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doi:10.2204/iodp.proc.313.102.2010

Lithostratigraphy

This section outlines procedures followed to document the sedimentology of cores recovered during Expedition 313. The first part outlines the methodology of core description and sediment classification. The second part introduces the interpreted depositional environments, the nomenclature of clinoform physiography, and sequence stratigraphy. Information presented here concerns onshore operations and analyses described in the site chapters. Shipboard descriptions of core catcher samples and liner observations were consulted in making these descriptions, but offshore procedures are not described here.

Methodology of sediment description

Visual core description

Unsampled archive halves of split cores arrived in the sedimentology laboratory of the BCR along with paper copies of description forms (barrel sheets) that included the line-scan image of the accompanying core section on the left side of the sheet. The archive half was then examined, and visual observations were recorded manually on the barrel sheets. This information was then condensed and entered into the ExpeditionDIS to generate a simplified database of each core section unit described. Digital barrel sheets were generated from the information entered into the ExpeditionDIS and are presented in "Core descriptions."

Grain-size divisions for clay, silt, sand (very fine, fine, medium, coarse, and very coarse), granules, and pebbles follow Wentworth (1922) and were assessed using hand lenses and grain size cards. The lithology of each core section is represented on barrel sheets by graphic patterns in the column on the left side of the sheet and by drawing grain size out to the dominant grain size division (Fig. F4). Sediments recovered from the New Jersey continental shelf are generally siliciclastic but have a strong component of authigenic and detrital glauconite. Minor quantities of biogenic particles also occur. Diagenetic phases include pyrite and carbonate in dispersed and nodular form. Sediment composition is defined by the different proportions of clay, silt, and sand size classes as shown on the ternary diagram (Fig. F5).

A wide variety of features that characterize the sediment are indicated in the columns to the right of the graphic log on the digital barrel sheets and include items such as primary sedimentary structures, body and trace fossils, accessories, bioturbation intensity, core disturbance, sample locations, and general description. Where described, contacts between different sediment bedsets, beds, or laminasets are given in the Description column. Accessories (e.g., biogenic particles and macroscopically identified authigenic or diagenetic minerals) are minor components of the cores, and their relative abundance is assessed using the standard visual composition chart of Rothwell (1989). The symbols are schematic and are placed in the paper barrel sheets centered on the unit in which they were observed and do not necessarily indicate the precise stratigraphic position of the observation. Exact positions of sedimentary features are shown in the detailed section-by-section paper core description forms. Full sets of symbols used on the VCD sheets are keyed in Figure F4.

Ichnological analysis included evaluation of the intensity of bioturbation, as well as identification of trace-fossil types. To assess the degree of bioturbation semiquantitatively, a modified version of the Droser and Bottjer (1991) ichnofabric index (ii = 1 to 5) scheme was employed (e.g., 1 = barren or no bioturbation and 5 = abundant bioturbation or homogeneous) (Fig. F4). These indexes are illustrated using colored intervals in the Bioturbation column of the barrel sheets. For completely bioturbated sediments (ii = 5), ichnofabrics were assessed using a modified version of the scheme of Droser and Bottjer (1991) in an attempt to distinguish homogeneous or diffusely burrow-mottled backgrounds from discrete biogenic structures (e.g., ii5/4 refers to completely bioturbated background fabrics heavily overprinted by discrete ichnofossils). Finally, if the degree of bioturbation could not be determined, the ichnofabric index was assigned 0. The photographic atlas of Gerard and Bromley (2008) was used as a basis for trace fossil identification.

Hue and chroma attributes of sediment color were determined visually using Munsell Soil Color Charts (Munsell Color Company, Inc., 1988). Deformation and disturbance of sediment that clearly resulted from the coring process are illustrated in the Drilling Disturbance column, using symbols shown in Figure F4. Blank regions indicate an absence of apparent disturbance.

