Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.
Sequence stratigraphy is the subdivision of the stratigraphic record on
the basis of bounding discontinuities.
Sequence St...
Formal Definitions of a Sequence
• A relatively conformable succession of genetically related strata
bounded at their uppe...
A depositional sequence is defined as a relatively conformable succession of
genetically-related (according to Walther’s L...
Depositional Sequence
Photo by W. W. Little
Photo by W. W. Little
Photo by W. W. Little
The stratigraphic record consists various scales of bedding separated by
bounding surfaces (disconti...
Photo by W. W. Little
Bedding planes are surfaces
between beds and bedsets that
represent breaks between episodic
depositi...
Photo by W. W. Little
Flooding Surfaces
Flooding surfaces bound parasequences and represent relative rises in
base-level. ...
Both transgressive and regressive events can develop erosional surfaces
associated with shoreface erosion by wave base.
Sh...
Photo by W. W. Little
Sequence Boundaries
Sequence boundaries are surfaces bounding depositional sequences.
Depending upon...
Photo by W. W. Little
Photo by W. W. Little
Photo by W. W. Little
Possible future flooding surface
Sequence boundary
Subsurface (seismic) Expression
Seismic sections record changes in impedance across
discontinuities; therefore, unless dis...
Upper Bounding Surface
Toplap Concordant Erosion
Lower Bounding Surface
Onlap
Onlap
Downlap
Offlap
Bedset Terminations
Bed...
Erosion
Overlying Surface
Toplap Concordant
Underlying Surface
Onlap Downlap Concordant
Types of Terminations
Bedset termi...
Reflector Terminations & Systems Tracts
Discontinuities & Chronostratigraphy
Lithostratigraphic cross-section
showing space/space relationships.
Wheeler diagram s...
Litho- vs. Chronostratigraphy
Lithostratigraphic units (formations, members, groups) are
time transgressive and are differ...
Effects of Changing Accommodation
on the Stratigraphic Record
Base-level curves are based
primarily on facies changes
(FUS...
A parasequence is a relatively conformable succession of genetically-
related beds or bedsets bounded by marine flooding s...
Marine Flooding Surface
Marine Flooding Surface
Marine Flooding Surface
Though parasequences represent progradational pulses of deposition,
internally they can either coarsen- or fine-upward, de...
Flooding surfaces and sequence boundaries are produced in response
to rises and falls, respectively, in base-level. Latera...
A systems tract is a three-dimensional assemblage of genetically-
related (according to Walther’s Law) depositional system...
According to Walther’s Law, absent an unconformity, facies stacked
vertically were deposited laterally to one another. The...
Lithostratigraphy & Allostratigraphy
Lithostratigraphy
Based on
Lithology
Allostratigraphy
Based on
Discontinuities
Lithostratigraphy & Sequence Stratigraphy
Though diachronous over their
lateral extent, bounding surfaces
have chronostratigraphic
significance, in that everything
...
Depending upon the
direction and relative rate
of base-level fluctuation,
sets of parasequences can
form patterns that are...
The type of stacking pattern
is controlled largely by the
relative balance between
rates of accommodation
production (base...
Sediment supply exceeds
accomodation production and facies
shift basinward.
Sediment supply exceeds accomodation
productio...
Progradation during a stillstand or rising base-level lengthens the
graded profile, resulting in both aggradation (mostly ...
Relative base-level is the cumulative result
of rates and direction of eustatic base-level
fluctuation and basin subsidenc...
Sequence Boundary
A sequence boundary (SB) is
produced as relative base-
level drops. Erosion begins
in landward regions a...
Formation of Sequence Boundary: SB
Falling-stage Systems Tract
A FSST can form while
relative base level falls and the
SB is produced; however,
because of ca...
Photo by W. W. Little
Photo by W. W. Little
Photo by W. W. Little
Lowstand Systems Tract
A LST is produced during the
early stages of relative base-level
rise. Erosion continues in
landwar...
Lowstand Systems Tract: LST
Transgressive Surface
The transgressive surface (TS)
separates the LST below from the TST
above and forms during the maxim...
Transgressive Systems Tract
The transgressive systems tract is
typically thin and characterized by
a retrogradational para...
Transgressive Systems Tract: TST
formation of maximum flooding surface
Maximum Flooding Surface
The MFS forms the boundary
between the TST and HST and
represents the greatest landward
incursion...
Highstand Systems Tract
The HST is found between the
MFS and the upper SB. As
accommodation development
slows, parasequenc...
Highstand Systems Tract: HST
Complete Sequence
Long
Term
Cycles
Short
Term
Cycles
Recognition of stratigraphic surfaces in
measured sections can be used as a means
of de...
Sequence Stratigraphy & Eustasy
High-frequency
Sequence Stratigraphy
“Sequence Stratigraphy – Basics”
C. G. St. C. Kendall
SBSB
mfsmfs
TSTS
Sequence Stratigraphy - Principles
Sequence Stratigraphy - Principles
Sequence Stratigraphy - Principles
Sequence Stratigraphy - Principles
Sequence Stratigraphy - Principles
Sequence Stratigraphy - Principles
Sequence Stratigraphy - Principles
Sequence Stratigraphy - Principles
Sequence Stratigraphy - Principles
Sequence Stratigraphy - Principles
Upcoming SlideShare
Loading in …5
×

