1. LEG 182 SUMMARY: GREAT AUSTRALIAN BIGHT—CENOZOIC
Sediments recovered in the Great Australian Bight during Leg 182 record carbonate deposition in a middle- and high-latitude setting against the background of an evolving Southern Ocean and northward drift of the Australian continent. Approximately 3.5 km of sediment was recovered from nine sites, in...
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| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.460.949 http://www-odp.tamu.edu/publications/182_IR/VOLUME/CHAPTERS/IR182_01.PDF |
| Summary: | Sediments recovered in the Great Australian Bight during Leg 182 record carbonate deposition in a middle- and high-latitude setting against the background of an evolving Southern Ocean and northward drift of the Australian continent. Approximately 3.5 km of sediment was recovered from nine sites, in water depths ranging from 202 to 3875 m. Most drilling took place on the shelf edge and upper slope, in a water depth of 202–784 m, through a mainly carbonate succession. Two distinct groups of strata, Eocene–middle Miocene and late Pliocene–Quaternary in age, form the upper Cenozoic component of the continental margin, separated by a thin, upper middle Miocene– lower Pliocene interval characterized by slumps, sediment gravity-flow deposits, and/or unconformities. Such erosion, corrosion, and/or mass wasting and redeposition processes reflect periods of margin instability, seismicity, or lowered sea level. The older succession consists of Eocene shallow-water terrigenous sands and carbonates that deepen upward into Oligocene and lower middle Miocene pelagic ooze and chalk. The carbonate component of this succession in shallow-water sites was poorly recovered because of irregular selective silicification. Available cored material indicates a se-quence dominated by nannofossil chalk with abundant sponge spicules and characterized by stained hardgrounds and numerous omission sur-faces. Downhole logs collected through all poorly recovered intervals will enable more detailed postcruise lithologic analysis for this part of the succession. In contrast, the middle Eocene–lower Oligocene succes-1Examples of how to reference the whole or part of this volume. |
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