We requested approval to deepen Hole1143C beyond the originally approved 400 m penetration to extend the paleoenvironmental record in time, after the sediment age turned out to be younger than expected. Hole conditions did not allow deployment of the GHMT string. Incomplete core recovery and decreased core quality precluded splice construction below this interval, but intervals of cores can be correlated over the 190-400 mcd interval. In general, the long-term decrease in sedimentation rates observed at Site 1143 from the upper Miocene to the Pleistocene is caused by declining accumulation rates of both carbonate and noncarbonate components. In general, bedding is not evident, and compositional changes are gradual throughout the site.
Minor lithologies vary with depth and include ash layers, turbidites, and green clay layers.
Benthic foraminifers are generally rare throughout the site. Changes in color define lithic subunits and are mainly controlled by carbonate content. Calcareous nannofossils and planktonic foraminifers are abundant and generally well preserved. The MS and NGR values reach a plateau in the mid-Pliocene and rapidly decrease in the lowermost Pliocene. Magnetic susceptibility spikes related to volcanic ashes occur between 120 and 190 mcd.