A Mid- to Late Cenozoic tectonostratigraphic framework for the Rockall Trough

Abstract

AbstractRegional subsidence in late Eocene time resulted in a marked change in the style of sedimentation in the Rockall Trough, coincident with the onset of bottom-current activity in the region. This subsidence is manifest by a shut-down of shelf-derived sediment supply, and the formation of a deep-water unconformity (reflector C30) caused by bottom-current erosion. The unconformity is particularly enhanced on the flanks of the basin where the downwarped and eroded surface of Eocene and older strata is onlapped by middle to upper Cenozoic sediments. The latter comprise three megasequences, RTc (of late Eocene to early Miocene age), RTb (of early Miocene to early Pliocene age) and RTa (of early Pliocene to Holocene age), which consist predominantly of deep-marine contourites, although a prograding clastic wedge has built out along the Hebrides-Malin margin since early Pliocene time. These megasequences reflect a gross three-stage depositional history; predominantly a response to intra-plate tectonism that modified sedimentation patterns and palaeoceanographic circulation. Megasequences RTc and RTb are separated by reflector C20, a reflective zone formed by lithification and diagenetic changes in lower Miocene strata, whereas RTb and RTa are separated by reflector C10, an early Pliocene angular unconformity. The development of C20 and C10 reflects major phases of Neogene basin evolution and can be linked, respectively, to the submergence of the Greenland-Scotland Ridge and the uplift and erosion of northern Britain and Ireland.