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Tools and techniques for studying mudstones (view source)

Revision as of 17:48, 26 June 2024

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=====Optical Microscope=====

Optical microscopy can, for example, inform about the not-always-so-obvious origin of quartz grains<ref name=Mllkn2013 /><ref name=Schbr1996>Schieber, J., 1996, Early diagenetic silica deposition in algal cysts and spores: A source of sand in black shales?: Journal of Sedimentary Research, v. 66, p. 175–183.</ref><ref> Milliken, K. L., W. L. Esch, R. M. Reed, and T. Zhang, 2012a, [https://archives.datapages.com/data/bulletns/2012/08aug/BLTN11129/BLTN11129.HTM Grain assemblages and strong diagenetic overprinting in siliceous mudrocks, Barnett Shale (Mississippian), Fort Worth Basin, Texas]: AAPG Bulletin, v. 96, p. 1553–1578.</ref>, the formation history of small spots of cherty-looking material<ref name=Mllknea2007 />, depositional parameters<ref name=Schbr1999 /><ref name=Lzrea2015a /><ref name=Lzrea2015b /><ref name=McqkrTlr1996 /><ref>Wilson, R., and J. Schieber, 2014, Muddy prodeltaic hyperpycnites in the Lower Genesee Group of Central New York, USA: Implications for mud transport in epicontinental seas: Journal of Sedimentary Research, v. 84, p. 866–874.

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</ref>, and sequence-stratigraphic packaging and parasequence stacking patterns<ref name=Lzr2007 /><ref name=Lzrea2015a /><ref name=Lzrea2015b /><ref>Schieber, J., and O. R. Lazar, 2004, Devonian black shales of the eastern U.S.: New insights into sedimentology and stratigraphy from the subsurface and outcrops in the Illinois and Appalachian basins: Indiana Geological Survey Open File Study 04-05, 90 p.</ref>. For example, Schieber<ref name=Schbr1996 /> was able to show that diagenetic infilling of algal cysts produced sand-size diagenetic quartz grains that are easily mistaken for detrital grains, which can lead to erroneous interpretations of mudstone-associated sandstone beds. This avenue of research was extended further when in distal mudstones, large proportions of silt-size (and presumably detrital) quartz grains were linked to early diagenetic processes as well<ref name=Schbrea2000 />. Chertlike grains may initially suggest a diagenetic origin, however, these grains can also be detrital with some help from grain-concentrating benthic agglutinated foraminifera<ref name=Schbr2009 /><ref name=Mllknea2007>.

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</ref>, and sequence-stratigraphic packaging and parasequence stacking patterns<ref name=Lzr2007 /><ref name=Lzrea2015a /><ref name=Lzrea2015b /><ref>Schieber, J., and O. R. Lazar, 2004, Devonian black shales of the eastern U.S.: New insights into sedimentology and stratigraphy from the subsurface and outcrops in the Illinois and Appalachian basins: Indiana Geological Survey Open File Study 04-05, 90 p.</ref>. For example, Schieber<ref name=Schbr1996 /> was able to show that diagenetic infilling of algal cysts produced sand-size diagenetic quartz grains that are easily mistaken for detrital grains, which can lead to erroneous interpretations of mudstone-associated sandstone beds. This avenue of research was extended further when in distal mudstones, large proportions of silt-size (and presumably detrital) quartz grains were linked to early diagenetic processes as well<ref name=Schbrea2000 />. Chertlike grains may initially suggest a diagenetic origin, however, these grains can also be detrital with some help from grain-concentrating benthic agglutinated foraminifera<ref name=Schbr2009 /><ref name=Mllknea2007 />.

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When examined closely, many mudstone successions also show a wide variety of primary sedimentary structures and bioturbation features at thin-section scale and can provide excellent clues to sedimentary conditions, such as the presence of bottom currents<ref name=Schbr1999 /><ref>Schieber, J., J. B. Southard, and K. G. Thaisen, 2007, Accretion of mudstone beds from migrating floccule ripples: Science, v. 318, p. 1760–1763.</ref>, event deposition<ref name=Schbr1989 /><ref name=Schbr1999 /><ref>Loucks, R. G., and S. C. Ruppel, 2007, [https://archives.datapages.com/data/bulletns/2007/04apr/BLTN06059/BLTN06059.HTM Mississippian Barnett Shale: Lithofacies and depositional setting of a deep-water shale-gas succession in the Fort Worth Basin, Texas]: AAPG Bulletin, v. 91, no. 4, p. 579–601.</ref><ref> Macquaker, J. H. S., S. J. Bentley, and K. M. Bohacs, 2010, Wave-enhanced sediment-gravity flows and mud dispersal across continental shelves: Reappraising sediment transport processes operating in ancient mudstone successions: Geology, v. 38, p. 947–950.</ref> and microbial mats<ref name=Schbr1999 /><ref name=Schbr1989 />, as well as to substrate consistency<ref name=LbzSchbr><ref name=WtzlUchmn>Wetzel, A., and Uchman, A., 1998, Biogenic sedimentary structures in mudstones—an overview, ‘’in’’ J. Schieber, W. Zimmerle, and P. Sethi, eds., Shales and mudstones, Volume I: Stuttgart, Germany, E. Schweizerbart’sche Verlagsbuchhandlung (Nagele u. Obermiller), p. 351–369.</ref> and more subtle forms of animal–sediment interaction<ref name=Schbr2003 /><ref name=Pmbrtnea2008>Pemberton, S. G., J. A. MacEachern, M. K. Gingras, and T. D. Saunders, 2008, Biogenic chaos: Cryptobioturbation and the work of sedimentologically friendly organisms: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 270, no. 3, p. 273–279.</ref>. See [[Mudstone nomenclature]], and [[Laminasets, beds, and bedsets]], as well as all of the case study chapters (Bohacs and Ferrin<ref> Bohacs, K. M., and A. Ferrin, 2022, Monterey Formation, Miocene, California, USA—A Cenozoic biosiliceous-dominated continental slope to basin setting: A billion-barrel deep-water mudstone reservoir and source rock, in K. M. Bohacs and O. R. Lazar, eds., Sequence stratigraphy: Applications to fine-grained rocks: AAPG Memoir 126, p. 475–504.</ref>, Bohacs and Grabowski<ref>Bohacs, K. M., and G. J. Grabowski, 2022, Green River formation, Laney Member, Eocene, Wyoming, USA—A balanced-fill lake system with microbial carbonate and oil shale, an analog for part of the South Atlantic pre-salt, in K. M. Bohacs and O. R. Lazar, eds., Sequence stratigraphy: Applications to fine-grained rocks: AAPG Memoir 126, p. 505–536.</ref>; Bohacs and Guthrie<ref> Bohacs, K. M., and J. M. Guthrie, 2022, Chimney Rock Shale Member, Paradox Formation, Utah: Paleozoic, shallow carbonate-dominated shelf-to-basin billion-barrel source rocks, in K. M. Bohacs and O. R. Lazar, eds., Sequence stratigraphy: Applications to fine-grained rocks: AAPG Memoir 126, p. 223–248.</ref>; Bohacs et al<ref> Bohacs, K. M., O. R. Lazar, R. D. Wilson, and J. H. S. Macquaker, 2022d, Mowry Shale–Belle Fourche Shale, Bighorn Basin, Wyoming, USA—A Mesozoic clastic-biosiliceous shelf system: A prolific source rock with associated mudstone reservoir potential, in K. M. Bohacs and O. R. Lazar, eds., Sequence stratigraphy: Applications to fine-grained rocks: AAPG Memoir 126, p. 395–474.</ref><ref>Bohacs, K. M., J. H. S. Macquaker, and O. R. Lazar, 2022e, Kimmeridge Clay Formation, United Kingdom—A Mesozoic clastic-carbonate shelf-to-intrashelf basin system: An outcrop-to-subsurface analog for the Haynesville, Vaca Muerta, and Bazhenov formations, in K. M. Bohacs and O. R. Lazar, eds., Sequence stratigraphy: Applications to fine-grained rocks: AAPG Memoir 126, p. 345–394.</ref>, Campo et al.<ref> Campo, C., A. Morelli, A. Amorosi, L. Bruno, D. Scarponi, V. Rossi, K. M. Bohacs, and T. Drexler, 2022, Last glacial maximum depositional sequence, Po River Plain, Italy—Ultra-high resolution sequence stratigraphy of a Cenozoic coastal-plain-to-shallow-marine Foreland Basin, in K. M. Bohacs and O. R. Lazar, eds., Sequence stratigraphy: Applications to fine-grained rocks: AAPG Memoir 126, p. 537–598.</ref>; Lazar and Schieber<ref> Lazar, O. R. and J. Schieber, 2022, New Albany Shale, Illinois Basin, USA—Devonian carbonaceous mudstone accumulation in an epicratonic sea: Stratigraphic insights from outcrop and subsurface data, in K. M. Bohacs and O. R. Lazar, eds., Sequence stratigraphy: Applications to fine-grained rocks: AAPG Memoir 126, p. 249–294.</ref>; Potma et al.<ref> Potma, K., R. Jonk, and K. M. Bohacs, 2022, Canol Formation, Northwest Territories, Canada—An outcrop-to-subsurface analog for the Paleozoic Horn River Shale-gas play, in K. M. Bohacs and O. R. Lazar, eds., Sequence stratigraphy: Applications to fine-grained rocks: AAPG Memoir 126, p. 295–344.</ref> for other representative examples.

