Leg 180 sediment classification is based on visual core description and smear-slide analysis. Data are condensed to ODP standard barrel-sheet format and presented using the program AppleCORE. The shipboard sedimentologists adopted the widely used classification scheme of Mazzullo et al. (1988). The only significant modification is a further subdivision of volcaniclastic sediment, which is described in "Classification of Sediments and Sedimentary Rocks". The shipboard sedimentologists also collected spectrophotometer reflectance and magnetic susceptibility data on the archive multisensor track.

Sediment type is represented graphically on the core description forms (barrel sheets) using the symbols illustrated in Figure F2. In the "Graphic Lithology" column, major and minor lithologies are represented. Only lithologies that constitute at least 10% of the core are shown, and only lithologic units that are 10 cm or greater in thickness are portrayed in this column. Thin interbeds (<20 cm) of contrasting sediments or sedimentary rocks are indicated in the "Graphic Lithology" column by a vertical subdivision into average percentages.

The location and nature of sedimentary structures in the cores are shown in the "Structure" column of the core description form, using the nomenclature of Miall (1984), Mazzullo et al. (1988), and Frey and Pemberton (1984). Standard key symbols are used on ODP visual core description (VCD) forms and barrel sheets (Fig. F2).

Observations of drilling-related disturbance over an interval of 20 cm or more are recorded in the "Disturbance" column using the symbols in Figure F2. The degree of drilling disturbance is described for soft and firm sediments using the following categories:

1. Slightly disturbed: bedding contacts are slightly deformed.
2. Moderately disturbed: bedding contacts have undergone extreme bowing.
3. Highly disturbed: bedding is completely deformed as flow-in, coring/drilling slurry, and other soft stretching and/or compressional shearing structures attributed to the coring/drilling.
4. Soupy: intervals are water saturated and have lost all aspects of original bedding.

The degree of fracturing within indurated sediments is described using the following categories:

1. Slightly fractured: core pieces are in place and broken.
2. Moderately fractured: core pieces are in place or partly displaced, but original orientation is preserved, or recognizable (drilling slurry may surround fragments; i.e. drilling/coring "biscuits" are evident).
3. Highly fractured: core pieces are probably in correct stratigraphic sequence, but original orientation is lost.
4. Drilling breccia: core is crushed and broken into many small and angular pieces, with original orientation and stratigraphic position lost; often drilling breccia is completely mixed with drilling slurry.

The position of samples taken for analysis from each core are indicated by letters in the "Sample" column of the core description form as follows: SS (smear slide), THS (thin section), PAL (micropaleontology), IW (interstitial water), XRF (X-ray fluorescence), XRD (X-ray diffraction), and PMG (palaeomagnetic plug), WRMB (whole-round microbiology), WROC (whole-round organic chemistry), and WRSC (whole-round permeability).

The lithologic description that appears on each of the VCD forms consists of a list of major lithologies followed by a more detailed description of the composition (as determined from smear slides), color, sedimentary characteristics, and other notable features. Descriptions and locations of thin, interbedded, or minor lithologies are also included in the text.

Nomenclature for the thickness of sedimentary beds and laminae remains unchanged from Mazzullo et al. (1988), using standard terms such as thinly laminated (1-3 mm), laminated (3 mm-1 cm), very thin bedded (1-3 cm), thin bedded (3-10 cm), medium bedded (10-30 cm), thick bedded (30-100 cm), and very thick bedded (>100 cm).

Tables are included that summarize data from smear slides. Because smear slides are generally unreliable for quantitative analysis, relative abundances are estimated qualitatively using the following categories:

Abundant (a) = 51%-100%,
Common (c) = 11%-50%,
Rare (r) = 1%-10%, and
Trace (Tr) = 1%.

Initials of the shipboard scientists who described the smear slides are given in the table. The sedimentary categories recognized in smear slides were customized to reflect the actual recovery during Leg 180 (Table T1). Grain sizes were routinely estimated using smear slides combined with visual observation of the cores to produce data shown in the "Grain Size" column of the core description forms (barrel sheets). These data were smoothed and processed to show downhole variation where recovery was sufficient.

Bulk-rock XRD analyses were undertaken on a limited number of samples to determine mineral composition. Standard XRD operating procedure and conditions were adhered to, and an interactive software package (R. Petschick, Macdiff 3.1, 1995) was used to help identify the main minerals. Only qualitative estimates of mineral abundances were made.

Thin sections were used to help identify the composition of siltstones and sandstones. Tables are included that summarize data from these slides. Percentages of minerals, rock fragments, matrix (including cement), and bioclasts are given (Table T2). The main constituents were estimated qualitatively using the following categories:

Abundant (A) = 51%-100%,
Common (C) = 11%-50%, and
Rare (R) = 1%-10%.