Sediment classification

The sediment classification scheme used during Expedition 313 is descriptive and is largely the same as the scheme previously used by the Ocean Drilling Program (ODP) (Figs. F4, F5), particularly during Leg 174A offshore New Jersey (Austin et al., 1998). Composition and texture are the only criteria used to define lithology. Genetic/interpretative terms such as pelagic, hemipelagic, turbidite, debrite, and so on, do not appear in this classification. The term "clay" is used for both clay minerals and other siliciclastic material <4 µm in size. The term "mud" as used herein describes a subequal mixture of silt and clay. If sand, silt, or clay is >50% of the sediment or rock, the principal name is determined by the relative proportions of sand, silt, and clay sizes when plotted on a modified Shepard (1954) classification diagram (Fig. F5). Examples of nonbiogenic principal names are clay, silty clay, silt, sandy silt, or sand. For lithified sediments, the suffix "-stone" is added to the principal names of sand, silt, clay, or mud. Where quartz is not the dominant mineral, a modifier (e.g., glauconite sand) is used to indicate the dominant mineral. A mineral that comprises >25% but <50% of the sediment is indicated with a modifier (e.g., glauconitic sand). Biogenic components are not described in textural terms. Thus, sediment with 55% sand-sized foraminifers and 45% siliciclastic clay is called foraminifer clay, not clayey foraminifer sand.

Smear slides

Smear slide observations are a complimentary technique in the identification of fine-grained sediments (clay, silt, and very fine sand). Grain-size estimates were made using polarizing and binocular microscopes with an ocular micrometer. The microscope (Olympus BH-2) was calibrated so that 8, 16, and 32 scale bars in the ocular micrometer under 100× magnification corresponded to the maximum size of silt, very fine sand, and fine sand. Sediments were classified using the scheme of Mazzullo et al. (1988). Percent composition of sand, silt, and clay were estimated semiquantitatively using the standard visual composition chart of Rothwell (1989), though clay-sized grains tend to be underestimated using this method.

Preliminary petrographic analysis of sediments was also performed using smear slides. Microfossil identification in smear slides during core descriptions can help steer sampling strategies. Major minerals, including quartz, orthoclase, plagioclase, mica, calcite, dolomite, pyrite, and glauconite, were identified. Rock fragments, opaque heavy minerals, and black organic grains were also recognized, though positive identification requires thin sectioning or additional microscopic analysis. Identifiable whole microfossils and fragments include diatoms, silicoflagellates, sponge spicules, ostracodes, calcareous nannofossils, echinoid spines, and foraminifers. The percent abundance of bioclasts was also crudely estimated if their abundance was >1% of the sample.

Thin sections

Specific lithified intervals within cores were prepared as thin sections to allow material to be examined under a microscope using transmitted light as well as reflected light. This technique is particularly useful for examining microscopic details of clastic particles and their surrounding cement, as well as sedimentary textures. Attributes that can be determined include dominant grain types (mineralogy), presence or absence of inclusions, accessory minerals, and mineralogy of matrix or cement between sand grains.

Thin section mineralogy was also used as a check on descriptions provided using hand lenses by sedimentologists. For example, when cut by the rock saw, lithified cores are sometimes difficult to describe. In addition, fine-grained cements are difficult to identify except under higher magnification. Thin sections provided additional means to identify more accurately the lithified sedimentary deposits. Locations of thin sections are marked on the barrel sheets.

Following requests from sedimentologists, the location and orientation of samples for thin section preparation were flagged on the cores. After the thin section billets were cut with a diamond saw, they were dried in a furnace for 24 h at not more than 25°C. The billets then underwent stepwise impregnation with epoxy-resin in a vacuum desiccator for 48 h. After the sample was covered with resin, the base was ground until the sample surface was reached. This surface was lapped for ~45 min with 9 µm silicon carbide powder and water. The surface was then cleaned with water. The sample was glued onto the slide with the same resin used for impregnation. A pressure block was used to press the sample against the slide during the gluing process. The surface of the slide was cleaned and the sample identification scribed with a diamond pen. After trimming the sample to a thickness of ~250 µm, the thin section was lapped down to a thickness of 30 µm. A 150 µm thick glass cover was then glued to the thin section using cyanacrylate (ultraviolet resin). Finally, the thin section was cleaned with alcohol. For all lapping steps the automated system LP-50 auto from LOGITECH was used.

Computed tomography

A limited number of two-dimensional (2-D) and three-dimensional (3-D) X-ray CT scans were collected from unsplit cores prior to the OSP, using facilities in Bremen. CT is a useful technique for the investigation of the internal structures of 3-D objects. Measurements provide a digital data set of density variation. The CT scanner, originally developed for medical purposes, has several advantages: it is nondestructive, rapid, does not need slab preparation (cf. conventional geological X-ray analysis), and can be completed on full cores, giving 3-D images of undisturbed sediment prior to core splitting. The resolution of scans ranges between 1 mm and 1 cm.

