− | Identifying a depositional systems tract can be achieved by analyzing seismic geometries ([[:file:sedimentary-basin-analysis_fig4-19.png|Figures 1]] and [[:file:sedimentary-basin-analysis_fig4-21.png|2]]), [[Basic open hole tools|wireline log]] motifs ([[:file:sedimentary-basin-analysis_fig4-22.png|Figure 3]]), and [[Biostratigraphy in sequence stratigraphy|biostratigraphic data]] ([[:file:sedimentary-basin-analysis_fig4-20.png|Figures 4]] and [[:file:sedimentary-basin-analysis_fig4-23.png|5]]). Carefully integrating multiple data sets increases the probability of a correct interpretation.<ref name=ch04r7>Armentrout, J. M., 1991, Paleontological constraints on depositional [[modeling]]: examples of integration of biostratigraphy and seismic stratigraphy, Pliocene–Pleistocene, Gulf of Mexico, ''in'' Weimer, P., Link, M. H., eds., Seismic Facies and Sedimentary Processes of Submarine Fans and Turbidite Systems: New York, Springer-Verlag, p. 137–170.</ref><ref name=ch04r15>Armentrout, J. M., Malacek, S. J., Mathur, V. R., Neuder, G. L., Ragan, G. M., 1996, Intraslope basin reservoirs deposited by gravity-driven processes: south Ship Shoal and Ewing Banks areas, offshore Louisiana, in Pacht, J. A., Sheriff, R. E., Perkins, B. F., eds., Stratigraphic Analysis: Utilizing Advanced Geophysical, Wireline, and Borehole Technology for Petroleum Exploration and Production: Proceedings, Gulf Coast Section SEPM 17th Annual Research conference, p. 7–18.</ref><ref name=ch04r8>Armentrout, J. M., 1993, Relative seal-level variations and fault-salt response: offshore Texas examples: Proceedings, Gulf Coast Section SEPM 14th Annual Research Conference, p. 1–7.</ref><ref name=ch04r101>Vail, P. R., Wornardt, W. W., 1990, Well log seismic stratigraphy: a new tool for exploration in the '90s: Proceedings, Gulf Coast Section SEPM 11th Annual Research conference, p. 379–388.</ref> | + | Identifying a depositional systems tract can be achieved by analyzing [[Reflection configuration patterns|seismic geometries]] ([[:file:sedimentary-basin-analysis_fig4-19.png|Figures 1]] and [[:file:sedimentary-basin-analysis_fig4-21.png|2]]), [[Basic open hole tools|wireline log]] motifs ([[:file:sedimentary-basin-analysis_fig4-22.png|Figure 3]]), and [[Biostratigraphy in sequence stratigraphy|biostratigraphic data]] ([[:file:sedimentary-basin-analysis_fig4-20.png|Figures 4]] and [[:file:sedimentary-basin-analysis_fig4-23.png|5]]). Carefully integrating multiple data sets increases the probability of a correct interpretation.<ref name=ch04r7>Armentrout, J. M., 1991, Paleontological constraints on depositional [[modeling]]: examples of integration of biostratigraphy and seismic stratigraphy, Pliocene–Pleistocene, Gulf of Mexico, ''in'' Weimer, P., Link, M. H., eds., Seismic Facies and Sedimentary Processes of Submarine Fans and Turbidite Systems: New York, Springer-Verlag, p. 137–170.</ref><ref name=ch04r15>Armentrout, J. M., Malacek, S. J., Mathur, V. R., Neuder, G. L., Ragan, G. M., 1996, Intraslope basin reservoirs deposited by gravity-driven processes: south Ship Shoal and Ewing Banks areas, offshore Louisiana, in Pacht, J. A., Sheriff, R. E., Perkins, B. F., eds., Stratigraphic Analysis: Utilizing Advanced Geophysical, Wireline, and Borehole Technology for Petroleum Exploration and Production: Proceedings, Gulf Coast Section SEPM 17th Annual Research conference, p. 7–18.</ref><ref name=ch04r8>Armentrout, J. M., 1993, Relative seal-level variations and fault-salt response: offshore Texas examples: Proceedings, Gulf Coast Section SEPM 14th Annual Research Conference, p. 1–7.</ref><ref name=ch04r101>Vail, P. R., Wornardt, W. W., 1990, Well log seismic stratigraphy: a new tool for exploration in the '90s: Proceedings, Gulf Coast Section SEPM 11th Annual Research conference, p. 379–388.</ref> |
