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Geol 755: Basin Analysis Geophysics Week 4.5

Geol 755: Basin Analysis Geophysics Week 4.5. John N. Louie, Presenter Seismic Stratigraphy Basics Reflector Terminations Sequence Boundary Identification Seismic Sequence Analysis Procedure Example. Seismic Sequence Analysis.

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Geol 755: Basin Analysis Geophysics Week 4.5

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  1. Geol 755: Basin AnalysisGeophysics Week 4.5 John N. Louie, Presenter Seismic Stratigraphy Basics Reflector Terminations Sequence Boundary Identification Seismic Sequence Analysis Procedure Example Taken From: Christopher G St. C. Kendall, Univ. South Carolina Sequence Stratigrapy Web, http://strata.geol.sc.edu/seismic.html

  2. Seismic Sequence Analysis • Objective: Define the genetic reflection packages that envelope seismic sequences and systems tracts. • These bounding discontinuities are identified on the basis of reflection termination patterns and their continuity. • References • 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. • Boggs, S. Jr., 2001, Principles of Sedimentology and stratigraphy, 3rd Ed., Prentice-Hall, Inc., New Jersey, 726 p. Taken From: Christopher G St. C. Kendall, Univ. South Carolina Sequence Stratigrapy Web, http://strata.geol.sc.edu/seismic.html

  3. Seismic Sequence Analysis • Boundaries are defined on a seismic line by identifying the termination of seismic reflectors at the discontinuity surfaces. Terminations occur: • Below a discontinuity and the definition of the upper sequence boundary. Examples of this include: • Toplap • Truncation • Above a discontinuity and the definition of the lower sequence boundary: • Onlap • Downlap • References • 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. • Boggs, S. Jr., 2001, Principles of Sedimentology and stratigraphy, 3rd Ed., Prentice-Hall, Inc., New Jersey, 726 p. Taken From: Christopher G St. C. Kendall, Univ. South Carolina Sequence Stratigrapy Web, http://strata.geol.sc.edu/seismic.html

  4. Seismic Sequence Analysis • Toplap: Termination of strata against an overlying surface mainly as a result of nondeposition (sedimentary bypassing) with perhaps only minor erosion. • References • 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. Taken From: Christopher G St. C. Kendall, Univ. South Carolina Sequence Stratigrapy Web, http://strata.geol.sc.edu/seismic.html

  5. Seismic Sequence Analysis • Truncation: Termination of strata or seismic reflections interpreted as strata along an unconformity surface due to post-depositional erosional or structural effects. • This implies the deposition of strata and their subsequent tilting and removal along an unconformity surface. • This termination is the most reliable top-discordant criterion of a sequence boundary. • Such truncation can also be caused by termination against an erosional surface, as for instance a channel. • References • 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. Taken From: Christopher G St. C. Kendall, Univ. South Carolina Sequence Stratigrapy Web, http://strata.geol.sc.edu/seismic.html

  6. Seismic Sequence Analysis • Onlap: A base-discordant relationship in which initially horizontal strata progressively terminate against an initially inclined surface, or in which initially inclined strata terminate progressively updip against a surface of greater initial inclination. • References • 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. Taken From: Christopher G St. C. Kendall, Univ. South Carolina Sequence Stratigrapy Web, http://strata.geol.sc.edu/seismic.html

  7. Seismic Sequence Analysis • Downlap: a relationship in which seismic reflections of inclined strata terminate downdip against an inclined or horizontal surface. Examples of downlap surfaces include a top basin floor fan surface, a top slope fan surface, and a maximum flooding surface. • References • 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. Taken From: Christopher G St. C. Kendall, Univ. South Carolina Sequence Stratigrapy Web, http://strata.geol.sc.edu/seismic.html

  8. Seismic Sequence Analysis • Note: If onlap cannot be distinguished from downlap because of subsequence deformation, the term baselap is used. • References • 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. Taken From: Christopher G St. C. Kendall, Univ. South Carolina Sequence Stratigrapy Web, http://strata.geol.sc.edu/seismic.html

  9. Seismic Sequence Analysis • Recommended procedures for performing seismic sequence analysis include: • Identifying the unconformities in the area of interest. Unconformities are recognized as surfaces onto which reflectors converge. • Mark these terminations with arrows. • Draw the unconformity surface between the onlapping and downlapping reflections above; and the truncating and toplapping reflections below. • Extend the unconformity surface over the complete section. If the boundary becomes conformable, trace its position across the section by visually correlating the reflections. • References • 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. • Boggs, S. Jr., 2001, Principles of Sedimentology and stratigraphy, 3rd Ed., Prentice-Hall, Inc., New Jersey, 726 p. Taken From: Christopher G St. C. Kendall, Univ. South Carolina Sequence Stratigrapy Web, http://strata.geol.sc.edu/seismic.html

  10. Seismic Sequence Analysis • Recommended procedures for performing seismic sequence analysis (cont.): • Continue identifying the unconformities on all the remaining seismic sections for the basin. • Make sure the interpretation ties correctly among all the lines. • Identify the type of unconformity: • Sequence boundary: this is characterized by regional onlap above and truncation below. • Downlap surface: this is characterized by regional downlap. • References • 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. • Boggs, S. Jr., 2001, Principles of Sedimentology and stratigraphy, 3rd Ed., Prentice-Hall, Inc., New Jersey, 726 p. Taken From: Christopher G St. C. Kendall, Univ. South Carolina Sequence Stratigrapy Web, http://strata.geol.sc.edu/seismic.html

  11. Seismic Sequence Analysis • Recommended color codes: • Red: Reflection patterns and reflection terminations. • Green: Downlap surfaces • Blue: Transgressive surfaces • Other colors: Sequence boundaries • If using only black and white: • Thin solid lines: Reflection pattens • Thicker solid lines: Sequence boundaries • Dashed lines: Downlap surfaces • Dotted lines: Transgressive surfaces Taken From: Christopher G St. C. Kendall, Univ. South Carolina Sequence Stratigrapy Web, http://strata.geol.sc.edu/seismic.html

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

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