Three types of scan were completed:

1. Exploratory scans (single radiographic plane/overview scan) limited to 50 cm length. This method required three scans on average to cover an entire 1.5 m section (Fig. F6A). These scans were made through the core axis longitudinally in two orthogonal sections (Fig. F6B) with a resolution of ~1 mm.

2. Transverse scans of 1 mm thickness (Fig. F7).

3. Transverse scans of 1 mm thickness every 1 mm through variable core lengths (up to 5 cm). Slices arranged this way allowed 3-D core views using the software visualization package, AMIRA (Fig. F7).

All scans were recorded in Digital Imaging and Communications in Medicine (DICOM) data format. The data files have a "tagged format" with a variable number of tags (DICOM data elements), which means that a core can be segmented into several small parts and later integrated into larger data sets. Each image is defined by a unique file name, referring to expedition, site, core number, core type, section, and depth in section.

CT scans provide useful sedimentological information that helps characterize sedimentary structures, including bioturbation, the arrangement of mollusk shells, mineral inclusions, heterogeneities such as fractures or erosion surfaces, structures in compact sandstones such as water transfer conduits, and successions of sedimentary laminae.

CT images are digital pictures, and all the current techniques designed for image processing such as smoothing or contrast enhancing can be easily used. Images are displayed as negatives, with high-density mineral components showing a lighter tone and low-density material, such as organic matter, appearing much darker or black in the case of voids (Fig. F7).

Sedimentological interpretations and physiographic nomenclature

Clinoform nomenclature

The term "clinoform" is applied to both sigmoid sedimentary slopes and any accretionary feature with sigmoidal bounding surfaces (Mitchum et al., 1977). However, Rich (1951) used the term "clinothem" to describe the body of rock bounded by individual clinoform surfaces. Clinoforms and clinothems range in scale from bedform features of centimeter size to continental margin accumulations (shelf-slope-basin clinoforms) that are kilometers deep (Pirmez et al., 1998). Clinoform deposits are composed of three fundamental components: topsets, foresets, and bottomsets (Gilbert, 1885) (Fig. F8).

Intrashelf clinoforms are intermediate in scale and are located on the continental shelf seaward of clastic shorelines and/or major river mouths (shoreline clinoforms) and landward of shelf-slope-basin clinoforms (Fig. F8). Clinoform deposits are part of sedimentary successions that accrete and prograde in response to the interplay between sediment supply and local sea level change (Mitchum et al., 1977). This interplay drives progradation of clinoforms at all scales such that the shoreline clinoform slope can merge with the intrashelf clinoform slope and the intrashelf clinoform can merge with the shelf-slope-basin clinoform slope to form compound clinoforms (Fig. F8).

The topset deposits form the upper portion of the clinoform succession, whose depositional slopes dip gently seaward. Foreset deposits form from progradation of the steepest part of the clinoform sigmoid (typical dip is 1°–3° at the clinoform inflection point), which is referred to as the clinoform slope. The bottomset deposits dip gently seaward.

The upper clinoform break in slope (an area not a point) between the topset surface and the foreset surface is referred to as the (clinoform) rollover (Fig. F8). The lower clinoform break in slope, which defines the transition between foreset surface and bottomset surface, is referred to as the toe of (clinoform) slope (Fig. F8).

The New Jersey intrashelf clinoforms are typically 100–300 m in height (elevation between rollover and toe of slope), and the length of the foreset surface between these same upper and lower clinoform breaks in slope is 5–15 km.

Sedimentary facies and depositional environments

Assemblages of sedimentary structures, ichnofabric, sediment texture and composition, and fossil content were used to define individual sedimentary facies. These sedimentary facies form facies associations that can be interpreted in terms of depositional environments. The vertical succession of facies defines progressive trends interrupted by physical surfaces that can be correlated to changes of physical properties measured on core (MSCL logs) and downhole logs.

