Changes

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

=====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.

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.

</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>.

</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 />.

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.

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).

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).