Site 329

Abstract

Site 329, in 1519 meters of water some 55 km northeast of Site 327 on the Maurice Ewing Bank, was chosen to obtain the shallow-water Neogene biostratigraphic section deliberately avoided at the earlier site. The single hole was cored continuously to 179.5 meters and intermittently to 464.5 meters, yielding 33 cores with 69% recovery and bottoming in Paleocene nanno chalk. It thus provides some stratigraphic overlap with the section cored at Site 327. Apart from ice-rafted terrigenous debris in the uppermost 4.5 meters of Quaternary diatomaceous ooze, the entire section is biogenic. About 220 meters of upper Miocene nanno and diatom ooze overlies 125 meters of more consolidated middle to upper Miocene ooze and chalk. Beneath this, a Paleocene to lower or middle Miocene nanno chalk, locally silicified, extends to the base of the hole. The sedimentation rate is about five times as high in the uppermost 350 meters of Miocene sediments as in the older sediments beneath. Hiatuses probably span the late Oligocene to early or middle Miocene, and the middle to early Eocene. The former represents an unconformity which reflection profiles show to form the base of a 100- km-long bank of Miocene oozes. This and the presence of reworked Oligocene fossils in the Miocene sediments indicate that strong bottom currents swept the region in the Neogene, possibly as a result of the opening of Drake Passage.