DSpace JSPUI

Title : PALEOCEANOGRAPHIC EVOLUTION OF THE SOUTHEASTERN INDIAN OCEAN DURING THE NEOGENE: PROXY RECORDS FROM OCEAN DRILLING PROGRAM HOLES 752A AND 757B
The Neogene has an important place in Earth history since this period marks numerous turnovers leading to the modern conditions. One hundred ninety four samples from Hole 757B and one hundred forty two samples from Hole 752A were used to understand the paleoceanography and paleoclimatology of the southeastern Indian Ocean during the Neogene. In total 243 species belonging to 100 genera of benthic foraminifera are reported in this study. Ten biofacies are recognized at Hole 757B and eight biofacies at Hole 752A using coherent results of both factor and cluster analyses of benthic faunal census data. The environmental preferences of these biofacies are used to assess the deep-sea paleoceanographic changes in the southeastern Indian Ocean that may have been driven by the Indian monsoon system as well as high latitude climate variability. The biofacies pattern suggested that the deep sea conditions at Hole 757B were oligotrophic, wellventilated, which continued upto 10.5 Ma punctuated by two short-lived peaks of moderate oxygenation and intermediate flux of organic matter at ~19.2 and ~18.0 Ma. During the middle Miocene, this hole underwent a major cooling phase causing appearance of cool, carbonate corrosive, oligotrophic environment which continued upto 8.7 Ma. A major change occurred at 8.7 Ma, when Hole 757B entered the monsoon regime of the Indian Ocean continuing upto 2.3 Ma. The deep sea conditions were cool with strongly pulsed, low to intermediate organic flux and intermediate seasonality from ~1.9 Ma to the Recent following the intensification of the Northern Hemisphere Glaciation (NHG). At southern shallow Hole 752A, the deep sea environments were well oxygenated with cold deep waters and low organic carbon flux, intermediate to high seasonality during 24.6 to 13 Ma. The deep sea productivity increased and deep water oxygen content decreased from 13- 4.6 Ma. From 4.5 and 3.9 Ma, the deep waters were warmer coinciding with the early Pliocene warmth and became less-oxygenated between 1.4 and 0.9 Ma. However, this deep-sea warming is not observed at deeper Hole 757B. During the mid-Pleistocene Transition (~0.9-0.7 Ma), strong deep sea currents swept Hole 752A with low and seasonal food supply which might have driven an ocean-wide extinction event of numerous elongated species of benthic foraminifera.