Abyssal benthic foraminifera from the northwestern Pacific (Shatsky Rise) during the last 298 kyr

Benthic foraminifera in a gravity core from Shatsky Rise (northwestern Paci fic, water depth 2612 m) show large fluctuations in accumulation rate, spec ies composition and diversity over the last 298 kyr, The most important flu ctuations (explaining more than 90% of the faunal variance) result from var iations in relative abundance of the three most abundant species: Epistomin ella exigua, Alabaminella weddellensis and Uvigerina peregrina. High accumu lation rates of U. peregrina, a species linked to high, continuous producti vity, occurred with a 100 kyr periodicity at the end of glacial stages, and correspond to high mass accumulation rates of organic carbon. Peak accumul ation rates of E. exigua occurred during glacial stage 4 and the middle par t of glacial stages 8 and 6, whereas A. weddellensis was dominant in the ea rly part of stages 8 and 6, and the late part of stage 3. A high abundance of these species probably indicates lower overall productivity than a high abundance of U, peregrina, and their relative and absolute abundances may b e linked not simply to the amount of organic matter delivered to the sea fl oor, but to the intermittent delivery of fresh, easily degraded organic mat ter. The overall species diversity is negatively correlated to the relative abundance of E. exigua, but not to that of A. weddellensis, implying that these species have different environmental preferences, although both have been linked to periodic phytodetritus deposition in the present oceans. (C) 2000 Elsevier Science B.V. All rights reserved.