EVOLUTION IN THE SOUTHWEST PACIFIC AND AUSTRALIAN CLIMATE1

• Main Author: R. Stein
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Antarctic; Pacific; Antarc*
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.581.9596; http://www.deepseadrilling.org/90/volume/dsdp90pt2_45.pdf

Clay minerals, grain sizes, and flux rates of terrigenous sediments in the Lord Howe Rise area provide important in-formation about the Neogene evolution of climate and physical processes in the southwest Pacific region. Temporal var-iations in these data suggest that the Neogene history of desertification in Australia was controlled by both the north-ward drift of the Indo-Australian Plate and the buildup of Antarctic ice sheets. Increased aridity, as defined by a dis-tinct decrease in smectite/illite ratios and increased accumulation rates of terrigenous matter, occurred in northern Australia about 13 m.y. ago, expanding to the south during the late Miocene. Periods of maximum aridity coincided with major cooling events near 12, 9, 5, and 3 m.y. ago. Increased eolian sediment supply and intensified atmospheric circulation are inferred from the grain size and flux rates of the terrigenous sediments at Site 591 during the last 4 m.y., that is, about 0.8 m.y. earlier than similar observations recorded in the Northern Hemisphere. An enhanced oceanic in-termediate-water circulation is inferred from decreased accumulation rates and a coarsening of both the bulk-sediment and the terrigenous-sediment fraction at Sites 588 and 590 during the last 3 m.y. Volcanic activity increased in the southwest Pacific region during the Miocene (21 to 9 m.y. ago) and in the Quater-nary (0.4 m.y. ago).