Contents

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Contents

• Introduction
• Sedimentology concepts
• Fluvial environments
• Deltaic environments
• Coastal environments
• Offshore marine environments

• Sea-level change
• Sequence stratigraphy concepts
• Marine sequence stratigraphy
• Nonmarine sequence stratigraphy
• Basin and reservoir modeling
• Reflection

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Sequence stratigraphy concepts

• Sequence stratigraphy highlights the role of
  allogenic controls on patterns of deposition, as
  opposed to autogenic controls that operate within
  depositional environments
• Eustasy (sea level)
• Subsidence (basin tectonics)
• Sediment supply (climate and hinterland tectonics)

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Sequence stratigraphy concepts

• Accommodation is the space available, at any
  given point in time, for sediments to accumulate
  accommodation is created or destroyed by RSL
  changes
• Water depth is controlled by changes in
  accommodation as well as sedimentation
• Base level is the horizontal surface to which
  subaerial erosion proceeds therefore it
  corresponds to sea level
• Base level is a principal control of
  accommodation, and, hence, whether erosion or
  deposition is likely to occur at any given
  location attempts to extend the concept landward
  are controversial

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Sequence stratigraphy concepts

• Allostratigraphy is a relatively new approach to
  stratigraphic subdivision, and is based on the
  separation of strata based on unconformities or
  other discontinuities (e.g., paleosols)
• Sequence stratigraphy is the analysis of
  genetically related depositional units bounded by
  unconformities and their correlative conformities
• A depositional sequence is a stratigraphic unit
  bounded at its top and base by unconformities or
  their correlative conformities (allostratigraphic
  unit), and typically embodies a continuum of
  depositional environments, from updip
  (continental) to downdip (deep marine)
• The subtle balance between RSL and sediment
  supply controls whether aggradation, regression
  (progradation), forced regression, or
  transgression (retrogradation) will occur

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Sequence stratigraphy concepts

• Allostratigraphy is a relatively new approach to
  stratigraphic subdivision, and is based on the
  separation of strata based on unconformities or
  other discontinuities (e.g., paleosols)
• Sequence stratigraphy is the analysis of
  genetically related depositional units bounded by
  unconformities and their correlative conformities
• A depositional sequence is a stratigraphic unit
  bounded at its top and base by unconformities or
  their correlative conformities (allostratigraphic
  unit), and typically embodies a continuum of
  depositional environments, from updip
  (continental) to downdip (deep marine)
• The subtle balance between RSL and sediment
  supply controls whether aggradation, regression
  (progradation), forced regression, or
  transgression (retrogradation) will occur

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Sequence stratigraphy concepts

• Allostratigraphy is a relatively new approach to
  stratigraphic subdivision, and is based on the
  separation of strata based on unconformities or
  other discontinuities (e.g., paleosols)
• Sequence stratigraphy is the analysis of
  genetically related depositional units bounded by
  unconformities and their correlative conformities
• A depositional sequence is a stratigraphic unit
  bounded at its top and base by unconformities or
  their correlative conformities (allostratigraphic
  unit), and typically embodies a continuum of
  depositional environments, from updip
  (continental) to downdip (deep marine)
• The subtle balance between RSL and sediment
  supply controls whether aggradation, regression
  (progradation), forced regression, or
  transgression (retrogradation) will occur

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Sequence stratigraphy concepts

• A RSL fall on the order of tens of meters or more
  will lead to a basinward shift of the shoreline
  and an associated basinward shift of depositional
  environments commonly (but not always) this will
  be accompanied by subaerial exposure, erosion,
  and the formation of a widespread unconformity
  known as a sequence boundary
• Sequence boundaries are the key stratigraphic
  surfaces (high-order bounding surfaces) that
  separate successive sequences and are
  characterized by subaerial exposure/erosion, a
  basinward shift in facies, a downward shift in
  coastal onlap, and onlap of overlying strata
• Parasequences are lower order stratal units
  separated by (marine) flooding surfaces they are
  commonly autogenic and not necessarily the result
  of smaller-scale RSL fluctuations

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Sequence stratigraphy concepts

• Systems tracts are contemporaneous, linked
  depositional environments (or depositional
  systems) they are the building blocks of
  sequences and different types of systems tracts
  represent different limbs of a RSL curve
• Falling-stage (forced regressive) systems tract
  (FSST)
• Lowstand systems tract (LST)
• Transgressive systems tract (TST)
• Highstand systems tract (HST)
• The various systems tracts are characterized by
  their position within a sequence, by shallowing
  or deepening upward facies successions, or by
  parasequence stacking patterns

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Sequence stratigraphy concepts

• Systems tracts are contemporaneous, linked
  depositional environments (or depositional
  systems) they are the building blocks of
  sequences and different types of systems tracts
  represent different limbs of a RSL curve
• Falling-stage (forced regressive) systems tract
  (FSST)
• Lowstand systems tract (LST)
• Transgressive systems tract (TST)
• Highstand systems tract (HST)
• The various systems tracts are characterized by
  their position within a sequence, by shallowing
  or deepening upward facies successions, or by
  parasequence stacking patterns

