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            "1701": {
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                "title": "Recognizing stacked depositional sequences from well data",
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                        "*": "{{publication \n | image   = exploring-for-oil-and-gas-traps.png\n | width   = 120px\n | series  = Treatise in Petroleum Geology\n | title   = Exploring for Oil and Gas Traps\n | part    = Critical elements of the petroleum system\n | chapter = Sedimentary basin analysis\n | frompg  = 4-40\n | topg    = 4-44\n | author  = John M. Armentrout\n | link    = http://archives.datapages.com/data/specpubs/beaumont/ch04/ch04.htm\n | pdf     = \n | store   = http://store.aapg.org/detail.aspx?id=545\n | isbn    = 0-89181-602-X\n}}\nStacked depositional sequences can be recognized in well data using\n\n* variations in well log response\n* biostratigraphic data such as microfossil abundance patterns and [[Fossil assemblage|biofacies]] distribution\n\nArmentrout<ref name=ch04r9>Armentrout, J., M., 1996, High-resolution sequence biostratigraphy: examples from the Gulf of Mexico Plio\u2013Pleistocene, in Howell, J., Aiken, J., eds., High Resolution Sequence stratigraphy: Innovations and Applications: The Geological Society of London Special Publication 104, p. 65\u201386.</ref> discusses integration of these data sets.\n\n==Building regional log cross sections==\nRegional stratigraphic well-log [[cross section]]s form the foundation for many basin studies. They give a regional view of basin stratigraphy and can be integrated with seismic and biostratigraphic data. The list below outlines the steps for building regional well-log cross sections.\n\n# Build a grid of well-log sections that crosses the entire basin, either along depositional [[dip]] or depositional strike. Use as many wells as practical. Where available, add measured sections and [[core description]]s to the grid.\n# Correlate cross sections. Look for [[Unconformity|unconformities]] and flooding surfaces.\n# Tie the correlations from depositional-dip sections to depositional-strike sections.\n# Confirm correlations on seismic reflection profiles.\n\n==Biostratigraphic patterns==\nUsing chronostratigraphically significant bioevents as defined by microfossil extinction events and abundance patterns, local cycles of transgression and [[regression]] can be correlated from well to well, providing a high-resolution calibration of depositional cyclicity. Patterns of relative dilution vs. concentration of fossils that correlate over a significant geographic area, such as a large portion of a basin margin, can be interpreted as reflecting cycles of regional transgression and regression rather than local [[lateral]] shifting of sediment input points.\n\nStratigraphic intervals rich in calcareous nannoplankton and foraminiferal fossils and having maximum gamma-ray values are interpreted to correlate with condensed depositional intervals deposited during relative sediment starvation related to transgression.<ref name=ch04r59>Loutit, T., S., Hardenbol, J., Vail, P., R., Baum, G., R., 1988, Condensed sections: the key to age determination and correlation of continental margin sequences: SEPM Special Publication 42, p. 183\u2013213.</ref> Intervals devoid of fossils or having low abundance values, often associated with sandy [[lithofacies]], can be interpreted as deposited during relative high rates of accumulation related to [[Depocenter#Sediment_supply_rate_and_facies_patterns|progradation]] of the sediment supply into the area of the well, marking a phase of regression. Biofacies are interpreted using benthic foraminiferal assemblages indicative of water mass conditions.<ref name=ch04r97>Tipsword, H., L., J., Setzer, F., M., Smith, F., L. Jr., 1966, Interpretation of depositional environment in Gulf Coast exploration from paleoecology and related stratigraphy: Gulf Coast Assoc. of Geological Societies Transactions, vol. 16, p. 119\u2013130.