Paleocene and Eocene kaolinite distribution in the South Atlantic and Southern Ocean: Antarctic climatic and paleoceanographic implications

Abstract

Clay mineral associations of Paleocene and Eocene age have been examined in six drilled sequences from the southern South Atlantic and Southern Ocean. These sites are located to provide three depth transects across intermediate water masses. Widespread abundance of pedogenic smectite at all locations suggests globally warm climates and alternating wet and dry seasons on the adjacent continental margins, including Antarctica as was the case during the Late Cretaceous. Remarkably, kaolinite is observed only in Paleocene/Eocene sediments at the highest latitudes of these sites and must have originated from Antarctica. The restriction of kaolinite to the Antarctic region is inferred to have resulted from especially higher rainfall there during the Paleocene-Eocene relative to the lower latitude areas examined. This inferred high rainfall is considered to have resulted from globally warm temperatures that increased poleward latent heat transport, compensating for a strong heat deficit in the Antarctic region relative to the tropics. Kaolinite was not observed in the latest Cretaceous (Maastrichtian) sediments of Maud Rise, Antarctica. Kaolinite first appears in the clay mineralogical assemblages in the earliest Paleocene (∼ 64 to 64.5 Ma) at a time of relatively cool intermediate waters and before a warming trend of surface waters. Currents at intermediate water depths transported fine terrigenous sediments from the Antarctica during the latest Paleocene and early Eocene (∼ 59 to 52 Ma) at a time when the oxygen isotopic strongly in East Antarctica during the latest Paleocene and early Eocene (∼ 59 to 59 Ma) at a time when the oxygen isotopic data indicate maximum warmth of surface and intermediate waters of the Southern Ocean. These are interpreted to reflect a Paleocene maximum of Antarctic rainfall. This development peaked at 57.3 M, close to the Paleocene-Eocene boundary, a time of maximum warmth, based on oxygen isotopic data. Increased illite content (and associated chlorite and random mixed-layer clays) at the end of the middle Eocene (41 Ma) suggest local development of poorly weathered soils on Antarctica, favored by a cooling of the Southern Ocean. Coeval extension of kaolinite into shallower water depths, and similar clay mineral associations in shallower and deeper sites, indicate the development of cooler conditions led to an increasing influence of Antarctic environments upon intermediate water masses at high latitudes.