Palaeogene ocean opening south of Tasmania, and palaeoceanographic implications: preliminary results of clay mineral analyses (ODP Leg 189). ODP Leg 189 was designed to test the hypothesis that opening of the Tasmanian Seaway and initiation of circumpolar circulation contributed to the thermal isolation of Antarctica, leading to the development of initial ice-sheet and oceanic thermohaline circulation. The clay assemblages of the Tasmanian region contain the traces of two tectonic stages associated with ocean opening south of the south Tasman Rise near the Palaeocene-Eocene boundary and strike-slip activity between the western Tasmanian land-bridge and Antarctica during the Late Eocene. Earliest Oligocene clays indicate that cooling of Antarctic margins and activity of western boundary circulation progressed with the regional subsidence. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.
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