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When examined closely, many mudstone successions also show a wide variety of primary sedimentary structures and bioturbation features at thin-section scale and can provide excellent clues to sedimentary conditions, such as the presence of bottom currents<ref name=Schbr1999 /><ref>Schieber, J., J. B. Southard, and K. G. Thaisen, 2007, Accretion of mudstone beds from migrating floccule ripples: Science, v. 318, p. 1760–1763.</ref>, event deposition<ref name=Schbr1989 /><ref name=Schbr1999 /><ref>Loucks, R. G., and S. C. Ruppel, 2007, [https://archives.datapages.com/data/bulletns/2007/04apr/BLTN06059/BLTN06059.HTM Mississippian Barnett Shale: Lithofacies and depositional setting of a deep-water shale-gas succession in the Fort Worth Basin, Texas]: AAPG Bulletin, v. 91, no. 4, p. 579–601.</ref><ref> Macquaker, J. H. S., S. J. Bentley, and K. M. Bohacs, 2010, Wave-enhanced sediment-gravity flows and mud dispersal across continental shelves: Reappraising sediment transport processes operating in ancient mudstone successions: Geology, v. 38, p. 947–950.</ref> and microbial mats<ref name=Schbr1999 /><ref name=Schbr1989 />, as well as to substrate consistency<ref name=LbzSchbr /><ref name=WtzlUchmn>Wetzel, A., and Uchman, A., 1998, Biogenic sedimentary structures in mudstones—an overview, ‘’in’’ J. Schieber, W. Zimmerle, and P. Sethi, eds., Shales and mudstones, Volume I: Stuttgart, Germany, E. Schweizerbart’sche Verlagsbuchhandlung (Nagele u. Obermiller), p. 351–369.</ref> and more subtle forms of animal–sediment interaction<ref name=Schbr2003 /><ref name=Pmbrtnea2008>Pemberton, S. G., J. A. MacEachern, M. K. Gingras, and T. D. Saunders, 2008, Biogenic chaos: Cryptobioturbation and the work of sedimentologically friendly organisms: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 270, no. 3, p. 273–279.</ref>. See [[Mudstone nomenclature]], and [[Laminasets, beds, and bedsets]], as well as all of the case study chapters (Bohacs and Ferrin<ref> Bohacs, K. M., and A. Ferrin, 2022, Monterey Formation, Miocene, California, USA—A Cenozoic biosiliceous-dominated continental slope to basin setting: A billion-barrel deep-water mudstone reservoir and source rock, in K. M. Bohacs and O. R. Lazar, eds., Sequence stratigraphy: Applications to fine-grained rocks: AAPG Memoir 126, p. 475–504.</ref>, Bohacs and Grabowski<ref>Bohacs, K. M., and G. J. Grabowski, 2022, Green River formation, Laney Member, Eocene, Wyoming, USA—A balanced-fill lake system with microbial carbonate and oil shale, an analog for part of the South Atlantic pre-salt, in K. M. Bohacs and O. R. Lazar, eds., Sequence stratigraphy: Applications to fine-grained rocks: AAPG Memoir 126, p. 505–536.</ref>; Bohacs and Guthrie<ref> Bohacs, K. M., and J. M. Guthrie, 2022, Chimney Rock Shale Member, Paradox Formation, Utah: Paleozoic, shallow carbonate-dominated shelf-to-basin billion-barrel source rocks, in K. M. Bohacs and O. R. Lazar, eds., Sequence stratigraphy: Applications to fine-grained rocks: AAPG Memoir 126, p. 223–248.</ref>; Bohacs et al<ref> Bohacs, K. M., O. R. Lazar, R. D. Wilson, and J. H. S. Macquaker, 2022d, Mowry Shale–Belle Fourche Shale, Bighorn Basin, Wyoming, USA—A Mesozoic clastic-biosiliceous shelf system: A prolific source rock with associated mudstone reservoir potential, in K. M. Bohacs and O. R. Lazar, eds., Sequence stratigraphy: Applications to fine-grained rocks: AAPG Memoir 126, p. 395–474.</ref><ref>Bohacs, K. M., J. H. S. Macquaker, and O. R. Lazar, 2022e, Kimmeridge Clay Formation, United Kingdom—A Mesozoic clastic-carbonate shelf-to-intrashelf basin system: An outcrop-to-subsurface analog for the Haynesville, Vaca Muerta, and Bazhenov formations, in K. M. Bohacs and O. R. Lazar, eds., Sequence stratigraphy: Applications to fine-grained rocks: AAPG Memoir 126, p. 345–394.</ref>, Campo et al.<ref> Campo, C., A. Morelli, A. Amorosi, L. Bruno, D. Scarponi, V. Rossi, K. M. Bohacs, and T. Drexler, 2022, Last glacial maximum depositional sequence, Po River Plain, Italy—Ultra-high resolution sequence stratigraphy of a Cenozoic coastal-plain-to-shallow-marine Foreland Basin, in K. M. Bohacs and O. R. Lazar, eds., Sequence stratigraphy: Applications to fine-grained rocks: AAPG Memoir 126, p. 537–598.</ref>; Lazar and Schieber<ref> Lazar, O. R. and J. Schieber, 2022, New Albany Shale, Illinois Basin, USA—Devonian carbonaceous mudstone accumulation in an epicratonic sea: Stratigraphic insights from outcrop and subsurface data, in K. M. Bohacs and O. R. Lazar, eds., Sequence stratigraphy: Applications to fine-grained rocks: AAPG Memoir 126, p. 249–294.</ref>; Potma et al.<ref> Potma, K., R. Jonk, and K. M. Bohacs, 2022, Canol Formation, Northwest Territories, Canada—An outcrop-to-subsurface analog for the Paleozoic Horn River Shale-gas play, in K. M. Bohacs and O. R. Lazar, eds., Sequence stratigraphy: Applications to fine-grained rocks: AAPG Memoir 126, p. 295–344.</ref> for other representative examples.

Another microscopic approach to mudstone petrography is the examination of silt- and sand-size constituents in grain mounts after separation from the mudstone matrix. This furnishes additional information on the provenance of the fine-grained sediment and the diagenetic alteration of grains. Separation of this grain population by means of heavy liquids or magnetic separators or both allows a further split into light and heavy minerals, and facilitates the study of rare constituents that are not manifest in conventional thin sections. Auxiliary methods for analysis are an SEM with an attached energy-dispersive x-ray analysis system (EDS) or an electron microprobe (discussed in “Elemental Mapping” paragraphs in the “Scanning Electron Microscope” section).

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Millimeter-to-centimeter-scale observations of mudstone strata and their stacking patterns are recorded keeping track of the abundance of each physical, biological, and chemical attribute. One can then recognize laminae, laminasets, beds, and bedsets, and aggregate these observations into facies, facies associations, and facies-association successions<ref name=Bhcsea2014 /><ref name=Lzrea2015a /><ref name=Lzrea2015b />. An example of a description form and symbols we use to capture lamina-to-bedset-scale observations in mudstone successions is given in [[:file:M126CH03-Figure2.jpeg|Figure 2]]. Such a form clearly separates observations from interpretations, along with differentiating the various levels of interpretations; it captures observations on the left side; first to the right are lower level interpretations (e.g., sedimentary structures) and then higher level interpretations (e.g., benthic-energy and oxygen levels, depositional environments; [[:file:M126CH03-Figure2.jpeg|Figure 2]]).

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[[file:~~M126CH03~~-Figure2.jpeg|thumb|300px|{{figure number|2}}2A. Example of a form that we recommend using to capture the key attributes of mudstones observed in cores. 2B. Example of symbols useful for capturing mudstone observations in cores and hand specimens (after Lazar et al. <ref name=Lzrea2015b /> used with permission).

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[[file:M126CH3-Figure2.jpeg|thumb|300px|{{figure number|2}}2A. Example of a form that we recommend using to capture the key attributes of mudstones observed in cores. 2B. Example of symbols useful for capturing mudstone observations in cores and hand specimens (after Lazar et al. <ref name=Lzrea2015b /> used with permission).

=====Observations=====

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Key attributes to capture include the following (see also [[:file:~~M126CH03~~-Table2|Table 2]] and [[Mudstone nomenclature]] and [[Laminasets, beds, and bedsets]]:

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Key attributes to capture include the following (see also [[:file:M126Ch3-Table2.jpeg|Table 2]] and [[Mudstone nomenclature]] and [[Laminasets, beds, and bedsets]]:

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[[file:~~M126CH03~~-Table2|thumb|300px|’’Table 2.’’ Mudstone Attributes Most Useful for Sequence-stratigraphic Analyses.]]

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[[file:M126Ch3-Table2.jpeg|thumb|300px|’’Table 2.’’ Mudstone Attributes Most Useful for Sequence-stratigraphic Analyses.]]

* Depth or elevation

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=====Interpretations=====

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It is important to comment on the following (see also [[:file:~~M126CH03~~-Table2|Table 2]] , [[Laminasets, beds, and bedsets]], and [[Parasequences]]<ref>Bohacs, K. M., O. R. Lazar, and T. M. Demko, 2022a, Parasequences, in K. M. Bohacs and O. R. Lazar, eds., Sequence stratigraphy: Applications to fine-grained rocks: AAPG Memoir 126, p. 107–148.</ref>):

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It is important to comment on the following (see also [[:file:M126CH3-Table2.jpeg|Table 2]] , [[Laminasets, beds, and bedsets]], and [[Parasequences]]<ref>Bohacs, K. M., O. R. Lazar, and T. M. Demko, 2022a, Parasequences, in K. M. Bohacs and O. R. Lazar, eds., Sequence stratigraphy: Applications to fine-grained rocks: AAPG Memoir 126, p. 107–148.</ref>):

* Origin of grains

* Transportation, depositional, and reworking processes

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=====Consistency of Marine Substrate=====

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Organisms bioturbating fine-grained sediments may produce different burrows depending on substrate consistency<ref name=LbzSchbr><ref name=Schbr2003 /><ref name=WtzlUchmn /><ref>Wetzel, A., 1991, Ecologic interpretation of deep-sea trace fossil communities: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 85, p. 7–69.</ref><ref>Bromley, R. G., 1996, Trace fossils biology, taphonomy and applications, 2nd ed.: London, Chapman and Hall, 361 p.</ref><ref>Brett, C. E., and P. A. Allison, 1998, Paleontological approaches to the environmental interpretation of marine mudrocks, in J. Schieber, W. Zimmerle, and P. Sethi, eds., Shales and mudstones I.: Stuttgart, Germany, E. Schweizerbart’sche Verlagsbuchhandlung (Nagele u. Obermiller), p. 301–349.</ref>. Five levels of substrate consistency can be inferred from ichnofossil analysis—from “soupground” to “hardground” ([[file:~~M126CH03~~-Table3]]).

