formation of Ypresian (early Eocene Epoch, c. 54-50 million years ago) age which outcrop, crops out in the southeast of England. The London C ...
were laid down. And, as the Palaeocene period progressed, subsidence in this region led to the formation of the
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. The basin formed as a result of compr ...
, with its approximately west-east axis. The Ancestral Thames thus flowed from the north-west, into this basin. By the
Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...
period, around 30 million years ago, the coastline had retreated to the east of the London Basin. It is believed that, at that time, the Ancestral Thames was still flowing from the north-west, into the London Basin. From there, the river flowed broadly eastwards towards the North Sea basin of that period. And, also by the Oligocene period, the Wealden (or Weald-Artois) Anticline, to the south of the London Basin, was uplifted as a result of the
Alpine orogeny The Alpine orogeny, sometimes referred to as the Alpide orogeny, is an orogenic phase in the Late Mesozoic and the current Cenozoic which has formed the mountain ranges of the Alpide belt. Cause The Alpine orogeny was caused by the African c ...
. Gibbard & Lewin 2003, ''Neogene (Miocene and Pliocene)'' section. Rivers which were draining from the northern flank of that anticline - precursors of watercourses like today's
Mole Mole (or Molé) may refer to: Animals * Mole (animal) or "true mole" * Golden mole, southern African mammals * Marsupial mole Marsupial moles, the Notoryctidae family, are two species of highly specialized marsupial mammals that are found i ...
, Wey and
Darent The Darent is a Kentish tributary of the River Thames and takes the waters of the River Cray as a tributary in the tidal portion of the Darent near Crayford. ' Darenth' is frequently found as the spelling of the river's name in older books and ...
rivers - would have begun feeding into the Thames from the south. Further east, a proto-
Medway Medway is a Unitary authorities of England, unitary authority area with Borough status in the United Kingdom, borough status in the ceremonial county of Kent in South East England. It was formed in 1998 by merging the boroughs of City of Roche ...
river also flowed northwards from the Weald. But that watercourse flowed parallel to the proto-Thames towards the North Sea basin, and it did not form a confluence with the Thames until later on, in the Pleistocene period. There were periodic marine transgressions towards the London Basin during the
Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
period (around 10-20 million years ago), but it is thought that these did not significantly alter pre-existing drainage systems.


Pliocene period to early Middle Pleistocene period

At times during the
Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Crag Crag may refer to: * Crag (climbing), a cliff or group of cliffs, in any location, which is or may be suitable for climbing * Crag (dice game), a dice game played with three dice * Crag, Arizona, US * Crag, West Virginia, US * Crag and tail, a ...
formations in an area now occupied by parts of
East Anglia East Anglia is an area of the East of England, often defined as including the counties of Norfolk, Suffolk and Cambridgeshire, with parts of Essex sometimes also included. The name derives from the Anglo-Saxon kingdom of the East Angles, ...
. But, again, this appears not to have had any significant effect on the Thames drainage system. However, in the Late Pliocene and early
Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...
periods (c.3-2 million years ago), the London Basin became submerged. Fossiliferous sands were deposited. Subsequent Pleistocene uplift caused a relative displacement of c.180 metres between the western London Basin and the
Suffolk Suffolk ( ) is a ceremonial county in the East of England and East Anglia. It is bordered by Norfolk to the north, the North Sea to the east, Essex to the south, and Cambridgeshire to the west. Ipswich is the largest settlement and the county ...
coast, and remnants of those fossiliferous sands are now found at up to that altitude in the
North Downs The North Downs are a ridge of chalk hills in south east England that stretch from Farnham in Surrey to the White Cliffs of Dover in Kent. Much of the North Downs comprises two Area of Outstanding Natural Beauty, Areas of Outstanding Natural Be ...
and
Chiltern Hills The Chiltern Hills or the Chilterns are a chalk escarpment in southern England, located to the north-west of London, covering across Oxfordshire, Buckinghamshire, Hertfordshire and Bedfordshire; they stretch from Goring-on-Thames in the south- ...
. As the sea retreated eastwards, the River Thames system occupied the basin vacated by the sea. There is evidence that, for a time during the Early and possibly Middle Pleistocene period (c.2-0.5 million years ago), the headwaters of the River Thames extended north-westwards as far as north
Wales Wales ( ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by the Irish Sea to the north and west, England to the England–Wales border, east, the Bristol Channel to the south, and the Celtic ...
