radiation. Instrument conditions were as follows: 40 kV, 35 mA; goniometer scan from 2 to 70 °2
(air-dried samples) and from 2 to 12 °2 (glycolated samples); step size of 0.01 °2; scan speed at 1.2 °2/min; and count time of 0.5 s each.
Core-description forms, or "barrel sheets," provide a summary of the data obtained during shipboard analysis of each sediment core. Detailed observations of each section were recorded initially by hand on standard ODP visual core description (VCD) forms. Copies of original VCD forms are available from ODP upon request. This information was subsequently entered into AppleCORE software (version 8.1m), which generates a simplified, annotated graphical description (barrel sheet) for each core (Fig. F2). These barrel sheets appear alongside corresponding core photographs (see the "Core Descriptions" contents list). Site, hole, and depth (in mbsf) are given at the top of the barrel sheet, with mbsf positions of core sections along the left margin. Columns on the barrel sheets include graphic lithology, bioturbation, sediment disturbance, sample types, color, and remarks. Features related to sedimentary structures, lithologic accessories, and fossils are plotted on the graphic lithology near the depth interval where they are present. These columns are discussed below, followed by an outline of the lithologic classification used during Leg 199. In addition to lithologic information, graphs showing measurements collected by the MST were plotted alongside each core interval. These data include gamma ray attenuation (GRA) densitometer bulk density (g/cm3), corrected magnetic susceptibility (MS) (10-5 SI units), and lightness as determined by color reflectance (L*).
Lithologies of the core intervals recovered are represented on barrel sheets by graphic patterns in the column titled "Graphic Lithology" (Fig. F3). For intervals containing homogeneous mixtures of multiple lithologies, symbols are arranged within the column from left to right in order of their relative abundance. Graphic lithologies are used for all components that comprise 25% or more of the total sediment. The width of each pattern in the column approximates the relative abundance of that component. Relative abundances reported in this volume are useful for general characterization of the sediment but are not precise, quantitative data.
Sedimentary structures formed by natural processes (i.e., not a result of drilling disturbance) are represented on the barrel sheet with symbols placed on the graphic lithology (Fig. F4). Structures formed by both biogenic and physical processes are included. These include varying degrees of bioturbation, types of trace fossils, parallel laminations, macro- and microfaults, and soft sediment deformation structures.
Five levels of bioturbation are recognized using a scheme similar to that of Droser and Bottjer (1986). Bioturbation intensity is classified as abundant (>75%), common (>50%-75%), moderate (10%-50%), rare (<10%), and absent (none). These levels are illustrated with graphic symbols in the "Bioturbation" column (Fig. F4).
Symbols are used to denote accessory lithologies, authigenic minerals, concretions, fossils, and coring-induced sediment disturbance (Fig. F4). Symbols are positioned near the location in the section where that feature is observed. If the feature extends over an interval, the symbol appears centered on a vertical line to denote the extent of occurrence.
Colors are determined qualitatively using Munsell Soil Color Charts (Munsell Color Company, 1994) and described immediately after cores are split in order to avoid color changes associated with drying and redox reactions. Colors for some chert and pumice fragments are identified using the Geological Society of America (GSA) color chart (Rock-Color Chart Committee, 1991). Munsell and GSA color names are provided in the color column on the barrel sheet, and the corresponding hue, value, and chroma data are provided with the remarks.
Sample material taken for shipboard sedimentologic and chemical analysis consisted of pore water whole rounds, micropaleontology samples, "toothpick" samples, smear slides, thin section billets, and discrete samples for XRD. Typically, four or five smear slides were made per core, one pore water sample was taken at a designated interval, and a micropaleontology sample was obtained from the core catcher of most cores. XRD samples were taken only where needed to assess the lithologic components. Additional samples were selected to better characterize lithologic variability within a given interval. Tables summarizing relative abundance of sedimentary components from the smear slides were generated using a spreadsheet program (Sliders).
The written description for each core contains a brief overview of both major and minor lithologies present and notable features such as sedimentary structures and disturbances resulting from the coring process.
Lithologic names consist of a principal name based on composition, degree of lithification and/or texture as determined from visual description, and smear slide observations. For a mixture of components, the principal name is preceded by major modifiers (in order of increasing abundance) that refer to components making up >25% of the sediment. Minor components that represent between 10% and 25% of the sediment follow the principal name (after a "with") in order of increasing abundance. An unconsolidated sediment containing 30% nannofossils, 25% clay minerals, 20% foraminifers, 15% quartz silt, and 10% manganese nodules would be described as a clayey nannofossil ooze with manganese nodules, quartz silt, and foraminifers. Sedimentary components ranging from 10% to 25% are reflected in the sediment name in the description column as "with," but these components are not designated in the graphic lithology column. These naming conventions follow the ODP sediment classification scheme (Mazzullo et al., 1988), with the exception that during Leg 199 a separate "mixed sediment" category was not distinguished. During Leg 199 neritic and chemical sediments were not encountered, except as accessory minerals; therefore, these categories are not addressed below.