− | Relative changes in sea level can also be inferred from detailed analysis of local depositional geometries on [[Seismic data|seismic reflection profiles]]. On the seismic reflection profile schematic in [[:file:sedimentary-basin-analysis_fig4-27.png|Figure 8]]<ref name=ch04r6>Armentrout, J. M., 1987, Integration of biostratigraphy and seismic stratigraphy: Pliocene–Pleistocene, Gulf of Mexico: Proceedings, Gulf Coast Section SEPM 8th Annual Research Conference, p. 6–14.</ref> clinoforms 1-5 [[pinch out]] with [http://homepage.ufp.pt/biblioteca/Seismic/Pages/Page22.htm toplap] against a common horizon, suggesting oblique clinoforms.<ref name=ch04r68>Mitchum, R., M., Jr., 1977, [http://archives.datapages.com/data/specpubs/seismic1/data/a165/a165/0001/0200/0205.htm Seismic stratigraphy and global changes in sea level, 11: Glossary of terms used in seismic stratigraphy], in Seismic Stratigraphy—Applications in Hydrocarbon Exploration: [http://store.aapg.org/detail.aspx?id=1157 AAPG Memoir 26], p. 205–212.</ref> These oblique [http://unterm.un.org/DGAACS/unterm.nsf/8fa942046ff7601c85256983007ca4d8/6d701a3f58b3c00d852570d70052c711?OpenDocument clinoforms] can be interpreted as forming when sediment supply exceeds the accommodation space and causes shelf-margin [[Depocenter#Sediment_supply_rate_and_facies_patterns|progradation]]; sea level falls at the same rate as subsidence, completely bypassing the shelf with no accumulation of seismic-scale [http://www.merriam-webster.com/dictionary/topset%20beds topset] beds. Clinoforms 6 and 7 are sigmoidal<ref name=ch04r68 /> These can be interpreted as sediment supply exceeding accommodation space, forcing progradation but with subsidence exceeding the relative change in sea level and consequent accumulation of topset beds. The change from no topset beds to [[Depocenter#Sediment_supply_rate_and_facies_patterns|aggradational]] topset beds indicates a turnaround from apparent still-stand to apparent rise in sea level at the site of deposition. | + | Relative changes in sea level can also be inferred from detailed analysis of local depositional geometries on [[Reflection configuration patterns|seismic reflection profiles]]. On the seismic reflection profile schematic in [[:file:sedimentary-basin-analysis_fig4-27.png|Figure 8]]<ref name=ch04r6>Armentrout, J. M., 1987, Integration of biostratigraphy and seismic stratigraphy: Pliocene–Pleistocene, Gulf of Mexico: Proceedings, Gulf Coast Section SEPM 8th Annual Research Conference, p. 6–14.</ref> clinoforms 1-5 [[pinch out]] with [http://homepage.ufp.pt/biblioteca/Seismic/Pages/Page22.htm toplap] against a common horizon, suggesting oblique clinoforms.<ref name=ch04r68>Mitchum, R., M., Jr., 1977, [http://archives.datapages.com/data/specpubs/seismic1/data/a165/a165/0001/0200/0205.htm Seismic stratigraphy and global changes in sea level, 11: Glossary of terms used in seismic stratigraphy], in Seismic Stratigraphy—Applications in Hydrocarbon Exploration: [http://store.aapg.org/detail.aspx?id=1157 AAPG Memoir 26], p. 205–212.