The carbonate fraction consists of nannofossils, foraminifers, bioclasts, micrite, inorganic calcite, and dolomite. Laminated beds of diatomaceous ooze, up to 5 cm thick, can be correlated between holes. Downhole variations in detrital siliciclastic grains suggest that Unit I contains three major cycles of upward-increasing terrigenous input. The ORL's range in thickness from 2 m. Examination of the smear slides reveals an amorphous organic component, as well as terrigenous plant fragments and spores. Bioturbation is extensive, and Chondrites and Zoophycos ichnofacies are found throughout the unit.
Laminations are present in a few intervals and, in places, are delineated by aligned organic matter.
In Hole 976B, Unit IV consists of coarse-grained, poorly sorted, coarse pebbly sand. The pebbly sand, which is Serravallian in age, is of marine facies and composed of quartz, biotite, feldspar, and rock and shell fragments. Rounded, gravel-sized, metamorphic clasts are present as minor components throughout the sandy interval. The contact between basement and the middle Miocene sediments is sharp and has an irregular topography, possibly produced by faulting. In the upper 40 m of basement, some fault breccias are formed by highly angular metamorphic clasts in a matrix with a Miocene sedimentary component.