Geol 755: Basin Analysis Geophysics Week 4.5

Taken From: Christopher G St. C. Kendall, Univ. South Carolina Sequence Stratigrapy Web, http://strata.geol.sc.edu/seismic.html

John N. Louie, Presenter

Seismic Stratigraphy BasicsReflector Terminations

Sequence Boundary Identification

Seismic Sequence Analysis Procedure

Example

John N. Louie, Presenter

Seismic Stratigraphy BasicsReflector Terminations

Sequence Boundary Identification

Seismic Sequence Analysis Procedure

Example

Geol 755: Basin AnalysisGeol 755: Basin AnalysisGeophysics Week 4.5Geophysics Week 4.5

Geol 755: Basin AnalysisGeol 755: Basin AnalysisGeophysics Week 4.5Geophysics Week 4.5


Seismic Sequence AnalysisSeismic Sequence Analysis

Objective: Define the genetic reflection packages Objective: Define the genetic reflection packages that envelope seismic sequences and systems that envelope seismic sequences and systems tracts.tracts.

These bounding discontinuities are identified on These bounding discontinuities are identified on the basis of reflection termination patterns and the basis of reflection termination patterns and their continuity.their continuity.

ReferencesReferences Vail, P. R., 1987, Seismic stratigraphy interpretation procedure, in Bally, A.W. (ed.), Atlas of Vail, P. R., 1987, Seismic stratigraphy interpretation procedure, in Bally, A.W. (ed.), Atlas of

seismic stratigraphy: AAPG Studies in Geology No. 27, Vol. 1, p. 1-10.seismic stratigraphy: AAPG Studies in Geology No. 27, Vol. 1, p. 1-10. Boggs, S. Jr., 2001, Principles of Sedimentology and stratigraphy, 3rd Ed., Prentice-Hall, Inc., Boggs, S. Jr., 2001, Principles of Sedimentology and stratigraphy, 3rd Ed., Prentice-Hall, Inc.,

New Jersey, 726 p.New Jersey, 726 p.


Seismic Sequence AnalysisSeismic Sequence Analysis Boundaries are defined on a seismic line by Boundaries are defined on a seismic line by

identifying the termination of seismic reflectors at identifying the termination of seismic reflectors at the discontinuity surfaces. Terminations occur:the discontinuity surfaces. Terminations occur:

Below a discontinuity and the definition of the upper Below a discontinuity and the definition of the upper sequence boundary. Examples of this include:sequence boundary. Examples of this include:1.1. ToplapToplap2.2. TruncationTruncation

Above a discontinuity and the definition of the lower Above a discontinuity and the definition of the lower sequence boundary:sequence boundary:1.1. OnlapOnlap2.2. DownlapDownlap

ReferencesReferences Vail, P. R., 1987, Seismic stratigraphy interpretation procedure, in Bally, A.W. (ed.), Atlas of Vail, P. R., 1987, Seismic stratigraphy interpretation procedure, in Bally, A.W. (ed.), Atlas of

seismic stratigraphy: AAPG Studies in Geology No. 27, Vol. 1, p. 1-10.seismic stratigraphy: AAPG Studies in Geology No. 27, Vol. 1, p. 1-10. Boggs, S. Jr., 2001, Principles of Sedimentology and stratigraphy, 3rd Ed., Prentice-Hall, Boggs, S. Jr., 2001, Principles of Sedimentology and stratigraphy, 3rd Ed., Prentice-Hall,

Inc., New Jersey, 726 p.Inc., New Jersey, 726 p.


Seismic Sequence AnalysisSeismic Sequence Analysis ToplapToplap: : Termination of strata against an Termination of strata against an

overlying surface mainly as a result of overlying surface mainly as a result of nondeposition (sedimentary bypassing) with nondeposition (sedimentary bypassing) with perhaps only minor erosion.perhaps only minor erosion.

ReferencesReferences Mitchum Jr., R.M., 1977. Seismic stratigraphy and global changes of sea level. Part 11: glossary of terms Mitchum Jr., R.M., 1977. Seismic stratigraphy and global changes of sea level. Part 11: glossary of terms

used in seismic stratigraphy. In: Payton, C.E. (Ed.), Seismic Stratigraphy––Applications to Hydrocarbon used in seismic stratigraphy. In: Payton, C.E. (Ed.), Seismic Stratigraphy––Applications to Hydrocarbon Exploration, vol. 26. A.A.P.G. Memoir, pp. 205–212.Exploration, vol. 26. A.A.P.G. Memoir, pp. 205–212.

