Short Course: Biostratigraphy in Integrated Basin Studies Department of Geoscience, University of Os

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Short Course Biostratigraphy in Integrated Basin
Studies
Department of Geoscience,
University of Oslo, March 6-10, 2006 Sequence
Stratigraphy Principles, classification and
terminolgy Johan Petter Nystuen
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Sequence Stratigraphy

• A tool for interpretation of dynamics of basin
  sediment infill
• A tool for predicting sedimentary facies, source
  rocks and reservoir rocks
• Applies for all types of sedimentary basins
• Optimal use presupposes knowledge of geological
  processes in time and space

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What is a sequence?
A sequence is a succession of genetically
related strata that can be delineated
chronologically and spatially, and which
possesses some characteristic property that
defines the sequence as a particular product of
the total geological history, with respect to
events and processes.
Nystuen 1998, p. 33
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.genetically related strata

• Succession of strata deposited during one set of
  external (extrinsic, allogenic) and internal
  (intrinsic, autogenic) factors, like
• Constant, rising or falling base level
• Same type of sediment availability
• Same range and type of transporting and
  depositional energy conditions
• Same type of depositional environment

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can be delineated chronologically and
spatially

• Means that we need some kind of surface that is
  of the same age, or approximately of the same
  age, through the whole area it can be followed.
• Candidate surfaces
• Biostratigraphically defined surface
• Stratigraphic surface of same depositional age
  
• Seismic surface supposed to represent a
  depositional surface

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........some characteristic property..

• Similar sedimentary facies or facies
  association
• Similar biofacies association
• Bounded by same type of stratigraphic surface
  below as above
• - Subaerial erosional unconformity
• - Transgressional surface
• - Maximum flooding surface
• - Ravinement surface

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..particular product of the total geological
history with respect to events and processes.

• Means that the sequence tells about an event or
  episode in the infill history of a basin, as
• An episode of fall-and-rise of base level
• A tectonic episode
• A climatic episode
• A period of change in sediment population, or
  other environmental characteristics

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• Sequence stratigaphy stratigraphic surfaces
• Subaerial unconformity sequence boundary (SB)
  in the Exxon systematics
• Equivalent conformity marine surface being
  time equivalent to the youngest part of the Exxon
  SB
• Flooding surface (FS) surface representing
  increase in the water depth
• Maximum flooding surface (MFS) surface of
  maximum relative sea level (sequence boundary in
  genetic stratigraphic sequences)
• Transgressive surface (TS) maximum surface of
  regression (sequence boundary in
  transgressive-regressive sequences, T-R)
• Marine ravinement surface (MRS) Erosional
  surface formed by marine processes during
  transgression or regression

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A classic Exxonian type of sequence boundary
below fluvial sandstone overlying open-marine
shale (Lower Cretaceous Helvetiafjellet Formation
above Upper Jurassic Janusfjellet Subgroup,
Spitsbergen)
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Sequence stratigraphy applied on outcrops
Where is the sequence boundary? Flooding surface?
Transgressive surface? Maximum flooding surface?
Parasequences? Time lines?
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Seismic stratigraphy the classic sequence
stratigraphic discipline..but, how to use it?
Top lap? Onlap? Downlap? Erosional truncation?
Time lines? Clinoforms? Lithofacies? SB? FS? MFS?
Depositional environment?
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Sequence stratigraphy applied on well logs
Is there any sequence here? Sequence boundary?
Transgressive surface? Flooding surface? Maximum
flooding surface? Parasequence? Parasequence
set? Systems tract?
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3 main types of sequences

• A Bounded by surfaces of maximum transgression
  (MFS) genetic stratigraphic sequence
  (Galloway model)
• B Bounded by surfaces of maximum regression
  (TS) transgressive-regressive sequence (Embry
  model)
• C Bounded by subaerial erosional
  unconformites and their correlative conformities
  (SB) depositional sequence (Exxon model)