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Organisms bioturbating fine-grained sediments may produce different burrows depending on substrate consistency<ref name=LbzSchbr><ref name=Schbr2003 /><ref name=WtzlUchmn /><ref>Wetzel, A., 1991, Ecologic interpretation of deep-sea trace fossil communities: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 85, p. 7–69.</ref><ref>Bromley, R. G., 1996, Trace fossils biology, taphonomy and applications, 2nd ed.: London, Chapman and Hall, 361 p.</ref><ref>Brett, C. E., and P. A. Allison, 1998, Paleontological approaches to the environmental interpretation of marine mudrocks, in J. Schieber, W. Zimmerle, and P. Sethi, eds., Shales and mudstones I.: Stuttgart, Germany, E. Schweizerbart’sche Verlagsbuchhandlung (Nagele u. Obermiller), p. 301–349.</ref>. Five levels of substrate consistency can be inferred from ichnofossil analysis—from “soupground” to “hardground” ([[file:M126Ch3-Table3.jpeg|Table 3]]).

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[[file:~~M126CH03~~-Table3|thumb|300px|’’Table 3.’’ Inferred Substrate Consistency Based on Ichnofossils Analysis.]]

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[[file:M126Ch3-Table3.jpeg|thumb|300px|’’Table 3.’’ Inferred Substrate Consistency Based on Ichnofossils Analysis.]]

=====Rock-Color Charts=====

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====Total Organic Carbon Content====

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Vertical and lateral profiles of total organic carbon (TOC) content have been used for rapid screening of the quality and distribution of mudstones as source, reservoirs, and seals of hydrocarbons ([[:file:~~M126CH03~~-Table4|Table 4]]). The TOC content of a rock is the result of the nonlinear interaction of the rates of organic-matter production, destruction, and dilution<ref name=Bhcsea2005 /><ref name=Lzr2007 /><ref name=Sgmnea2003 /><ref name=Rmmrea2004 /><ref name=Tsn1995>Tyson, R. V., 1995, Sedimentary organic matter: Organic facies and palynofacies: Amsterdam, the Netherlands, Springer, 615 p.</ref><ref>Tyson, R. V., 2001, Sedimentation rate, dilution, preservation and total organic carbon: Some results of a modelling study: Organic Geochemistry, v. 32, p. 333–339.</ref><ref>Tyson, R. V., 2005, The “productivity versus preservation” controversy: Cause, flaws, and resolution, ‘’in’’ N. B. Harris, ed., The deposition of organic-carbon-rich sediments: Models, mechanisms, and consequences: SEPM Special Publication 82, p. 17–33.</ref><ref name=Bhcsea2000>Bohacs, K. M., A. R. Carroll, J. E. Neal, and P. J. Mankiewicz, 2000, Lake-basin type, source potential, and hydrocarbon character: An integrated sequence-stratigraphic-geochemical framework, in E. Gierlowski-Kordesch, and K. Kelts, eds., Lake basins through space and time: AAPG Studies in Geology 46, p. 3–37.</ref><ref>Harris, N. B., 2005, The deposition of organic-carbon-rich sediments: Models, mechanisms, and consequences-introduction, in N. B. Harris, ed., The deposition of organic-carbon-rich sediments: Models, mechanisms, and consequences: SEPM Special Publication 82, p. 1–5.</ref><ref> Katz, B. J., 2005, Controlling factors on source rock development-a review of productivity, preservation, and sedimentation rate, in N. B. Harris, ed., The deposition of organic-carbon-rich sediments: Models, mechanisms, and consequences: SEPM Special Publication 82, p. 7–16.</ref>. High TOC contents record the optimized combinations of moderately high production, low destruction, and low dilution rates. Low TOC contents can be the result of low production, high dilution, or high destruction rates, as well as high thermal maturity. As referenced in the section on Well-Log Tools (and discussed in [[Sequence sets and composite sequences]]<ref name=Bhcs22b>Bohacs, K. M., O. R. Lazar, T. M. Demko, J. Ottmann, and K. Potma, 2022b, Sequence sets and composite sequences, in K. M. Bohacs and O. R. Lazar, eds., Sequence stratigraphy: Applications to fine-grained rocks: AAPG Memoir 126, p. 195–222.</ref>), the vertical profile of TOC has been related to physiographic setting and sequence-stratigraphic units (i.e., parasequence, parasequence set, sequence, and sequence-set scale; see discussions in Creaney and Passey<ref>Creaney, S., and Q. R. Passey, 1993, Recurring patterns of total organic carbon and source rock quality within a sequence stratigraphic framework: AAPG Bulletin, v. 77, p. 386–401.</ref>, Bohacs<ref name=Bhcs1998 />, and Bohacs et al.<ref name=Bhcsea2005 />).

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Vertical and lateral profiles of total organic carbon (TOC) content have been used for rapid screening of the quality and distribution of mudstones as source, reservoirs, and seals of hydrocarbons ([[:file:M126Ch3-Table4.jpeg|Table 4]]). The TOC content of a rock is the result of the nonlinear interaction of the rates of organic-matter production, destruction, and dilution<ref name=Bhcsea2005 /><ref name=Lzr2007 /><ref name=Sgmnea2003 /><ref name=Rmmrea2004 /><ref name=Tsn1995>Tyson, R. V., 1995, Sedimentary organic matter: Organic facies and palynofacies: Amsterdam, the Netherlands, Springer, 615 p.</ref><ref>Tyson, R. V., 2001, Sedimentation rate, dilution, preservation and total organic carbon: Some results of a modelling study: Organic Geochemistry, v. 32, p. 333–339.</ref><ref>Tyson, R. V., 2005, The “productivity versus preservation” controversy: Cause, flaws, and resolution, ‘’in’’ N. B. Harris, ed., The deposition of organic-carbon-rich sediments: Models, mechanisms, and consequences: SEPM Special Publication 82, p. 17–33.</ref><ref name=Bhcsea2000>Bohacs, K. M., A. R. Carroll, J. E. Neal, and P. J. Mankiewicz, 2000, Lake-basin type, source potential, and hydrocarbon character: An integrated sequence-stratigraphic-geochemical framework, in E. Gierlowski-Kordesch, and K. Kelts, eds., Lake basins through space and time: AAPG Studies in Geology 46, p. 3–37.</ref><ref>Harris, N. B., 2005, The deposition of organic-carbon-rich sediments: Models, mechanisms, and consequences-introduction, in N. B. Harris, ed., The deposition of organic-carbon-rich sediments: Models, mechanisms, and consequences: SEPM Special Publication 82, p. 1–5.</ref><ref> Katz, B. J., 2005, Controlling factors on source rock development-a review of productivity, preservation, and sedimentation rate, in N. B. Harris, ed., The deposition of organic-carbon-rich sediments: Models, mechanisms, and consequences: SEPM Special Publication 82, p. 7–16.</ref>. High TOC contents record the optimized combinations of moderately high production, low destruction, and low dilution rates. Low TOC contents can be the result of low production, high dilution, or high destruction rates, as well as high thermal maturity. As referenced in the section on Well-Log Tools (and discussed in [[Sequence sets and composite sequences]]<ref name=Bhcs22b>Bohacs, K. M., O. R. Lazar, T. M. Demko, J. Ottmann, and K. Potma, 2022b, Sequence sets and composite sequences, in K. M. Bohacs and O. R. Lazar, eds., Sequence stratigraphy: Applications to fine-grained rocks: AAPG Memoir 126, p. 195–222.</ref>), the vertical profile of TOC has been related to physiographic setting and sequence-stratigraphic units (i.e., parasequence, parasequence set, sequence, and sequence-set scale; see discussions in Creaney and Passey<ref>Creaney, S., and Q. R. Passey, 1993, Recurring patterns of total organic carbon and source rock quality within a sequence stratigraphic framework: AAPG Bulletin, v. 77, p. 386–401.</ref>, Bohacs<ref name=Bhcs1998 />, and Bohacs et al.<ref name=Bhcsea2005 />).

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[[file:~~M126CH03~~-Table4|thumb|300px|’’Table 4.’’ Essential Attributes of Mudstones as Hydrocarbon Sources, Reservoirs, and Seals.]]

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[[file:M126Ch3-Table4.jpeg|thumb|300px|’’Table 4.’’ Essential Attributes of Mudstones as Hydrocarbon Sources, Reservoirs, and Seals.]]

TOC content can be measured through direct combustion, modified direct combustion, indirect (by difference), and pyrolysis plus combustion products. Each method has advantages and disadvantages; see Peters and Cassa<ref name=PtrsCss1994>Peters, K. E., and M. R. Cassa, 1994, Applied source rock geochemistry, in L. B. Magoon, and W. G. Dow, eds., The Petroleum system—From source to trap: AAPG Memoir 60, p. 93–120.</ref> for a detailed discussion. We recommend the direct combustion method for most mudstones.