. Pebbles from formations of that area have been found in deposits laid down by the Thames in East Anglia. It has also been established that, during that time, the Thames, after entering the London Basin somewhere around the
Goring Gap The Goring Gap is a topographical feature on the course of the River Thames. The Gap is located in southern England where the river, flowing from north to south, cuts through and crosses a line of chalk hills in a relatively narrow gap between ...
, then followed a course north-eastwards and northwards into North
Norfolk Norfolk ( ) is a Ceremonial counties of England, ceremonial county in England, located in East Anglia and officially part of the East of England region. It borders Lincolnshire and The Wash to the north-west, the North Sea to the north and eas ...
, on a course towards the North Sea Basin. At times, "the southern North Sea was occupied by the huge delta complex of the North German Rivers, the Rhine, Thames, Meuse and Scheldt". The Early and Middle Pleistocene gravel which was deposited by the Thames in East Anglia also contains
chert Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a prec ...
from
Lower Greensand The Lower Greensand Group is a geological unit present across large areas of Southern England. It was deposited during the Aptian and Albian ages of the Early Cretaceous. It predominantly consists of sandstone and unconsolidated sand that were d ...
beds to the south of London, and this "can only have been transported northwards by south-bank tributaries of the Thames and then the Thames itself". Thus, ancestral versions of today's Mole, Wey and Darent rivers were feeding into the Thames from the Weald at that time. (The Mole and Wey joined to form one river in south
London London is the Capital city, capital and List of urban areas in the United Kingdom, largest city of both England and the United Kingdom, with a population of in . London metropolitan area, Its wider metropolitan area is the largest in Wester ...
, and that Mole-Wey watercourse flowed north-eastwards across London and south
Hertfordshire Hertfordshire ( or ; often abbreviated Herts) is a ceremonial county in the East of England and one of the home counties. It borders Bedfordshire to the north-west, Cambridgeshire to the north-east, Essex to the east, Greater London to the ...
before joining the Thames. ) The deposits laid down by the Thames in East Anglia are also said to contain material from "
Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...
and
Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...
sandstones from southern Wales". This suggests that the headwaters of the
River Kennet The Kennet is a tributary of the River Thames in Southern England. Most of the river is straddled by the North Wessex Downs AONB (Area of Outstanding Natural Beauty). The lower reaches have been made navigable as the Kennet Navigation, which â ...
(which today has its source in
Wiltshire Wiltshire (; abbreviated to Wilts) is a ceremonial county in South West England. It borders Gloucestershire to the north, Oxfordshire to the north-east, Berkshire to the east, Hampshire to the south-east, Dorset to the south, and Somerset to ...
and meets the Thames at
Reading Reading is the process of taking in the sense or meaning of symbols, often specifically those of a written language, by means of Visual perception, sight or Somatosensory system, touch. For educators and researchers, reading is a multifacete ...
), extended back into south Wales during the Early and Middle Pleistocene periods. During the Early and Middle Pleistocene, prior to the Anglian glaciation, the Thames in the Chilterns and in East Anglia moved progressively south-eastwards. In the Chilterns, it moved south-eastwards to a line approximately along the Vale of
St Albans St Albans () is a cathedral city in Hertfordshire, England, east of Hemel Hempstead and west of Hatfield, Hertfordshire, Hatfield, north-west of London, south-west of Welwyn Garden City and south-east of Luton. St Albans was the first major ...
. In East Anglia, it moved down to around
Colchester Colchester ( ) is a city in northeastern Essex, England. It is the second-largest settlement in the county, with a population of 130,245 at the 2021 United Kingdom census, 2021 Census. The demonym is ''Colcestrian''. Colchester occupies the ...
. East of that, around Clacton, the Thames finally formed a confluence with the River Medway. It seems likely that, at some time prior to the Anglian glaciation, the River Darent was captured by a left-bank tributary of the Medway. The Darent thus ceased to be a right-bank tributary of the Ancestral Thames, and instead turned east somewhere just north of
Dartford Dartford is the principal town in the Borough of Dartford, Kent, England. It is located south-east of Central London and is situated adjacent to the London Borough of Bexley to its west. To its north, across the Thames Estuary, is Thurrock in ...
, and flowed into the Medway. As noted below, it is thought that, when the Thames was diverted by the Anglian glaciation, it followed this lower section of the Darent into the Medway.


