Site 327

Abstract

Site 327, in 2400 meters of water on the western nose of the elevated eastern part of the Falkland Plateau, the Maurice Ewing Bank, was chosen to examine Southern Ocean shallow-water pre-Neogene biostratigraphy and to identify seismic reflectors of regional extent. The first hole was abandoned in bad weather after recovery of only a surface core, but the second was cored continuously to 118 meters and intermittently to 469.5 meters before also being abandoned due to excessive ship motion. Twenty-eight cores were taken, with 50{%} recovery. Ten meters of Quaternary ice-rafted terrigenous debris with manganese nodules overlie a sequence of upper-Paleocene to lower Eocene alternating siliceous ooze and zeolitic clay 80 meters thick. Hiatuses occur above this sequence (Eocene to Quaternary) and below (late Maestrichtian to late Paleocene). Below 52 meters of Maestrichtian foramnanno ooze lies a condensed section, up to 12 meters, of Santonian zeolitic clay with probably a Turonian- Coniacian hiatus. Below 154 meters subbottom, about 170 meters of a mostly Albian nanno claystone (uppermost part is Cenomanian) overlies an Aptian to ?Neocomian sapropelic claystone which extends to the base of the hole. Thus, restricted circulation in Aptian times gave way to more open ocean conditions in the Albian, following the development of a deep-water connection between the Atlantic and Indian oceans as the Falkland Plateau cleared southern Africa. Subsidence and improved circulation followed, with the CCD largely above the sea bed at the site. Possible Late Cretaceous, and very probable Neogene, submarine erosion results from changes in circulation patterns, the latter possibly consequent upon opening of Drake Passage 20 to 30 m.y. ago. Cores contain unique siliceous flora and fauna at the Paleocene-Eocene boundary, with many new forms, and excellently preserved Maestrichtian calcareous fossils. Hole 327A penetrated about half of the sedimentary cover at the site.