Quaternary River Diversions in the London Basin and the Eastern
Total Page:16
File Type:pdf, Size:1020Kb
Document generated on 09/30/2021 1:52 p.m. Géographie physique et Quaternaire Quaternary River Diversions in the London Basin and the Eastern English Channel Les captures quaternaires des fleuves du bassin de Londres et de la Manche orientale Fluss-Ablenkungen im Quartär im Londoner Becken und im östlichen Ärmelkanal D. R. Bridgland and P. L. Gibbard Volume 51, Number 3, 1997 Article abstract The principal river of the London basin, the Thames, has experienced a URI: https://id.erudit.org/iderudit/033132ar number of course changes during the Quaternary. Some, at least, of these are DOI: https://doi.org/10.7202/033132ar known to result directly from glaciation. In the early Quaternary the river flowed to the north of London across East Anglia to the north coast of Norfolk. See table of contents By the early Middle Pleistocene it had changed its course to flow eastwards near the Suffolk - Essex border into the southern North Sea. The Thames valley to the north of London was blocked by ice during the Anglian/Elsterian Publisher(s) glaciation, causing a series of glacial lakes to form. Overflow of these lakes brought the river into its modern valley through London. It is thought that this Les Presses de l'Université de Montréal valley already existed by the Anglian in the form of a tributary of the north-flowing River Medway, which joined the old Thames valley near Clacton. ISSN Also during the Anglian/Elsterian glaciation. British and continental ice masses are thought to have joined in the northern part of the North Sea basin, causing 0705-7199 (print) a large lake to form between the east coast of England and the Netherlands. It 1492-143X (digital) is widely believed that the overflow from this lake caused the first breach in the Weald-Artois Ridge, bringing about the formation of the Strait of Dover. Explore this journal Prior to the glaciation the Thames, in common with rivers from the continent (including the Rhine and Meuse), flowed into the North Sea Basin. It seems that, after the lake overflow, these rivers together drained southwards into the Cite this article English Channel. Whether this southern drainage route was adopted during all later periods of low sea level remains to be determined, but it seems certain Bridgland, D. R. & Gibbard, P. L. (1997). Quaternary River Diversions in the that this was the case during the last glacial. London Basin and the Eastern English Channel. Géographie physique et Quaternaire, 51(3), 337–346. https://doi.org/10.7202/033132ar Tous droits réservés © Les Presses de l'Université de Montréal, 1997 This document is protected by copyright law. Use of the services of Érudit (including reproduction) is subject to its terms and conditions, which can be viewed online. https://apropos.erudit.org/en/users/policy-on-use/ This article is disseminated and preserved by Érudit. Érudit is a non-profit inter-university consortium of the Université de Montréal, Université Laval, and the Université du Québec à Montréal. Its mission is to promote and disseminate research. https://www.erudit.org/en/ Géographie physique et Quaternaire, 1997, vol. 51, n" 3, p. 337-346, 5 fig. QUATERNARY RIVER DIVERSIONS IN THE LONDON BASIN AND THE EASTERN ENGLISH CHANNEL D.R. BRIDGLAND* and P.L. GIBBARD, respectively, Department of Geography, University of Durham, South Road, Durham DH1 3LE, United Kingdom, and Quaternary Stratigraphie Group, Godwin Institute of Quaternary Research, Department of Geography, University of Cambridge, Downing Place, Cambridge CB2 3EN, United Kingdom. ABSTRACT The principal river of the Lon RÉSUMÉ Les captures quaternaires des ZUSAMMENFASSUNG Fluss-Ablenkungen don basin, the Thames, has experienced a fleuves du bassin de Londres et de la Man im Quartàr im Londoner Becken und im number of course changes during the Qua che orientale De nombreuses captures ont ôstlichen Àrmelkanal. Der wichtigste Fluss ternary. Some, at least, of these are known modifé le cours de la Tamise et des autres des Londoner Beckens, die Themse, erlebte to result directly from glaciation. In the early fleuves du bassin de Londres au cours du wâhrend des Quartàrs eine Reihe von Quaternary the river flowed to the north of Quaternaire. L'une d'entre elles au moins est Verlaufsànderungen. Mindestens einige London across East Anglia to the north coast le résultat direct des glaciations. Au Quater davon sind ein direktes Résultat der of Norfolk. By the early Middle Pleistocene it naire inférieur. Ia Tamise coulait au nord de Vereisung. Im frùhen Quarter floss der Fluss had changed its course to flow eastwards Londres à travers l'East Anglia, vers la côte vom Norden Londons durch Ost-England zur near the Suffolk - Essex border into the south nord du Norfolk. Au début du Pleistocene Nordkùste von Norfolk. Zu Anfang des ern North Sea. The