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====Rock-Eval® Pyrolysis: Hydrogen and Oxygen Indices====

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Rock-Eval® pyrolysis is a rapid screening method for estimating the hydrogen and oxygen content of organic matter and provides insights into (1) the character of the original organic material (algal versus land plant), (2) the preservational conditions in the depositional environment<ref name=Ptrsea2005>Peters, K. E., C. C. Walters, and J. M. Moldowan, 2005, The biomarker guide: Biomarkers and isotopes in the environment and human history, 2nd ed.: Cambridge, U.K., Cambridge University Press, 1155 p.</ref>, and (3) the quality and distribution of hydrocarbon sources and reservoirs ([[:file:~~M126CH03~~-Table4|Table 4]]). Vertical profiles of hydrogen indices (HIs) have been related to physiographic setting and sequence-stratigraphic units and surfaces<ref name=Bhcs1998 /><ref name=CrnyPssy1993 /><ref>Bohacs, K. M., O. R. Lazar, J. Ottmann, K. Potma, and T. M. Demko, 2013, Shale-gas-reservoir families—translating sequence stratigraphy into robust predictions of reservoir distribution and potential: AAPG Search and Discovery article #90163.</ref>. For more information on the Rock-Eval method and parameters, see Espitalié et al.<ref>Espitalié, J., G. Deroo, and F. Marquis, 1985, La pyrolyse Rock-Eval et ses applications: Review Institut Français du Pétrole, Partie 1 and 2, v. 40, p. 563–784, Partie 3, v. 41, p. 73–89.</ref><ref>Espitalié, J., J. L. Laporte, M. Madec, F. Marquis, P. Lepat, J. Paulet, and A. Boutefeu, 1977, Méthode rapide de caractérisation des roches mères, de leur potentiel petrolier et leur degré d’évolution: Review Institut Français du Pétrole, v. 32, p. 23–42.</ref>, Lafargue et al.<ref>Lafargue, E., F. Marquis, and D. Pillot, 1998, Rock-Eval 6 applications in hydrocarbon exploration, production, and soil contamination studies: Institut Français du Pétrole, v. 53, p. 421–437.</ref>, Peters<ref>Peters, K. E., 1986, Guidelines for evaluating petroleum source rock using programmed pyrolysis: AAPG Bulletin, v. 70, p. 329.</ref>, and Tissot and Welte<ref name=TsstWlt>Tissot, B. P., and D. H. Welte, 1984, Petroleum formation and occurrence: Berlin, Springer-Verlag, 699 p.</ref>.

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Rock-Eval® pyrolysis is a rapid screening method for estimating the hydrogen and oxygen content of organic matter and provides insights into (1) the character of the original organic material (algal versus land plant), (2) the preservational conditions in the depositional environment<ref name=Ptrsea2005>Peters, K. E., C. C. Walters, and J. M. Moldowan, 2005, The biomarker guide: Biomarkers and isotopes in the environment and human history, 2nd ed.: Cambridge, U.K., Cambridge University Press, 1155 p.</ref>, and (3) the quality and distribution of hydrocarbon sources and reservoirs ([[:file:M126Ch3-Table4.jpeg|Table 4]]). Vertical profiles of hydrogen indices (HIs) have been related to physiographic setting and sequence-stratigraphic units and surfaces<ref name=Bhcs1998 /><ref name=CrnyPssy1993 /><ref>Bohacs, K. M., O. R. Lazar, J. Ottmann, K. Potma, and T. M. Demko, 2013, Shale-gas-reservoir families—translating sequence stratigraphy into robust predictions of reservoir distribution and potential: AAPG Search and Discovery article #90163.</ref>. For more information on the Rock-Eval method and parameters, see Espitalié et al.<ref>Espitalié, J., G. Deroo, and F. Marquis, 1985, La pyrolyse Rock-Eval et ses applications: Review Institut Français du Pétrole, Partie 1 and 2, v. 40, p. 563–784, Partie 3, v. 41, p. 73–89.</ref><ref>Espitalié, J., J. L. Laporte, M. Madec, F. Marquis, P. Lepat, J. Paulet, and A. Boutefeu, 1977, Méthode rapide de caractérisation des roches mères, de leur potentiel petrolier et leur degré d’évolution: Review Institut Français du Pétrole, v. 32, p. 23–42.</ref>, Lafargue et al.<ref>Lafargue, E., F. Marquis, and D. Pillot, 1998, Rock-Eval 6 applications in hydrocarbon exploration, production, and soil contamination studies: Institut Français du Pétrole, v. 53, p. 421–437.</ref>, Peters<ref>Peters, K. E., 1986, Guidelines for evaluating petroleum source rock using programmed pyrolysis: AAPG Bulletin, v. 70, p. 329.</ref>, and Tissot and Welte<ref name=TsstWlt>Tissot, B. P., and D. H. Welte, 1984, Petroleum formation and occurrence: Berlin, Springer-Verlag, 699 p.</ref>.

=====Sample Selection and Analytical Considerations=====

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Well-log analysis is the most complete and least expensive method of characterizing mudstones down-hole. This method provides robust characterization of the stratigraphic distribution of potential source, reservoir, and seal rocks. It is particularly valuable where sample data are not available or for lake strata where thin-bedded source rocks are common. Few well-log types, however, directly measure the rock properties sought to evaluate source, reservoir, or seal potential—it is essential to understand the assumptions made, and caution must be used in interpretation.

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The three main categories of well logs are electric, radioactive, and structural; most well logs were originally designed and mainly used for estimating lithology, porosity, rock strength, pressure, hydrocarbon presence and type, and structural characteristics (fractures, faults, folds, in situ stress). [[:file:~~M126CH03~~-Table5|Table 5]] summarizes the principles of well-logs commonly used for sequence-stratigraphic analysis and provides helpful tips and traps of log applications to mudstone successions. Many excellent textbooks provide more detail on well-logs and their interpretation<ref name=Srr>Serra, O., 1984, Fundamentals of well-log interpretation: Developments in Petroleum Science, v. 15, Part A, p. iii–vii, 1–423.</ref><ref name=Schlmbrgr1991>Schlumberger Limited, 1991, Log interpretation principles/applications: Houston, Texas, Schlumberger Educational Services, 142 p.</ref><ref name=EmryMyrs>Emery, D., and K. J. Myers, 1996, Sequence stratigraphy: Oxford, Blackwell Science, 297 p.</ref><ref name=Rdr2002>Rider, M., 2002, The geological interpretation of well logs: Marsa, Malta, Interprint, 280 p.</ref><ref name=Evnck2008>Evenick, J. C., 2008, Introduction to well logs and subsurface maps: Tulsa, Oklahoma, PennWell, 236 p.</ref>. A few general tips and traps to have in mind when using well logs are as follows:

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The three main categories of well logs are electric, radioactive, and structural; most well logs were originally designed and mainly used for estimating lithology, porosity, rock strength, pressure, hydrocarbon presence and type, and structural characteristics (fractures, faults, folds, in situ stress). [[:file:M126Ch3-Table5.jpeg|Table 5]] summarizes the principles of well-logs commonly used for sequence-stratigraphic analysis and provides helpful tips and traps of log applications to mudstone successions. Many excellent textbooks provide more detail on well-logs and their interpretation<ref name=Srr>Serra, O., 1984, Fundamentals of well-log interpretation: Developments in Petroleum Science, v. 15, Part A, p. iii–vii, 1–423.</ref><ref name=Schlmbrgr1991>Schlumberger Limited, 1991, Log interpretation principles/applications: Houston, Texas, Schlumberger Educational Services, 142 p.</ref><ref name=EmryMyrs>Emery, D., and K. J. Myers, 1996, Sequence stratigraphy: Oxford, Blackwell Science, 297 p.</ref><ref name=Rdr2002>Rider, M., 2002, The geological interpretation of well logs: Marsa, Malta, Interprint, 280 p.</ref><ref name=Evnck2008>Evenick, J. C., 2008, Introduction to well logs and subsurface maps: Tulsa, Oklahoma, PennWell, 236 p.</ref>. A few general tips and traps to have in mind when using well logs are as follows:

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[[file:~~M126CH03~~-Table5|thumb|300px|’’Table 5.’’ Well-logs: Applications, Tips, and Traps. See, for Example, Serra<ref name=Srr />, Schlumberger><ref name=Schlmbrgr1991 />, Emery and Myers<ref name=EmryMyrs />, Rider<ref name=Rdr2002 />, and Evenick<ref name=Evnck2008 /> for More Detail on Well-log Interpretations, Applications, and Caveats.]]

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[[file:M126Ch3-Table5.jpeg|thumb|300px|’’Table 5.’’ Well-logs: Applications, Tips, and Traps. See, for Example, Serra<ref name=Srr />, Schlumberger><ref name=Schlmbrgr1991 />, Emery and Myers<ref name=EmryMyrs />, Rider<ref name=Rdr2002 />, and Evenick<ref name=Evnck2008 /> for More Detail on Well-log Interpretations, Applications, and Caveats.]]

* Direct measurement of rock properties from samples is always the most accurate information you can obtain and is invaluable for calibrating well-log estimates. Sample coverage, however, tends to be sparse and unevenly distributed; hence, calibrated well-logs are essential for evaluating the entire section under examination.

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* Well-log analyses of mudstones require special attention to the standard procedures for depth alignment in combined log techniques, tool calibration, and tool baseline. Pay particular attention to the caliper log, for some mudstones tend to wash out, whereas others drill “gunbarrel straight.”

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For source evaluation, TOC depth profiles estimated from well-log data can be used to calculate TOC thickness, organic-matter volume, and the amount of hydrocarbon generated from a source rock over a particular area of a basin. The TOC profile also helps to interpret mudstone depositional environments and to correlate stratigraphic sequences<ref name=Bhcs1998 /><ref name=CrnyPssy1993 /><ref>Bessereau, G., and F. Guillocheau, 1995, Stratgraphie sequentielle et distribution de la matiere organique dans le Lias du bassin de Paris: Comptes Rendu de l’Académie des Sciences, v. 316, p. 1271–1278.</ref>. Mudstone reservoir and seal character can be estimated through analogous analyses using combinations of various well-logs<ref>Spears, R. W., and S. L. Jackson, 2009, Development of a predictive tool for estimating well performance in horizontal shale gas wells in the Barnett Shale, North Texas, USA: Petrophysics, v. 50, p. 19–31.</ref> (see [[:file:~~M126CH03~~-Table5|Table 5]]); the vertical profiles generated also provide useful insights for constructing sequence-stratigraphic frameworks<ref name=Bhcs1998 />.

