Neogene calcareous nannofossils in ODP Leg 116 holes

The three sites (717, 718, and 719) drilled on the distal Bengal Fan during ODP Leg 116 cored turbidite sediments almost exclusively. Calcareous nannofossils were recovered sporadically and, although all of them probably have been redeposited, it is possible to date the sediments at all three sites with reasonable confidence. Site 717 penetrated the uppermost middle Miocene Catinaster coalitus highest occurrence datum and represents the most nearly continuous succession of turbidites. Site 718 penetrated the lower Miocene, well below the Helicosphaera ampliaperta highest occurrence datum, but this site contains a major late Pliocene to mid-Pleistocene hiatus. Site 719, the shallowest hole, penetrated only into the upper Miocene. Identification of several critical lowest occurrence datums allows using the poorly constrained but more numerous highest occurrence datums for comparison with the model succession (zonal markers) and thereby to derive a reasonably accurate time framework for the sediments.

Calcareous nannofossils of the Soithern Coral Sea

Leg 90 of the Deep Sea Drilling Project drilled 18 holes at eight sites (Sites 587-594) on several shallow-water platforms in the southern Coral Sea, Tasman Sea, and southwestern Pacific Ocean. The results from an additional hole (Hole 586B) drilled at Site 586 during Leg 89 are included in this report. Together, these sites form a latitudinal traverse which extends from the equator (Site 586) to 45°S (Site 594) and includes all the major water masses from tropical to subantarctic. Samples recovered at these sites range in age from middle Eocene to late Quaternary. The calcareous nannoplankton biostratigraphy for Leg 90 has divided into two parts: part 1, the Neogene and Quaternary of Sites 586-594. (this chapter); and part 2, the Paleogene of Sites 588, 592, and 593 (Martini, 1986). A slightly modified version of the Martini (1971) standard Tertiary and Quaternary zonation scheme was used to make age determinations on over 700 samples. All of the relevant Neogene and Quaternary zone-defining nannoplankton are present at Sites 586-591 (0°-30°S) but become increasingly rare or are absent at Sites 592-594 (35°-45°S). Species diversity increases southward from the equator (Site 586) and reaches a peak at 20°S (Site 587). A decrease at 25°S (Site 588) and 30°S (Sites 589-591) is followed by an increase in species diversity at 35°S (Site 592). South of 35°S, species diversity again decreases and reaches a low at 45 °S (Site 594). Species diversity for all sites as a group generally increases through the early, middle, and late Miocene, reaches a peak in the early Pliocene, then gradually decreases through the late Pliocene and Quaternary