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Seismic Sequence AnalysisSeismic Sequence Analysis Truncation: Truncation: Termination of strata or seismic reflections Termination of strata or seismic reflections

interpreted as strata along an unconformity surface due interpreted as strata along an unconformity surface due to post-depositional erosional or structural effects.to post-depositional erosional or structural effects.

This implies the deposition of strata and their subsequent tilting This implies the deposition of strata and their subsequent tilting and removal along an unconformity surface.and removal along an unconformity surface.

This termination is the most reliable top-discordant criterion of a This termination is the most reliable top-discordant criterion of a sequence boundary.sequence boundary.

Such truncation can also be caused by termination against an Such truncation can also be caused by termination against an erosional surface, as for instance a channel.erosional surface, as for instance a channel.

ReferencesReferences Mitchum Jr., R.M., 1977. Seismic stratigraphy and global changes of sea level. Part 11: glossary of terms used in seismic Mitchum Jr., R.M., 1977. Seismic stratigraphy and global changes of sea level. Part 11: glossary of terms used in seismic

stratigraphy. In: Payton, C.E. (Ed.), Seismic Stratigraphy––Applications to Hydrocarbon Exploration, vol. 26. A.A.P.G. Memoir, pp. stratigraphy. In: Payton, C.E. (Ed.), Seismic Stratigraphy––Applications to Hydrocarbon Exploration, vol. 26. A.A.P.G. Memoir, pp. 205–212.205–212.




Seismic Sequence AnalysisSeismic Sequence Analysis OnlapOnlap: A base-discordant relationship in which initially : A base-discordant relationship in which initially

horizontal strata progressively terminate against an horizontal strata progressively terminate against an initially inclined surface, or in which initially inclined strata initially inclined surface, or in which initially inclined strata terminate progressively updip against a surface of terminate progressively updip against a surface of greater initial inclination.greater initial inclination.

ReferencesReferences Mitchum Jr., R.M., 1977. Seismic stratigraphy and global changes of sea level. Part 11: glossary of terms used in seismic stratigraphy. In: Mitchum Jr., R.M., 1977. Seismic stratigraphy and global changes of sea level. Part 11: glossary of terms used in seismic stratigraphy. In:

Payton, C.E. (Ed.), Seismic Stratigraphy––Applications to Hydrocarbon Exploration, vol. 26. A.A.P.G. Memoir, pp. 205–212.Payton, C.E. (Ed.), Seismic Stratigraphy––Applications to Hydrocarbon Exploration, vol. 26. A.A.P.G. Memoir, pp. 205–212.




Seismic Sequence AnalysisSeismic Sequence Analysis DownlapDownlap: a relationship in which seismic : a relationship in which seismic

reflections of inclined strata terminate downdip reflections of inclined strata terminate downdip against an inclined or horizontal surface. against an inclined or horizontal surface. Examples of downlap surfaces include a top Examples of downlap surfaces include a top basin floor fan surface, a top slope fan surface, basin floor fan surface, a top slope fan surface, and a maximum flooding surface.and a maximum flooding surface.

ReferencesReferences Mitchum Jr., R.M., 1977. Seismic stratigraphy and global changes of sea level. Part 11: glossary of terms used in seismic stratigraphy. In: Payton, C.E. (Ed.), Mitchum Jr., R.M., 1977. Seismic stratigraphy and global changes of sea level. Part 11: glossary of terms used in seismic stratigraphy. In: Payton, C.E. (Ed.),

Seismic Stratigraphy––Applications to Hydrocarbon Exploration, vol. 26. A.A.P.G. Memoir, pp. 205–212.Seismic Stratigraphy––Applications to Hydrocarbon Exploration, vol. 26. A.A.P.G. Memoir, pp. 205–212.






Seismic Sequence AnalysisSeismic Sequence Analysis Note: If onlap cannot be distinguished from Note: If onlap cannot be distinguished from

downlap because of subsequence downlap because of subsequence deformation, the term deformation, the term baselapbaselap is used. is used.