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For source evaluation, TOC depth profiles estimated from well-log data can be used to calculate TOC thickness, organic-matter volume, and the amount of hydrocarbon generated from a source rock over a particular area of a basin. The TOC profile also helps to interpret mudstone depositional environments and to correlate stratigraphic sequences<ref name=Bhcs1998 /><ref name=CrnyPssy1993 /><ref>Bessereau, G., and F. Guillocheau, 1995, Stratgraphie sequentielle et distribution de la matiere organique dans le Lias du bassin de Paris: Comptes Rendu de l’Académie des Sciences, v. 316, p. 1271–1278.</ref>. Mudstone reservoir and seal character can be estimated through analogous analyses using combinations of various well-logs<ref>Spears, R. W., and S. L. Jackson, 2009, Development of a predictive tool for estimating well performance in horizontal shale gas wells in the Barnett Shale, North Texas, USA: Petrophysics, v. 50, p. 19–31.</ref> (see [[:file:M126Ch3-Table5.jpeg|Table 5]]); the vertical profiles generated also provide useful insights for constructing sequence-stratigraphic frameworks<ref name=Bhcs1998 />.

===Seismic Tools===

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====Seismic-Stratigraphy Procedure====

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The first step in seismic stratigraphy is to identify seismic terminations, and then use those terminations to recognize surfaces and delineate them. Next, key surfaces such as sequence boundaries and maximum flooding surfaces (maximum transgressive surfaces) are traced on the intersecting lines in a grid of seismic lines or propagated through a seismic-data volume until the boundaries have been correlated and tied within the entire dataset. This is intended to verify the regional extent of major discontinuity surfaces and to identify which other potentially significant surfaces are local in nature. [[:file:~~M126CH03~~-Table6|Table 6]] outlines the workflow for seismic stratigraphy. [[:file:~~M126CH03~~-Table7|Table 7]] details the criteria for identifying key stratigraphic surfaces.

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The first step in seismic stratigraphy is to identify seismic terminations, and then use those terminations to recognize surfaces and delineate them. Next, key surfaces such as sequence boundaries and maximum flooding surfaces (maximum transgressive surfaces) are traced on the intersecting lines in a grid of seismic lines or propagated through a seismic-data volume until the boundaries have been correlated and tied within the entire dataset. This is intended to verify the regional extent of major discontinuity surfaces and to identify which other potentially significant surfaces are local in nature. [[:file:M126Ch3-Table6.jpeg|Table 6]] outlines the workflow for seismic stratigraphy. [[:file:M126Ch3-Table7.jpeg|Table 7]] details the criteria for identifying key stratigraphic surfaces.

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[[file:~~M126CH03~~-Table6|thumb|300px|’’Table 6.’’ Seismic-stratigraphy Workflow.]]

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[[file:M126Ch3-Table6.jpeg|thumb|300px|’’Table 6.’’ Seismic-stratigraphy Workflow.]]

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[[file:~~M126CH03~~-Table7|thumb|300px|’’Table 7.’’ Surface Definitions With Translation Terms, and Primary and Secondary Recognition Criteria.]]

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[[file:M126Ch3-Table7.jpeg|thumb|300px|’’Table 7.’’ Surface Definitions With Translation Terms, and Primary and Secondary Recognition Criteria.]]

====Seismic Facies Analysis====

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=====Seismic-Facies Parameters: Internal Form=====

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Seismic-facies units are mappable, 3-D seismic units composed of groups of reflections whose parameters differ from those of adjacent facies units<ref name=Mtchmea1977 />. These parameters include the configuration or geometry, continuity, amplitude, frequency, and interval velocity ([[:file:~~M126CH03~~-Table8|Table 8]]). Each parameter provides considerable information on the geology of the subsurface ([[:file:~~M126CH03~~-Table8|Table 8]]). Reflection configuration reveals gross stratification patterns from which depositional processes, erosion, and paleotopography can be interpreted. In addition, fluid contact reflections (flat spots) are commonly identifiable. Reflection continuity is closely associated with continuity of strata; continuous reflections suggest widespread, uniformly stratified deposits. Reflection amplitude contains information on the velocity and density contrasts of individual bedding interfaces and their spacing. It is used to predict lateral bedding changes and hydrocarbon occurrences. “Frequency” (reflection spacing), although a characteristic of the seismic pulse, is also related to such geologic factors as the spacing of reflectors or lateral changes in interval velocity (because of organic-matter or hydrocarbon content or lithofacies changes).

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Seismic-facies units are mappable, 3-D seismic units composed of groups of reflections whose parameters differ from those of adjacent facies units<ref name=Mtchmea1977 />. These parameters include the configuration or geometry, continuity, amplitude, frequency, and interval velocity ([[:file:M126Ch3-Table8.jpeg|Table 8]]). Each parameter provides considerable information on the geology of the subsurface ([[:file:M126Ch3-Table8.jpeg|Table 8]]). Reflection configuration reveals gross stratification patterns from which depositional processes, erosion, and paleotopography can be interpreted. In addition, fluid contact reflections (flat spots) are commonly identifiable. Reflection continuity is closely associated with continuity of strata; continuous reflections suggest widespread, uniformly stratified deposits. Reflection amplitude contains information on the velocity and density contrasts of individual bedding interfaces and their spacing. It is used to predict lateral bedding changes and hydrocarbon occurrences. “Frequency” (reflection spacing), although a characteristic of the seismic pulse, is also related to such geologic factors as the spacing of reflectors or lateral changes in interval velocity (because of organic-matter or hydrocarbon content or lithofacies changes).

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[[file:~~M126CH03~~-Table8|thumb|300px|’’Table 8.’’ Seismic-reflection Characteristics of Seismically Definable Rock Bodies.]]

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[[file:M126Ch3-Table8.jpeg|thumb|300px|’’Table 8.’’ Seismic-reflection Characteristics of Seismically Definable Rock Bodies.]]

Grouping these seismic parameters into mappable seismic-facies units facilitates their interpretation in terms of depositional environment, sediment provenance, and geologic setting. Seismic-reflection configuration or geometry is the most obvious and directly analyzable seismic parameter. Stratal configuration or geometry is interpreted from seismic-reflection configuration and refers to the geometric patterns and relations of strata within a stratigraphic unit. These commonly indicate depositional setting and processes as well as later structural movement.

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=====External Form and Internal Geometry: A-B/C Mapping=====

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Seismic-facies mapping was definitively explained by Ramsayer<ref name=Rmsyr1979 />, based on 2-D seismic data. It is referred to as the “A-B/C” mapping approach, as observations are made upon the upper boundary (A), the lower boundary (B), and the internal reflection character (C). The A, B, and C categories of Ramsayer’s<ref name=Rmsyr1979 /> seismic facies codes each included five types initially, thus providing 15 different variations for a given seismic interval of interest ([[:file:~~M126CH03~~-Table9|Table 9]]). For example, a prograding seismic package with oblique clinoforms, toplap at its upper surface, and downlap at its base would be noted as Tp-Dn/Ob. Subsequent work and incorporation of Campbell’s<ref name=Cmpbll1967> Campbell, C. V., 1967, Lamina, laminaset, bed and bedset: Sedimentology, v. 8, p. 7–26.</ref> approach to stratal description expanded the range of descriptors for “C” (internal character) to span continuity, reflection shape, reflection inter-relations, and amplitude ([[:file:~~M126CH03~~-Table9|Table 9]], the lower part). We highly recommend using all these aspects of reflection character to describe the internal reflection configuration.

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Seismic-facies mapping was definitively explained by Ramsayer<ref name=Rmsyr1979 />, based on 2-D seismic data. It is referred to as the “A-B/C” mapping approach, as observations are made upon the upper boundary (A), the lower boundary (B), and the internal reflection character (C). The A, B, and C categories of Ramsayer’s<ref name=Rmsyr1979 /> seismic facies codes each included five types initially, thus providing 15 different variations for a given seismic interval of interest ([[:file:M126Ch3-Table9.jpeg|Table 9]]). For example, a prograding seismic package with oblique clinoforms, toplap at its upper surface, and downlap at its base would be noted as Tp-Dn/Ob. Subsequent work and incorporation of Campbell’s<ref name=Cmpbll1967> Campbell, C. V., 1967, Lamina, laminaset, bed and bedset: Sedimentology, v. 8, p. 7–26.</ref> approach to stratal description expanded the range of descriptors for “C” (internal character) to span continuity, reflection shape, reflection inter-relations, and amplitude ([[:file:M126Ch3-Table9.jpeg|Table 9]], the lower part). We highly recommend using all these aspects of reflection character to describe the internal reflection configuration.

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[[file:~~M126CH03~~-Table9|thumb|300px|’’Table 9.’’ Seismic Facies A, B, and C (Expanded after Mitchum et al., <ref name=Mtchmea1977 />; Ramsayer<ref name=Rmsyr1979 />).]]

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[[file:M126Ch3-Table9.jpeg|thumb|300px|’’Table 9.’’ Seismic Facies A, B, and C (Expanded after Mitchum et al., <ref name=Mtchmea1977 />; Ramsayer<ref name=Rmsyr1979 />).]]

The A-B/C mapping is still necessary even with the most advanced and high-resolution 3-D datasets and visualization tools because seismic facies are most meaningful within their stratigraphic context—that is, when applied to genetically related strata (which is the whole point of sequence stratigraphy). Bounding surfaces provide important geological and stratigraphic information. Seismic facies are nonuniquely related to depositional environment and lithofacies (e.g., clinoform reflections can occur in deltaic sandstones, carbonate platforms, and mudstone-dominated shelves); hence, one needs more information from the stratigraphic context of the seismic facies—their relation to lower and upper bounding surfaces and position along the depositional profile.

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Another innovation in seismic facies involves discrimination and classification of seismic wavelet trace shapes (using various computer programs). The approach must be used within an individual sequence or systems tract to extend what is essentially a one-dimensional seismic-facies analysis to a volume of genetically related strata.

