Scientists aboard the Glomar Challenger collected a 235-m core of marine sediment specifically for geochemical study. This core, obtained with the hydraulic piston corer from site 532 (leg 75) in the South Atlantic, was frozen immediately upon its retrieval to preserve its organic geochemical properties. Samples from this core are now available to researchers.
Site 532 is a reoccupation of deep-sea drilling (DSDP) site 362 of leg 40. The organic carbon content in this bioturbated core ranges between 1 and 6% and appears to fluctuate markedly on a time scale of 20,000–50,000 years. The lowest values occur in deeper sediments, and they generally are higher in younger sediments, reflecting an intensification of upwelling conditions at this location. An organic carbon maximum in upper Pliocene sediments records stronger upwelling conditions during that time.