Comas, M.C., Zahn, R., Klaus, A., et al., 1996 Proceedings of the Ocean Drilling Program, Initial Reports, Vol. 161 2. EXPLANATORY NOTES1 Shipboard Scientific Party2 INTRODUCTION the height of the rig floor dual elevator stool (DES) above sea level and the recovery of the mudline core to calculate water depth. In this chapter, we have assembled information that will help the reader understand the shipboard scientific methods used to collect the Graphic Lithology Column data presented in the site reports in this Initial Reports volume of the Leg 161 Proceedings of the Ocean Drilling Program (ODP). Meth- The lithology of the recovered material is represented on the com- ods for shore-based analyses of Leg 161 data will be described in the puter-generated core description forms by symbols representing as individual scientific contributions to be published in the Scientific many as three components in the column titled "Graphic Lithology" Results volume. (see lower right of Fig. 2). Where an interval of sediment or sedimen- The separate sections of the site chapters were written by the ship- tary rock is a homogeneous mixture, the constituent categories are board scientific specialists for each scientific discipline (see Ship- separated by solid vertical lines, with each category represented by a board Scientific Participants list at the front of this volume). symbol (Fig. 2). Constituents accounting for <10% of the sediment in Coring techniques and core handling, including the numbering of a given lithology (or others remaining after the representation of the sites, holes, cores, sections, and samples were the same as those re- three most abundant lithologies) are not shown in the graphic lithol- ported in previous Initial Reports volumes of the Proceedings of the ogy column, but are listed in the "Description" section of the core de- Ocean Drilling Program (Fig. 1). Following Leg 161, the cores were scription form. In an interval composed of two or more sediment transferred from the ship in refrigerated containers to cold storage at lithologies that are quite distinct, such as thinly interbedded or highly the Bremen Core Repository of the Ocean Drilling Program, in Bre- variegated sediments, the column is subdivided by a dashed line(s) men, Federal Republic of Germany. separating the different lithologic symbols according to their relative abundances within the cored interval. Only the composition of layers or intervals exceeding 20 cm in thickness are shown on the graphic LITHOSTRATIGRAPHY lithology column because of limitations in the software used for gen- erating core summaries. In addition, the software does not allow for combinations of interbedded (dashed line) and mixed (solid line) The first part of this section summarizes the methods used to de- lithologies within a given interval. scribe cored sedimentary sequences and the manner in which data collected manually on Visual Core Description Forms (VCDs) were summarized and condensed into computer-generated descriptions for Age Column each core. The second part of this section reviews the sedimentolog- ical classifications and terms used in the descriptions. The chronostratigraphic unit, as recognized on the basis of pale- ontological and paleomagnetic data, is shown in the "Age" column Visual Core Descriptions (VCDs) of Sedimentary Units on the core summary sheets. Boundaries between assigned ages are Core Description Forms indicated as follows: Leg 161 sedimentologists were responsible for visual core log- 1. Sharp boundary = straight line; ging, smear-slide analyses, high-resolution sediment color analysis, 2. Unconformity or hiatus = line with "+" signs above it; and thin-section descriptions of sedimentary and volcaniclastic mate- 3. Uncertain = line with question marks. rial. Detailed information recorded on section-by-section description forms (VCD sheets available from ODP) was condensed into core- Structure Column by-core computer-generated descriptions that give graphic and textu- al summaries for each core (see Section III, "Cores," this volume). Sedimentary structures such as cross stratification, grading, and Cores were designated using leg number, site number, hole letter, bioturbation are indicated in the "Structure" column of the core sum- core number, and core type according to standard ODP procedures mary sheet (Fig. 3). Core summary software also enables color band- (see "Introduction" section, this chapter). The cored interval was ing to be indicated, but does not include symbols to record bed specified in terms of meters below sea level (mbsl) and meters below thickness. On Leg 161, the shipboard sedimentologists decided to use seafloor (mbsf) on the basis of drill-pipe measurements (dpm), re- the color-banding symbols to indicate both color banding and inter- ported by the SEDCO Coring Technician and the ODP Operations bedded lithologies because smear-slide and carbonate analyses indi- Superintendent. Detailed coring summaries can be found on the CD- cate that color changes are associated with lithological variations. ROM in the back pocket of this volume. Depths were corrected for The following definitions were adopted (Blatt et al., 1980, p. 128): 1. Thick bedding/color banding = >30 cm; 'Comas, M.C., Zahn, R., Klaus, A., et al., 1996. Proc. ODP, Init. Repts., 161: College Station, TX (Ocean Drilling Program). 