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Numerous other methods, both automated and semiautomated, for classifying the seismic data based on detailed geophysical parameters (frequency, wavelet duration, etc.) and on image analysis are available. Techniques using image analysis are particularly suitable for use in seismic facies mapping<ref name=Ga2011 /><ref> Vinther, R., K. Mosegaard, K. Kierkegaard, I. Abatzis, C. Andersen, and F. If, 1995, Seismic texture classification: A computer-aided approach to stratigraphic analysis, in SEG 65th Annual International Meeting Technical Program Expanded Abstracts, Houston, Texas, October 8–13, 1995, p. 153–155.</ref><ref> DeGroot, P., 1999, Volume transformation by way of neural network mapping: EAGE 61st Conference, Helsinki, Finland, June 7–11, paper 3-37, 5 p.</ref><ref>West, B. P., and S. R. May, 2003, A method for training a probabilistic neural network to map seismic attributes or similar quantities: U.S. Patent No. 192467 filed on 2002-07-10.</ref><ref>Marroquin, I. D., J.-J. Brault, and B. S. Hart, 2009, A visual data mining methodology to conduct seismic facies analysis: Part 2—Application to 3D seismic data: Geophysics, v. 74, p. P1–P11.</ref>. In one way, they represent just another way to describe and classify seismic facies and can be slotted into the general workflow at step 4 ([[:file:~~M126CH03~~-Table6|Table 6]]). Remember that no matter how high-powered these techniques appear, they still must be applied to a genetically related volume of strata to provide the maximum amount of information on the depositional setting.

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Numerous other methods, both automated and semiautomated, for classifying the seismic data based on detailed geophysical parameters (frequency, wavelet duration, etc.) and on image analysis are available. Techniques using image analysis are particularly suitable for use in seismic facies mapping<ref name=Ga2011 /><ref> Vinther, R., K. Mosegaard, K. Kierkegaard, I. Abatzis, C. Andersen, and F. If, 1995, Seismic texture classification: A computer-aided approach to stratigraphic analysis, in SEG 65th Annual International Meeting Technical Program Expanded Abstracts, Houston, Texas, October 8–13, 1995, p. 153–155.</ref><ref> DeGroot, P., 1999, Volume transformation by way of neural network mapping: EAGE 61st Conference, Helsinki, Finland, June 7–11, paper 3-37, 5 p.</ref><ref>West, B. P., and S. R. May, 2003, A method for training a probabilistic neural network to map seismic attributes or similar quantities: U.S. Patent No. 192467 filed on 2002-07-10.</ref><ref>Marroquin, I. D., J.-J. Brault, and B. S. Hart, 2009, A visual data mining methodology to conduct seismic facies analysis: Part 2—Application to 3D seismic data: Geophysics, v. 74, p. P1–P11.</ref>. In one way, they represent just another way to describe and classify seismic facies and can be slotted into the general workflow at step 4 ([[:file:M126Ch3-Table6.jpeg|Table 6]]). Remember that no matter how high-powered these techniques appear, they still must be applied to a genetically related volume of strata to provide the maximum amount of information on the depositional setting.

==Techniques==

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The steps of the workflow we recommend for examining mudstones in outcrops, cores, and thin sections are:

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# ~~‘’Make observations’’~~

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# '''Make observations'''

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## ~~‘’Establish~~ stratigraphic ~~context’’~~

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## '''Establish stratigraphic context'''

### Step back, examine, and photograph the entire exposure, walking the section several times.

### Check core depths and core box order, clean the core, and photograph the entire core. Step back, examine, and walk the section several times with well logs in hand.

### Look for changes in texture, bedding, composition, thickness, continuity, and stacking; and presence of erosional surfaces. Tentatively identify stratigraphic packages.

### Make note of weathering characteristics and their vertical and lateral distribution.

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## ~~‘’Start~~ at the base of the section or core, identify, examine, and describe stratigraphic packages and surfaces as you proceed up-section. Integrate outcrop or core observations with thin-section observations.’’ Observe and take pictures of stratigraphic features at all scales (laminae, laminasets, beds, bedsets, parasequences, parasequence sets, and sequences).

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## '''Start at the base of the section or core, identify, examine, and describe stratigraphic packages and surfaces as you proceed up-section. Integrate outcrop or core observations with thin-section observations.''' Observe and take pictures of stratigraphic features at all scales (laminae, laminasets, beds, bedsets, parasequences, parasequence sets, and sequences).

### Examine a fresh face of rocks from each potential stratigraphic package; sample each significant facies; mudstones tend to weather deeply and may require much digging to remove the weathered rock and to obtain fresh exposure and samples ([[:file:M91Ch6FG47.JPG|Figure 1]]).

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### Describe the mudstones: ~~‘’texture~~, bedding,’’ and ~~‘’composition’’~~. Figure 1A–D in [[Mudstone nomenclature]] summarize the terms and definitions we recommend for texture, bedding, and composition. A practical, proxy method, the “scratch test,” we recommend to use to determine the dominant grain size at hand specimen scale is detailed in [[:file:~~M126CH03~~-Table10|Table 10]]. Fine-tune outcrop and core estimations of texture, bedding, and composition by integrating observations under optical and electronic microscopes and analytical data obtained on samples taken in sedimentologic and stratigraphic context.

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### Describe the mudstones: '''texture, bedding,''' and '''composition'''. Figure 1A–D in [[Mudstone nomenclature]] summarize the terms and definitions we recommend for texture, bedding, and composition. A practical, proxy method, the “scratch test,” we recommend to use to determine the dominant grain size at hand specimen scale is detailed in [[:file:M126Ch3-Table10.jpeg|Table 10]]. Fine-tune outcrop and core estimations of texture, bedding, and composition by integrating observations under optical and electronic microscopes and analytical data obtained on samples taken in sedimentologic and stratigraphic context.

### Describe biogenic sedimentary structures and characterize the degree of bioturbation using a 0–5 scale (figure 1E of [[Mudstone nomenclature]]).

### Describe the type, size, diversity, abundance (figure 1F of [[Mudstone nomenclature]]), preservation, and taphonomy (figure 1G of [[Mudstone nomenclature]]) of body fossils. Similarly, describe trace fossils.

### Describe the type, size, composition, and abundance of diagenetic products (figures 1C, F of [[Mudstone nomenclature]]).

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### Organize recurring, representative, and diagnostic facies attributes into ~~‘’facies associations’’~~.

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### Organize recurring, representative, and diagnostic facies attributes into '''facies associations'''.

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### Identify and describe ~~‘’stratal~~ packages and key ~~surfaces’’~~ (sequence boundaries and flooding surfaces; [[:file:M126CH03-Figure3.jpeg|Figure 3]]; Tables 7, 11). Obtain a spectral gamma-ray profile to further characterize stratigraphic units ([[:file:M126CH03-Figure4.jpeg|Figure 4]]).

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### Identify and describe '''stratal packages and key surfaces''' (sequence boundaries and flooding surfaces; [[:file:M126CH03-Figure3.jpeg|Figure 3]]; Tables 7, 11). Obtain a spectral gamma-ray profile to further characterize stratigraphic units ([[:file:M126CH03-Figure4.jpeg|Figure 4]]).

### Record all information consistently in an appropriate format, designed for your particular setting or unit.

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# ~~‘’Make interpretations’’~~

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# '''Make interpretations'''

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## ~~‘’Integrate’’~~ outcrop, core, or thin-section observations with analytical, well-log, and seismic data as available. Make a hierarchical interpretation of stratal units (laminae, laminasets, beds, bedsets, parasequences, parasequence sets, sequences; significant stratal boundaries).

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## '''Integrate''' outcrop, core, or thin-section observations with analytical, well-log, and seismic data as available. Make a hierarchical interpretation of stratal units (laminae, laminasets, beds, bedsets, parasequences, parasequence sets, sequences; significant stratal boundaries).

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## ~~‘’Make interpretations’’~~ of dominant sediment provenance, input mode, physical reworking, sediment accumulation rate, completeness of sedimentary record, bottom-water redox conditions, and environment of deposition<ref name=Bhcsea2005 /><ref name=Bhcsea2014 /><ref name=Lzrea2015a /><ref name=Lzrea2015b /> (e.g., [[:file:~~M126CH03~~-Table2|Table 2]] ; see also [[Laminasets, beds, and bedsets]], [[Parasequences]], and [[Parasequence sets and depositional sequences]]).

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## '''Make interpretations''' of dominant sediment provenance, input mode, physical reworking, sediment accumulation rate, completeness of sedimentary record, bottom-water redox conditions, and environment of deposition<ref name=Bhcsea2005 /><ref name=Bhcsea2014 /><ref name=Lzrea2015a /><ref name=Lzrea2015b /> (e.g., [[:file:M126Ch3-Table2|Table 2]] ; see also [[Laminasets, beds, and bedsets]], [[Parasequences]], and [[Parasequence sets and depositional sequences]]).

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[[file:~~M126CH03~~-Table10|thumb|300px|~~’’Table~~ 10.’’ Scratch Test (After Lazar et al.<ref name=Lzrea2015a /><ref name=Lzrea2015b />).]]

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[[file:M126Ch3-Table10.jpeg|thumb|300px|'''Table 10.''' Scratch Test (After Lazar et al.<ref name=Lzrea2015a /><ref name=Lzrea2015b />).]]

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[[file:M126CH03-Figure3.jpeg|thumb|300px|{{figure number|3}}Accommodation succession showing key stratigraphic surfaces, stacking patterns, and depositional sequence expression using definitions outlined in [[:file:M126CH03-Table7|Tables 7]] and [[:file:~~M126CH03~~-Table11|11]]<ref name=Abrea2010 /> (after Neal and Abreu<ref name=NlABr>Neal, J., and V. Abreu, 2009, Sequence stratigraphy hierarchy and the accommodation succession method: Geology, v. 37, p. 779–782.</ref>, and Abreu et al.<ref name=Abrea2014>Abreu, V., K. Pederson, J. Neal, and K. M. Bohacs, 2014, A simplified guide for sequence stratigraphy: Nomenclature, definitions and method: Geological Society of America Annual Meeting, 19–22 October 2014, Vancouver, British Columbia, Abstracts with Programs, v. 46, no. 6, p. 832.</ref>).]]