ReferencesReferences Mitchum Jr., R.M., 1977. Seismic stratigraphy and global changes of sea level. Part 11: glossary of terms used in seismic stratigraphy. In: Payton, C.E. (Ed.), Mitchum Jr., R.M., 1977. Seismic stratigraphy and global changes of sea level. Part 11: glossary of terms used in seismic stratigraphy. In: Payton, C.E. (Ed.),

Seismic Stratigraphy––Applications to Hydrocarbon Exploration, vol. 26. A.A.P.G. Memoir, pp. 205–212.Seismic Stratigraphy––Applications to Hydrocarbon Exploration, vol. 26. A.A.P.G. Memoir, pp. 205–212.






Seismic Sequence AnalysisSeismic Sequence Analysis Recommended procedures for performing Recommended procedures for performing

seismic sequence analysis include:seismic sequence analysis include: Identifying the unconformities in the area of interest. Identifying the unconformities in the area of interest.

Unconformities are recognized as surfaces onto which Unconformities are recognized as surfaces onto which reflectors converge.reflectors converge.

Mark these terminations with arrows.Mark these terminations with arrows. Draw the unconformity surface between the onlapping Draw the unconformity surface between the onlapping

and downlapping reflections above; and the truncating and downlapping reflections above; and the truncating and toplapping reflections below.and toplapping reflections below.

Extend the unconformity surface over the complete Extend the unconformity surface over the complete section. If the boundary becomes conformable, trace section. If the boundary becomes conformable, trace its position across the section by visually correlating its position across the section by visually correlating the reflections.the reflections.

ReferencesReferences Vail, P. R., 1987, Seismic stratigraphy interpretation procedure, in Bally, A.W. (ed.), Atlas of seismic stratigraphy: AAPG Studies in Vail, P. R., 1987, Seismic stratigraphy interpretation procedure, in Bally, A.W. (ed.), Atlas of seismic stratigraphy: AAPG Studies in

Geology No. 27, Vol. 1, p. 1-10.Geology No. 27, Vol. 1, p. 1-10. Boggs, S. Jr., 2001, Principles of Sedimentology and stratigraphy, 3rd Ed., Prentice-Hall, Inc., New Jersey, 726 p.Boggs, S. Jr., 2001, Principles of Sedimentology and stratigraphy, 3rd Ed., Prentice-Hall, Inc., New Jersey, 726 p.


Seismic Sequence AnalysisSeismic Sequence Analysis Recommended procedures for performing Recommended procedures for performing

seismic sequence analysis (cont.):seismic sequence analysis (cont.): Continue identifying the unconformities on all the Continue identifying the unconformities on all the

remaining seismic sections for the basin.remaining seismic sections for the basin. Make sure the interpretation ties correctly among all Make sure the interpretation ties correctly among all

the lines.the lines. Identify the type of unconformity:Identify the type of unconformity:

• Sequence boundary: this is characterized by regional onlap Sequence boundary: this is characterized by regional onlap above and truncation below.above and truncation below.

• Downlap surface: this is characterized by regional downlap.Downlap surface: this is characterized by regional downlap.

ReferencesReferences Vail, P. R., 1987, Seismic stratigraphy interpretation procedure, in Bally, A.W. (ed.), Atlas of seismic Vail, P. R., 1987, Seismic stratigraphy interpretation procedure, in Bally, A.W. (ed.), Atlas of seismic

stratigraphy: AAPG Studies in Geology No. 27, Vol. 1, p. 1-10.stratigraphy: AAPG Studies in Geology No. 27, Vol. 1, p. 1-10. Boggs, S. Jr., 2001, Principles of Sedimentology and stratigraphy, 3rd Ed., Prentice-Hall, Inc., New Jersey, Boggs, S. Jr., 2001, Principles of Sedimentology and stratigraphy, 3rd Ed., Prentice-Hall, Inc., New Jersey,

726 p.726 p.


Seismic Sequence AnalysisSeismic Sequence Analysis Recommended color codes:Recommended color codes:

RedRed: Reflection patterns and reflection terminations.: Reflection patterns and reflection terminations.

GreenGreen: Downlap surfaces: Downlap surfaces

BlueBlue: Transgressive surfaces: Transgressive surfaces

Other colorsOther colors: Sequence boundaries: Sequence boundaries

If using only black and white:If using only black and white: Thin solid lines: Reflection pattensThin solid lines: Reflection pattens Thicker solid lines: Sequence boundariesThicker solid lines: Sequence boundaries Dashed lines: Downlap surfacesDashed lines: Downlap surfaces Dotted lines: Transgressive surfacesDotted lines: Transgressive surfaces


Seismic Sequence AnalysisSeismic Sequence Analysis





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Geol 755: Basin Analysis Geophysics Week 4.5