Late Neogene evolution of paleoclimate and paleoceanic circulation in the Northern and Southern Hemispheres - A comparison

Oxygen isotopes and clay minerals, grain size, and accumulation rates of terrigenous (i. e., mainly eolian) sediments from northeast Atlantic DSDP-Sites 141, 366, 397 and 544B and from southwest Pacific DSDP-Sites 588, 590 and 591 were used to assess parallelisms and differences in the evolution of paleoclimate and paleoceanic circulation in the Northern and Southern Hemispheres during the last 7 Ma. Concomitant with the Messinian cooling event, both northwest African and Australian deserts expanded, as defined by increased supply of illite and increased accumulation rates of terrigenous matter. After an early Pliocene phase of more humid climatic conditions in Australia, as well as in northwest Africa, the accumulation rates of terrigenous sediments distinctly increased in the Southwest Pacific at about 4 Ma, whereas the northeast Atlantic Sites were still characterized by low terrigenous sediment supply until 3.2 Ma. Coincident with the build-up of major Arctic ice sheets during the last 3 Ma, increased aridity and enhanced atmospheric and oceanic circulation in the Northern and Southern Hemispheres were inferred from distinct changes in the terrigenous sediment supply and a coarsening of both bulk and terrigenous sediment fractions.