SeaLevel Magnitudes Recorded by Continental Margin Sequences on the Marion Plateau, Northeast Austra

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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
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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 (8630 m) at
  131 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.