</ref><ref name=ch04r28>Culver, S., J., 1988, New foraminiferal depth zonation of the northwestern Gulf of Mexico: Palaios, vol. 3, p. 69\u201385., 10., 2307/3514545</ref><ref name=ch04r7>Armentrout, J., M., 1991, Paleontological constraints on depositional [[modeling]]: examples of integration of biostratigraphy and seismic stratigraphy, Pliocene\u2013Pleistocene, 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\u2013170.</ref>\n\n==GOM basin example==\nIn the GOM basin, variations in well-log response and [[Fossil assemblage|biofacies]] distribution are analyzed for recognition of stacked depositional sequences. The [[Basic open hole tools#Gamma ray|gamma-ray]] log display provides a measure of sediment type, with curve deflections to the left suggesting increased sand content while high values to the right indicate increases in clay content. Use of multiple logs, especially [[Basic open hole tools#Spontaneous potential|spontaneous potential]], [[Basic open hole tools#Resistivity|resistivity]], density, and velocity logs calibrated by well-cutting descriptions and formation microscanner displays, provides a data set for reliable rock type identification. The figure below illustrates an interpretation template for log motif analysis.\n\nPatterns of forestepping vs. backstepping log-motif funnels can define transgressive vs. [[Regression|regressive]] depositional trends and candidate systems tracts and sequences. Vail and Wornardt<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\u2013388.</ref> and Armentrout et al.<ref name=ch04r8>Armentrout, J. M., S. J. Malacek, L. B. Fearn, C. E. Sheppard, P. H. Naylor, A. W. Miles, R. J. Desmarais, and R. E. Dunay, 1993, Log-motive analysis of Paleogene depositional systems tracts, central and northern North Sea: Defined by sequence stratigraphic analysis ''in'' J. R. Parker, ed., Petroleum Geology of Northwest Europe: Proceedings of the 4th Conference, The Geological Society of London, p. 45-57.</ref> detail the process.\n\n==GOM basin example chart==\n<gallery mode=packed heights=200px widths=200px>\nfile:sedimentary-basin-analysis_fig4-17.png|{{figure number|1}}Map of the study area, showing the named offshore exploration areas and bathymetry. It also shows the locations of the East Breaks 160-161 field, illus- trated seismic profiles and a reference well.\nfile:sedimentary-basin-analysis_fig4-22.png|{{figure number|2}}Interpretation template for log motif analysis. From Armentrout et al.<ref name=ch04r8 /> Courtesy The Geological Society of London.\nfile:sedimentary-basin-analysis_fig4-23.png|{{figure number|3}}Histogram patterns of foraminiferal and calcareous nannoplankton abundance for the South Galveston Mobil A-158 #3 well. From Armentrout.<ref name=ch04r7 /><ref name=ch04r9 /> Courtesy Springer-Verlag and The Geological Society of London.\nfile:sedimentary-basin-analysis_fig4-24.png|{{figure number|4}}Candidates for maximum flooding surfaces are identified by abundance peaks in both foraminifera and nannoplankton and by extinction events known to be associated with regionally significant maximum transgressions. From Armentrout.<ref name=ch04r9 /> Courtesy Springer-Verlag and The Geological Society of London.\n</gallery>\n\nThe histogram patterns of foraminiferal and calcareous nannoplankton abundance for the South Galveston Mobil A-158 #3 well are shown in [[:file:sedimentary-basin-analysis_fig4-23.png|Figure 3]]. The histogram is based on a detailed checklist of the relative abundance of each species of fossil in each well-cutting sample.<ref name=ch04r10>Armentrout, J., M., Clement, J., F., 1990, Biostratigraphic calibration of depositional cycles: a case study in High Island\u2013Galveston\u2013East Breaks areas, offshore Texas: Proceedings, Gulf Coast Section SEPM 11th Annual Research Conference, p. 21\u201351.