Oligocene to Miocene Benthic Foraminiferal and Abyssal Circulation Changes in the North Atlantic

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Abstract
We reconstructed Oligocene-Miocene abyssal circulation changes in the North Atlantic using seismic, isotope, and sediment accumulation data, and evaluated the response of benthic foraminifera to these abyssal circulation changes. North Atlantic Oligocene-early Miocene abyssal benthic foraminiferal assemblages were relatively stable, showing few first or last occurrences. Late Oligocene subsidence at Sites 558 and 563 caused the local disappearance of a buliminid assemblage. Nuttallides umbonifera increased in abundance at the deepest locations (Sites 10, 119, 400; > 3.5 km paleodepth) during the "middle" Oligoene in response to increased carbonate corrosivity and reduced bottom-water supply to the North Atlantic. A period of accelerated faunal change (disappearances) lasted from about 16 to 13.5 Ma (late early to early middle Miocene) at Sites 558 and 563; benthic foraminiferal relative abundance and flux changes began earlier, at 17 Ma and 19 Ma, respectively. These benthic foraminiferal changes correspond with a series of productivity and bottom-water changes. We speculate that increased primary productivity triggered these changes. The benthic foraminiferal taxonomic composition at Sites 558 and 563 have remained essentially unchanged from 13.5 Ma to the present.