The Quaternary Channel River: seismic stratigraphy of its palaeo‐valleys and deeps

Abstract

Based on the interpretation of geophysical data (very high resolution seismic data combined with EM1000 swath bathymetry), this paper reviews the history of the Channel River throughout the late Cenozoic. New evidence does illustrate how the interplay of tectonics, eustacy and climate have influenced this northwest European drainage system.The concepts of sequence stratigraphy allow the subdivision of the sedimentary record into depositional sequences bounded by unconformities, resulting from globally synchronous sea-level changes. However, the recognition of eustatic sea-level changes in a cold climate environment is very difficult, because of the interplay of additional phenomena such as glacio-isostatic sealevel changes with glacio-eustatic changes. For our interpretation, it was necessary to adjust these concepts with the relative importance of geomorphological processes determining the behaviour of rivers and steering their evolution.The foundations of the modern drainage system were laid after the Oligocene Channel inversion. In general these early rivers occupied shallow valleys. The Pleistocene cold climates resulted in fluvial incision. Through time, the Channel River has adopted a drainage system that can be divided into three parts: (i) the drainage basin comprising the Southern Bight, the eastern Channel and the London and Paris basins, (ii) the river zone itself, which begins at the Cotentin peninsula and passes through the Hurd Deep, before reaching the continental shelf-break in the Celtic Sea, (iii) the depositional basin represented by the Celtic Banks complex and by the deep sea fans, located at the foot of Shamrock and Black Mud canyons. During important lowstands (marine oxygen isotope stages 22, 16, 10, 6 and 2), the Channel River seems to have reached the shelf-break, as indicated by the internal structure of the banks.

The first estimation of Fleuve Manche palaeoriver discharge during the last deglaciation: Evidence for Fennoscandian ice sheet meltwater flow in the English Channel ca 20–18 ka ago

“…However, the existence of a proglacial lake is highly debated for the last glacial period (e.g. Laban, 1995;Cohen et al, 2005) and the depth of the Hurd Deep during the studied interval is uncertain, the chronostratigraphic framework of its filling being still unknown (Lericolais, 1997;Lericolais et al, 2003). To circumvent this problem, we estimate the Fleuve Manche sediment load using (1-Te) varying from 0.1 (extreme sediment trapping) to 1 (no sediment trapping).…”

“…1). This drainage pattern, supported by the complex network of shelf valley systems on both sides of the Dover Strait and in the English Channel (Larsonneur et al, 1982;Lericolais, 1997;Bourillet et al, 2003;Lericolais et al, 2003;Gupta et al, 2007), resulted from the complex interactions between the confluence of the Fennoscandian (FIS) and British (BIS) ice sheets in the North Sea basin and associated glacio-isostatic processes. The latter are known to be of primary importance for the drainage connection between the North Sea and the Channel, and the southwards flow of the North Sea fluvial systems, particularly the Elbe and Weser rivers and associated FIS meltwater (Bridgland and D'Olier, 1995;Gibbard, 1995;Van Vliet Lanoë et al, 1998;Busschers et al, 2007;Busschers et al, 2008).…”

Topographic registers of paleo-valleys on the southeastern Brazilian continental shelf

“…oceanogr. da Usp. studies have considered these factors as indicators of the paleogeography of the subaerial surface and the fluvial and hydrological regime during regressive periods (see REYNAUD et al, 1999;LERICOLAIS et al, 2003;TESSON et al, 2005;MEIJER, 2002;BLUM;THORNQVIST, 2000). Although most of these studies have focused on the direct analysis of the chanel incision surface and its relation to quaternary stratigraphy based on seismic analysis (THORNE, 1994;LERICOLAIS et al, 2001;HORI et al, 2002;NORDFJORD et al, 2005;SCHIMANSKI and STATTEGGER 2005), it is possible to identify and classify the main paleo-valley axis in the surface topography even though they are covered by marine sediments deposited during and after rises in sea-level (CORREA, 1996;HARRIS;O'BRIEN, 1996;COLLINA-GIRARD, 1999;ABREU;CAGLIARI, 2005;FINKL et al, 2005;STRAUB et al, 2007).…”

Fault activity in the epicentral area of the 1580 Dover Strait (Pas-de-Calais) earthquake (northwestern Europe)

“…This palaeochannel extends to the southwest into a complex anastomosing system of valleys that can be mapped continuously from a few kilometres northeastward of the Dover Strait to the western approaches (e.g. Smith 1985;Lericolais et al 2003;Gupta et al 2007). Presently, two main hypotheses are proposed to explain this major erosional feature.…”