The association of sedimentary facies shows that some of the Expedition 313 depositional environments share characteristics of wave-dominated shoreline facies models (Reineck and Singh, 1972; Harms et al., 1975, 1982; McCubbin, 1982; Browning et al., 2006) and mixed river/wave delta facies models (Galloway, 1975; Bhattacharya and Walker, 1992). The team of Expedition 313 sedimentologists arrived at the OSP familiar with incompatible terms for the nearshore environments of linear clastic shorelines (Fig. F9). Early discussion resulted in a terminological framework based on one that has been used onshore New Jersey (Browning et al., 2006) and modified by integrating the multisource terminology found in, for example, Aigner (1982), Walker and James (1992), Guillocheau et al. (2009), Ando (1990), and Coe (2003), among many others. A generalized shoreface to offshore facies model has been adopted that includes key aspects of these settings (Fig. F10). It was agreed that environments above mean fair-weather wave base (MFWWB) would be termed shoreface and environments below mean storm wave base (MSWB) would be offshore (Figs. F9, F10). The depositional environment between MFWWB and MSWB (variously called lower shoreface, offshore transition zone, and upper offshore; see cited authors) would herein be the shoreface–offshore transition (SOT) zone. Where there are large amounts of allochthonous plant debris, micaceous sand, and current ripples (unidirectional flows), the presence of a mixed fluvial/wave-influenced system is inferred (Bhattacharya and Walker, 1992) (Fig. F10). In these instances, a river-influenced or river-dominated modifier was added to the environment of deposition (Fig. F10).

Coarse sediments deposited seaward of the clinoform rollover in the clinoform-slope (foreset) and toe-of-slope (bottomset) settings dominated by sediment gravity flow processes (debris flow and turbidity currents) were also identified (Fig. F11). Classification of clinoform-slope and toe-of-slope environments are based on facies models of Nelson et al. (1983), Stow et al. (1984), Reading and Richards (1994), Pickering et al. (1989), Posamentier and Kolla (2003), and Posamentier and Walker (2006). The term "toe-of-clinoform-slope apron" is used to describe a line-source system that supplies coalesced submarine fans.

The facies association model used in this study is summarized in Figures F9, F10, and F11, and the following broad depositional environments are recognized:

• Fluvial: dominantly sand, including evidence of cut-and-fill channels, floored by gravels, mostly comprising clean sand with little clay or silt; sand commonly poorly sorted and subangular; commonly with plant debris.

• Estuarine: poorly sorted sand admixed with interlaminated and interbedded sand and clay, with steepening cross-laminae indicating migration of bedforms; commonly with plant debris.

• Proximal shoreface/foreshore: clean beach sand of fine to coarse grain size, with opaque heavy-mineral laminae highlighting cross-bedding and low-angle laminae with low-angle truncation, indicating migration of bedforms; mostly representing proximal shoreface, due to poor preservation of foreshore deposits.

• Shoreface: fine to medium sand, well sorted with rare to absent silt, and rare clay layers that may indicate lagoonal settings, rare low-angle cross-beds (swaley cross stratification [SCS] and hummocky cross stratification [HCS]), and rare symmetrical ripple laminae (oscillatory flow), but physical structures tend to be obscured by moderate to heavy bioturbation (mostly from Skolithos ichnofacies); thick-walled shell fragments. River-influenced and river-dominated shoreface deposits are interbedded fine and very fine sand with significant content of plant debris and micaceous sand.

• Shoreface–offshore transition (SOT): interbedded fine and very fine sand, commonly silty because of mixing and commonly rich in shelly material with whole shells preserved; deposited below fair-weather wave base but above storm wave base. Commonly, the SOT contains discrete sharp-based normally graded sand beds (Aigner, 1982) with clean-sand bases, shell debris, convex-upward laminae (HCS), and symmetrical-ripple lamination, which show combined flow characteristics and little evidence of burrowing apart from at bed tops. By contrast, intercalated beds of silt and clay are intensely bioturbated. River-influenced and river-dominated SOT deposits are well bioturbated to thinly laminated silt and clay with significant amounts of plant debris and micaceous sand. Intercalated sharp-based normally and/or inversely graded sand beds with cross-lamination, subparallel lamination, and occasional mud clasts are rich in plant debris and mica. These beds indicate episodic influx of coarse sediments that are evidence of river flood events. Soft-sediment deformation features indicate rapid deposition and dewatering processes.

• Offshore: dominantly clay and silty clay with thinly laminated silt beds, with common benthic foraminifers and thin-walled (articulated) shells deposited below the storm wave base. Discrete beds of intensely bioturbated sediment with common horizontal burrows alternating with unbioturbated and interlaminated beds. River-influenced and river-dominated offshore deposits are silty, contain visible plant debris and mica with rare graded very fine sand beds, and share characteristics with distal prodelta environments (Figs. F9, F10). "Deep" offshore is used for clay or silt successions deposited seaward of the lower clinoform break in slope.

