Disappearance of stilostomella lepidula (schwager) across the mid-pleistocene transition and its paleoceanographic implication

Abstract

Stilostomella lepidula (Schwager), an infaunal benthic foraminifer, is an important component of the deepsea environment, showing wide geographical distribution and variation in test morphology. The ecological preference and timing of its disappearance across the mid-Pleistocene Transition (MPT) is widely debated. To understand the ecological preference, and timing and cause(s) of disappearance of S. lepidula, we analysed Neogene record of this taxon from Ocean Drilling Programme and Deep Sea Drilling Project sites located at bathyal to abyssal depths in the Atlantic and Indian oceans. Population plots of this species at various sites reveal that this taxon showed a substantial increase during the warm late Oligocene to the middle Miocene and suffered a major decline across the middle Miocene cooling event (15-13 Myr). S. lepidula disappeared at ~0.6 Myr very close to the MPT (0.9-0.8 Myr) from the Indian and Atlantic oceans, coinciding with a change from a 40 to 100 Kyr world with amplified ice-age cycles. We suggest that high-amplitude glacial cycles, frigid deep-water temperatures and strong circulation drove S. lepidula to nearly disappear across the MPT.