Do benthic foraminifer records represent a productivity index in oxygen minimum zone areas? An evaluation from the Oman Margin, Arabian Sea

Benthic foraminifer accumulation rates (BFAR) and benthic to planktic foraminifer ratios (BP) have been suggested to represent an index of paleoproductivity in the world oceans. It is shown here, however, that BFAR and BP do not record the surface-water productivity signal in the intense upwelling and oxygen minimum zone (OMZ) along the Oman Margin. Greater BFAR and BP values are noticed during the last glacial period, when the monsoon and upwelling strength were weaker and the surface-water productivity was reduced. This is in contrast to the suggestion that BFAR and BP values are an indication of enhanced productivity. On the other hand, BFAR and BP values were lower during the Holocene as a consequence of intensified monsoon and upwelling and resulting enhanced productivity in the Arabian Sea. This appears to suggest that BFAR and BP do not reflect the productivity variations in the OMZ of the Arabian Sea. We speculate that dissolved oxygen concentrations might instead be controlling the benthic foraminifer abundance.