Authors / CoAuthors
Exon, N.F. | Brinkhuis, H. | Robert, C.M. | Kennett, J.P. | Hill, P.J. | Macphail, M.K.
Abstract
The opening of the Tasmanian Gateway between Australia and Antarctica at the Eocene-Oligocene boundary (~33.5 Ma) was a profoundly important event that affected global oceanographic circulation and climate. Ocean Drilling Program Leg 189 (in the gateway), together with other geoscience information, has increased our understanding of the tectonic and depositional history of the region from the Late Cretaceous until the present day. From the mid-Cretaceous until the latest Eocene, Australia and Antarctica faced each other across an ever-widening Australo-Australian Gulf, terminated to the east by a Tasmanian land bridge (Tasmania and South Tasman Rise [STR]). Siliciclastic sediments poured into the rifts from Antarctica, Australia and parts of the land bridge, forming deltas in a low-oxygen environment. Sedimentation kept up with subsidence, except on oceanic crust in the spreading Tasman Sea. Until the Paleocene/Eocene boundary (~55 Ma), Australia moved northwestward along a fracture west of the land bridge. Thereafter, Australia-Antarctic motion changed to N-S along the Tasman Fracture Zone west of STR, and an oceanic basin opened south of eastern STR. In the middle Eocene (~43 Ma), spreading rates increased between Australia and Antarctica, and Tasman Sea spreading ceased. By the latest Eocene, the STR had subsided until parts of it were current swept, and winnowing reduced sedimentation rates there and on ETP. Rapid and major increases in subsidence marked the final (earliest Oligocene) separation of STR and Antarctica. In the Pacific Ocean, strong currents eroded the shelves and opening straits, and a latest Eocene to early Oligocene hiatus was followed by deposition of bathyal carbonate oozes. The Indian Ocean was different. In nearby areas of Antarctica, non-marine and shelfal siliciclastic sedimentation gave way to glacigene detrital or diatomaceous sedimentation at the Eocene/Oligocene transition. Along the southern margin of mainland Australia, the siliciclastic-carbonate transition came at different times, but largely in the late Eocene and early Oligocene. The west Tasmanian margin ODP site had gradual increases in carbonate content through the Oligocene.
Product Type
nonGeographicDataset
eCat Id
61243
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Custodian
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Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
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Keywords
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- External Publication
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- AU-TAS
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
Publication Date
2004-04-29T00:00:00
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unknown
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geoscientificInformation
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Unknown
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Extents
[-50.0, -40.0, 140.0, 155.0]
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