Contents

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Contents

• Introduction
• Unconsolidated clastic sediments
• Sedimentary rocks
• Diagenesis
• Sediment transport and deposition
• Sedimentary structures
• Facies and depositional environments
• Glacial/eolian/lacustrine environments
• Fluvial/deltaic/coastal environments
• Shallow/deep marine environments

• Stratigraphic principles
• Sequence stratigraphy
• Sedimentary basins
• Models in sedimentary geology
• Applied sedimentary geology
• Reflection

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Fluvial/deltaic/coastal environments

• Fluvial environments
• Bedrock rivers essentially do not contribute to
  the stratigraphic record, contrary to alluvial
  rivers
• Alluvial fans are relatively steep (gt1-2) cones
  consisting of coarse-grained facies and
  constitute the most proximal fluvial depositional
  environments (usually at the break of slope on
  the edge of a floodplain)
• Debris flows dominate on small and steep alluvial
  fans
• Sheetfloods are common on larger and gentler
  alluvial fans

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Fluvial/deltaic/coastal environments

• Fluvial environments
• Ephemeral rivers are dry during a significant
  part of the year, contrary to perennial rivers
• Floodplains are the areas occupied by river
  channels, as well as the surrounding, flat
  (overbank) areas that are subject to flooding
• Discharge is confined to the channel until
  bankfull discharge is reached from that point on
  overbank flow can occur, submerging the entire
  floodplain

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Fluvial/deltaic/coastal environments

• Fluvial environments
• Channel patterns (fluvial styles) are commonly
  classified as
• Braided rivers
• Meandering rivers
• Straight rivers
• Anastomosing rivers
• Fluvial style is primarily controlled by specific
  stream power (W m-2) and grain size, but also by
  bank stability and the amount of bed load
• ?fluid density Qdischarge sslope (gradient)
  wchannel width

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Animation
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Fluvial/deltaic/coastal environments

• Fluvial environments
• Channel patterns (fluvial styles) are commonly
  classified as
• Braided rivers
• Meandering rivers
• Straight rivers
• Anastomosing rivers
• Fluvial style is primarily controlled by specific
  stream power (W m-2) and grain size, but also by
  bank stability and the amount of bed load
• ?fluid density Qdischarge sslope (gradient)
  wchannel width

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Fluvial/deltaic/coastal environments

• Fluvial environments
• Bars are sandy or gravelly macroforms in channels
  that are emergent, mostly unvegetated features at
  low flow stage, and undergo submergence and rapid
  modification during high discharge
• Point bars form on inner banks and typically
  accrete laterally, commonly resulting in
  lateral-accretion surfaces mid-channel or braid
  bars accrete both laterally and downstream
• Braided rivers are characterized by a dominance
  of braid bars meandering rivers primarily
  contain point bars in straight (and most
  anastomosing) rivers bars are almost absent

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Fluvial/deltaic/coastal environments

• Fluvial environments
• Channel belts consist of channel-bar and
  channel-fill deposits the proportion of the two
  generally decreases markedly from braided rivers
  to straight or anastomosing rivers
• The geometry of a channel belt (width/thickness
  ratio) is a function of the channel width and the
  degree of lateral migration values are typically
  much higher for braided systems (gtgt100) than for
  straight or anastomosing systems (lt25)
• Residual-channel deposits are predominantly muddy
  (occasionally organic) deposits that accumulate
  in an abandoned channel where flow velocities are
  extremely small

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Fluvial/deltaic/coastal environments

• Fluvial environments
• Overbank environments are dominated by
  fine-grained facies (predominantly muds)
• Natural-levee deposits are wedges of sediment
  that form adjacent to the channel, dominated by
  fine sand and silt exhibiting planar
  stratification or (climbing) ripple cross
  stratification
• Crevasse-splay deposits are usually cones of
  sandy to silty facies with both coarsening-upward
  and fining-upward successions, and are formed by
  small, secondary channels during peak flow
• Flood-basin deposits are the most distal facies,
  consisting entirely of sediments deposited from
  suspension, and are volumetrically very important
  (mainly in low-energy fluvial settings)

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Fluvial/deltaic/coastal environments

• Fluvial environments
• Paleosols (well drained conditions) and peats
  (poorly drained conditions) occur frequently in
  overbank environments and are important
  indicators of variations of clastic aggradation
  rates and the position relative to active
  channels
• Lacustrine deposits can be important in overbank
  environments characterized by high water tables,
  and are also found in distal settings

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Fluvial/deltaic/coastal environments

• Fluvial environments
• Facies successions in sandy to gravelly channel
  deposits typically fine upward, from a coarse
  channel lag, through large-scale to small-scale
  cross stratified sets (commonly with decreasing
  set height), and finally overlain by muddy
  overbank deposits
• Facies successions produced by different fluvial
  styles can be extremely similar!
• The geometry and three-dimensional arrangement of
  architectural elements therefore provides a much
  better means of inferring fluvial styles from the
  sedimentary record

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Fluvial/deltaic/coastal environments

• Fluvial environments
• Avulsion is the sudden diversion of a channel to
  a new location on the floodplain, leading to the
  abandonment of a channel belt and the initiation
  of a new one
• Alluvial architecture refers to the
  three-dimensional arrangement of channel-belt
  deposits and overbank deposits in a fluvial
  succession
• The nature of alluvial architecture (e.g., the
  proportion of channel-belt to overbank deposits)
  is dependent on fluvial style, aggradation rate,
  and the frequency of avulsion

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Fluvial/deltaic/coastal environments

