Changes

Careful visual observation at the macro-to-microscale is the essential first step in characterizing mudstones, selecting appropriate samples for additional analyses, and deciphering the depositional conditions. We recommend that mudstone be examined visually at a millimeter-to-centimeter scale in outcrops, cores, and thin sections to determine texture, bedding, and composition, as well as physical sedimentary structures; type, diversity, and abundance of body and trace fossils; bioturbation index; taphonomy of macrofossils; type, habit, and distribution of diagenetic products; fractures; and color<ref name=Lzrea2015a /><ref name=Lzrea2015b /><ref name=Lzrea2022a>Lazar, O. R., K. M. Bohacs, J. Schieber, J. H. S. Macquaker, and T. M. Demko, 2022a, [https://archives.datapages.com/data/specpubs/memoir126/data/21_aapg-sp2160021.htm Mudstone nomenclature], in K. M. Bohacs and R. Lazar, eds., Sequence stratigraphy: Applications to fine-grained rocks: [https://archives.datapages.com/data/alt-browse/aapg-special-volumes/m126.htm AAPG Memoir 126], p. 21–34.</ref>.

Careful visual observation at the macro-to-microscale is the essential first step in characterizing mudstones, selecting appropriate samples for additional analyses, and deciphering the depositional conditions. We recommend that mudstone be examined visually at a millimeter-to-centimeter scale in outcrops, cores, and thin sections to determine texture, bedding, and composition, as well as physical sedimentary structures; type, diversity, and abundance of body and trace fossils; bioturbation index; taphonomy of macrofossils; type, habit, and distribution of diagenetic products; fractures; and color<ref name=Lzrea2015a /><ref name=Lzrea2015b /><ref name=Lzrea2022a>Lazar, O. R., K. M. Bohacs, J. Schieber, J. H. S. Macquaker, and T. M. Demko, 2022a, [https://archives.datapages.com/data/specpubs/memoir126/data/21_aapg-sp2160021.htm Mudstone nomenclature], in K. M. Bohacs and R. Lazar, eds., Sequence stratigraphy: Applications to fine-grained rocks: [https://archives.datapages.com/data/alt-browse/aapg-special-volumes/m126.htm AAPG Memoir 126], p. 21–34.</ref>.

Visual observations should be made on surfaces of fresh rock in outcrops and cores ([[:file:M91Ch6FG47.JPG|Figure 1]]), and then supplemented with observations made using tools that include high-intensity white and ultraviolet light, and optical, electronic, and digital imaging of hand specimens and thin sections. Observations should include the abundance of each physical, biological, and chemical attribute to assist in the identification of facies, facies associations, and associated stacking patterns<ref name=Bhcsea2014 /><ref name=Lzrea2015a /><ref name=Lzrea2015b />. Visual observations can be facilitated and enhanced by using the tools and approaches that are discussed next.

Visual observations should be made on surfaces of fresh rock in outcrops and cores ([[:file:M126CH03-Figure1.jpg|Figure 1]]), and then supplemented with observations made using tools that include high-intensity white and ultraviolet light, and optical, electronic, and digital imaging of hand specimens and thin sections. Observations should include the abundance of each physical, biological, and chemical attribute to assist in the identification of facies, facies associations, and associated stacking patterns<ref name=Bhcsea2014 /><ref name=Lzrea2015a /><ref name=Lzrea2015b />. Visual observations can be facilitated and enhanced by using the tools and approaches that are discussed next.

[[file:M126CH03-Figure1|thumb|300px|{{figure number|1}}Example of the Cretaceous Mowry Shale in outcrop, Wyoming, contrasting weathered and fresh surfaces. A variety of sedimentary features become apparent in mudstones once we obtain a fresh surface of an outcrop or core.]]

[[file:M126CH03-Figure1.jpg|thumb|300px|{{figure number|1}}Example of the Cretaceous Mowry Shale in outcrop, Wyoming, contrasting weathered and fresh surfaces. A variety of sedimentary features become apparent in mudstones once we obtain a fresh surface of an outcrop or core.]]

====Preparation of Hand Specimens and Core Slabs====

====Preparation of Hand Specimens and Core Slabs====

====Procedures to Capture Mudstone Description in Cores and Outcrops====

====Procedures to Capture Mudstone Description in Cores and Outcrops====

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-Figure2A|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-Figure2A|Figure 2]]).

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]]).

[[file:M126CH03-Figure2A|thumb|300px|{{figure number|2A}}Example of a form that we recommend using to capture the key attributes of mudstones observed in cores (after Lazar et al. <ref name=Lzrea2015b /> used with permission).

[[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).

[[file:M126CH03-Figure2B|thumb|300px|{{figure number|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=====

=====Observations=====

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

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

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

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

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

### 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.

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

# ‘’Make interpretations’’

# ‘’Make interpretations’’

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

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

[[file:M126CH03-Figure3|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>).]]

[[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>).]]

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

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

[[file:M126CH03-Figure4|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>).]]

[[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>).]]

===Introduction to Sequence Stratigraphy===

===Introduction to Sequence Stratigraphy===

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>).

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>).

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|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]]).

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]]).

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.

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.

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

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

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|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 />.

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 />.

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.

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.

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|Figure 3]]).

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]]).

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.

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.

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>.

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>.

‘’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|Figure 3]]).

‘’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]]).

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

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

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.

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.

[[file:M126CH03-Figure5|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.]]

[[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.]]

==See also==

==See also==