Granular sediments were subdivided on the basis of composition and abundance of different grain types estimated from visual examination of the core, smear slides, thin sections, and by shipboard measurements of carbonate content (see below) and shipboard XRD analyses (see below) (Fig. F5). In volcaniclastic sediments, the term ash (or tuff if lithified) is used in place of sand, whereas lapilli is used for granule and cobble size categories. Larger volcanic clasts (breccia) were not encountered, except for fragments of pumice, which are noted in each barrel sheet. Size divisions for grains are those of Wentworth (1922) (Fig. F6). Size-textural qualifiers were not used for pelagic sediment names (e.g., nannofossil clay implies that the dominant component is detrital clay rather than clay-sized nannofossils).
Terms that describe lithification vary depending upon the dominant composition as described below:
In addition to visual estimates of the color, reflectance of visible light from soft sediment cores was routinely measured using a Minolta spectrophotometer (model CM-2002) mounted on the AMST. The AMST measures the archive half of each core section and provides a high-resolution stratigraphic record of color variations for visible wavelengths (400-700 nm). Freshly split cores were covered with clear plastic wrap and placed on the AMST. Measurements were taken at 2.0-cm spacing. The AMST skips empty intervals and intervals where the core surface is well below the level of the core liner but does not recognize relatively small cracks or disturbed areas of core. Thus, AMST data may contain spurious measurements that should to the extent possible, be edited out of the data set before use. Each measurement recorded consists of 31 separate determinations of color reflectance in 10-nm-wide spectral bands from 400 to 700 nm. Additional detailed information about measurement and interpretation of spectral data with the Minolta spectrophotometer can be found in Balsam et al. (1997, 1998) and Balsam and Damuth (2000).
To describe important mineralogic and structural features in both the archive and working halves, we examined core sections containing igneous rocks prior to cutting the core with a diamond-impregnated saw. Each piece was numbered sequentially from the top of the core section and labeled on the outside surface. Pieces that could be fit together were assigned the same number and lettered consecutively (e.g., 1A, 1B, 1C, etc.). Plastic spacers were placed between pieces with different numbers. The presence of a spacer may represent a substantial interval of no recovery. If it was evident that an individual piece had not rotated about a horizontal axis during drilling, an arrow was added pointing to the top of the section.
The few fragments of basalt recovered during Leg 199 were described on the VCD forms for sediments.
Selected samples were taken for qualitative mineral analysis by using an XRD Philips model PW1729 X-ray diffractometer using Ni-filtered CuK radiation. Instrument conditions were as follows: 40 kV, 35 mA; goniometer scan from 2 to 70 °2 (air-dried samples) and from 2 to 12 °2 (glycolated samples); step size of 0.01 °2; scan speed at 1.2 °2/min; and count time of 0.5 s each.
Some samples were decalcified using 10% acetic acid then washed repeatedly with demineralized water in a centrifuge. The carbonate-free fraction was deflocculated with a 1% Calgon (sodium hexametaphosphate) solution and homogenized in a sonic dismembrator for 1 min. MacDiff software (version 4.1.1 PPC by Rainer Petschick) was used to display diffractograms, and identifications are based on multiple peak matches, using the mineral database provided with MacDiff. Diffractograms were peak corrected to match the calcite peak at 3.035 Å. In the absence of calcite, no peak correction was applied.
Systematic, high-resolution line-scan digital core images of the archive half of each core were obtained using the GEOTEK X-Y Imaging system (Geoscan II). This digital imaging system (DIS) collects digital images with three linescan charge coupled device arrays (1024 pixels each) behind an interference filter to create three channels (red, green, blue). The image resolution is dependent on the width of the camera and core. The standard configuration for GEOSCAN II produces 300 dpi on an 8-cm-wide core with a zoom capability up to 1200 dpi on a 2-cm-wide core. Synchronization and track control are better than 0.02 mm. The dynamic range is 8 bits for all three channels. The Framestore Card has 48 MByte of onboard RAM for the acquisition of images with an ISA Interface card for personal computers. After cores were visually described, they were placed in the DIS and scanned. A spacer holding a neutral gray color chip and a label identifying the section was placed at the base of each section and scanned along with each section. Output from the DIS includes a Windows bitmap (.BMP) file and a Mr.Sid (.SID) file for each section scanned. The bitmap file contains the original data with no compressional algorithms applied, whereas the Mr. Sid files apply extensive compressional algorithms. Additional postprocessing of data was done to achieve a medium-resolution JPEG image of each section and a composite JPEG image (stored as a Microsoft PowerPoint slide) of each core, which is comparable to the traditional photographic image of each core. The JPEG image of each section was produced by an Adobe Photoshop batch job that opened the bitmap file, resampled the file to a width of 0.6 in (~15 mm) at a resolution of 300 pixels/in, and saved the result as a maximum-resolution JPEG. The DIS system was calibrated for black and white approximately every 12 hr. No significant change in this calibration was observed during Leg 199. For Sites 1215-1220, the lens aperture was reset whenever significant changes in core color were observed. The resetting of the lens aperture, however, resulted in undesirable side effects when compiling composite digital core images of multiple sections across critical boundaries; color changes in composite images were often the result of aperture changes, rather than changes in sedimentary characteristics, and overwhelmed true sediment color change. For Sites 1221 and 1222, a constant aperture setting of f11 was used. This resulted in underexposed images in some of the darker-colored intervals, which obscured some of the sediment features. These image files were adjusted for brightness and contrast using a suitable software application, such as Adobe Photoshop or Microsoft PowerPoint, before inclusion in the core composite images.
