Enhanced supply of fossil organic carbon to the Okinawa trough since the last deglaciation
Journal
Paleoceanography
Journal Volume
23
Journal Issue
2
Pages
1-10
Date Issued
2008
Author(s)
Abstract
Significantly older 14C ages by 2500-7900 years are found for sedimentary total organic carbon (TOC) when compared to ages of codeposited surface-dwelling foraminifera in the southern Okinawa Trough. This age discrepancy increases with rising sea level since the Last Glacial Maximum. A progressive shift in TOC δ13C toward more negative values with rising sea level reflects an increasing fractional contribution of terrestrial organics (soil organics, plant debris, and/or fossil organics) to the buried organic pool. Organic matter previously stored on the East China Sea shelf during sea level lowstand and riverine material from Taiwan may be the sources that cause the δ13 CTOC to shift to more terrestrial values. During the Holocene when sea level is above -40 m, δ 13 CTOC values stabilize within a narrow range (-22.3 to -22.8‰) while age discrepancies continue to increase and less chemically weathered sediments are deposited. The increase in age discrepancy between TOC and foraminifera in the Holocene may be due to a wetter climate that drove higher rates of physical weathering on Taiwan and greater transport rates of fossil organic C-bearing lithogenic sediment to the ocean. The climate impact on the relative delivery of fossil and nonfossil TOC in depositional settings influenced by fluvial sources should be considered in interpretations of sedimentary C isotope records. Copyright 2008 by the American Geophysical Union.
Other Subjects
climate effect; deglaciation; foraminifera; fossil; Holocene; Last Glacial Maximum; organic carbon; sea level change; sediment chemistry; East China Sea; Okinawa Trough; Pacific Ocean; Foraminifera
Type
journal article