</ref> Display of this data in two-way time facilitates integration with seismic reflection profiles using the [[synthetic seismogram]] to match the well data with the seismic reflection profile at the well site. Patterns of shallow vs. deep [[Fossil assemblage|biofacies]] and fossil abundance (i.e., concentration vs. dilution) can be correlated with [[Depocenter#Sediment_supply_rate_and_facies_patterns|progradation]] of sandstone vs. [[mudstone]] interpreted from wireline log patterns. Bioevents (abbreviated acronyms such as 2B and SG) and faunal discontinuity events (abbreviated FDA-3 and FDA-4) provide correlation horizons between which the abundance patterns provide additional events for correlation.<ref name=ch04r7 />\n\nIn the histogram in [[:file:sedimentary-basin-analysis_fig4-23.png|Figure 3]] (see [[:file:sedimentary-basin-analysis_fig4-17.png|Figure 1]] for well location), the foraminiferal abundance scale is 0-1000 specimens and the nannoplankton abundance scale is 0-800 specimens. Biofacies include inner neritic (IN, 0-50 m), middle neritic (MN, 50-100 m), outer neritic (ON, 100-200 m), upper bathyal (UPPB, 200-500 m), middle bathyal (MDLB, 500-1000 m), and lower bathyal (LOWB, 1000\u20132000 m). This figure is the leftmost (southern) well panel in [[:file:sedimentary-basin-analysis_fig4-24.png|Figure 4]]. The wireline log (gamma ray) motif patterns ([[:file:sedimentary-basin-analysis_fig4-22.png|Figure 2]]), biostratigraphic abundance events, and extinction datums provide correlation events.\n\n==Biostratigraphic correlation of stacked sequences==\nThe well correlation section on the next page is an example of using high-resolution biostratigraphic correlation to recognize depositional successions within stacked depositional sequences. In some basins containing nondescript fill that lacks unique marker beds, like the Gulf of Mexico, high-resolution biostratigraphic correlation is the best method for subdividing basin fill into sequences and systems tracts.<ref name=ch04r6>Armentrout, J., M., 1987, Integration of biostratigraphy and seismic stratigraphy: Pliocene\u2013Pleistocene, Gulf of Mexico: Proceedings, Gulf Coast Section SEPM 8th Annual Research Conference, p. 6\u201314.</ref><ref name=ch04r34>Galloway, W., E., 1989a, [http://archives.datapages.com/data/bulletns/1988-89/data/pg/0073/0002/0100/0125.htm Genetic stratigraphic sequences in basin analysis I: architecture and genesis of flooding-surface bounded depositional units]: AAPG Bulletin, vol. 73, p. 125\u2013142.</ref><ref name=ch04r35>Galloway, W., E., 1989b, [http://archives.datapages.com/data/bulletns/1988-89/data/pg/0073/0002/0100/0143.htm Genetic stratigraphic sequences in basin analysis II: application to northwest Gulf of Mexico Cenozoic basin]: AAPG Bulletin, vol. 73, p. 143\u2013154.</ref>\n\nThe four wells in the [[cross section]] are in a depositionally dip-oriented transect.<ref name=ch04r9 /> The correlation horizons, based on seven chronostratigraphically significant bioevents (mostly extinction events), partition the strata into age-correlative intervals.<ref name=ch04r10 /> Most of the chronostratigraphically significant bioevents occur in association with maximum fossil abundance, resulting in the interpretation of these correlation horizons as maximum flooding surface-condensed section data.<ref name=ch04r34 /><ref name=ch04r35 /><ref name=ch04r10 /><ref name=Shaffer1987a>Schaffer, B. L., 1987a, The potential of calcareous nannofossils for recognizing Plio-Pleistocene climactic cycles and sequence boundaries on the shelf: Proceedings, Gulf Section SEPM 8th Annual Research Conference, p. 142-145.</ref><ref name=Shaffer1987b>Schaffer, B. L., 1987b, The nature and significance of condensed sections in Gulf Coast late Neogene sequence stratigraphy: Gulf Coast Assoc. of Geological Societies Transactions, vol. 40, p. 186-195.</ref><ref name=ch04r72>Pacht, J., A., Bowen, B., E., Bearn, J., H., Schaffer, B., L., 1990, Sequence stratigraphy of Plio\u2013Pleistocene depositional facies in the offshore Louisiana south additions: Gulf Coast Assoc. of Geological Societies Transactions, vol. 40, p. 1\u201318.