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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 - PowerPoint PPT Presentation
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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
Survey Lines and Site Locations
Original Interpretation
Southern Marion Platform
Northern Marion Platform Margin
W ESite 1194Site 1193
Lithostratigraphy at Sea-Level Section
Highstand/Lowstand Platform Superposition
Timing I: Age Model for Site 1193
Timing II: Age Model for Site 1194
Paleo-water Depths
Compensation for Sediment Compaction
??
Compensation for Sediment Compaction
Potential Effect of Crustal Flexure
Potential Effect of Crustal Flexure
Potential Effect of Crustal Flexure
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.