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[[file:M126CH03-Figure3.jpeg|thumb|300px|{{figure number|3}}Accommodation succession showing key stratigraphic surfaces, stacking patterns, and depositional sequence expression using definitions outlined in [[:file:M126CH03-Table7.jpeg|Tables 7]] and [[:file:M126Ch3-Table11.jpeg|11]]<ref name=Abrea2010 /> (after Neal and Abreu<ref name=NlABr>Neal, J., and V. Abreu, 2009, Sequence stratigraphy hierarchy and the accommodation succession method: Geology, v. 37, p. 779–782.</ref>, and Abreu et al.<ref name=Abrea2014>Abreu, V., K. Pederson, J. Neal, and K. M. Bohacs, 2014, A simplified guide for sequence stratigraphy: Nomenclature, definitions and method: Geological Society of America Annual Meeting, 19–22 October 2014, Vancouver, British Columbia, Abstracts with Programs, v. 46, no. 6, p. 832.</ref>).]]

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[[file:~~M126CH03~~-Table11|thumb|300px|’’Table 11.’’ Definitions of Systems Tracts With Stacking Patterns and Recognition Criteria (after Abreu et al.<ref name=Abrea2014 />).]]

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[[file:M126Ch3-Table11.jpeg|thumb|300px|’’Table 11.’’ Definitions of Systems Tracts With Stacking Patterns and Recognition Criteria (after Abreu et al.<ref name=Abrea2014 />).]]

[[file:M126CH03-Figure4.jpeg|thumb|300px|{{figure number|4}}Schematic diagram of using a gamma-ray spectrometer in the field (after Schwalbach and Bohacs<ref name=SchwlbchBhcs1992 /><ref>Schwalbach, J. R., and K. M. Bohacs, 1995, Stratigraphic sections and gamma-ray spectrometry from five outcrops of the Monterey Formation in southwestern California; Naples Beach, Point Pedernales, Lion’s Head, Shell Beach, and Point Buchon: US Geological Survey Bulletin 1995, p. Q1–Q39.</ref>).]]

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Stratal Units—Sequence-stratigraphic stratal units are defined using geometric criteria, with the supporting evidence of other physical, biogenic, and chemical attributes. Although thickness, areal extent, and time for formation are neither essential attributes nor part of the definition of sequence-stratigraphic units, these units do tend to have characteristic spatial and temporal scales as well as common modes of formation. Note that characteristic thicknesses tend to be a function of grain size and are typically thinner in mudstones. Characteristic timescales tend to be strongly related to depositional setting and basin size, with relatively short intervals in small lacustrine basins and relatively long intervals in large marine basins (according to the response time of the basin, which scales to the second power of its characteristic length scale; see Paola et al.<ref>Paola, C., P. L. Heller, P. L., and C. L. Angevine, 1992, The large-scale dynamics of grain-size variation in alluvial basins, 1: Theory: Basin Research, v. 4, p. 73–90.</ref>).

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The ‘’depositional sequence’’ is the fundamental unit of sequence stratigraphy; it is a relatively conformable succession of strata bounded at base and top by laterally extensive (regional scale) unconformities and their correlative conformities<ref name=Abrea2010 /><ref name=NlABr /><ref name=Mtchm1977 /> ([[:file:~~M126CH03~~-Figure3.jpeg|Figure 3]]). Depositional sequences are meters to hundreds of meters thick and extend over many thousands of square kilometers. They are inferred to represent multiple episodes of shoreline progradation with significant shifts in coastal onlap and base level over tens to thousands of millennia. A complete depositional sequence can be subdivided into ‘’systems tracts’’ defined by their position within the sequence and by the stacking patterns of the ‘’parasequence sets’’ within each systems tract. Parasequence sets are bounded by ‘’parasequence set boundaries’’ that are ‘’flooding surfaces’’ and their equivalents. Systems tracts include lowstand, trans-gressive, and highstand (see [[:file:~~M126CH03~~-Table11|Table 11]]).

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The ‘’depositional sequence’’ is the fundamental unit of sequence stratigraphy; it is a relatively conformable succession of strata bounded at base and top by laterally extensive (regional scale) unconformities and their correlative conformities<ref name=Abrea2010 /><ref name=NlABr /><ref name=Mtchm1977 /> ([[:file:M126Ch3-Figure3.jpeg|Figure 3]]). Depositional sequences are meters to hundreds of meters thick and extend over many thousands of square kilometers. They are inferred to represent multiple episodes of shoreline progradation with significant shifts in coastal onlap and base level over tens to thousands of millennia. A complete depositional sequence can be subdivided into ‘’systems tracts’’ defined by their position within the sequence and by the stacking patterns of the ‘’parasequence sets’’ within each systems tract. Parasequence sets are bounded by ‘’parasequence set boundaries’’ that are ‘’flooding surfaces’’ and their equivalents. Systems tracts include lowstand, trans-gressive, and highstand (see [[:file:M126Ch3-Table11.jpeg|Table 11]]).

A ‘’parasequence’’, the main building block of the depositional sequence, is a relatively conformable succession of beds or bedsets bounded below and above by parasequence boundaries (surfaces that record a pause in sediment accumulation, formed by nondeposition, local erosion, or very slow sedimentation and include flooding, abandonment, or reactivation surfaces and their correlative surfaces; after Van Wagoner et al.<ref name=VnWgnrea1990 /><ref name=VnWgnres1988 />; Bohacs<ref name=Bhcs1998 />, Bohacs et al.<ref name=Bhcsea2014 />). Parasequences range from tens of centimeters to tens of meters in thickness and extend over significant parts of a basin, on the order of hundreds to thousands of square kilometers. In shelf or lacustrine settings, they typically represent one episode of shoreline or mudbelt progradation—the dominant depositional “motif” or building block. Equivalent-scale units in other settings include fan “lobes” in submarine-fan settings and channel-belt sets in fluvial or submarine-slope settings. Parasequences are interpreted to form in centuries to millennia.

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=====Stratal Surfaces=====

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The two distinct types of widespread and mappable surfaces are parasequence boundaries and sequence boundaries<ref name=BhcSchwlbch1992 /><ref name=Bhcs1998 /><ref name=MtchmVl1977 /><ref name=Vl1975 /><ref name=Vl1977a /><ref name=Vlea1991 /><ref name=Psmntr1988 /><ref name=VnWgnres1988 /><ref name=Bhcsea2004>Bohacs, K. M., G. J. Grabowski Jr., and J. E. Neal, 2004, Unlocking geological history: The key roles of mudstones and sequence stratigraphy, in J. Schieber, and O. R. Lazar, eds., Devonian black shales of the Eastern US: New insights into sedimentology and stratigraphy from the subsurface and outcrops in the Illinois and Appalachian basins: Indiana Geological Survey Open File Study 04-05, p. 78.</ref> ([[:file:~~M126CH03~~-Figure3.jpeg|Figure 3]]). Identification of these surfaces in a stratal succession relies on both their local character and their lateral extent<ref name=BhcSchwlbch1992 /><ref name=Bhcs1998 /><ref name=Bhcsea2014 /><ref name=Lzr2007 /><ref name=Lzrea2015a /><ref name=Lzrea2015b /><ref name=Abrea2010 /><ref name=VnWgnrea1990 /><ref name=Bhcsea2004 />.

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The two distinct types of widespread and mappable surfaces are parasequence boundaries and sequence boundaries<ref name=BhcSchwlbch1992 /><ref name=Bhcs1998 /><ref name=MtchmVl1977 /><ref name=Vl1975 /><ref name=Vl1977a /><ref name=Vlea1991 /><ref name=Psmntr1988 /><ref name=VnWgnres1988 /><ref name=Bhcsea2004>Bohacs, K. M., G. J. Grabowski Jr., and J. E. Neal, 2004, Unlocking geological history: The key roles of mudstones and sequence stratigraphy, in J. Schieber, and O. R. Lazar, eds., Devonian black shales of the Eastern US: New insights into sedimentology and stratigraphy from the subsurface and outcrops in the Illinois and Appalachian basins: Indiana Geological Survey Open File Study 04-05, p. 78.</ref> ([[:file:M126Ch3-Figure3.jpeg|Figure 3]]). Identification of these surfaces in a stratal succession relies on both their local character and their lateral extent<ref name=BhcSchwlbch1992 /><ref name=Bhcs1998 /><ref name=Bhcsea2014 /><ref name=Lzr2007 /><ref name=Lzrea2015a /><ref name=Lzrea2015b /><ref name=Abrea2010 /><ref name=VnWgnrea1990 /><ref name=Bhcsea2004 />.

A ‘’parasequence boundary’’ (‘’flooding surface’’ and correlative surfaces) records a supercritical increase in accommodation relative to sediment supply that significantly changes system behavior<ref name=Bhcs1998 /><ref name=Bhcsea2004 />. Commonly, strata above a parasequence boundary are deposited in deeper water, and less energetic and more distal environments, whereas strata below a flooding surface are deposited in shallower water, and more energetic and proximal environments<ref name=Bhcs1998 /><ref name=Bhcsea2014 /><ref name=Lzrea2015a /><ref name=Lzrea2015b /><ref name=Bhcsea2004 />. Parasequence boundaries are marked by a sharp decrease in coarse sediment supply, increased and laterally extensive accumulation of pelagic and authigenic components (e.g., organic matter, remains of plankton and nekton, volcanic ash, dropstones; cements, nodules, and concretions), early lithification or cementation, and increased continuity of laminae, beds, and bedsets<ref name=BhcSchwlbch1992 /><ref name=Bhcs1998 /><ref name=Bhcsea2014 /><ref name=McqkrTlr1996 /><ref name=Bhcs1990><ref name=Bhcsea2004 />. See [[Parasequences]] for a full discussion.

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Within each depositional sequence, two specific parasequence boundaries are interpreted as lower order surfaces, one as the transgressive surface (TS) and another as the maximum flooding surface (MFS), based on their position and geometric relations<ref name=Bhcs22c /> ([[:file:~~M126CH03~~-Figure3.jpeg|Figure 3]]).

