Records of past methane discharges from Holocene cold seeps of Hidaka Trough based on carbon isotope values of benthic foraminifera

Abstract

Hidaka Trough, a marine hydrate reservoir in the northwestern Pacific, is characterized by its gas chimney structures, faults, methane plumes, and degassing structures, providing pathways for the upward migration of free hydrocarbon gases from deep sediments to the seabed. A comprehensive understanding of methane emissions from Hidaka Trough sediments in the past and present holds the key to predicting future scenarios of methane emission. This study applied a multi-proxy approach to three sediment cores (PC1609, PC1611, and PC1727) from cold seep regions of the Hidaka Trough in the northwestern Pacific to reconstruct the local history of methane emissions. The chronostratigraphic framework of the cores was established using accelerator mass spectrometry (AMS) radiocarbon dates and δ18O profiles of benthic foraminifera, indicating that the cores were deposited during the Holocene. The geochemical composition of hydrocarbon gases within the sediments suggested a microbial origin or a mixture of microbial and thermogenic gases.