Heat flow measurements over bottom simulating reflectors, offshore southwestern Taiwan

Abstract

The submarine accretionary wedge offshore of southwestern Taiwan consists of an intensively deformed upper slope and a lower slope characterized by mostly west-vergent anticlines and thrusts. The fast accumulation of sediment covers and seals organic material before it is oxidized within the accretionary wedge. The bottom simulating reflectors (BSRs) associated with the accretionary prism and imbricate wedge are often observed in marine seismic reflection data from continental slopes and rises. A total of 23 heat flow measurements were carried out along seismic profiles with obvious BSRs offshore of southwestern Taiwan. On average, through sedimentation-correction heat flows have increased by 10%, and the base of gas hydrate stability zone (BGHS) predicted by geotherm has up-shifted by 11 %. The average depth of BGHSs is 304 mbsf versus 358 mbsf for BSRs. The average heat flow from measurements is 64 mW m-2, while that estimated from BSRs is 54 mW m-2 (16 percent less) which is reasonable compared with past results of other researchers. They are both increasing from coastal waters southward to the front of the accretionary wedge. One interesting fact found is that one of our heat flow measurements showed no indication of impact friction raised temperature on data recordings. The friction may have been absorbed by gas hydrate for dissociation.