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UNIVERSITY OF SOUTH ALABAMA
Sequence Stratigraphy
GY 305: Geophysics
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The basic concept (systems tracts)
All sorts of STs (systems tracts)
Lecture 14:
Sequence Stratigraphy 2
Sequence Stratigraphy
A Short History
Accommodation Space: The thickness of sediment that can be
deposited (it’s sea level-controlled)
Sequence Stratigraphy
Those packages of sediment may have distinctive internal
structures (like clinoforms) that allow you to determine how
and when they formed relative to sea level position.
http://strata.geol.sc.edu/terminology/system-tract.html
http://strata.geol.sc.edu/terminology/system-tract.html
Sequence Stratigraphy
Sequence Stratigraphy
Is derived from
seismic profiles
whereby you
recognize distinct
sedimentary
packages (systems
tracts)
From Carter et al., 1991
http://strata.geol.sc.edu/terminology/system-tract.html
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Sequence Stratigraphy
A Short History
Note: Vail’s surfaces
actually define
packages of
sedimentary rock.
Those associated
with specific states
of sea level are
called systems tracts.
Sequence Stratigraphy (System Tracts)
LST: Low stand systems tract: includes deposits that accumulate
after the onset of relative a sea-level rise.
Lowstand Systems Tract sediments often fill or partially infill
incised valleys that were cut into the HST, and other earlier
deposits, during the FSST (falling stand systems tract)
http://strata.geol.sc.edu/terminology/system-tract.html
Sequence Stratigraphy (System Tracts)
LST: Low stand systems tract: includes deposits that accumulate
after the onset of relative a sea-level rise.
http://strata.geol.sc.edu/terminology/system-tract.html
Sequence Stratigraphy (System Tracts)
HST: High stand systems tract: the progradational deposits that
form when sediment accumulation rates exceed the rate of
increase in accommodation space. Stacking patterns exhibit
prograding aggrading clinoforms that thin upward.
http://strata.geol.sc.edu/terminology/system-tract.html
Sequence Stratigraphy (System Tracts)
HST: High stand systems tract: the progradational deposits that
form when sediment accumulation rates exceed the rate of
increase in accommodation space. Stacking patterns exhibit
prograding aggrading clinoforms that thin upward.
http://strata.geol.sc.edu/terminology/system-tract.html
Sequence Stratigraphy
Is derived from
seismic profiles
whereby you
recognize distinct
sedimentary
packages (systems
tracts)
From Carter et al., 1991
http://strata.geol.sc.edu/terminology/system-tract.html
2
Sequence Stratigraphy (System Tracts)
Today
More Sequence Stratigraphy
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Chalkboard version of systems tract generation
More system Tracts
Boundaries and surfaces
Outcrops and sequence stratigraphy
Movies
Sequence Stratigraphy (System Tracts)
System Tracts come in numerous styles and are named
according to sea level position/state during deposition.
The 6 most important are
1) LST: Low stand systems tract
2) HST: High stand systems tract
3) TST: Transgressive systems tract
4) FSST: Falling stage systems tract
5) RST: Regressive systems tract
6) FRST: Forced regressive systems tract
System Tracts come in numerous styles and are named
according to sea level position/state during deposition.
The 6 most important are
1) LST: Low stand systems tract
2) HST: High stand systems tract
3) TST: Transgressive systems tract
4) FSST: Falling stage systems tract
5) RST: Regressive systems tract
6) FRST: Forced regressive systems tract
Sequence Stratigraphy (System Tracts)
TST: Transgressive systems tract: the deposits accumulated
from the onset of coastal transgression until the time of
maximum transgression of the coast. Parasequences onlap the
sequence boundary in a landward direction and downlap onto
the transgressive surface in a basinward direction.
Chalk Board
http://strata.geol.sc.edu/terminology/system-tract.html
Sequence Stratigraphy (System Tracts)
Sequence
Stratigraphy
Summary
TST: Transgressive systems tract: the deposits accumulated
from the onset of coastal transgression until the time of
maximum transgression of the coast. Parasequences onlap the
sequence boundary in a landward direction and downlap onto
the transgressive surface in a basinward direction.
http://strata.geol.sc.edu/terminology/system-tract.html
http://strata.geol.sc.edu/terminology/system-tract.html
3
Sequence
Stratigraphy
Summary
Boundaries
Systems tracts are separated by sequence boundaries (SB) which
by definition, occur at the base of LSTs.
Bounding Surfaces
http://www.uga.edu/~strata/sequence/tracts.html
http://strata.geol.sc.edu/terminology/system-tract.html
Boundaries
Boundaries
Systems tracts are separated by sequence boundaries (SB) which
by definition, occur at the base of LSTs. These are
unconformable surfaces generally overlain by fluvial sediments.
Transgressive surfaces (TS) are commonly marked by lag deposits
Correlative conformities
are lateral equivalents to
SB’s. They still separate
LSTs from earlier HSTs
but are really hard to
spot in seismic profiles.
http://www.uga.edu/~strata/sequence/tracts.html
Boundaries
The maximum flooding surface (MFS) is the point of maximum
sea level rise. It is commonly marked by a lag deposit of shells.
http://strata.geol.sc.edu/ss-well-log.html
Evolution of an idea
Sequence
stratigraphy is still
evolving…
..unfortunately, that
means more jargon.
http://strata.geol.sc.edu/terminology/transgression.html
http://strata.geol.sc.edu/terminology/transgression.html
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Outcrops and Sequence Stratigraphy
Outcrops and Sequence Stratigraphy
Since the mid 1980s,
researchers have
attempted to relate
outcrops with
sequence
stratigraphy.
Haywick et al. (2000)
Haywick et al. (2000)
Outcrops and Sequence Stratigraphy
S5
Outcrops and Sequence Stratigraphy
SB
S4
CC
S3
SB
CC
S3
S2
Haywick et al. (2000)
Movies
1) Clastic systems tracts.mov
2) Transgressive systems tract.mov
3) Incised valleys.mov
Not available on the web page
Haywick et al. (2000)
Upcoming Stuff
Thursday’s Lab
Seismic mapping
Next Monday’s Lecture
Last words on sequence stratigraphy
Decide on exam format (closed versus open book exam)
Next Wednesday’s Lecture
Exam Review,
Work on final lab assignment
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