• Fluvial environments
• Avulsion is the sudden diversion of a channel to
  a new location on the floodplain, leading to the
  abandonment of a channel belt and the initiation
  of a new one
• Alluvial architecture refers to the
  three-dimensional arrangement of channel-belt
  deposits and overbank deposits in a fluvial
  succession
• The nature of alluvial architecture (e.g., the
  proportion of channel-belt to overbank deposits)
  is dependent on fluvial style, aggradation rate,
  and the frequency of avulsion

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Fluvial/deltaic/coastal environments

• Deltaic environments
• Deltas form where a river enters a standing body
  of water (ocean, sea, lake) and forms a thick
  deposit that may or may not form protuberances
• The delta plain is the subaerial part of a delta
  (gradational upstream to a floodplain) the delta
  front (delta slope and prodelta) is the
  subaqueous component
• Delta plains are commonly characterized by
  distributaries and flood basins (upper delta
  plain) or interdistributary bays (lower delta
  plain), as well as numerous crevasse splays
• Upper delta plains contain facies assemblages
  that are very similar to fluvial settings

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Fluvial/deltaic/coastal environments

• Deltaic environments
• Mouth bars form at the upper edge of the delta
  front, at the mouth of distributaries they are
  mostly sandy and tend to coarsen upwards
• The delta slope is commonly 1-2 and consists of
  finer (usually silty) facies the most distal
  prodelta is dominated by even finer sediment
• Progradation (basinward building) of deltas leads
  to coarsening-upward successions, and
  progradation rates depend on sediment supply and
  basin bathymetry (water depth)

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Fluvial/deltaic/coastal environments

• Deltaic environments
• Delta morphology reflects the relative importance
  of fluvial, tidal, and wave processes, as well as
  gradient and sediment supply
• River-dominated deltas occur in microtidal
  settings with limited wave energy, where
  delta-lobe progradation is significant and
  redistribution of mouth bars is limited
• Wave-dominated deltas are characterized by mouth
  bars reworked into shore-parallel sand bodies and
  beaches
• Tide-dominated deltas exhibit tidal mudflats and
  mouth bars that are reworked into elongate sand
  bodies perpendicular to the shoreline

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Fluvial/deltaic/coastal environments

• Deltaic environments
• Coarse-grained deltas are composed of gravelly
  facies and form where alluvial fans or relatively
  steep braided rivers enter a water body
• Delta cycles are the result of repetitive
  switching of delta lobes, comparable to avulsion
  in fluvial environments this leads to
  characteristic vertical successions with
  progradational facies and transgressive facies

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Fluvial/deltaic/coastal environments

• Deltaic environments
• Coarse-grained deltas are composed of gravelly
  facies and form where alluvial fans or relatively
  steep braided rivers enter a water body
• Delta cycles are the result of repetitive
  switching of delta lobes, comparable to avulsion
  in fluvial environments this leads to
  characteristic vertical successions with
  progradational facies and transgressive facies

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Fluvial/deltaic/coastal environments

• Coastal environments
• Erosional coasts are commonly characterized by
  cliffs, whereas constructional coasts can be
  formed by clastic, carbonate, or evaporite facies
• The morphology of constructional coasts is
  determined by sediment supply, wave energy, and
  tidal range, as well as climate and sea-level
  history

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Fluvial/deltaic/coastal environments

• Coastal environments
• Beaches form when sand or gravel is available and
  wave energy is significant, and result in
  low-angle cross-stratified deposits and cross
  strata formed by wave ripples
• Beaches can either be connected directly to the
  land and form strand plains or chenier plains
  (the latter consisting of beach ridges separated
  by muds), or be separated by lagoons or tidal
  basins (the latter consisting of tidal channels,
  tidal flats, and salt marshes) and form either
  spits or barrier islands

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Fluvial/deltaic/coastal environments

• Coastal environments
• Beaches form when sand or gravel is available and
  wave energy is significant, and result in
  low-angle cross-stratified deposits and cross
  strata formed by wave ripples
• Beaches can either be connected directly to the
  land and form strand plains or chenier plains
  (the latter consisting of beach ridges separated
  by muds), or be separated by lagoons or tidal
  basins (the latter consisting of tidal channels,
  tidal flats, and salt marshes) and form either
  spits or barrier islands

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Fluvial/deltaic/coastal environments

• Coastal environments
• Barrier islands are especially prolific in
  environments with a high wave energy and a
  limited tidal range, that have experienced
  transgression (relative sea-level rise)
• The tidal inlets between barrier islands are
  sites of deep erosional scour and are associated
  with flood-tidal deltas (lagoonal side) and
  ebb-tidal deltas (seaward side)
• Washovers can form during major storm events, and
  are found elsewhere across barrier islands
• Coastal dunes are common features associated with
  sandy beaches

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Fluvial/deltaic/coastal environments

• Coastal environments
• Estuaries are semi-enclosed coastal water bodies
  where fluvial and marine processes interact
• Tide-dominated estuaries have tidal channels with
  bars and tidal mudflats that contain tidal
  sedimentary structures (e.g., tidal bundles,
  heterolithic stratification)
• Wave-dominated estuaries are partly enclosed by a
  coastal barrier and have well-developed bay-head
  deltas

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Fluvial/deltaic/coastal environments

• Coastal environments
• Carbonate coastal environments can exhibit
  comparable characteristics as clastic coasts
  (i.e., barriers and lagoons), consisting of
  carbonate sands and muds, respectively
• Stromatolites (algal or bacterial mats) commonly
  form on carbonate-rich tidal flats
• Arid coastal environments are characterized by
  sabkhas and salinas, coastal plains frequently
  inundated by saline water and hypersaline
  lagoons, respectively, where evaporites (notably
  anhydrite and gypsum) can accumulate

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