Deep-sea benthic foraminifera from gas hydrate-rich zone, Blake Ridge, Northwest Atlantic (ODP Hole 997A)

Abstract

Certain species of benthic foraminifera feed on rich bacterial food sources at methane seeps, indicating their potential as proxy for methane fluxes in the geological record. Several of these species have been reported in different methane-rich marine settings and have proved to be good indicators of methane eruptions. The Blake Ridge, located ~350 km off the coast of South Carolina, northwestern Atlantic, is a large drift deposit and a proven gas hydrate field, as is evident by the geochemical anomalies and presence of a bottom simulating reflector. This area thus offers good opportunity to analyse benthic faunal-gas hydrate relationship over different timescales. Our newly generated benthic foraminiferal faunal and published total organic carbon data from Ocean Drilling Program Hole 997A suggest in situ production of methane by bacterial decomposition of organic matter. We suggest that the fluctuating sea level in response to changes in the Northern Hemisphere continental ice volume may have caused the release of methane from the Blake Ridge gas hydrates during the past 3 Ma. We expect the results of this study to help in the exploration of gas hydrates on the continental shelf of India, which archives a thick pile of sediments with high organic carbon content - ideal for gas hydrate formation.