Alexandra Isern, National Science Foundation
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Transcript of Alexandra Isern, National Science Foundation
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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
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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
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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
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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
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Marion Plateau Setting
Next Figure
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Survey Lines and Site Locations
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Original Interpretation
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Southern Marion Platform
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Northern Marion Platform Margin
W ESite 1194Site 1193
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Lithostratigraphy at Sea-Level Section
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Highstand/Lowstand Platform Superposition
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Timing I: Age Model for Site 1193
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Timing II: Age Model for Site 1194
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Paleo-water Depths
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Compensation for Sediment Compaction
??
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Compensation for Sediment Compaction
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Potential Effect of Crustal Flexure
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Potential Effect of Crustal Flexure
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Potential Effect of Crustal Flexure
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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.