Timing and cause of the disappearance of some elongated taxa in the Indian Ocean: Study from NGHP Hole 17A

Abstract

Disappearance of many elongated benthic foraminifera across the Mid-Pleistocene Transition (MPT) is popularly known as ‘Stilostomella extinction’. This event is reported from several sites across the world and it is believed that most of the elongated benthic families disappeared within 0.76–0.5 Ma. It is assumed that the presence of cold bottom water triggered their disappearance. The present study is pursued on sediment cores collected from National Gas Hydrate Program Hole 17A, Andaman Sea, Indian Ocean to examine the precise timing and cause of the disappearance of elongated taxa as well as their ecological preference. Our study reveals that elongated species prefer warm and low to intermediate food condition. This study documents the disappearance of 5 major species and 13 minor species from 0.6 to 0.2 Ma which is younger than the earlier estimates. We assume that change in 41–100 kyr climatic cycle along the MPT was responsible for a major decline in their number. However, amplified glacial–interglacial cycles along Mid-Brunhes (0.5–0.2 Ma) finally played a major role in their disappearance. Both of these consecutive events extended intensified cooling and dropped the deep-ocean temperature by which the shallow infaunal elongated species disappeared and deep-infaunal species survived.