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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Sedimentary structures

• Sedimentary structures occur at very different
  scales, from less than a mm (thin section) to
  100s1000s of meters (large outcrops) most
  attention is traditionally focused on the
  bedform-scale
• Microforms (e.g., ripples)
• Mesoforms (e.g., dunes)
• Macroforms (e.g., bars)

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Sedimentary structures

• Laminae and beds are the basic sedimentary units
  that produce stratification the transition
  between the two is arbitrarily set at 10 mm
• Normal grading is an upward decreasing grain size
  within a single lamina or bed (associated with a
  decrease in flow velocity), as opposed to reverse
  grading
• Fining-upward successions and coarsening-upward
  successions are the products of vertically
  stacked individual beds

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Animation
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Animation
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Sedimentary structures

• Cross stratification
• Cross lamination (small-scale cross
  stratification) is produced by ripples
• Cross bedding (large-scale cross stratification)
  is produced by dunes
• Cross-stratified deposits can only be preserved
  when a bedform is not entirely eroded by the
  subsequent bedform (i.e., sediment input
  sediment output)
• Straight-crested bedforms lead to planar cross
  stratification sinuous or linguoid bedforms
  produce trough cross stratification

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Sedimentary structures

• Cross stratification
• The angle of climb of cross-stratified deposits
  increases with deposition rate, resulting in
  climbing ripple cross lamination
• Antidunes form cross strata that dip upstream,
  but these are not commonly preserved
• A single unit of cross-stratified material is
  known as a set a succession of sets forms a
  co-set

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Sedimentary structures

• Planar stratification
• Planar lamination (or planar bedding) is formed
  under both lower-stage and upper-stage flow
  conditions
• Planar stratification can easily be confused with
  planar cross stratification, depending on the
  orientation of a section (strike sections!)

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Sedimentary structures

• Cross stratification produced by wave ripples can
  be distinguished from current ripples by their
  symmetry and by laminae dipping in two directions
• Hummocky cross stratification (HCS) forms during
  storm events with combined wave and current
  activity in shallow seas (below the fair-weather
  wave base), and is the result of aggradation of
  mounds and swales
• Heterolithic stratification is characterized by
  alternating sand and mud laminae or beds
• Flaser bedding is dominated by sand with
  isolated, thin mud drapes
• Lenticular bedding is mud-dominated with isolated
  ripples

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Sedimentary structures

• Cross stratification produced by wave ripples can
  be distinguished from current ripples by their
  symmetry and by laminae dipping in two directions
• Hummocky cross stratification (HCS) forms during
  storm events with combined wave and current
  activity in shallow seas (below the fair-weather
  wave base), and is the result of aggradation of
  mounds and swales
• Heterolithic stratification is characterized by
  alternating sand and mud laminae or beds
• Flaser bedding is dominated by sand with
  isolated, thin mud drapes
• Lenticular bedding is mud-dominated with isolated
  ripples

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Sedimentary structures

• Tide-influenced sedimentary structures can take
  different shapes
• Herringbone cross stratification indicates
  bipolar flow directions, but are rare
• Mud-draped cross strata are much more common, and
  are the result of alternating bedform migration
  during high flow velocities and mud deposition
  during high or low tide (slackwater)
• Tidal bundles are characterized by a sand-mud
  couplet with varying thickness tidal bundle
  sequences consist of a series of bundles that can
  be related to neap-spring cycles

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Sedimentary structures

• Gravity-flow deposits
• Debris-flow deposits are typically poorly sorted,
  matrix-supported sediments with random clast
  orientation and no sedimentary structures
  thickness and grain size commonly remain
  unchanged in a proximal to distal direction
• Turbidites, the deposits formed by turbidity
  currents, are typically normally graded, ideally
  composed of five units (Bouma-sequence with
  divisions a-e), reflecting decreasing flow
  velocities and associated bedforms

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Sedimentary structures

• Gravity-flow deposits
• Debris-flow deposits are typically poorly sorted,
  matrix-supported sediments with random clast
  orientation and no sedimentary structures
  thickness and grain size commonly remain
  unchanged in a proximal to distal direction
• Turbidites, the deposits formed by turbidity
  currents, are typically normally graded, ideally
  composed of five units (Bouma-sequence with
  divisions a-e), reflecting decreasing flow
  velocities and associated bedforms

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Sedimentary structures

• Imbrication commonly occurs in water-lain gravels
  and conglomerates, and is characterized by
  discoid (flat) clasts consistently dipping
  upstream
• Sole marks are erosional sedimentary structures
  on a bed surface that have been preserved by
  subsequent burial
• Scour marks (caused by erosive turbulence)
• Tool marks (caused by imprints of objects)
• Paleocurrent measurements can be based on any
  sedimentary structure indicating a current
  direction (e.g., cross stratification,
  imbrication, flute casts)

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Sedimentary structures

• Imbrication commonly occurs in water-lain gravels
  and conglomerates, and is characterized by
  discoid (flat) clasts consistently dipping
  upstream
• Sole marks are erosional sedimentary structures
  on a bed surface that have been preserved by
  subsequent burial
• Scour marks (caused by erosive turbulence)
• Tool marks (caused by imprints of objects)
• Paleocurrent measurements can be based on any
  sedimentary structure indicating a current
  direction (e.g., cross stratification,
  imbrication, flute casts)

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Sedimentary structures

• Imbrication commonly occurs in water-lain gravels
  and conglomerates, and is characterized by
  discoid (flat) clasts consistently dipping
  upstream
• Sole marks are erosional sedimentary structures
  on a bed surface that have been preserved by
  subsequent burial
• Scour marks (caused by erosive turbulence)
• Tool marks (caused by imprints of objects)
• Paleocurrent measurements can be based on any
  sedimentary structure indicating a current
  direction (e.g., cross stratification,
  imbrication, flute casts)

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Sedimentary structures

• Trace fossils (ichnofossils) are the tracks,
  trails or burrows left behind in sediments by
  organisms (e.g., feeding traces, locomotion
  traces, escape burrows)
• Disturbance of sediments by organisms is known as
  bioturbation, which can lead to the total
  destruction of primary sedimentary structures
• Since numerous trace fossils are connected to
  specific depositional environments, they can be
  very useful in sedimentologic interpretations

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Sedimentary structures

• Soft-sediment deformation structures are
  sometimes considered to be part of the initial
  diagenetic changes of a sediment, and include
• Slump structures (on slopes)
• Dewatering structures (upward escape of water,
  commonly due to loading)
• Load structures (density contrasts between sand
  and underlying wet mud can in extreme cases
  cause mud diapirs)