Lowercase letters based on the same system were used to indicate subcategories (e.g., quartz [A], strained quartz [a], and unstrained quartz ([c]) of the following major constituents: quartz, feldspar, mica, accessory minerals, volcanic rock fragments, sedimentary rock fragments, metamorphic rock fragments, and foraminiferal types. Initials of the shipboard scientists who described the thin sections are given in the table.

During Leg 180, the newly developed AMST was utilized for the first time, following the procedures set out in the accompanying instruction manual. Spectral color (false color) and magnetic susceptibility (except for Cores 180-1108B-1R through 20R) were collected. The data collected are displayed as two graphs on the visual display unit. The first graph (top) displays the height of the core as measured by the LB1011 laser displacement transducer. The second graph displays the spectral data measured by the Minolta CM2002 spectrophotometer. Color in the graph indicates the intensity (0%-100%) at the specific wavelength (400-700 nm at 10-nm bins). The data were stored in the central shipboard computer system for processing and archiving (see ASCII Tables). During operation it was noted that the recorded color spectrum varied according to whether the sediment was wet or dry. This was problematic, especially for sands that dried quickly. Details of the magnetic susceptibility methods are described in "Paleomagnetism".

The sediment classification system used during Leg 180 closely follows that proposed for ODP by Mazzullo et al. (1988). This classification is descriptive rather than genetic and is based mainly on sediment composition and texture. The classification depends entirely on the data collected on board the JOIDES Resolution (Fig. F3), including smear-slide analysis and thin-section analysis for components and grain size, visual core descriptions, and coulometrically determined calcium carbonate contents. During Leg 180 we encountered a need to classify several different sediment types as follows:

1. Volcaniclastic sediments. Clastic sediments of volcanic provenance are described in the same fashion as siliciclastic sediments, noting the dominant composition of the volcanic grains.
2. Unsorted to poorly sorted sediments. The ODP classification does not adequately address unsorted or poorly sorted siliciclastic or volcaniclastic sediments, such as those characterized by debris flows (debrites).
3. Carbonate rocks. Wackestones are defined as fine-grained limestones; packstones are limestones with a packed fabric including fine-grained interstitial sediment; and grainstones have a packed fabric without matrix.

The following types of grains are found in granular sediments: (1) pelagic, (2) neritic (calciclastic), (3) siliciclastic, (4) volcaniclastic, and (5) mixed grain. Pelagic grains are composed of the organic remains of open-marine siliceous and calcareous microfauna and microflora (e.g., radiolarians and nannofossils), and associated organisms. Neritic grains are composed of coarse-grained calcareous (i.e., fossil) debris and fine-grained calcareous grains of nonpelagic origin (e.g., micrite). Siliciclastic grains are composed of mineral and rock fragments derived from igneous, sedimentary, and metamorphic rocks. Volcaniclastic grains are composed of rock fragments, glass, and minerals derived from volcanic sources.

Granular sediments are identified as follows:

1. Pelagic sediments are composed of >60% pelagic and neritic grains and <40% siliciclastic grains. They also contain a higher proportion of pelagic rather than neritic grains.
2. Neritic sediments are composed of >60% neritic and pelagic grains and <40% siliciclastic and volcaniclastic grains.
3. Siliciclastic (terrigenous) sediments are those having >50% terrigenous component, classified on the basis of grain size as shown in Figure F4. This classification follows that of ODP Leg 178 (Shipboard Scientific Party, 1999a) in that sediments having >75% of a single component are given that name (e.g., 23% silt, 77% sand = SAND or 24% clay, 76% silt = SILT).
4. Volcaniclastic sediments are composed of >60% siliciclastic and volcaniclastic grains and <40% pelagic and calciclastic grains. They contain a higher proportion of volcaniclastic than siliciclastic grains. This class includes epiclastic sediment (volcanic detritus produced by erosion of volcanic rocks by wind, water, and ice), pyroclastic sediment (products of degassing of magma), and hydroclastic sediment (produced by granulation of steam explosions and quenching).

For pelagic sediment, the principal name describes the composition and degree of consolidation using the following terms:

1. Ooze: unconsolidated calcareous and/or siliceous pelagic sediments;
2. Chalk: firm pelagic sediment composed predominantly of calcareous pelagic grains; and
3. Limestone: hard pelagic sediment composed predominantly of calcareous pelagic grains.

For siliciclastic sediments, the principal name describes the texture and is assigned according to the following guidelines: (1) the Udden-Wentworth grain-size scale (Wentworth, 1922) defines the grain-size ranges and the names of the textural groups (gravel, sand, silt, and clay) and subgroups (fine sand, coarse silt, etc.) that are used as the principal names of granular sediment; and (2) the suffix "-stone" is affixed to the principal names sand, silt, and clay if the sediment is lithified.