Thames valley to the moyen, elle avait changé de cours pour se mittleren Pleistozàn hatte er seinen Lauf north of London was blocked by ice during diriger vers l'est, à la frontière entre Essex et geândert, um ostwàrts nahe der Suffolk-Es- the Anglian/Elsterian glaciation, causing a Suffolk, vers le sud de la mer du Nord. Au sex-Grenze in die sùdliche Nordsee zu series of glacial lakes to form. Overflow of cours du maximum glaciaire de l'Anglien/ fliessen. Das Themse-Tal nôrdlich Londons these lakes brought the river into its modern Elstérien, les glaces ont bloqué la vallée de war wâhrend der Anglia-Elster-Vereisung valley through London. It is thought that this la Tamise au nord de Londres, provoquant durch Eis blockiert, was zur Bildung einer valley already existed by the Anglian in the la formation de lacs. La vidange de ces lacs Reihe von glazialen Seen fùhrte. Der form of a tributary of the north-flowing River a provoqué le déversement de la rivière vers Ùberlauf dieser Seen brachte den Fluss in Medway, which joined the old Thames val sa basse vallée actuelle. Celle-ci existait déjà, sein modernes TaI quer durch London. Man ley near Clacton. Also during the Anglian/ mais était alors parcourue par un affluent de glaubt, dass dieses TaI schon im Anglium Elsterian glaciation. British and continental ice la Medway qui coulait vers le nord, et rejoi existierte in Form eines Zuflusses des nach masses are thought to have joined in the gnait l'ancienne vallée de la Tamise aux en Norden fliessenden Medwey-Flusses, der in northern part of the North Sea basin, caus virons de Clacton. Il semble que durant les das alte Themse-Tal bei Clacton eintrat. ing a large lake to form between the east glaciations de l'Anglien et de l'Elstérien, les Genauso denkt man, dass wâhrend der An- coast of England and the Netherlands. It is calottes glaciaires britannique et continentale glia-Elster-Vereisung britische und widely believed that the overflow from this étaient coalescentes dans la partie septen kontinentale Eismassen sich im nôrdlichen lake caused the first breach in the Weald- trionale du bassin de la mer du Nord. Il en Teil des Nordsee-Beckens vereinigt haben Artois Ridge, bringing about the formation of est résulté la formation d'un vaste lac entre und so zur Bildung eines grossen Sees the Strait of Dover. Prior to the glaciation the les côtes de l'Angleterre orientale, du Dane zwischen der Ostkùste Englands und den Thames, in common with rivers from the con mark et des Pays-Bas. L'écoulement de ce Niederlanden gefùhrt haben. Man nimmt tinent (including the Rhine and Meuse), lac s'est probablement fait par la Manche, allgemein an, dass der Ùberlauf von diesem flowed into the North Sea Basin. It seems entre le Weald et le massif de l'Artois, pro See die erste Bresche im Weald-Artois- that, after the lake overflow, these rivers to voquant la formation du Pas de Calais. Avant Kamm verursachte und so zur Bildung der gether drained southwards into the English la glaciation. Ia Tamise confluait avec les fleu Meerenge von Dover fùhrte. Vor der Channel. Whether this southern drainage ves issus du continent, le Rhin et la Meuse, Vereisung floss die Themse gemeinsam mit route was adopted during all later periods of et se jetait dans la mer du Nord. Il semble den vom Kontinent kommenden Flùssen low sea level remains to be determined, but que se soit seulement après le débordement (einschliesslich Rhein und Maas) in das it seems certain that this was the case dur du lac que ces fleuves se sont écoulés vers Nordseebecken. Nach dem Ùberlauf des ing the last glacial. le sud en direction de la Manche. Il reste à Sees scheint es, dass dièse Flùsse déterminer si les fleuves ont conservé ce zusammen sùdwârts in den Àrmelkanal cours vers le sud durant chaque épisode de abflossen. Ob dièse Entwàsserungsroute bas niveau marin. Quoi qu'il en soit, il est nach Sùden in alien spâteren Perioden mit certain que c'était le cas durant la dernière niedrigem Meeresspiegelniveau beibehalten glaciation. wurde, bleibt zu erforschen. Doch scheint es sicher, dass dies der Fall in der letzten Eiszeit war. Manuscrit reçu le 11 janvier 1996 ; manuscrit révisé accepté le 2 juin 1997 * E-mail address: [email protected] 338 D.R. BRIDGLAND and RL. GIBBARD INTRODUCTION Channel is one that remains open, although the most likely solution will be explored below. The River Thames, in its middle and lower reaches, cur rently flows approximately along the axis of the London syncline, from the area of Reading to the estuary at South- EARLY PLEISTOCENE DIVERSION BETWEEN end-on-Sea. This trend is continued upstream by the tribu HIGH-LEVEL AND LOW-LEVEL KESGRAVE tary River Kennet, which drains the London syncline west of COURSES; RIVER CAPTURE? Reading, whereas the various headwaters of the Upper Figure 1A shows the earliest known route of the Thames Thames are located to the north-west of the London Basin.