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Sequence stratigraphy concepts

• Maximum flooding surfaces form during the
  culmination of RSL rise, and maximum landward
  translation of the shoreline, and constitute the
  stratigraphic surface that separates the TST and
  HST
• In the downdip realm (deep sea), where
  sedimentation rates can be very low during
  maximum flooding, condensed sections may develop
• LSTs are separated from overlying TSTs by
  transgressive surfaces transgression is further
  characterized by coastal onlap
• An alternative approach to sequence analysis uses
  genetic stratigraphic sequences that are bounded
  by maximum flooding surfaces

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Sequence stratigraphy concepts

• Maximum flooding surfaces form during the
  culmination of RSL rise, and maximum landward
  translation of the shoreline, and constitute the
  stratigraphic surface that separates the TST and
  HST
• In the downdip realm (deep sea), where
  sedimentation rates can be very low during
  maximum flooding, condensed sections may develop
• LSTs are separated from overlying TSTs by
  transgressive surfaces transgression is further
  characterized by coastal onlap
• An alternative approach to sequence analysis uses
  genetic stratigraphic sequences that are bounded
  by maximum flooding surfaces

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Sequence stratigraphy concepts

• In a very general sense, RSL fall leads to
  reduced deposition and formation of sequence
  boundaries in updip areas, and increased
  deposition in downdip settings (e.g., submarine
  fans)
• RSL rise leads to trapping of sediment in the
  updip areas (e.g., coastal plains with a littoral
  energy fence) and reduced transfer of sediment to
  the deep sea (hemipelagic deposition condensed
  sections)

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Sequence stratigraphy concepts

• Seismic stratigraphy is based on the principle
  that seismic reflectors follow stratal patterns
  and approximate isochrons (time lines)
• Reflection terminations provide the data used to
  identify sequence-stratigraphic surfaces, systems
  tracts, and their internal stacking patterns
• Technological developments have been prolific
• Vertical resolution improved to a few tens of
  meters
• Widespread use of 3D seismic
• Seismic data should preferably always be
  interpreted in conjunction with well log or core
  data

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Sequence stratigraphy concepts

• Seismic stratigraphy is based on the principle
  that seismic reflectors follow stratal patterns
  and approximate isochrons (time lines)
• Reflection terminations provide the data used to
  identify sequence-stratigraphic surfaces, systems
  tracts, and their internal stacking patterns
• Technological developments have been prolific
• Vertical resolution improved to a few tens of
  meters
• Widespread use of 3D seismic
• Seismic data should preferably always be
  interpreted in conjunction with well log or core
  data

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Sequence stratigraphy concepts

• Seismic stratigraphy is based on the principle
  that seismic reflectors follow stratal patterns
  and approximate isochrons (time lines)
• Reflection terminations provide the data used to
  identify sequence-stratigraphic surfaces, systems
  tracts, and their internal stacking patterns
• Technological developments have been prolific
• Vertical resolution improved to a few tens of
  meters
• Widespread use of 3D seismic
• Seismic data should preferably always be
  interpreted in conjunction with well log or core
  data

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Sequence stratigraphy concepts

• A better understanding of stratigraphic sequences
  can be obtained by the construction of
  chronostratigraphic charts (Wheeler diagrams)
  these can subsequently be used to infer
  coastal-onlap curves
• Variations in sediment supply can produce stratal
  patterns that are very similar to those formed by
  RSL change (except for forced regression) in
  addition, variations in sediment supply can cause
  stratigraphic surfaces at different locations to
  be out of phase
• In principle, sequence-stratigraphic concepts
  could be applied with some modifications to
  sedimentary successions that are entirely
  controlled by climate change and/or tectonics
  (outside the realm of RSL control)

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Sequence stratigraphy concepts

• A better understanding of stratigraphic sequences
  can be obtained by the construction of
  chronostratigraphic charts (Wheeler diagrams)
  these can subsequently be used to infer
  coastal-onlap curves
• Variations in sediment supply can produce stratal
  patterns that are very similar to those formed by
  RSL change (except for forced regression) in
  addition, variations in sediment supply can cause
  stratigraphic surfaces at different locations to
  be out of phase
• In principle, sequence-stratigraphic concepts
  could be applied with some modifications to
  sedimentary successions that are entirely
  controlled by climate change and/or tectonics
  (outside the realm of RSL control)

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Sequence stratigraphy concepts

• The global sea-level curve for the Mesozoic and
  Cenozoic (inferred from coastal-onlap curves)
  contains first, second, and third-order eustatic
  cycles that are supposed to be globally
  synchronous, but it is a highly questionable
  generalization
• Conceptual problems spatially variable RSL
  change due to differential isostatic and tectonic
  movements undermines the notion of a globally
  uniform control
• Dating problems correlation is primarily based
  on biostratigraphy that typically has a resolving
  power comparable to the period of third-order
  cycles

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