Middle and Late Pleistocene periods

During the Anglian glaciation, some 450,000 years ago, ice sheets of a significantly greater amplitude than that of any ice sheets which had previously developed in the Pleistocene moved down from Scandinavia and the north of Britain. They coalesced and reached as far south as the southern part of the North Sea basin, East Anglia, London, the
Cotswolds The Cotswolds ( ) is a region of central South West England, along a range of rolling hills that rise from the meadows of the upper River Thames to an escarpment above the Severn Valley and the Vale of Evesham. The area is defined by the bedroc ...
and South Wales. One result of this was that the Thames lost those of its headwaters which had previously extended back into the
Midlands The Midlands is the central region of England, to the south of Northern England, to the north of southern England, to the east of Wales, and to the west of the North Sea. The Midlands comprises the ceremonial counties of Derbyshire, Herefor ...
and Wales. The Anglian glaciation had the effect of causing a breach of the land bridge between Britain and north-west Europe, across the Weald-Artois anticline. This was because of the formation and overflow southwards of a large pro-glacial lake which was fed by the Thames,
Rhine The Rhine ( ) is one of the List of rivers of Europe, major rivers in Europe. The river begins in the Swiss canton of Graubünden in the southeastern Swiss Alps. It forms part of the Swiss-Liechtenstein border, then part of the Austria–Swit ...
and other major north-west European rivers and which was blocked to the north by the coalesced ice sheets. The lake drained, with immense force, into the Channel River to the south-west, thus carving out what was later to become the
Dover Strait The Strait of Dover or Dover Strait, historically known as the Dover Narrows, is the strait at the narrowest part of the English Channel, marking the boundary between the Channel and the North Sea, and separating Great Britain from continental ...
. The Anglian ice sheet in East Anglia, and its powerful outwash, completely overrode and engulfed the course of the Thames east of around
Watford Watford () is a town and non-metropolitan district with Borough status in the United Kingdom, borough status in Hertfordshire, England, northwest of Central London, on the banks of the River Colne, Hertfordshire, River Colne. Initially a smal ...
. The flow of the Thames was blocked and a proglacial lake was formed. The Thames was diverted away from its course along the Vale of St Albans, and it moved southwards to a line running from
Uxbridge Uxbridge () is a suburban town in west London, England, and the administrative headquarters of the London Borough of Hillingdon, northwest of Charing Cross. Uxbridge formed part of the parish of Hillingdon in the county of Middlesex. As part ...
to
Richmond Richmond most often refers to: * Richmond, British Columbia, a city in Canada * Richmond, California, a city in the United States * Richmond, London, a town in the London Borough of Richmond upon Thames, England * Richmond, North Yorkshire, a town ...
, then north-east to
Walthamstow Walthamstow ( or ) is a town within the London Borough of Waltham Forest in east London. The town borders Chingford to the north, Snaresbrook and South Woodford to the east, Leyton and Leytonstone to the south, and Tottenham to the west. At ...
, then eastwards, following in part the line of the pre-Anglian lower section of the River Darent, to about the current position of the Thames estuary. There, it joined the Medway coming from
Kent Kent is a Ceremonial counties of England, ceremonial county in South East England. It is bordered by Essex across the Thames Estuary to the north, the Strait of Dover to the south-east, East Sussex to the south-west, Surrey to the west, and Gr ...
. From there, the Thames flowed roughly northwards, along the course of the Medway, to re-join its former course at Clacton. Then the river flowed into the North Sea basin of that time. The Mole-Wey river was also blocked by the advancing Anglian ice sheet, and a proglacial lake was formed in that river's valley, south of
Finchley Finchley () is a large district of north London, England, in the London Borough of Barnet. north of Charing Cross, nearby districts include: Golders Green, Muswell Hill, Friern Barnet, Whetstone, London, Whetstone, Mill Hill and Hendon. It is ...
. The river subsequently joined the Thames at Richmond. The Thames's north bank tributary, the Lea, extended its course southwards from Hertfordshire to join the diverted Thames somewhere south of
Tottenham Tottenham (, , , ) is a district in north London, England, within the London Borough of Haringey. It is located in the Ceremonial counties of England, ceremonial county of Greater London. Tottenham is centred north-northeast of Charing Cross, ...
