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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Nonmarine sequence stratigraphy

• The nonmarine realm is considered here to include
  all environments landward of the shoreline
  (fluvial, delta plain, coastal plain)
• Updip (nonmarine) sections of stratigraphic
  sequences not only record RSL changes (downstream
  control), but also climatic and tectonic signals
  from the hinterland (upstream control)

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Nonmarine sequence stratigraphy

• The fluvial longitudinal profile (graded profile)
  is crucial, because changes herein determine
  whether incision or aggradation occurs, including
  the formation of sequence boundaries it responds
  to changes in RSL (base level), as well as
  climate and tectonics (sediment supply)
• Fluvial scour represents local, autogenic erosion
  of the channel bed (e.g., in sharp bends or at
  confluences)
• Fluvial incision constitutes the regional,
  allogenic degradation of the longitudinal
  profile, commonly including both lowering of the
  channel bed and the genetically associated
  floodplain surface
• Distinction of incision vs. scour is crucial!

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Nonmarine sequence stratigraphy

• The fluvial longitudinal profile (graded profile)
  is crucial, because changes herein determine
  whether incision or aggradation occurs, including
  the formation of sequence boundaries it responds
  to changes in RSL (base level), as well as
  climate and tectonics (sediment supply)
• Fluvial scour represents local, autogenic erosion
  of the channel bed (e.g., in sharp bends or at
  confluences)
• Fluvial incision constitutes the regional,
  allogenic degradation of the longitudinal
  profile, commonly including both lowering of the
  channel bed and the genetically associated
  floodplain surface
• Distinction of incision vs. scour is crucial!

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Nonmarine sequence stratigraphy

• The fluvial longitudinal profile (graded profile)
  is crucial, because changes herein determine
  whether incision or aggradation occurs, including
  the formation of sequence boundaries it responds
  to changes in RSL (base level), as well as
  climate and tectonics (sediment supply)
• Fluvial scour represents local, autogenic erosion
  of the channel bed (e.g., in sharp bends or at
  confluences)
• Fluvial incision constitutes the regional,
  allogenic degradation of the longitudinal
  profile, commonly including both lowering of the
  channel bed and the genetically associated
  floodplain surface
• Distinction of incision vs. scour is crucial!

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Nonmarine sequence stratigraphy

• Whenever the longitudinal profile is graded to a
  more or less stable RSL for any prolonged time
  interval, and given sufficient sediment supply, a
  coastal prism will develop, representing a delta
  plain (possibly laterally connected to a more
  extensive coastal plain), with a very low
  gradient that increases rapidly across the
  shoreline
• The coastal prism is highly sensitive to erosion
  during RSL fall therefore, incision and the
  formation of sequence boundaries is likely to
  occur even if RSL does not fall below the shelf
  edge

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Nonmarine sequence stratigraphy

• Fluvial incision leads to valley cutting
  paleovalleys (also known as incised valleys)
  are valleys that have been subsequently filled
  with sediment
• Even during incision a fluvial deposit is always
  left behind (terraces) rivers act as conveyor
  belts, not as vacuum cleaners!
• Unequivocal recognition of paleovalleys requires
  incision that must substantially exceed channel
  depth, with interfluves topped by mature
  paleosols
• The distinction between paleovalleys and channel
  belts is tricky
• RSL fall does not necessarily always lead to the
  formation of well-developed sequence boundaries
  (e.g., fluvial systems do not always respond to
  RSL fall by means of incision) sequence
  boundaries may therefore be very indistinct and
  difficult to detect

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Nonmarine sequence stratigraphy

• Fluvial incision leads to valley cutting
  paleovalleys (also known as incised valleys)
  are valleys that have been subsequently filled
  with sediment
• Even during incision a fluvial deposit is always
  left behind (terraces) rivers act as conveyor
  belts, not as vacuum cleaners!
• Unequivocal recognition of paleovalleys requires
  incision that must substantially exceed channel
  depth, with interfluves topped by mature
  paleosols
• The distinction between paleovalleys and channel
  belts is tricky
• RSL fall does not necessarily always lead to the
  formation of well-developed sequence boundaries
  (e.g., fluvial systems do not always respond to
  RSL fall by means of incision) sequence
  boundaries may therefore be very indistinct and
  difficult to detect

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Nonmarine sequence stratigraphy

• Paleovalleys are commonly occupied by estuaries
  during transgression their stratigraphy is a
  sensitive recorder of RSL change
• A typical vertical succession, depending on the
  position in dip direction, includes
• A basal, fluvial FSST/LST overlying a sequence
  boundary
• An overlying TST that is either fully marine,
  estuarine, or tide-influenced fluvial
• A capping HST that is again more fluvial-dominated

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Panorama
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Nonmarine sequence stratigraphy

• In view of the difficulty to identify
  parasequence stacking patterns, identification of
  systems tracts in upper deltaic to fluvial
  environments is problematic however, there is a
  close relationship between fluvial style,
  alluvial architecture, and systems tracts
• FSST/LST destruction of accommodation high
  channel-deposit proportion
• TST rapid creation of accommodation low
  channel-deposit proportion, possibly with tidal
  influence
• HST moderate accommodation intermediate
  channel-deposit proportion

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Nonmarine sequence stratigraphy

• In view of the difficulty to identify
  parasequence stacking patterns, identification of
  systems tracts in upper deltaic to fluvial
  environments is problematic however, there is a
  close relationship between fluvial style,
  alluvial architecture, and systems tracts
• FSST/LST destruction of accommodation high
  channel-deposit proportion
• TST rapid creation of accommodation low
  channel-deposit proportion, possibly with tidal
  influence
• HST moderate accommodation intermediate
  channel-deposit proportion

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Nonmarine sequence stratigraphy

• Coastal prisms are essentially composed of TSTs
  and HSTs, and in view of their sensitivity to
  erosion during RSL fall, the FSST/LST has a
  relatively high preservation potential this is
  particularly the case when subsidence rates are
  low
• Vertical stacking of relatively amalgamated
  channel belts, characteristic of the FSST/LST,
  leads to sequence boundaries that are hard to
  identify (cryptic sequence boundaries)
• Climatic and tectonic controls can operate in an
  opposite direction than RSL, rendering nonmarine
  sequence-stratigraphic interpretations
  considerably more difficult than their marine
  counterparts

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Nonmarine sequence stratigraphy

• Coastal prisms are essentially composed of TSTs
  and HSTs, and in view of their sensitivity to
  erosion during RSL fall, the FSST/LST has a
  relatively high preservation potential this is
  particularly the case when subsidence rates are
  low
• Vertical stacking of relatively amalgamated
  channel belts, characteristic of the FSST/LST,
  leads to sequence boundaries that are hard to
  identify (cryptic sequence boundaries)
• Climatic and tectonic controls can operate in an
  opposite direction than RSL, rendering nonmarine
  sequence-stratigraphic interpretations
  considerably more difficult than their marine
  counterparts