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Within each depositional sequence, two specific parasequence boundaries are interpreted as lower order surfaces, one as the transgressive surface (TS) and another as the maximum flooding surface (MFS), based on their position and geometric relations<ref name=Bhcs22c /> ([[:file:M126Ch3-Figure3.jpeg|Figure 3]]).

The ‘’transgressive surface’’ is the parasequence boundary atop the most basinward position of the shoreline of the progradational-aggradational (PA) or lowstand systems tract. It defines the top of the lowstand systems tract and separates progradationally to aggradationally (stepping basinward) stacked parasequences below from retrogradationally (stepping landward) stacked parasequences above (after Bohacs and Schwalbach<ref name=BhcSchwlbch1992 />, Bohacs<ref name=Bhcs1998 />). It is also known as the maximum regressive surface (MRS) <ref name=Abrea2014 />. The surface is interpreted beneath the first landward shift (backstep) of the shelf–slope break; in vertical successions, at the turn-around in parasequence stacking pattern from progradation or aggradation to retrogradation.

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A ‘’maximum flooding surface’’ is the one particular parasequence boundary representing the maximum landward extent of basinal facies within a sequence. It defines the top of the transgressive systems tract and separates retrogradationally (stepping landward) stacked parasequences below from aggradationally to progradationally (stepping basinward) stacked parasequences above (after Bohacs and Schwalbach<ref name=BhcSchwlbch1992 />, Bohacs<ref name=Bhcs1998 />). It is also known as the maximum transgressive surface (MTS)<ref name=Abrea2014 />. The presence of prograding strata above identifies the maximum flooding surface as a downlap surface on reflection seismic profiles. It represents the greatest landward extent of the sea or lake within a depositional sequence<ref name=BhcSchwlbch1992 /><ref name=Lttitea1988><ref>Posamentier, H. W., and P. R. Vail, 1988, Eustatic controls on clastic deposition II—sequence and systems tract models, in C. K. Wilgus, B. S. Hastings, C. G. St. C. Kendall, H. W. Posamentier, C. A. Ross, and J. C. Van Wagoner, eds., Sea level changes-an integrated approach: SEPM Special Publication 42, p. 125–154</ref>.

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‘’Sequence boundaries’’ are the laterally extensive (regional scale) unconformities and correlative conformities that bound a depositional sequence<ref name=Mtchm1977 />; they are fundamentally different from flooding surfaces. Sequence boundaries (in contrast to flooding surfaces) record a supercritical decrease in accommodation relative to sediment supply, commonly accompanied by an increase in depositional energy or a significant change in sediment supply (e.g., erosional bypass in marine environments), over hundreds to thousands of square kilometers<ref name=Bhcs1998 /><ref name=Lzr2007 /><ref name=Bhcsea2004 /><ref name=BhcsLzr2008>Bohacs, K. M., and O. R. Lazar, 2008, The role of sequence stratigraphy in unraveling and applying the complex controls from mudstone reservoir properties: AAPG Search and Discovery article #90078.</ref><ref>Bohacs, K. M., and O. R. Lazar, 2010, Sequence stratigraphy in fine-grained rocks, in J. Schieber, O. R. Lazar, and K. M. Bohacs, eds., Sedimentology and stratigraphy of shales: Expression and correlation of depositional sequences in the Devonian of Tennessee, Kentucky, and Indiana: SEPM Field Trip Guidebook, p. 15–30.</ref>. They are easiest to recognize in medial reaches of the shelf. Common attributes of sequence boundaries are summarized in [[:file:~~M126CH03~~-Table7|Table 7]] and discussed further in [[Parasequence sets and depositional sequences]]. Sequence boundaries are surfaces across which there is a basinward shift in coastal onlap, marked by laterally extensive erosional truncation of underlying strata (with evidence of exposure and presence of reworked clastics in lag deposits) and toplap below and onlap and downlap above<ref name=Bhcs1998 /><ref name=Schbr1998a /><ref name=Lzr2007 /><ref name=SchwlbchBhcs1992 /><ref name=Mtchm1977 /><ref name=Bhcsea2004 /><ref name=BhcsLzr2008 />. It occurs below the abrupt basinward shift in shoreline position at the base of a depositional sequence. It is placed at the surface beneath the first increase in accommodation above progradationally or degradationally stacked parasequences, at the break in shoreline sandstone trajectory ([[:file:~~M126CH03~~-Figure3.jpeg|Figure 3]]).

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‘’Sequence boundaries’’ are the laterally extensive (regional scale) unconformities and correlative conformities that bound a depositional sequence<ref name=Mtchm1977 />; they are fundamentally different from flooding surfaces. Sequence boundaries (in contrast to flooding surfaces) record a supercritical decrease in accommodation relative to sediment supply, commonly accompanied by an increase in depositional energy or a significant change in sediment supply (e.g., erosional bypass in marine environments), over hundreds to thousands of square kilometers<ref name=Bhcs1998 /><ref name=Lzr2007 /><ref name=Bhcsea2004 /><ref name=BhcsLzr2008>Bohacs, K. M., and O. R. Lazar, 2008, The role of sequence stratigraphy in unraveling and applying the complex controls from mudstone reservoir properties: AAPG Search and Discovery article #90078.</ref><ref>Bohacs, K. M., and O. R. Lazar, 2010, Sequence stratigraphy in fine-grained rocks, in J. Schieber, O. R. Lazar, and K. M. Bohacs, eds., Sedimentology and stratigraphy of shales: Expression and correlation of depositional sequences in the Devonian of Tennessee, Kentucky, and Indiana: SEPM Field Trip Guidebook, p. 15–30.</ref>. They are easiest to recognize in medial reaches of the shelf. Common attributes of sequence boundaries are summarized in [[:file:M126Ch3-Table7.jpeg|Table 7]] and discussed further in [[Parasequence sets and depositional sequences]]. Sequence boundaries are surfaces across which there is a basinward shift in coastal onlap, marked by laterally extensive erosional truncation of underlying strata (with evidence of exposure and presence of reworked clastics in lag deposits) and toplap below and onlap and downlap above<ref name=Bhcs1998 /><ref name=Schbr1998a /><ref name=Lzr2007 /><ref name=SchwlbchBhcs1992 /><ref name=Mtchm1977 /><ref name=Bhcsea2004 /><ref name=BhcsLzr2008 />. It occurs below the abrupt basinward shift in shoreline position at the base of a depositional sequence. It is placed at the surface beneath the first increase in accommodation above progradationally or degradationally stacked parasequences, at the break in shoreline sandstone trajectory ([[:file:M126Ch3-Figure3.jpeg|Figure 3]]).

====Constructing and Testing a Sequence-Stratigraphic Framework for Mudstones====

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* Inferring the mechanisms that led to the formation of the surfaces and strata, nesting small-scale processes of grain formation, erosion, transport, and deposition within larger scale processes of climate, tectonics, and biological evolution and their forcing functions

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Details of this workflow are given in [[:file:~~M126CH03~~-Table12|Table 12]] and elaborated throughout the following chapters.

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Details of this workflow are given in [[:file:M126Ch3-Table12.jpeg|Table 12]] and elaborated throughout the following chapters.

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[[file:~~M126CH03~~-Table12|thumb|300px|Table 12. Construction of a Sequence-stratigraphic Framework.]]

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[[file:M126Ch3-Table12.jpeg|thumb|300px|Table 12. Construction of a Sequence-stratigraphic Framework.]]

Now, we can proceed to apply these tools and techniques at successively larger scales, starting with the smallest scales, laminae, [[laminasets, beds, and bedsets]].

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This chapter introduced key tools and techniques that provide data about texture, bedding, composition, and grain origin. Such data enable characterization of mudstone strata at lamina to sequence-set scales. The application of such tools and techniques to decipher depositional conditions and construct sequence-stratigraphic frameworks was specifically addressed. Outlines of our approach to making detailed and systematic observations of key attributes of mudstones in outcrops, cores, and thin sections as well as an introduction to key sequence-stratigraphic concepts that we find useful for studying mudstones were included for quick reference. Our approach is elaborated and illustrated in all of the following chapters.

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[[file:M126CH03-Figure5.jpeg|thumb|300px|{{figure number|5}}Figure 5. Illustration of the sequence-stratigraphic approach in siliciclastic nearshore strata (after Bohacs and Schwalbach<ref name=BhcSchwlbch1992 />). The stratigraphic section is divided into large-scale stratal packages bounded by significant surfaces that are identified by their characteristics and stratigraphic context (place in stacking patterns, etc.). See [[:file:~~M126CH03~~-Table12|Table 12]] for more details. MFS = maximum flooding surface; SB = sequence boundary; TS = transgressive surface.]]

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[[file:M126CH03-Figure5.jpeg|thumb|300px|{{figure number|5}}Figure 5. Illustration of the sequence-stratigraphic approach in siliciclastic nearshore strata (after Bohacs and Schwalbach<ref name=BhcSchwlbch1992 />). The stratigraphic section is divided into large-scale stratal packages bounded by significant surfaces that are identified by their characteristics and stratigraphic context (place in stacking patterns, etc.). See [[:file:M126Ch3-Table12.jpeg|Table 12]] for more details. MFS = maximum flooding surface; SB = sequence boundary; TS = transgressive surface.]]

==See also==

Case studies ch 9-15

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~~==References==~~

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~~{{reflist}}~~

==Further Reading==

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* Zhu, Y., E. Liu, A. Martinez, M. A. Payne, and C. E. Harris, 2011, Understanding geophysical responses of shale-gas plays: The Leading Edge, March 2011, p. 332–338.

* Zhu, Y., S. Xu, M. Payne, A. Martinez, E. Liu, C. Harris, and K. Bandyopadhyay, 2012, Improved rock physics model for shale gas: SEG Conference, Las Vegas, Nevada, November 5–9, 2012, SEG-2012-0927, 5p.

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==References==

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