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3 Main types of sequences
Helland-Hansen 1995
A Genetic stratigraphic sequence B T-R
sequence C Depositional sequence
4 Forced regressive systems tract, or Falling
stage systems tract (FSST) 3 Highstand systems
tract, HST 2 Transgressive systems tract, TST 1
Lowstand systems tract, LST
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Eustacy Global sea level Relative Sea Level
Sea level relative to datum plane Water Depth
Relative sea level Accumulated
sediment Accommodation space available for
sediments to accumulate Sediment supply Total
volume of sediments input to the basin A/S rate
of Accommodation versus rate of Sediment supply
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Accommodation Space available for sediments to
accumulate Accommodation is controlled by base
level and equilibrium profiles that in turn are
controlled by eustacy and tectonics Geomorphologic
base level (or ultimate base level) sea level,
control the geomorphology of continents Stratigrap
hic base level controls accumulation of
sediments below theoretical energy surfaces
called equlibrium profiles
Coe 2003
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The alluvial equilibrium profile (graded stream
profile) Represents the base level of alluvial
systems. Incision, sediment by-pass or
accumulation as response of fall in relative
sea-level depend on slope of the elongated
alluvial profile in relation to the slope of the
emerged shelf
Coe 2003
Emery and Myers 1996
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• Stratigraphic base level in the marine
  environment is controlled by a series of
  equilibrium profiles from the littoral zone down
  to the abyssal plain
• Note
• The importance of sea-level mean high tide and
  sea-level mean low tide for the foreshore
  morphology
• The importance of fairweather wave-base and
  storm.wave base for the shoreface to offshore
  shelf morphology

Coe 2003
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Walthers Law in Sequence Stratigraphy Morpholog
y of paralic depositional environment from
coastal plain to open shelf
Superposition of facies belts during normal
regression of paralic depositional systems
Reineck and Singh 1975
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External or extrensic control mechanisms on
sequence formation in marine environment
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Hierarchies of stratigraphic sequences and
cycles The concept of repated sequences of
various time orders (cycles) depends on the
paradigm that recurrent sea level fluctuations
are controlled by long-term and short-term
factors like Tectono-eustacy (long-term) Milanko
vitch variables Glacio-euastacy (short- to
long-term) Orbital variables (short-term) Others
(short-term)
Coe 2003
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Main extrensic factors controling sequence
development
TECTONICS Global tectonics Time range in the 10
to 100 Ma order, world-wide to
regional Local teconics Time range of Ka to some
few Ma, local effects EUSTASY Tectono-eustasy 3
Ma 400 Ma Glacio-eustasy 100 ka
1600 ka Non-glacial orbital climatic forcing 20
ka 100 ka CLIMATE Sea- and lake level Time
range of Ka to Ma Sediment discharge
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Relationship between global sea-level cycles and
hydrocarbon potentials
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• Part of the global (eustatic) sea-level curve,
  from Haque et al. (1988 and 1989)
• The eustatic curve shows long-term and
  short-term sea-level fluctuations
• The coastal onlap curve shows coastal sediment
  encroachments recorded in various basins
• Application of the curves as an instrument of
  global correlation presupposes that events of
  eustatic sea-level changes result in similar
  types of sedimentary response, independant of
  structural basin type and impact of other
  controlling factors as regional and local
  tectonics, regional and local variation in
  climate, sediment discharge, etc.

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Modeling of sequence stratigraphic cyclicity as a
function of rate of eustatic change and rate of
subsidence
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The Exxon sea slug diagram - type 1 sequence
in a basin with a shelf break
Van Wagoner et al. 1988 and 1990
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Exxon sea slug diagram Type 1 sequence in a
basin with a ramp margin
Van Wagoner et al. 1988 and 1990
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Exxon sea slug diagram Type 2 sequence in a
basin with a shelf break
Van Wagoner et al. 1988 and 1990
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The Exxon sea slug diagram and the
corresponding chronstratigraphic diagram
(Wheeler diagram) Note that open spaces in the
chronostratigraphic diagram represents hiati,
time inervals of no deposition or deposition
followed by erosion
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Parasequences fundamental building stones of
sequences
Coe (2003) above and Van Wagoner et al. (1988) to
the right
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• Parasequences Facies, fossils and boundaries
• Siliciclastic strandplain succession
• Deltaic succession
• Intertidal to supratidal carbonate ramp
  succession
• HWM High Water Mean
• LWM Low Water Mean
• FWWB Fair Weather Wave Base