</ref> These oblique [http://unterm.un.org/DGAACS/unterm.nsf/8fa942046ff7601c85256983007ca4d8/6d701a3f58b3c00d852570d70052c711?OpenDocument clinoforms] can be interpreted as forming when sediment supply exceeds the accommodation space and causes shelf-margin [[Depocenter#Sediment_supply_rate_and_facies_patterns|progradation]]; sea level falls at the same rate as subsidence, completely bypassing the shelf with no accumulation of seismic-scale [http://www.merriam-webster.com/dictionary/topset%20beds topset] beds. Clinoforms 6 and 7 are sigmoidal<ref name=ch04r68 /> These can be interpreted as sediment supply exceeding accommodation space, forcing progradation but with subsidence exceeding the relative change in sea level and consequent accumulation of topset beds. The change from no topset beds to [[Depocenter#Sediment_supply_rate_and_facies_patterns|aggradational]] topset beds indicates a turnaround from apparent still-stand to apparent rise in sea level at the site of deposition. |
| Note that the first downhole well-cutting sample occurrence of the bioevent ''Glob alt'' is at the interface of outer [http://www.onr.navy.mil/focus/ocean/regions/bluewater1.htm neritic] and upper [http://www.thefreedictionary.com/bathyal bathyal] [[Fossil assemblage|biofacies]], except in the two southern wells, A446-1 and A267-1, where the first occurrences occur within stratigraphic intervals containing bathyal biofacies. ''Glob alt'' is a [http://www.thefreedictionary.com/planktonic planktonic] [http://www.ucmp.berkeley.edu/foram/foramintro.html foraminifer] normally found associated with open marine faunas and floras interpreted as upper bathyal [[Fossil assemblage|assemblages]]. The occurrences of ''Glob alt'' coincident with the first upper bathyal biofacies assemblage suggests a facies-controlled top, depressed below the true extinction top by environmental factors. The two occurrences within upper bathyal biofacies are interpreted as true [[Wikipedia:Bioevent |extinction events]]. These true extinction events correlate with a seismic reflection, suggesting that specific reflection approximates a time line and can be used to extend the ''Glob alt'' extinction event datum (2.8 Ma) northward toward the basin margin (see Armentrout & Clement<ref name=ch04r10>Armentrout, J., M., Clement, J., F., 1990, Biostratigraphic calibration of depositional cycles: a case study in High Island–Galveston–East Breaks areas, offshore Texas: Proceedings, Gulf Coast Section SEPM 11th Annual Research Conference, p. 21–51.</ref>). | | Note that the first downhole well-cutting sample occurrence of the bioevent ''Glob alt'' is at the interface of outer [http://www.onr.navy.mil/focus/ocean/regions/bluewater1.htm neritic] and upper [http://www.thefreedictionary.com/bathyal bathyal] [[Fossil assemblage|biofacies]], except in the two southern wells, A446-1 and A267-1, where the first occurrences occur within stratigraphic intervals containing bathyal biofacies. ''Glob alt'' is a [http://www.thefreedictionary.com/planktonic planktonic] [http://www.ucmp.berkeley.edu/foram/foramintro.html foraminifer] normally found associated with open marine faunas and floras interpreted as upper bathyal [[Fossil assemblage|assemblages]]. The occurrences of ''Glob alt'' coincident with the first upper bathyal biofacies assemblage suggests a facies-controlled top, depressed below the true extinction top by environmental factors. The two occurrences within upper bathyal biofacies are interpreted as true [[Wikipedia:Bioevent |extinction events]]. These true extinction events correlate with a seismic reflection, suggesting that specific reflection approximates a time line and can be used to extend the ''Glob alt'' extinction event datum (2.8 Ma) northward toward the basin margin (see Armentrout & Clement<ref name=ch04r10>Armentrout, J., M., Clement, J., F., 1990, Biostratigraphic calibration of depositional cycles: a case study in High Island–Galveston–East Breaks areas, offshore Texas: Proceedings, Gulf Coast Section SEPM 11th Annual Research Conference, p. 21–51.</ref>). |