2. Medium bedding/color banding = 10-30 cm; 2 Shipboard Scientific Party is given in the list preceding the Table of Contents. 3. Thin bedding/color banding = <IO cm. 21 SHIPBOARD SCIENTIFIC PARTY The degree of fracturing in indurated sediments and igneous and metamorphic basement rocks is described using the following cate- While Coring gories: APC in situ temperature (ADARA) APC core orientation (Tensor) 1. Slightly fractured: core pieces are in place and contain little drilling slurry (ground rock and water) or breccia; Between XCB cores In situ temperature (WSTP) 2. Moderately fragmented: core pieces are in place or partly dis- placed, but the original orientation is preserved or recogniz- Core recovered on deck able (drilling slurry may surround fragments); Curation (cut into 1.5-m sections) 3. Highly fragmented: pieces are from the cored interval and Whole-round samples for interstitial water analysis Head space/vacutainer (gas monitoring) probably in the correct stratigraphic sequence (although they Micropaleontology using core-catcher samples may not represent the entire section), but the original orienta- Bacteria sampling tion is completely lost; 4. Drilling breccia: core pieces have lost their original orienta- Cores taken into laboratory Equilibrate to room temperature tion and stratigraphic position and may be mixed with drilling Multi-sensor track for core-core and core-log integration slurry. GRAPE, magnetic susceptibility, natural gamma radiation, compressional wave velocity Color Column Thermal conductivity Core are split into working and archive halves The hue and chroma attributes of color were determined using Archive half Munsell Soil Color Charts (1975) and a Minolta, CM-2002 hand-held Whole-core color and black-and-white photography spectrophotometer. The Munsell colors were recorded in the "Color" Core description: lithostratigraphy, petrology, structural geology column on the core description form. The spectrophotometer mea- Pass-through cryogenic magnetometer surements were made to establish semi-quantitative relationships be- tween spectral reflectance in distinctive wave bands and identified Working half lithologies, in addition to providing a continuous stratigraphic record Digital color spectrophotometer Physical properties (velocity, index properties, shear of color variations. strength) Spectrophotometer measurements were made every 2 cm on the Organic and inorganic geochemistry working half of cores from Sites 974 and 975, and at wider incre- Micropaleontology ments on cores from Sites 976 and 977 as soon as possible after the X-ray diffraction X-ray fluorescence core was split. The core was covered with plastic (Saran™) wrap be- Thin sections fore color analysis to protect the core from damage by the spectro- Sampling for post-cruise research photometer. A white standard (also covered with plastic wrap) was analyzed before and after incremental measurements on each core. After coring The spectrophotometer data are discussed in the "Composite Depths" Downhole logging chapter, this section. A more detailed discussion of this method of color analysis can be found in the ODP Leg 155 Initial Reports vol- ume (Leg 155 Shipboard Scientific Party, 1995b). Figure 1. Generalized sequence of scientific data collection and core flow. Detailed scientific methods for each lab are described below and the detailed Sample Column results from each site are reported in separate chapters in this volume. The positions of samples taken from each core for shipboard anal- ysis are indicated in the "Samples" column on the core description form, as follows: The core-summary software allows sharp and gradational bound- aries between color banding to be depicted. Banding showing one I = interstitial water; sharp boundary and one gradational boundary was arbitrarily desig- M = micropaleontology; nated as having gradational boundaries. S = smear slide; T = thin section. Disturbance Column Organic geochemistry and smear-slide samples were often taken Sediment disturbance resulting from coring may be difficult to from the same interval in order to calibrate petrographic estimates of distinguish from natural structures. Nonetheless,