A full wash barrel (Core 187-1157A-1W; 0.0-200.0 mbsf) was recovered from Hole 1157A. Most of the core is highly to moderately drilling disturbed but is characterized by intervals of contrasting color, from dark to medium brown siliceous clay (Fig. F37). Contacts between the different colored intervals are deformed; some are diffuse, and longer intervals of one color commonly contain wispy intervals of the other. In two cores (187-1157A-2W and 3W), there are 50-cm-thick intervals where the color change is gradational from dark to light and light to dark, respectively. The changes are manifested as increasing abundances of thin intervals of one hue within the other. In Section 187-1157A-1W-1, a distinct, originally planar, deformed contact dips ~70° across the cut face of the core. In Section 187-1157A-1W-5, an irregular, steeply dipping (~85°) contact between light brown and medium to dark brown clay. Rare light gray intervals occur sporadically throughout the core.
Toward the bottom of Section 187-1157A-1W-7 is a distinct color change to much lighter brown silty clay, but carbonate is only detectable in the lowermost 6 cm of the section (see Fig. F37), where it effervesces slightly with dilute HCl (~5%-10%). Carbonate-bearing clay is also present in the top of the core-catcher section. It is underlain by a sharp contact with dark brown siliceous clay that lacks a calcareous component. Below the dark brown siliceous clay is a 2-cm-thick interval of calcareous clay that effervesces violently with dilute HCl.
Five smear slides were prepared. In the predominant dark brown and medium brown clay, siliceous microfossil fragments are abundant. Honeycomb-textured fragments as large as 50 µm across have circular void spaces from 1 to 20 µm in diameter. Colorless acicular to semicircular spines are also abundant, as are elongate elliptical microfossils with subparallel, axis-perpendicular septa. Rare 4- to 6-µm rounded, translucent, brown fragments of volcanic glass and colorless crystal shards comprise <1% of the sediment. The only apparent differences among the dark brown, the medium brown, and the rare light gray clay intervals are slight color differences in aggregated clay particles. A smear slide from the interval at the base of Section 187-1157A-1W-7 contains a mixed assemblage of siliceous and calcareous microfossils and rare trace components as in the overlying sediment. The lowermost calcareous ooze contains abundant calcareous microfossils; no siliceous microfossils were recognized.