. In addition, the Colne river was formed as a new north bank tributary of the Thames, flowing south from Hertfordshire, along part of the former valley of the Thames, to join the Thames at Uxbridge. Between the end of the Anglian glaciation and the principal Wolstonian (or Saalian) glaciation about 150,000 years ago, sea level fell and rose as secondary glaciations came and went. But, during periods of low sea level in this time, it seems that the Thames turned to the south-west after leaving where
Essex Essex ( ) is a Ceremonial counties of England, ceremonial county in the East of England, and one of the home counties. It is bordered by Cambridgeshire and Suffolk to the north, the North Sea to the east, Kent across the Thames Estuary to the ...
is today, then went through the proto-Dover Strait, and reached the sea in the English Channel. The Rhine, however, continued to flow northwards towards the North Sea basin. Even at times of relatively high sea level, there was usually a land barrier between the estuaries of the Thames and the Rhine. And also between the Anglian glaciation and the principal Wolstonian glaciation, the Thames in eastern Essex migrated southwards, from around Clacton to around
Southend-on-Sea Southend-on-Sea (), commonly referred to as Southend (), is a coastal city and unitary authorities of England, unitary authority area with Borough status in the United Kingdom, borough status in south-eastern Essex, England. It lies on the nor ...
. During the principal Wolstonian glaciation, ice sheets from the north coalesced once again. As during the earlier Anglian glaciation, a pro-glacial lake built up, fed by the Rhine in particular. That lake too overflowed south-westwards, reinforcing the proto-Dover Strait. This process may have played a significant role in the formation of the relatively deep and box-shaped Lobourg Channel in the bed of what is now the Dover Strait. Once the Wolstonian lake was drained, the Rhine then flowed south-westwards, to turn towards the English Channel and join the Thames. The combined rivers presumably flowed through the Lobourg Channel. Sea level rose again in the Ipswichian/Eemian interglacial period, around 120,000 years ago. The land bridge between Britain and the continent was cut off again. The River Thames then joined the sea a little inland compared to now. Sea level fell again during the Devensian/Weichselian glaciation (115,000-12,000 years ago). This temporarily linked Britain and north-west Europe once more. However, the Thames and Rhine continued to flow south-westwards into the English Channel, not northwards towards the North Sea basin. Sea level rose again towards the end of the Devensian glaciation. This led to the creation of the current coastline from around 8,000 years ago, with the Thames reaching the sea at its Essex-Kent estuary. Inland of that estuary, and throughout post-Anglian times, the Thames shifted its course in various ways. (However, there were no further ''substantial'' changes to either the course of the river inland or to its catchment area.) For example, in west London, the Thames moved south from
Hillingdon Hillingdon is an area of Uxbridge within the London Borough of Hillingdon, centred 14.2 miles (22.8 km) west of Charing Cross. It was an ancient parish in Middlesex that included the market town of Uxbridge. During the 1920s the civil pari ...
to
Weybridge Weybridge () is a town in the Borough of Elmbridge, Elmbridge district in Surrey, England, around southwest of central London. The settlement is recorded as ''Waigebrugge'' and ''Weibrugge'' in the 7th century and the name derives from a cro ...
. And in east London the river moved southwards also, from Walthamstow to
Greenwich Greenwich ( , , ) is an List of areas of London, area in south-east London, England, within the Ceremonial counties of England, ceremonial county of Greater London, east-south-east of Charing Cross. Greenwich is notable for its maritime hi ...
.


Deposits of the Ancestral Thames and its tributaries

The onset of colder climatic conditions at the beginning of the Pleistocene period led to frequent downcutting by rivers in the Thames catchment area (and in north-west Europe in general).
Periglacial Periglaciation (adjective: "periglacial", referring to places at the edges of glacial areas) describes geomorphic processes that result from seasonal thawing and freezing, very often in areas of permafrost. The meltwater may refreeze in ice wedg ...
processes also supplied abundant material for periodic
aggradation Aggradation (or alluviation) is the term used in geology for the increase in land elevation, typically in a river system, due to the deposition of sediment. Aggradation occurs in areas in which the supply of sediment is greater than the amount o ...
, which mostly took place in
braided river A braided river (also called braided channel or braided stream) consists of a network of river channel (geography), channels separated by small, often temporary, islands called ''braid bars'' or, in British English usage, ''aits'' or ''eyots''. ...
environments. Thus, throughout the Pleistocene period, the Thames carved out a number of terraces as it flowed south through
Oxfordshire Oxfordshire ( ; abbreviated ''Oxon'') is a ceremonial county in South East England. The county is bordered by Northamptonshire and Warwickshire to the north, Buckinghamshire to the east, Berkshire to the south, and Wiltshire and Glouceste ...
, crossed the London Basin and then headed across East Anglia to the North Sea basin. The river also laid down on those terraces extensive deposits of (principally) silt, sand and gravel. Across Essex and Suffolk some of those deposits have been referred to as the
Kesgrave Kesgrave is a town and civil parish in the East Suffolk district of Suffolk, England. The town is close to both Ipswich and Woodbridge. Kesgrave forms part of the wider Ipswich Built-up area. History The area was recorded as ''Gressgrava'' in ...
