Publisher Summary Paleoclimatic inferences from biogenic materials in ocean sediments derive from the assemblages of dead organisms—thanatocoenoses—which make up the bulk of all but the deepest of deep-sea sediments (biogenic ooze). Biogenic oozes are primarily made up of the calcareous or siliceous skeletons of marine organisms. These may have been planktic or benthic. For paleoclimatic purposes, the most important calcareous materials are the tests of foraminifera and the much smaller tests, or test fragments, of coccolithophores known informally as “coccoliths.” The most important siliceous materials are the remains of radiolarians, silicoflagellates, and diatoms. By studying the morphology of the tests, individuals can be identified to species level and their ocean-floor distribution can then be related to the environmental conditions in the overlying water column. The species assemblage in the sediment is a composite of all the species living at different depths in the water column as well as species with only a seasonal distribution in that particular area. Oxygen isotope analyses have been carried out on cores from most of the important areas of calcareous sedimentation.