The Dynamic Chalk Sea: The Depositional Effects of a Collapsed Shelf-break Front, Erosional Contour Current Systems and Dry Borderlands

In the Late Cretacous NW Europe was covered by the deep, epeiric Chalk Sea (e.g. Surlyk et al., 2003). Oceanic conditions spread across the continent as revealed by deposition of up to several kilometres of coccolithic nannofossil ooze of the Chalk Group. This was probably due to the break-down of the oceanic front located at the shelf-slope break due to very high eustatic sea level. The chalk is generally considered as deposited by a gentle rain of coccolith debris in the form of zooplankton pellets or marine snow. Local downslope redeposition by slides, slumps, debris and turbidity flows took place mainly adjacent to major fault zones which were reactivated by inversion tectonics in several episodes in the Late Cretaceous. However, recent work based on reflection seismic data shows that this paradigm is in need of major revision.