Sequence Stratigraphy - Principles

25,932 views

Published on

Geol 370: Sedimentology and Stratigraphy
Topic 21: Principles of Sequence Stratigraphy

Published in: Science

Sequence Stratigraphy - Principles

  1. 1. Sequence stratigraphy is the subdivision of the stratigraphic record on the basis of bounding discontinuities. Sequence Stratigraphy
  2. 2. Formal Definitions of a Sequence • A relatively conformable succession of genetically related strata bounded at their upper surface and base by unconformities and their correlative conformities (Vail, et al., 1977). • Sequence is composed of a succession of genetically linked deposition systems (systems tracts) and is interpreted to be deposited between eustatic-fall inflection points (Posamentier, et al., 1988). • Study of rock relationships within a time-stratigraphic framework of repetitive, genetically related strata bounded by surfaces of erosion or non-deposition, or their correlative conformities (Posamentier et al., 1988; Van Wagoner et al., 1988). • The sequences and the system tracts they enclose are subdivided and/or bounded by a variety of "key" surfaces that bound or envelope these discrete geometric bodies of sediment. They mark changes in depositional regime "thresholds" across that boundary (Kendall).
  3. 3. A depositional sequence is defined as a relatively conformable succession of genetically-related (according to Walther’s Law) strata bound by unconformities and correlative conformities. Boundaries are diachronous, though the sequence represents an isochronous event; therefore, sequences have chronostratigraphic significance. Depositional Sequence
  4. 4. Depositional Sequence
  5. 5. Photo by W. W. Little
  6. 6. Photo by W. W. Little
  7. 7. Photo by W. W. Little The stratigraphic record consists various scales of bedding separated by bounding surfaces (discontinuities) that represent “gaps” in the sedimentary record. Types of Discontinuities
  8. 8. Photo by W. W. Little Bedding planes are surfaces between beds and bedsets that represent breaks between episodic depositional events, such as floods, storms, and turbidity flows. Bedding Planes
  9. 9. Photo by W. W. Little Flooding Surfaces Flooding surfaces bound parasequences and represent relative rises in base-level. They can be recognized by deeper-water (basinward) facies abruptly overlying shallower-water (landward) facies and often involve shoreface erosion, forming a ravinement surface. Shallower-water faciesDeeper-water facies
  10. 10. Both transgressive and regressive events can develop erosional surfaces associated with shoreface erosion by wave base. Shoreface Ravinement Surface
  11. 11. Photo by W. W. Little Sequence Boundaries Sequence boundaries are surfaces bounding depositional sequences. Depending upon the relative rate of base-level fall with respect to basin filling, they can be erosional (type 1) or conformable (type 2) and are recognized by placement of more landward facies over more basinward facies. Basinward facies Landward facies
  12. 12. Photo by W. W. Little
  13. 13. Photo by W. W. Little
  14. 14. Photo by W. W. Little Possible future flooding surface Sequence boundary
  15. 15. Subsurface (seismic) Expression Seismic sections record changes in impedance across discontinuities; therefore, unless disrupted by structures, patterns within a seismic profile reflect parts of a stratigraphic sequence.
  16. 16. Upper Bounding Surface Toplap Concordant Erosion Lower Bounding Surface Onlap Onlap Downlap Offlap Bedset Terminations Bedsets, defined by discontinuities, terminate against other bedsets and are defined by the angular relationship between the two.
  17. 17. Erosion Overlying Surface Toplap Concordant Underlying Surface Onlap Downlap Concordant Types of Terminations Bedset terminations are named according to their angular relationship with underlying and overlying bounding surfaces.
  18. 18. Reflector Terminations & Systems Tracts
