Gas hydrate occurrence and BSR-derived heat flow variations on the northeastern South Shetland continental margin, Antarctic Peninsula

Abstract

Multi-channel seismic data acquired on the northeastern South Shetland continental margin, Antarctic Peninsula, show that Bottom Simulating Reflectors (BSRs) are widespread in the area, implying large volumes of gas hydrates. The parameters used to estimate the total volume of gas hydrate in the study area were 145 km of total length of BSRs identified on seismic profiles, 350 m thickness and 15 km width of gas-hydrate-bearing sediments, and 6.3 % of the average volume gas hydrate concentration. Assuming that gas hydrates exist only where BSRs are observed, the total volume of gas hydrates along the seismic profiles in the area is about 4.81010 m3 (7.7 1012 m3 volume of methane at standard temperature and pressure). With the phase diagram for the gas hydrate stability field, heat flow can be derived from the BSR depth beneath the seafloor determined on multichannel seismic profiles. The heat flow values in the study area range from 50 mW/m2 to 85 mW/m2, averaging to 65 mW/m2. Small deviation from the average heat flow values suggests that heat flow regime of the study area is relatively stable. The landward decrease of heat flow from the South Shetland Trench to the continental shelf would be attributed to the landward thickening of the accretionary prism and the upward advection of heat associated with fluid expulsion. The local high heat flow anomalies observed along 1500 m to 3000 m depth contours of the continental slope may be caused by upward heat transport mechanisms along a NW-SE trending large-scale fault crossing the slope.