Practical Sequence Stratigraphy

1
Practical Sequence Stratigraphy

• Applications of Sequence Theory to Interpretation
  of the Stratigraphic Record

2
Some Definitions

• Sequence Stratigraphy Also see USC Sequence
  Stratigraphy Web
• Sequence Stratigraphy is an approach to the study
  of time, space, and lithologic relationships in
  the stratigraphic record that uses cycles of
  relative sea level change and accommodation space
  in sedimentary basins to explain and predict
  stratal geometry. (This term is tied to the
  version of allostratigraphy devised by the Exxon
  Production Research Group)
• This approach emphasizes the recognition of key
  stratal surfaces,
• their relationship to accommodation space
• their chronostratigraphic significance
• their predictive utility

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Some Definitions

• Depositional Sequence
• A succession of relatively conformable,
  genetically related strata bounded by
  unconformities (and their correlative
  conformities). A subdivision of the rock record.
• Depositional sequences are inferred to form
  through one cycle of relative sea level fall,
  rise and subsequent fall on a time frame between
  1 to 10 my (third order cycles of relative sea
  level change)
• Depositional sequences have a predictable
  internal structure consisting of major key
  stratal surfaces and depositional systems tracts

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Some Definitions

• Major Stratal Surfaces
• sequence boundaries (erosional unconformity
  disconformity)
• transgressive surfaces (ravinement surfaces)
• maximum flooding surfaces (condensed section
  paraconformities)

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Scales of Sequence Stratigraphy

• Depositional Sequences were defined using seismic
  data (resolution 10s to 100s of meters) Low
  Resolution Sequence Stratigraphy

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High Resolution Sequence Stratigraphy

• Integration of Log, Core, and/or Outcrop scale
  observations Parasequences
• relatively conformable successions of genetically
  related beds/bedsets bounded by marine flooding
  surfaces (and their correlative stratal surfaces)
• generally consist of upward coarsening/shoaling
  successions bounded by thin, upward deepening
  units

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Some Definitions

• Parasequences
• genetically related, progradational, shoaling or
  shallowing upwards bed sets bounded at the top
  (and base) by a (smaller scale time and
  amplitude) marine flooding surface. A subdivision
  of the rock record.
• Shoaling upwards packages of sediment related to
  one idealized cycle of relative sea level rise
  and fall on a time frame between 0.1 to 1 my
  (fourth or fifth order (higher) order cycles of
  relative sea level change or variations in
  sediment input due to autocyclic processes)
• Chronostratigraphic significance of flooding
  stratal surfaces, best represented in shore
  line to shelf successions

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Some Definitions

• Internal stratigraphic Architecture and Stacking
  patterns
• Retrogradational stacking patterns
• Aggradational stacking patterns
• Progradational Stacking patterns

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Sequence Stratigraphy First Principles and
Controls

• Implication of high resolution sequence concepts
  to aquifer/hydrocarbon reservoir correlation

Van Wagoner, et al., 1990
Retrogradational System
Progradational System