  19. 19. Discontinuities & Chronostratigraphy Lithostratigraphic cross-section showing space/space relationships. Wheeler diagram showing time/space relationships. By plotting time against space, facies migration, discontinuity development, and sea-level history can be reconstructed.
  20. 20. Litho- vs. Chronostratigraphy Lithostratigraphic units (formations, members, groups) are time transgressive and are different ages in different places.
  21. 21. Effects of Changing Accommodation on the Stratigraphic Record Base-level curves are based primarily on facies changes (FUS/CUS) and lapping relationships at bed terminations. Offlap and toplap typify progradation. Onlap represents retrogradation. Concordance demonstrates aggradation. Downlap can be developed during any of the three.
  22. 22. A parasequence is a relatively conformable succession of genetically- related beds or bedsets bounded by marine flooding surfaces or their correlative surfaces. Parasequence Flooding surface Flooding surface Shallowingupward
  23. 23. Marine Flooding Surface Marine Flooding Surface Marine Flooding Surface
  24. 24. Though parasequences represent progradational pulses of deposition, internally they can either coarsen- or fine-upward, depending upon the depositional system within which they form. Vertical Trends within a Parasequence Coarsening-upward Parasequence Fining-upward Parasequence
  25. 25. Flooding surfaces and sequence boundaries are produced in response to rises and falls, respectively, in base-level. Lateral facies shifts accompany vertical base-level fluctuations, affecting the character of systems tracts. Role of Accommodation Space
  26. 26. A systems tract is a three-dimensional assemblage of genetically- related (according to Walther’s Law) depositional systems. Systems tracts migrate and change character in response to the direction and rate of base-level fluctuation. These changes are recorded by geometrical relationships between bounding surfaces. Systems Tracts
  27. 27. According to Walther’s Law, absent an unconformity, facies stacked vertically were deposited laterally to one another. Therefore, facies boundaries within a parasequence are diachronous. Walther’s Law Shoaling-upward Deposit
  28. 28. Lithostratigraphy & Allostratigraphy Lithostratigraphy Based on Lithology Allostratigraphy Based on Discontinuities
  29. 29. Lithostratigraphy & Sequence Stratigraphy
  30. 30. Though diachronous over their lateral extent, bounding surfaces have chronostratigraphic significance, in that everything above is younger than everything below the surface. Because events producing bounding surfaces have identifiable beginning and ending points, they represent isochronous events (e.g. base- level fluctuations). Time relationships are typically shown by Wheeler Diagrams. Time Significance of Bounding Surfaces
  31. 31. Depending upon the direction and relative rate of base-level fluctuation, sets of parasequences can form patterns that are progradational (basinward- stepping), aggradational (vertical stacking), or retrogradational (landward- stepping). Parasequence Set Stacking Patterns
  32. 32. The type of stacking pattern is controlled largely by the relative balance between rates of accommodation production (base-level fluctuation) and basin filling (sediment supply). E.g., progradation can occur during either a base-level fall or rise, depending upon the amount of sediment delivered to the basin. Base-level & Sediment Supply Forced regression Transgression Regression Aggradation
  33. 33. Sediment supply exceeds accomodation production and facies shift basinward. Sediment supply exceeds accomodation production as accommodation is lost. Facies shift basinward as landward areas erode. Accommodation production exceeds sediment supply and facies shift landward. Sediment supply equal to accomodation production and facies stack vertically.
