LATE MIOCENE DEEP-SEA BENTHIC FORAMINIFERAL PALEOCEANOGRAPHY AT ODP SITE 806B IN WESTERN PACIFIC OCEAN

Abstract

The study of sediments will produce stratigraphic records across intervals of major paleoceanographic changes by evaluating variations of primary paleoceanographic indicators. It will also provide a detailed record of vertical oceanic gradients, their linkages to climatic parameters and bottom surface water properties. Similarly, the biological gradients can be determined. The result will be a multidimensional picture of the response of the water mass structure in the Western Pacific Ocean - Benthic foraminifera from 10 samples from theSite 80613, Ontong Java Plateau are analyzed to study their paleoceanography and response of deeep sea benthic foraminifera in Western Pacific • Ocean. 88 taxonomic groups covering 35 genera and 53 species have been reported. Taxonomic descriptions of 25 species have been given, covering 2 plates. A decline in species diversity is observed at the boundary, accompanied with changes in the assemblage. The first and last occurrences of 6 affected species are noted, along with faunal abundances of resistant species. An attempt has been made to interpret the paleo-environmental characteristics on the basis of trends in diversity indices as well as faunal abundances. Our results show that Valvulineria glabra, Cyclammina cancel/ala and Cibicides refulgens are highly abundant species throughout the section. Buliminids are present in high numbers, however, their diversity declines at the boundary. Pullenids, and infaunal taxa, are present in small numbers throughout the section. The presence of Alabarninoides exiguus and Bolivina spissa characterized the Paleocene assemblage, whereas the Miocene assemblage shows the presence of Trochammina nitida, Oridorsalis umbonatus and Rosa/ma globularis. The response of benthic foraminifera to the Pliocene- • Miocene thermal maximum appears muted at this site, however, trends can be delineated and the influence of cooling temperatures is apparent in the behavior of several species,