</ref><ref name=ch04r9 />\n\nEach well panel is formatted the same as [[:file:sedimentary-basin-analysis_fig4-23.png|Figure 3]]. The foraminiferal (left histogram) and calcareous nannoplankton (right histogram) abundance patterns of each well are very similar. Biostratigraphic correlation horizons (horizontal lines) provide ties between the wells, facilitating comparison between the abundance patterns and [[Fossil assemblage|biofacies]] variations within each chronostratigraphic interval. Each correlation was checked against correlations independently constructed using a regional grid of seismic reflection profiles.\n\n==Identifying sequence in the GOB basin example==\nIn [[:file:sedimentary-basin-analysis_fig4-24.png|Figure 4]], candidates for maximum flooding surfaces are identified by abundance peaks in both foraminifera and nannoplankton and by extinction events known to be associated with regionally significant maximum transgressions.<ref name=ch04r10 /><ref name=Shaffer1987a /><ref name=Shaffer1987b /><ref name=ch04r72 /> Sequence boundary candidates occur between the maximum flooding surfaces and are identified by low abundance of fossils and by wireline log patterns. The northern wells (right) are rich in sand deposited in shallow water (neritic biofacies); sequence boundaries are likely to occur at the top of forestepping parasequence sets. The southern wells (left) are sand-poor shale deposited in deep water (bathyal biofacies); sequence boundaries are likely to occur at or slightly below flat-based blocky sands and at faunal abundance minima.\n\n==See also==\n* [[East Breaks depositional sequence]]\n* [[Definitions of depositional system elements]]\n* [[Identifying depositional sequences]]\n* [[Identifying depositional sequences in seismic sections]]\n* [[Identifying depositional sequences from biostratigraphic data]]\n* [[Recognizing stacked depositional sequences in seismic profiles]]\n\n==References==\n{{reflist}}\n\n==External links==\n{{search}}\n* [http://archives.datapages.com/data/specpubs/beaumont/ch04/ch04.htm Original content in Datapages]\n* [http://store.aapg.org/detail.aspx?id=545 Find the book in the AAPG Store]\n\n[[Category:Critical elements of the petroleum system]] \n[[Category:Sedimentary basin analysis]]\n[[Category:Treatise Handbook 3]]"
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            "1699": {
                "pageid": 1699,
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                "title": "Recognizing stacked depositional sequences in seismic profiles",
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                        "*": "{{publication \n | image   = exploring-for-oil-and-gas-traps.png\n | width   = 120px\n | series  = Treatise in Petroleum Geology\n | title   = Exploring for Oil and Gas Traps\n | part    = Critical elements of the petroleum system\n | chapter = Sedimentary basin analysis\n | frompg  = 4-39\n | topg    = 4-39\n | author  = John M. Armentrout\n | link    = http://archives.datapages.com/data/specpubs/beaumont/ch04/ch04.htm\n | pdf     = \n | store   = http://store.aapg.org/detail.aspx?id=545\n | isbn    = 0-89181-602-X\n}}\nDepositional sequences can stack into successions of sequences if accommodation space permits preservation of successive sequences. Seismically, stacked sequences are expressed as repetitious reflection patterns.\n\n==GOM basin example==\n<gallery mode=packed heights=300px widths=300px>\nsedimentary-basin-analysis_fig4-25.png|{{figure number|1}}Correlation of the third-order eustatic curve of Haq et al.<ref>Haq, B., J. Hardenbol, and P. R. Vail, 1988, Mesozoic and Cenozoic chronostratigraphy and cycles of sea-level change: SEPM Special Publication 42, p. 71\u2013108.</ref> and the oxygen isotope curve of Williams and Trainor<ref>Williams, D. F., and D. M. Trainor, 1987, Integrated chemical stratigraphy of deep-water frontier areas of the northern Gulf of Mexico: Proceedings, Gulf Coast Section SEPM 8th Annual Research Conference, p. 151\u2013158.