Ancestral Thames
Encyclopedia
In central and southern Britain, during the Early and Middle Pleistocene
, two rivers drained Britain, the Bytham River
and the Thames. For most of Early Pleistocene, the ancestral Thames was the main river with, at its maximum extent, a catchment area
that extended into Wales
, and across East Anglia
, and what is now the North Sea, to join the ancestral Rhine. Initially, the Bytham River was a tributary
of the Thames, but progressively, extended its catchment and became the major river of Southern Britain. During the Anglian Stage, the Bytham river disappeared, and the Thames was diverted to its present route to London.
During the early Ice Age
the Thames flowed to the north of London
, through north Essex
, Suffolk
and Norfolk
and out across what is now the southern North Sea
to become a tributary of the Rhine. At that time, the Thames, and its tributaries, would have been a huge river system draining the Welsh mountains and bringing their characteristic volcanic rocks into the Thames basin. The evidence for this being a substantial thickness of what is called Kesgrave Sands and Gravels which represents the actual bed of the river. These old Thames gravels contain a variety of unusual pebbles from as far away as North Wales, proving that.
These gravels also contain large boulders of puddingstone and sarsens, which are very hard conglomerates
and sandstones respectively. They are believed to be derived from pebble and sand seams in the Reading Beds, and which have subsequently become cemented by quartz
. They have been put to use by man as ancient way markers at road junctions. The gravels have great commercial value and are worked in numerous gravel pits between Harlow, Chelmsford and Colchester, which was the route of the ancestral Thames at least 600,000 years ago.
During this time the River Medway flowed north across east Essex to join the Thames near Clacton, leaving behind a ribbon of distinctive gravel which can be found between Burnham-on-Crouch
and Bradwell-on-Sea
. There were also other northward-flowing tributaries of the early Thames. Evidence of these are the patches of gravel that are found on the tops of the hills in south Essex, such as the Langdon Hills
, Warley and High Beach in Epping Forest
.
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
, two rivers drained Britain, the Bytham River
Bytham River
The Bytham River has been proposed as an ancient river in Pleistocene Great Britain that has been suggested to have run through the English Midlands until around 450,000 years ago...
and the Thames. For most of Early Pleistocene, the ancestral Thames was the main river with, at its maximum extent, a catchment area
Drainage basin
A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...
that extended into Wales
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
, and across East Anglia
East Anglia
East Anglia is a traditional name for a region of eastern England, named after an ancient Anglo-Saxon kingdom, the Kingdom of the East Angles. The Angles took their name from their homeland Angeln, in northern Germany. East Anglia initially consisted of Norfolk and Suffolk, but upon the marriage of...
, and what is now the North Sea, to join the ancestral Rhine. Initially, the Bytham River was a tributary
Tributary
A tributary or affluent is a stream or river that flows into a main stem river or a lake. A tributary does not flow directly into a sea or ocean...
of the Thames, but progressively, extended its catchment and became the major river of Southern Britain. During the Anglian Stage, the Bytham river disappeared, and the Thames was diverted to its present route to London.
During the early Ice Age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
the Thames flowed to the north of London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
, through north Essex
Essex
Essex 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...
, Suffolk
Suffolk
Suffolk is a non-metropolitan county of historic origin in East Anglia, England. It has borders with Norfolk to the north, Cambridgeshire to the west and Essex to the south. The North Sea lies to the east...
and Norfolk
Norfolk
Norfolk is a low-lying county in the East of England. It has borders with Lincolnshire to the west, Cambridgeshire to the west and southwest and Suffolk to the south. Its northern and eastern boundaries are the North Sea coast and to the north-west the county is bordered by The Wash. The county...
and out across what is now the southern North Sea
North Sea
In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...
to become a tributary of the Rhine. At that time, the Thames, and its tributaries, would have been a huge river system draining the Welsh mountains and bringing their characteristic volcanic rocks into the Thames basin. The evidence for this being a substantial thickness of what is called Kesgrave Sands and Gravels which represents the actual bed of the river. These old Thames gravels contain a variety of unusual pebbles from as far away as North Wales, proving that.
These gravels also contain large boulders of puddingstone and sarsens, which are very hard conglomerates
Conglomerate (geology)
A conglomerate is a rock consisting of individual clasts within a finer-grained matrix that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts...
and sandstones respectively. They are believed to be derived from pebble and sand seams in the Reading Beds, and which have subsequently become cemented by quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
. They have been put to use by man as ancient way markers at road junctions. The gravels have great commercial value and are worked in numerous gravel pits between Harlow, Chelmsford and Colchester, which was the route of the ancestral Thames at least 600,000 years ago.
During this time the River Medway flowed north across east Essex to join the Thames near Clacton, leaving behind a ribbon of distinctive gravel which can be found between Burnham-on-Crouch
Burnham-on-Crouch
Burnham-on-Crouch is a town in the Maldon district of Essex in the East of England. It lies on the north bank of the River Crouch.-History:Historically, it has benefited from its location on the coast - first as a ferry port, later as a fishing port known for its oyster beds, and most recently as a...
and Bradwell-on-Sea
Bradwell-on-Sea
Bradwell-on-Sea is a village in Essex, England. The village is on the Dengie peninsula. It is located about north-northeast of Southminster and is east from the county town of Chelmsford. The village is in the District of Maldon in the parliamentary constituency of Maldon whose boundaries were...
. There were also other northward-flowing tributaries of the early Thames. Evidence of these are the patches of gravel that are found on the tops of the hills in south Essex, such as the Langdon Hills
Langdon Hills
Langdon Hills is a town located in the Basildon district of Essex, England. It is contiguous with the Basildon continuous urban area.It is located south of Laindon railway station on the London, Tilbury and Southend Railway. It is the location of the Langdon Hills Country Park, which is in the...
, Warley and High Beach in Epping Forest
Epping Forest
Epping Forest is an area of ancient woodland in south-east England, straddling the border between north-east Greater London and Essex. It is a former royal forest, and is managed by the City of London Corporation....
.
External links
- http://www.gsf.fi/publ/foregsatlas/article.php?id=12
- www.essexwt.org.uk/Geology/geology3.htm