Late Cenozoic Calcareous Microfossil Biostratigraphy, Paleo-oceanography, and Biogeography--Poles to Tropics: ABSTRACT

Abstract

Deep-sea drilling has provided a set of marine sedimentary sequences for global Cenozoic paleo-oceanographic studies. The CENOP (Cenozoic Paleo-oceanography) program is conducting paleo-oceanographic studies of the late Cenozoic from tropics to poles within the framework of plate tectonism and polar-glacial evolution. This requires detailed correlations between high- and low-latitude regions using different approaches. Quantitative planktonic foraminiferal investigations have been conducted on late Cenozoic sequences in the South Pacific ranging from temperate to warm subtropical latitudes (41 to 26°S). Previous nonquantitative biostratigraphic studies have enabled the establishment of biostratigraphic schemes and correlation between the sequences which differ markedly in faunal characteristics as a result of the latitudinal range. Species frequency, diversity, faunal groupings (principal component and factor analyses), and coiling directions of Neogloboquadrina pachyderma have been determined for each sequence. Oxygen- and carbon-isotopic stratigraphy also has aided in intersite correlation. During the Cenozoic, major changes have occurred in planktonic microfossil biogeography as reflected in the biostratigraphic sequences. These changes have been created largely in response to evolution of the Southern Ocean circulation system as obstructing landmasses moved apart. Included in these changes are the development of the Antarctic and Subantarctic water masses and the Antarctic Convergence and the evolution of cold, high-latitude climates. Nearly all evolution of calcareous planktonic microfossils has occurred outside of the Antarctic-Subantarctic, in subtropical-tropical areas, followed by limited migration into high latitudes. Virtually no endemism occurs among calcareous microfossils at high latitudes, but it is marked in late Cenozoic siliceous forms. End_of_Article - Last_Page 478------------