</ref> with seven prograding clinoform intervals from the High Island South Addition in the GOM basin. Copyright: Armentrout<ref name=Arm1993>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\u20137.</ref> courtesy Gulf Coast SEPM.\nsedimentary-basin-analysis_fig4-19.png|{{figure number|2}}Seismic reflection profile from the East Breaks field area illustrating both clinoform and parallel reflection patterns in late Pleistocene sediments immediately below the sea floor (between two sets of bold arrows). Modified from Armentrout;<ref name=Arm1993 /> courtesy Gulf Coast SEPM.\n</gallery>\n\nThe seismic reflection profile below is from the High Island South Addition area, GOM basin, [[distance::20 mi]] east of the East Breaks shelf-margin delta. It illustrates the vertical stacking of seven depositional sequences within a fault-bounded salt-withdrawal basin. Down arrows at the inflection point of each clinoform identify the top of the clinoform of each sequence. In general, each cycle consists of (1) a thick basinal package of relatively discontinuous, variable-amplitude, hummocky reflections that grade upward into (2) parallel, continuous, uniform amplitude reflections, overlain by (3) a [[Depocenter#Sediment_supply_rate_and_facies_patterns|prograding]] clinoform that downlaps the underlying facies. Each clinoform is interpreted as a shelf-margin delta prograding into this outer-shelf to upper-slope fault-bounded basin as shown by the presentday sea floor profile. The seven prograding clinoforms are mapped into a nearby well and are correlated with two-cycle charts ([[:file:sedimentary-basin-analysis_fig4-25.png|Figure 1]]). Cycle 1 of this figure correlates with the clinoform package of [[:file:sedimentary-basin-analysis_fig4-19.png|Figure 2]].\n\n==Interpretation of example==\nThe nearly vertical stacking of seven shelf-margin clinoforms suggests that accommodation space was created in the same area during seven cycles of progradation. The accommodation space is formed by down-to-the-north movement on the fault. This fault is part of a counter-regional listric [[growth fault]] that soles out into salt layers at depth. Movement on the fault occurred at a rate permitting the vertical stacking of shelf-margin clinoforms during each glacial/interglacial sea level cycle rather than progressive basinward progradation of successive clinoforms across a stable shelf-slope profile. This pattern clearly demonstrates the interplay of sediment supply, tectonics, climate, and sea level.<ref name=ch04r18>Beard, J., H., Sangree, J., B., Smith, L., A., 1982, [http://archives.datapages.com/data/bulletns/1982-83/data/pg/0066/0002/0150/0158.htm Quaternary chronology, paleoclimate, depositional sequences, and eustatic cycles]: AAPG Bulletin, vol. 66, p. 158\u2013169.</ref><ref name=ch04r3>Anderson, R., N., Abdulah, K., Sarzalejo, S., Siringan, F., Thomas, M., A., 1996, Late Quaternary sedimentation and high-resolution sequence stratigraphy of the East Texas shelf, in DeBatist, M., Jacobs, P., eds., Geology of Siliciclastic Shelf Seas: Geological Society of London Special Publication 117, p. 94\u2013124.</ref>\n\n==See also==\n* [[East Breaks depositional sequence]]\n* [[Definitions of depositional system elements]]\n* [[Identifying depositional sequences]]\n* [[Identifying depositional sequences in seismic sections]]\n* [[Identifying depositional sequences from biostratigraphic data]]\n* [[Recognizing stacked depositional sequences from well data]]\n\n==References==\n{{reflist}}\n\n==External links==\n{{search}}\n* [http://archives.datapages.com/data/specpubs/beaumont/ch04/ch04.htm Original content in Datapages]\n* [http://store.aapg.org/detail.aspx?id=545 Find the book in the AAPG Store]\n\n[[Category:Critical elements of the petroleum system]] \n[[Category:Sedimentary basin analysis]]\n[[Category:Treatise Handbook 3]]"
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