Coe (2003)
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Parasequence sets and architectural and
stratigraphic style
Van Wagoner et al. 1990
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Stacking pattern of parasequences as function of
rate of Accommodation to rate of Sediment supply
(A/S) and
changes in relative sea level
Coe 2003
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Correlation of parasequence sandstone bodies
between wells (A) to (D) Method A
Chronostratigraphic correlation Method B
Lithostratigraphic correlation
Progradational parasequence set
Retrogradational parasequence set
Van Wagoner et al. 1990
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The Exxon type of sequence cyclicity
3
4
1
2
5
1
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Shoreline movements Normal regression basinward
movement of shoreline when rate of sedimentation
gt rate of accommodation Forced regression
basinward movement of shoreline due to fall in
sea level Transgression landward movement of
shoreline
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Shoreline trajectories Helland-Hansen 1995
A 1
B
A 2
C1
C 2
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Forced regression (or falling stage) Plint
(1988) A. Slow fall in relative sea level
shoreline moves seaward realtively slowly B.
Faster fall in relative sea level shoreline
moves seaward at an increased rate C. Relatively
stable sea level shoreline moves seaward at
reduces rate D. Rapid rise in relative sea level
shoreline moves rapirdly landward
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• Highstand Systems Tract HST
• Theoretical relative sea-level curve
• Detail of relative sea-level curve with times t0
  to t7. Decreasin rate of accommodation is
  indicated by decreasing space between dashed
  horisontal lines
• (c) Typical geometry and features of the HST
  along a margin with shelf break
• Typical geometry and features of the HST along a
  ramp margin
• Note (c) and (d) are to scale

Coe (2003)
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• The Sequence Boundary (SB) (Exxonian type)
• Interval (t7 to t16) on the theoretical relative
  sea-level curve during which the SB forms
• Geometry and features of the SB along a margin
  with a shelf break. Falling stage sediments that
  may have formed are not shown
• Chronostratigraphic diagram from t0 to t22
  showing features in time corresponding to those
  of the depth-distance diagram in (b). Hemipelagic
  and pelagic sediments that may have been
  deposited are not shown. The correlative surface
  will pass through these

Coe 2003
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The Sequence Boundary(SB) Exxonian type,
continuous (d) Geometry and features of the
SB along a ramp margin. Falling stage sediments
that may have formed are not shown (e)
Chronostratigraphic diagram from t0 to t22
showing features in time corresponding to those
of the depth-distance diagram in (d). Hemipelagic
and pelagic sediments that may have been
deposited are not shown. The correlative surface
will pass through these
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• The Falling Stage Systems Tracts (FSST)
• Interval (t7 to t16) on the teorethical sea-level
  curve during which falling stage sediments have
  been deposited
• Detail of the sea-level curve and FSST sediments
  deposited during the interval t7 to t16. Note
  that the sediments have been deposited during
  first increasing then decreasing rate og
  sea-level fall
• Geometry and features of the FSST sediments along
  a margin with shelf break. t7 - t9 interval
  parsequences are deposited downstepping on the
  shelf, from t9 sediments were deposited directly
  onto the shelf slope and basin floor
• Geometry and features of FSST on a ramp margin

Coe 2003
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• The Lowstand Systems Tract (LST)
• Interval t16 to t21 on the theoretical relative
  sea-level curve
• Detail of the relative sea-level curve and the
  LST sediments deposited
• Geometry and features of the LST sediments along
  a margin with shelf break
• Geometry and features of LST sediments along a
  ramp shelf

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• The Transgressive Surface (TS)
• Position on the theorethical
• sea-level curve where the TS
• starts
• (b) Geometry and features of the
• TS along a margin with a shelf
• break
• (c) Geometry and features of the
• TS along a ramp margin
• Note that the transgressive surface is coinciding
  with the surface of maximum regressions

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• The Transgressive Systems Tract (TST)
• Interval (t21 to t23) during which the TST is
  deposited
• Detail of the relative sea-level curve and TST
  sediments deposited. The curve spans a phase
  where the rate in rise in relative sea-level is
  higher than rate of sediment supply.
  Parasequences show a retrogradational pattern.
  Individual parasequences represent short
  intervals of shore-line progradation (normal
  regression)
• Geometry and features of the TST along a margin
  with a shelf break
• Geometry and features of the TST along a ramp
  margin

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• The Maximum Flooding Surface (MFS)
• The MFS starts to form at time t23 and culminate
  at time t29. Exact position of the MFS depends on
  the balance between in the ratio A/S
• Geometry and features of a MFS along a margin
  with a shelf break (sediments deposited during
  the time of formation of MFS are not shown)
• Chronostratigraphical diagram from show the time
  represented by the MFS and the associated
  condensed section

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The Maximum Flooding Surface (MFS),
continuous (d) Geometry and features of the MFS
along a ramp margin. Hemipelagic and pelagic
sediments that will be deposited in the deeper
part of the basin are not shown (e)
Chronostratigraphical diagram from t0 to t38
showing the time represented b y the maximum
flooding and condensed section
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Shallow-marine to deep marine depositional
environment Biostratigraphic challenges High
resolution chronostratigraphy Biostratigraphic
criteria for identification of systems
tracts Biostratigraphic criteria for
identification of SB, TS, FS, MFS, MRS