Neogene evolution of surface marine climate in the Pacific and notes on related events

Abstract

Pacific Neogene events related to the evolution of the Neogene surface marine climate on the Pacific coast of central Japan and on the Pacific coast of central and northern South America are reviewed from a standpoint of future studies. The evolution of surface marine climate is presented here by utilizing variations in the ratio of warm water planktonic foraminifera to the total assemblage in respective horizons of reference sections. During the Neogene, three warm episodes in Japan at about 15.5 Ma, 5.7 Ma, and 3 Ma, and three warm episodes in South America at about 15.5 Ma, 11.5 Ma, and 5.7 Ma, respectively, are recognized. In addition, a prolonged cool episode is noticed in about 15-12 Ma on both sides of the Pacific Ocean. Revised chronological calibrations are made on accelerated lineage biotic evolutions in accordance with a stepwise decline of surface seawater temperature that occurred during the latest Neogene in central Japan and northern Chile, both in middle latitudes.