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Eustasy and Sea Level Change
Professor Christopher G. St. C.
Kendall University of South Carolina kendall_at_sc.ed
u 803 777 2410
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Eustasy Sea Level Change

• Recognized from examination of the framework of
  genetically related stratigraphic facies
  geometries and their bounding surfaces

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Lecture Series Overview

• Sequence stratigraphy stratigraphic surfaces
• Basics Ideal sequence of Vail et al 1977
  associated terminology
• Clastic system response to changing sea level and
  rates of sedimentation - with movie
• Carbonate systems response to changing sea level
  and rates of sedimentation - with movie
• Exercises Sequence stratigraphy of carbonates
  and clastics from chronostratigraphy, seismic,
  outcrop and well log character

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Eustasy?

• World wide change in elevation in sea level
• Can be used to identify relative sea-level
  changes be they caused by
• Local tectonic events
• Variations in earths rotational axis
• Absolute sea level cannot be untangled from
  sediment compaction, crustal flexure, and
  thermo-tectonic behavior

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Recognition of Sequences

• Louis Agassiz recognized Pleistocene Glaciations
  in northern Europe and N. America
• Inspired Suess in 1906 to be the first to
  identify eustasy on the basis of changes in the
  strandline relative to the sea on a world wide
  basis, paleobathymetry and ancient strandline
  deposits
• Sloss working in the continental interior sees
  major unconformities extended these ideas
• Vail then developed sequence stratigraphy!

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Determine Sea Level Change from record in Marine
Depositional Systems

• Wave-dominated coasts
• Tide-dominated coasts
• Fluvial-dominated coasts (deltas)
• Carbonate reefs
• Clastic shelves platforms
• Carbonate shelves platforms
• Deepwater fans
• Pelagic abyssal plains

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Sloss diagrammed sea level
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Sloss diagram Central N. America
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(No Transcript)
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Waite, among others, uses Slosss diagram to
explain sediment geometries
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Waites diagram Sediment SL
Petroleum explained in terms of response of
sediments to sea level
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MALLORCA MOVIE
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Llucmajor reef complex
The basic accretional units "sigmoidal" packages
of coral framestones bounded by submarine
subaerial erosion surfaces their correlative
basinward conformities

• Reef core facies is skeletal grainstone
  /packstone/wackestone rudstone within coral
  framework composed of massive coral reefs
• Overlie interfinger basinward with fore-reef
  slope lithofacies
• Landward with lagoonal lithofacies
• Character of platform determined by sea level
  change forming relative hierarchy of accretional
  units positions of facies belts developed
  within them.

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Llucmajor reef complex
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Llucmajor reef complex
Kendall Photo
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Lecture Conclusions

• Wide spread sea level events have been identified
• The origin of the accommodation produced by them
  has been ascribed to
• Eustasy
• Tectonic events
• Compaction
• This is used to interpret the sedimentary section
  and help find petroleum and model its reservoirs

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Lecture Ends!!

• And so to lunch