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Sea-Level Magnitudes Recorded by Continental Margin Sequences on the Marion Plateau, Northeast Australia: ODP Leg 194. Alexandra Isern, National Science Foundation Flavio Anselmetti, Federal Institute of Technology, Zurich Switzerland Peter Blum, Ocean Drilling Program
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Sea-Level Magnitudes Recorded by Continental Margin Sequences on the Marion Plateau, Northeast Australia: ODP Leg 194 Alexandra Isern, National Science Foundation Flavio Anselmetti, Federal Institute of Technology, Zurich Switzerland Peter Blum, Ocean Drilling Program and the Leg 194 Shipboard Scientific party
Acknowledgements • Collection of scientific data: • 22 Members of the Leg 194 Shipboard Scientific Party • Seismic Survey: • Australian Geological Survey Organization (AGSO) • Australian Research Council • Mike Sexton • Coring operations and core analysis: • ODP drill crew • ODP technical support personnel
Introduction • The Miocene Climatic Optimum (~14.5-17 Ma), a period of extreme warmth, was followed by global cooling • A series of sea level falls at ~14-12 Ma has been interpreted from the geological record (e.g., Haq et al. 1987, 100-200 m) • ODP Leg 194 embarked on a drilling mission in early 2001 to examine this event and associated processes as documented in the Marion carbonate platforms
ODP Drilling on Marion Plateau • ODP Leg 194 drilled at 8 sites: • Water depths of 304-419 m • Penetrations per hole of 265-675 m • Core recoveries per hole of 11% - 100% • late Oligocene to Pleistocene sediments • Principal results: • Magnitude of l. middle Miocene sea-level fall • Cool subtropical platform growth environment • bryozoans, larger benthic foraminifers, red algea • Ocean current rather than wind control • Records of higher-order sea-level changes in drifts • Fluid flow through the platform • Diagenetic history
Marion Plateau Setting Next Figure
Conclusions • ODP drilling on the Marion Plateau provided facies, timing, and porosity information necessary to quantify a major late middle Miocene sea level fall. • Preliminary data and their reduction suggest a sea level fall of at least 56-116 m (86±30 m) at ~13±1 Ma. • If differential isostatic response occurred between Sites 1193 and 1194, the magnitude of the sea level fall could have been significantly smaller. • The precision of our sea-level fall estimate depends strongly on the precision of the paleowater depth estimates, which are a few tens of meters under the best circumstances.