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

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 sea-level 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. Copyright © 2003 John Wiley & Sons, Ltd.