Abstract
AbstractExtensive submarine cold seep areas, i.e., the Beikang Basin and the Nansha Trough, were discovered on the southern continental slope of the South China Sea. Bottom-simulating reflections are widespread in these areas and show a close relationship to the cold seep system. High-resolution 2-D seismic data and multibeam bathymetry data have confirmed the existence of deep-routed conduits−mud volcanoes, diapirs, and gas chimneys. The geochemical characteristics of seep carbonates and headspace gas indicate that the fluid was mainly sourced from biogenic gas, with contributions from deep-rooted thermogenic gases. Additionally, negative pore water chloride anomalies and positive δ18O values (3.7‰ < δ18O < 5.0‰) of the seep carbonates provided indicators of hydrate water addition during carbonate precipitation. The negative δ13C excursion of planktonic foraminifera from the Nansha Trough indicated two methane release events, which occurred approximately 29–32 ka and 38–42 ka before present, and the driving mechanism for methane seepage in this area is possibly related to overpressure from the large sediment accumulation that occurred during sea level lowstands.
Publisher
Springer Nature Singapore
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