Orbitally Forced Hyperstratification of the Oligocene South Atlantic Ocean.

Pelagic sediments from the subtropical South Atlantic Ocean contain geographically extensive Oligocene ooze and chalk layers that consist almost entirely of the calcareous nannofossil Braarudosphaera. Poor recovery and the lack of precise dating of these horizons in previous studies has limited the understanding of the number of acmes, their timing and durations, and therefore their likely cause. Here we present a high-resolution, astronomically tuned stratigraphy of Braarudosphaera oozes (29.

Evolution of the early Antarctic ice ages.

Understanding the stability of the early Antarctic ice cap in the geological past is of societal interest because present-day atmospheric CO concentrations have reached values comparable to those estimated for the Oligocene and the Early Miocene epochs. Here we analyze a new high-resolution deep-sea oxygen isotope (δO) record from the South Atlantic Ocean spanning an interval between 30.1 My and 17.