Palaeogene ocean opening south of Tasmania, and palaeoceanographic implications: preliminary results of clay mineral analyses (ODP Leg 189).

Palaeogene ocean opening south of Tasmania, and palaeoceanographic implicat ions: preliminary results of clay mineral analyses (ODP Leg 189). ODP Leg 1 89 was designed to test the hypothesis that opening of the Tasmanian Seaway and initiation of circumpolar circulation contributed to the thermal isola tion of Antarctica, leading to the development of initial ice-sheet and oce anic thermohaline circulation. The clay assemblages of the Tasmanian region contain the traces of two tectonic stages associated with ocean opening so uth of the south Tasman Rise near the Palaeocene-Eocene boundary and strike -slip activity between the western Tasmanian land-bridge and Antarctica dur ing the Late Eocene. Earliest Oligocene clays indicate that cooling of Anta rctic margins and activity of western boundary circulation progressed with the regional subsidence. (C) 2001 Academie des sciences / Editions scientif iques et medicales Elsevier SAS.