Sands and Gravels. Overall, the Thames valley "includes the largest single spread of terrace deposits in the country". The Thames terrace deposits are remarkably diverse in composition and origin. For example:
- Rocks of volcanic origin from Wales have been found in some of the older deposits.
- " Pudding stone" and sarsen stones from lower
Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...
beds in the London Basin have also been found in places.
- Extensive spreads of wind-blown deposits, laid down in extremely cold, dry conditions during the most recent (Devensian) glaciation, are found in lower stretches of the Thames and Lea valleys. Such deposits are often shown as "
brickearth Brickearth is a term originally used to describe Superficial deposits, superficial windblown deposits found in southern England. The term has been employed in English-speaking regions to describe similar deposits. Brickearths are periglacial ...
" on geological maps. Some of those Thames deposits - especially sands, gravels and brickearth - have proved to be of considerable commercial value and have been extensively worked in quarries and pits. Some of them have also been dated, and, through often minute scientific investigation of the deposits, it has been possible to trace in detail the Pleistocene history of the Thames as it changed course and continually cut down into underlying geological formations. The oldest identified Thames deposits in the London Basin are those at
Nettlebed Nettlebed is a village and civil parish in Oxfordshire in the Chiltern Hills about north-west of Henley-on-Thames and south-east of Wallingford. The parish includes the hamlet of Crocker End, about east of the village. The 2011 Census r ...
(possibly) and
Stoke Row Stoke Row is a village and civil parish in the Chiltern Hills, about west of Henley-on-Thames in South Oxfordshire and about north of Reading. The 2011 Census recorded the parish population as 651. History The earliest known surviving recor ...
in the Oxfordshire Chilterns, at altitudes today of 200 and 175 metres respectively. The Stoke Row deposits are thought to have been laid down nearly two million years ago. Tributaries of the Thames, such as the Evenlode, Kennet, Lea, Mole, Wey and Darent, have also left behind spreads of fluvial deposits. In particular, those tributaries which flowed northwards from the Weald left behind deposits which, in some cases, now lie north of today's River Thames. This is because, as noted above, the confluences of those tributaries with the Thames moved south when the Thames was diverted by the Anglian ice sheet. The oldest of such tributary deposits appear to include spreads of "Pebble Gravel", now found on plateaus and hilltops in north London, Hertfordshire and Essex. It has been suggested that the Stanmore Pebble Gravel at Harrow Weald Common, for example, was laid down at about the same time as the Thames terrace at Stoke Row (see above) - that is, nearly two million years ago. This Stanmore Gravel is seen as representing a south-bank tributary (perhaps a precursor of the Mole-Wey drainage system) of the Early Pleistocene Thames. And the gravel which caps the
Langdon Hills Langdon Hills is an area of Basildon in the borough of Basildon in Essex, England. It is located south of Laindon railway station on the London, Tilbury and Southend line. It is the location of the Langdon Hills Country Park, which is in th ...
, near
Basildon Basildon ( ) is a town in Borough of Basildon, the borough of the same name, in the county of Essex, England. It had a recorded population of 115,955 at the 2021 United Kingdom census, 2021 census. In 1931, the town had a population of 1,159. ...
, is thought to have been laid down by a precursor of the River Darent. However, in the case of similar hilltop gravel deposits - such as those at
High Beach High Beach (or High Beech) is a village inside Epping Forest in south-west Essex, England. Part of the civil parish of Waltham Abbey, the village is within the Epping Forest District and the ward of Waltham Abbey High Beach, and lies approximatel ...
in
Epping Forest Epping Forest is a area of ancient woodland, and other established habitats, which straddles the border between Greater London and Essex. The main body of the forest stretches from Epping in the north, to Chingford on the edge of the Lond ...
, and at Warley, near Brentwood - it is difficult to say at present which former south-bank tributaries of the proto-Thames were responsible for their deposition. Further east, the former River Medway left pre-Anglian river terrace deposits (the "High-Level East Essex Gravel") across a strip of land which runs approximately northwards from Southend-on-Sea. Quartz-rich gravels were deposited by the ancestral
River Thames The River Thames ( ), known alternatively in parts as the The Isis, River Isis, is a river that flows through southern England including London. At , it is the longest river entirely in England and the Longest rivers of the United Kingdom, s ...
in southern Buckinghamshire and adjacent areas of Hertfordshire and Essex.


References

{{reflist Geology of England Former rivers Rivers of England River Thames