Leg 189 synthesis; Cretaceous-Holocene history of the Tasmanian gateway

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doi: 10.2973/odp.proc.sr.189.101.2004
Author(s): Exon, Neville F.; Kennett, James P.; Malone, Mitchell J.
Ocean Drilling Program, Leg 189, Shipboard Scientific Party, College Station, TX
Author Affiliation(s): Primary:
Geoscience Australia, Canberra, Australia
Other:
University of California at Santa Barbara, United States
Ocean Drilling Program, United States
Utrecht University, Netherlands
Australian National University, Australia
Pennsylvania State Universtiy, United States
University of Leicester, United Kingdom
University of Hawaii at Manoa, United States
University of Copenhagen, Denmark
Florida State University, United States
Woods Hole Oceanographic Institution, United States
Indiana University, United States
Christian-Albrechts-Universität zu Kiel, Federal Republic of Germany
Lamont-Doherty Earth Observatory, United States
Rutgers State University of New Jersey, United States
Université de Genève, Switzerland
University of Cambridge, United Kingdom
Centre d'Ocanologie de Marseille, France
University College London, United Kingdom
Tohoku University, Japan
CEREGE, France
Volume Title: Proceedings of the Ocean Drilling Program; scientific results; the Tasmanian gateway; Cenozoic climatic and oceanographic development; covering Leg 189 of the cruises of the drilling vessel JOIDES Resolution; Hobart, Tasmania, to Sydney, Australia; Sites 1168-1172; 11 March-6 May 2000
Volume Author(s): Exon, Neville F.; Kennett, James P.; Malone, Mitchell J.; Brinkhuis, Henk; Chaproniere, George C. H.; Ennyu, Atsuhito; Fothergill, Patrick; Fuller, Michael D.; Grauert, Marianne; Hill, Peter J.; Janecek, Thomas R.; Kelly, Daniel C.; Latimer, Jennifer C.; Nees, Stefan; Ninnemann, Ulysses S.; Nürnberg, Dirk; Pekar, Stephen F.; Pellaton, Caroline C.; Pfuhl, Helen A.; Robert, Christian M.; Roessig, Kristeen L. McGonigal; Röhl, Ursula; Schellenberg, Stephen A.; Shevenell, Amelia E.; Stickley, Catherine E.; Suzuki, Noritoshi; Touchard, Yannick; Wei, Wuchang; White, Timothy S.
Source: Proceedings of the Ocean Drilling Program; scientific results; the Tasmanian gateway; Cenozoic climatic and oceanographic development; covering Leg 189 of the cruises of the drilling vessel JOIDES Resolution; Hobart, Tasmania, to Sydney, Australia; Sites 1168-1172; 11 March-6 May 2000, Neville F. Exon, James P. Kennett, Mitchell J. Malone, Henk Brinkhuis, George C. H. Chaproniere, Atsuhito Ennyu, Patrick Fothergill, Michael D. Fuller, Marianne Grauert, Peter J. Hill, Thomas R. Janecek, Daniel C. Kelly, Jennifer C. Latimer, Stefan Nees, Ulysses S. Ninnemann, Dirk Nürnberg, Stephen F. Pekar, Caroline C. Pellaton, Helen A. Pfuhl, Christian M. Robert, Kristeen L. McGonigal Roessig, Ursula Röhl, Stephen A. Schellenberg, Amelia E. Shevenell, Catherine E. Stickley, Noritoshi Suzuki, Yannick Touchard, Wuchang Wei and Timothy S. White; Ocean Drilling Program, Leg 189, Shipboard Scientific Party, College Station, TX. Proceedings of the Ocean Drilling Program, Scientific Results (CD ROM), Vol.189, 38p. Publisher: Texas A&M University, Ocean Drilling Program, College Station, TX, United States. ISSN: 1096-2514
Note: In English. Also available on CD-ROM in PDF format and on the Web in PDF or HTML. 69 refs.CD-ROM format, ISSN 1096-2514; WWW format, ISSN 1096-7451; illus., incl. 1 table, sketch maps
Summary: During Ocean Drilling Program (ODP) Leg 189, five sites were drilled in bathyal depths on submerged continental blocks in the Tasmanian Gateway to help refine the hypothesis that its opening near the Eocene/Oligocene boundary led to formation of the Antarctic Circumpolar Current (ACC), progressive thermal isolation of Antarctica, climatic cooling, and development of an Antarctic ice sheet. A total of 4539 m of largely continuous upper Maastrichtian-Holocene marine sediments were recovered with a recovery rate of 89%. The sedimentary sequence broadly consists of shallow-marine mudstones until the late Eocene, glauconitic siltstones during that time, and pelagic carbonates thereafter. The microfossils in the mudstones and siltstones are largely palynomorphs and diatoms, and those in the carbonates are largely nannofossils and foraminifers. During the Late Cretaceous, northward movement of Australia away from Antarctica commenced, forming the Australo-Antarctic Gulf (AAG). However, a Tasmanian land bridge at 70°-65°S almost completely blocked the eastern end of the widening AAG until the late Eocene; there is no evidence of extensive current circulation across the ridge until the earliest Oligocene. Prior to the Oligocene, muddy marine siliciclastic sediments were deposited in temperate seas. During the late Eocene, the northeastern AAG was warmer and less ventilated than the gradually widening southwest sector of the Pacific Ocean, which was affected by a cool northwesterly flowing boundary current-a difference that may have existed since the Maastrichtian. In the late Eocene (∼37 Ma), the Tasmanian land bridge and its broad shelves began to subside, currents swept the still-shallow offshore areas, and condensed glauconitic siltstones were deposited. Palynological and diatom evidence suggest a general cooling. The southwestern South Tasman Rise finally separated from Antarctica at the time of the Eocene/Oligocene boundary (∼33.5 Ma), the rise subsided, and the continental margin of Tasmania collapsed. The Tasmanian Gateway opened to deep water, disrupting oceanic circulation at high southern latitudes and leading to one of the major climatic shifts of the Cenozoic. Thereafter, a marked reduction in siliciclastic supply, as well as the flow of warm currents from northern latitudes, favored deposition of carbonate. At the eastern sites, deposition of Oligocene bathyal carbonates directly followed an unconformity caused by the onset of the ACC, but change was more gradual in the west. In contrast, siliceous biogenic sediments typified the Antarctic margin, now isolated from warm water by the ACC. Steady northward movement kept the Tasmanian region north of the Polar Front throughout the Neogene, and pelagic carbonates accumulated.
Year of Publication: 2004
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Algae; Antarctic ice sheet; Antarctica; Biostratigraphy; Cenozoic; Climate change; Cores; Cretaceous; Currents; Depositional environment; Foraminifera; Gateways; Holocene; Ice sheets; Indian Ocean; Invertebrata; Leg 189; Lithostratigraphy; Mesozoic; Microfossils; Nannofossils; Ocean Drilling Program; Ocean currents; Pacific Ocean; Paleo-oceanography; Paleoclimatology; Paleogeography; Plantae; Protista; Quaternary; South Pacific; Southern Ocean; Southwest Pacific; Tasman Sea; Tectonics; West Pacific
Coordinates: S483000 S423000 E1500000 E1440000
Record ID: 2005011447
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