• Coarse clastic deposits at clinoform rollover positions: poorly sorted, weakly graded, muddy sand and gravel with mud clasts, benthic foraminifers, and shell fragments interbedded with bioturbated mud, indicating an episodically high energy setting. These deposits may represent small deltas and/or gulleys filled with concentrated density currents. Subangular to angular gravels and pebbles with a range of lithologies indicate high-energy coarse-grained sediment supply with a short transport history.

• Toe-of-clinoform-slope apron: two broad types of coarse clastic deposits are located in toe-of-clinoform-slope positions: (1) normally graded, moderately sorted, and cross-stratified sand and granules in inclined meter-thick bedsets interpreted as deposits from turbidity currents and (2) ungraded, poorly sorted, poorly stratified bioturbated muddy sand with floating granules, articulated shells, and pristine benthic foraminifers, supported by a finer grained matrix, interpreted as deposits from cohesive debris flows. Rounded intraformational mud clasts indicate upslope erosion. Interbedded clay laminae record background conditions. Typically, quartz and lithic granules are subrounded to subangular, although the full range of well-rounded to angular granules is observed. Typically, toe-of-clinoform-slope deposits are either glauconitic or glauconite dominated in the expedition boreholes.

Lithostratigraphic unit definition

Lithostratigraphic units are defined as coherent assemblages of sedimentary facies bounded by surfaces of lithologic change that commonly equate to stratigraphic discontinuities; subunits are defined on the same basis but at a smaller scale. Although the primary objective was to place sediments into objectively defined units within the core, where practical, the boundaries between lithostratigraphic units were placed in order that sediments in a numbered unit at one site would correspond in age to those found at the other Expedition 313 sites. Lithostratigraphic units have thus been defined and numbered to indicate correlation between all three sites. Subunits were also defined to have correlative value, except in the case of Unit I, for which recovery was highly incomplete.

Sequence stratigraphy

A principal expedition goal is to evaluate the depositional sequence model as a product of eustatic sea level change. The depositional sequence (papers in Wilgus et al., 1988) comprises assemblages of sedimentary strata showing distinct transgressive or regressive vertical trends, bounded by key stratigraphic surfaces. These surfaces are stratigraphic discontinuities, or their correlative surfaces, and have a hypothesized relationship to relative sea level change. Comprehensive summaries and discussion of the sequence stratigraphic model and its variants can be found in compilations such as Coe (2003) and Catuneanu (2006). The sequence boundary is defined as an unconformity and its correlative conformity, formed broadly around the time of sea level fall and lowstand. A sequence boundary is characterized in distal sedimentary environments by a seaward shift in sedimentary facies. The maximum flooding surface (MFS) is characterized by distal sediment starvation formed broadly at the time of relative sea level rise and highstand. Theoretically, each surface can also have a distinct expression in a seismic reflection profile where relationships are defined by the geometric relationship between packages of acoustically reflecting surfaces (reflection terminations) and not necessarily by individual stratal surfaces.

The approach of the expedition has been to ask the question, "Can depositional sequences recognized from geometric relationships within seismic reflection profiles be used to predict relative sea level change and, because the setting is an old passive margin, eustatic sea level change?" Because independent observational evidence for variation in water depth can come only from analysis of core materials (sediments and fossils), one of the major tasks of the OSP was to identify the principal sequence stratigraphic surfaces in core and determine how they relate to the surfaces identified in petrophysical logs and on seismic reflection profiles.

