The sediment drilled at Site 1086 exhibited only minor core disturbance resulting from gas expansion. Drilling disturbance was evident in the upper seven cores of Hole 1086A, whereas the core quality was significantly better at Hole 1086B. No flow-in structures were observed. Sediments from Site 1086 form one lithostratigraphic unit and are composed of olive (5Y 5/3) clay-rich nannofossil-foraminifer ooze and olive (5Y 5/3), light gray (5Y 7/1), pale olive (5Y 6/3) and light olive-gray (5Y 6/2) foraminifer-nannofossil ooze, foraminifer-rich nannofossil ooze, and nannofossil ooze.
Unit I is composed of olive (5Y 5/3) clay-rich nannofossil-foraminifer ooze and olive (5Y 5/3), light gray (5Y 7/1), pale olive (5Y 6/3) and light olive-gray (5Y 6/2) foraminifer-nannofossil ooze, foraminifer-rich nannofossil ooze, and nannofossil ooze (Fig. 8). Most of the sediment is moderately bioturbated, and burrows range in diameter from 1 mm to over 1 cm. Thicker burrows are dark gray, contain abundant pyrite, and are frequently infilled with coarser sediment consisting of abundant foraminifer tests in a nannofossil-ooze matrix. Occasionally, Zoophycos traces are identified (e.g., Core 175-1086A-17H-6). Intervals of different colored sediment range in thickness from 40 to 100 cm and grade into one another over 15 to 20 cm. Small, finely dispersed fine sand–sized pyrite grains are ubiqitous below Core 175-1086A-16H. Calcium carbonate content at Hole 1086A averages 79 wt%.
Cores 1751086A-1H through 4H and 175-1086B-1H through 3H contain nannofossil-rich foraminifer ooze with an increasing abundance of nannofossils downhole. These cores have little or no clay or silt fraction, except in Core 175-1086A-1H where silt-sized grains of quartz are frequent. Below these cores, the sediment is primarily either a foraminifer-rich nannofossil ooze or a nannofossil-foraminifer ooze. Egg-shaped carbonate concretions ~3 to 5 cm in diameter are present in Cores 175-1086A-16H and 19H. Bioturbated 1-cm-thick beds composed of very fine-grained, subrounded phosphate grains are present in Sections 175-1086A-11H-1, 134 cm, and 11H-6, 87 cm. A 2-mm-thick lamina composed of very fine-grained, subangular phosphate grains is also present in Section 175-1086B-13H-5, 144 cm.
The detrital component in sediments from Site 1086A is dominated by clay and trace abundances of silt-sized, subangular mono- and polycrystalline quartz grains. Authigenic minerals are rare or present in trace abundances. Pyrite is present as silt-sized aggregates of euhedral crystals or as framboids. Small phosphate grains are present in bioturbated beds in Core 175-1086A-11H and in a 2-mm-thick lam-ina in Core 175-1086B-13H. The biogenic component in all smear slides consists of abundant to dominant nannofossils and abundant to common foraminifers.
Color reflectance data were measured every 4 cm for Holes 1086A and 1086B. The total reflectance values range between 35% and 70% (Fig. 9). High average calcium carbonate contents at this site (see "Organic Geochemistry" section, this chapter) suggest that downcore variations in the total reflectance are controlled primarily by variations in calcium carbonate. At Hole 1086A, total reflectance values are, on average, 55% for the first 150 mbsf and show relatively high-amplitude variations between 70 and 150 mbsf (Fig. 9). Between 150 mbsf and the bottom of Hole 1086A, total reflectance values average 65%. Downcore stratigraphic trends of total reflectance as well as specific features are similar at Sites 1086 and 1085.