Volcanogenic sediments of various types were extensively recovered during Leg 180. We use the term volcanogenic for all sediments of mainly volcanogenic origin including clastic sediments (i.e., volcaniclastic sediments and sedimentary rocks), fine-grained (volcanic- derived) sediments and sedimentary rocks, and diagenetic sediments and sedimentary rocks of volcanic origin. We used a classification scheme followed by the shipboard sedimentologists during Leg 152 (Shipboard Scientific Party, 1994). This differs somewhat from the classification scheme recommended by Mazzullo et al. (1988). This (siliciclastic type) textural classification separates the various volcaniclastic sediments (and sedimentary rocks) into volcaniclastic gravel (volcaniclastic conglomerate; grain size = >2.0 mm), volcaniclastic sand (volcaniclastic sandstone; grain size = 2.0-0.063 mm), volcaniclastic silt (volcaniclastic siltstone; grain size = 0.063-0.002 mm), and volcanogenic clay (volcanogenic claystone; grain size = <0.002 mm). Sediment modifiers are vitric (glass), crystal (mineral fragments), and lithic (rock fragments). For example, a volcanic sand composed of 45% glass, 35% feldspar crystals, and 20% lithic fragments was named a crystal vitric volcanic sand with lithic fragments. Wherever appropriate, comments were added on the core description forms regarding the presumed pyroclastic or epiclastic origin. In addition, dispersed volcanic particles (<10% from smear-slide observations) were noted on the core description forms. We use the terms volcanic breccia and volcanic conglomerate for poorly sorted deposits that consist of angular or rounded clasts, respectively, of mainly volcanic origin in a fine-grained matrix. When evidence of primary (pyroclastic) origin was available for fine-grained sediments, we use the terms lapilli or lapillistone (2-64 mm in grain size) and ash or tuff (<2 mm in grain size), as defined by Mazzullo et al. (1988).

Where possible, sediment types are distinguished on the basis of the dominant component (>60%), which provides the principal lithologic name (e.g., volcaniclastic sediment and pelagic sediment). When a component comprises 25%-50% of the sediment, it is mentioned as a major modifier preceding the principal name (e.g., diatomaceous clay and nannofossil silty sand). Minor constituents (10%-25%) are included using the term "-bearing" (e.g., diatom-bearing clay and nannofossil-bearing silty sand). The sediment modifiers are ordered so that the minor modifier(s) precede the major modifier(s).

Coarse siliciclastic sediments (i.e., nonvolcanogenic) were recovered during Leg 180. These sediments were divided into conglomerates (rounded clasts) and breccias (angular clasts). Classification of clast types was the same as that employed for coarse (rudaceous) volcaniclastic sediments.

Conglomerates were subdivided according to texture and composition. Clast-supported conglomerates are termed orthoconglomerates, whereas matrix-supported conglomerates are termed paraconglomerates (synonymous with diamictite). Conglomerates composed of one rock type are termed oligomictic, whereas conglomerates composed of several rock types are termed polymictic. Clast-supported types (ortho-conglomerate) commonly relate to traction current depositional processes, whereas matrix-supported types (paraconglomerate) are commonly deposited by mass-flow processes and are known as debris flows, or debrites (but also include deposits from high-concentration turbidity currents). The classification used for different clast fabrics is shown in Figure F5 (after Schulz, 1984). Where practicable, conglomerates derived from clasts within the depositional basin (i.e., intraformational) were distinguished from those derived from outside the basin (i.e., extraformational).

Successions recovered during Leg 180 include turbidity current deposits that vary in grain size and bed thickness. Some other fine-grained laminated facies were deposited by bottom currents (contour-ites). Descriptive criteria used to separate these sediment types are as follows:

Turbidites are commonly recognized by reference to the classic descriptive scheme (Fig. F6) of Bouma (1962) (divisions T_A to T_E). These are often referred to as "classical turbidites." Many beds deposited by turbidity currents cannot be described using the Bouma (1962) scheme. Such beds commonly vary from massive to normally graded or inversely graded, and were deposited from high-concentration turbidity currents (Pickering et al., 1989). In addition, fine-grained turbidites recovered during Leg 180 commonly exhibit the T_C-D-E divisions corresponding to cross-laminated silt, parallel-laminated silt, and mud components. Bouma's (1962) original scheme is too generalized for application to these muddy turbidites. Accordingly, Piper (1978) further subdivided the T_D and T_E divisions of Bouma into laminated silt (D), laminated mud (E₁), graded mud (E₂), ungraded mud (E₃), and H (pelagic and hemipelagic) intervals (Fig. F7). Our interpretations of the fine-grained deposits recovered during Leg 180 were based upon detailed visual and hand-lens examinations using Piper's (1978) scheme.

Furthermore, some horizons recovered during Leg 180 were interpreted as contourites (i.e., current deposits). The most important characteristics for distinguishing turbidites from contourites are repetitive internal structure (the "Bouma" sequence) and a tendency to form thick and repetitively bedded stratigraphic successions (Stow and Piper, 1984).