  34. 34. Progradation during a stillstand or rising base-level lengthens the graded profile, resulting in both aggradation (mostly proximal areas) and progradation (distal regions). Role of Graded Profile
  35. 35. Relative base-level is the cumulative result of rates and direction of eustatic base-level fluctuation and basin subsidence or uplift, leading to creation or destruction of accommodation space. Relative Base-level and Accommodation Space Under constant basin subsidence coupled with eustatic fluctuation, four points of significance to sequence stratigraphy are identified: A: Maximum rise (highstand) B: Maximum rate of fall C: Maximum fall (lowstand) D: Maximum rate of rise
  36. 36. Sequence Boundary A sequence boundary (SB) is produced as relative base- level drops. Erosion begins in landward regions and progresses basinward (diachronous) with deposition in more basinal areas, producing the falling-stage systems tract (FSST). The SB separates the highstand systems tract (HSST) below from the FSST or lowstand systems tract (LSST) above.
  37. 37. Formation of Sequence Boundary: SB
  38. 38. Falling-stage Systems Tract A FSST can form while relative base level falls and the SB is produced; however, because of cannibalization, this systems tract is often missing or poorly developed. If base- level experiences an absolute fall, a forced regression occurs and depositional units can downstep (offlap) in a basinward direction.
  39. 39. Photo by W. W. Little
  40. 40. Photo by W. W. Little
  41. 41. Photo by W. W. Little
  42. 42. Lowstand Systems Tract A LST is produced during the early stages of relative base-level rise. Erosion continues in landward areas, but preservation potential is higher than for FSST sediments, as accommodation is produced in a progressively more landward direction. These are characterized by onlap onto FSST deposits and/or the sequence boundary. Parasequence patterns change from progradational to aggradational.
  43. 43. Lowstand Systems Tract: LST
  44. 44. Transgressive Surface The transgressive surface (TS) separates the LST below from the TST above and forms during the maximum rate of relative base-level rise, as basinal accommodation development surpasses sediment supply. Stacking patterns change from aggradational to retrogradational. It is the first significant flooding surface within a sequence and commonly marks the base of the most prominent onlap exhibited by the sequence. Erosion often accompanies formation of the TS.
  45. 45. Transgressive Systems Tract The transgressive systems tract is typically thin and characterized by a retrogradational parasequence set as landward regions become flooded. This systems tract is bounded by the TS below and the maximum flooding surface (MFS) above.
  46. 46. Transgressive Systems Tract: TST formation of maximum flooding surface
  47. 47. Maximum Flooding Surface The MFS forms the boundary between the TST and HST and represents the greatest landward incursion of the sea. Parasequence stacking patterns change from retrogradation to aggradation. Basinward regions are characterized by a lack of sedimentation, produced a starved zone or condensed interval. Typically forms a downlap surface for highstand systems tract (HST) deposits.
  48. 48. Highstand Systems Tract The HST is found between the MFS and the upper SB. As accommodation development slows, parasequence sets change from aggradational to progradational. Bed terminations are characterized by onlap in proximal regions and downlap in more basinal areas.
  49. 49. Highstand Systems Tract: HST
  50. 50. Complete Sequence
  51. 51. Long Term Cycles Short Term Cycles Recognition of stratigraphic surfaces in measured sections can be used as a means of determining sea-level history for one area and correlating that history to litholigically different strata of another. Sequences in Measured Sections
  52. 52. Sequence Stratigraphy & Eustasy
  53. 53. High-frequency Sequence Stratigraphy “Sequence Stratigraphy – Basics” C. G. St. C. Kendall SBSB mfsmfs TSTS

×