Previous New Jersey onshore and offshore sequence stratigraphy

Onshore New Jersey sequences provide an interpretive framework for some facies successions in the Expedition 313 drill cores, although the sedimentary record offshore is more complete and shows a wider range of facies (cf. Browning et al., 2006). Onshore sequences follow a pattern of basal transgressive sand dominated by quartz in the Miocene and glauconite in the Paleogene and overlain by regressive silt and sand deposited in offshore to shoreface, delta front, and fluvial environments (Sugarman et al., 1993). Generally, lowstand deposits are absent in the modern coastal plain sites, and thus transgressive surfaces merge with sequence boundaries. In addition, onshore sequences provide little guidance for predicting the nature of MFSs in Expedition 313 drill cores. This is because onshore MFSs range from subtle surfaces separating transgressive from regressive facies in New Jersey to heavily bioturbated omission surfaces in Delaware that look similar to sequence boundaries (Browning et al., 2006). In general, MFSs are differentiated from sequence boundaries by the lack of an age break at an MFS, as well as by deepening-upward successions below an MFS in contrast to shallowing-upward successions below sequence boundaries. Characteristics of MFSs in distal offshore settings have been discussed in work from ODP Leg 174A, where distal toesets of middle to late Miocene clinoforms have been sampled. At those locations, MFSs have been identified as bioturbated surfaces eroded into underlying muds overlain by thin concentrations of quartz sand, presumably derived from the abandoned clinoform front, and a mixture of in situ and reworked glauconite (Savrda et al. 2001; Hesselbo and Huggett, 2001).

Identification of candidate sequence stratigraphic surfaces in cores

Candidate sequence stratigraphic surfaces were interpreted based on physical stratigraphy, facies changes, inferred paleobathymetric changes, facies stacking patterns, and, with estimated ties to seismic reflection characteristics, physical properties and age breaks. Criteria for recognizing key stratigraphic surfaces from sedimentology of the cores in topset positions include

• Irregular contacts, with as much as 5 cm of relief on a 6.2 cm diameter core;

• Reworking, including rip-up clasts found above the contact;

• Strong bioturbation, including burrows in firm substrate filled with overlying material;

• Major sedimentary facies shifts, typically upward from deepwater to shallow-water environments, or from fine to coarse; and

• Shell lags.

Seismic geometries in profiles crossing the Expedition 313 boreholes predicted significant lowstand deposits would be sampled seaward of the clinoform rollover position. Several factors hinder the simple translation of sequence stratigraphic terms and principles defined for shallow-water systems to the interpretation of deepwater (below MSWB) deposits:

• The direct evidence of relative sea level change is not preserved in deepwater sediments, unlike in shallow-water systems (e.g., shoreline position and ravinement surfaces).

• There is insufficient temporal resolution to correlate shallow- and deepwater deposits (Catuneanu, 2006).

• A physical disconnection exists between deepwater deposits with coeval shallow-water systems because of the position of the shoreline, the instability and remobilization of sediment at a shelf-break, and the bypass of sediment in steeper portions of the submarine slope (Catuneanu, et al. 2009).

• The position of deepwater deposits at the distal end of the sediment transport pathway means that a variety of factors influence the timing and location of delivery of sediment to deepwater environments (Posamentier and Allen, 1999).

• Inaccessibility and inactivity of modern analogs means that, in general, sediment gravity flow processes are less well understood than fluvial and shallow-water counterparts.

Despite these limitations, there is a general consensus on the hypothesized sequence stratigraphic framework for deepwater deposits that relates cyclic change in shelfal accommodation (due to relative sea level variations) to repeated changes in the character of the lithology and stacking of depositional elements (e.g., Posamentier and Kolla, 2003; Posamentier and Walker, 2006; Catuneanu et al., 2009). Typically, a cycle of deepwater sedimentation begins during low sea level stand when a subaerial unconformity forms on the shelf and the shoreline and river mouths are at their most distal (basinward) positions close to or beyond the shelf-edge break. The deepwater expression of this regressive phase is the formation of a correlative conformity above which there is a marked increase in the supply of coarse-grained sediment via mass flow and density flow. In the core, a sequence boundary is evidenced by an abrupt increase in grain size and a basinward shift of facies. To prove such a surface is a sequence boundary rather than related to a local slide or slump or an autogenic process such as an avulsion, it has to be mappable regionally. A cycle of deepwater sedimentation commonly ends with a landward shift of facies during transgression, resulting in progressive deactivation of updip supply systems. During this transgressive phase, there is sufficient accommodation for much of the silt- and sand-grade material to be retained on the shelf and coastal plain. Ultimately, the delivery of sediment via turbidity currents to the deepwater environment becomes progressively more mud rich and infrequent as shelf accommodation becomes sufficient to store all coarse sediment. In core, the transgressive phase is marked by fining- and thinning-upward turbidite and debrite units. Identification of the deepwater equivalent of the MFS can be problematic, although a position within the interval with the lowest sedimentation rate and finest sediment is commonly used (Catuneanu et al., 2009).

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