Thermogenic hydrocarbons in surface sediments of the Bransfield Strait, Antarctic Peninsula

Abstract

Antarctica is the only continent from which petroleum deposits have not been encountered, despite the occurrence of potential hydrocarbon basins onshore and around its margins. We have discovered thermogenic hydrocarbons in unconsolidated Recent sediments from the King George Basin, Bransfield Strait, west Antarctica. These sediments possessed a marked petroliferous smell throughout the length of the 8.6-m gravity core. The basin sediments are glacial marine deposits dominated by turbidites and contain abundant autochthonous organic matter as a result of high seasonal primary productivity in this most fertile part of the circumpolar ocean¹. The maturation of this material into hydrocarbons may have been accelerated by the high geothermal gradient in the basin, associated with back-arc spreading created by the subduction of the Drake Plate into the South Shetland trench². Sediments in this rifted basin are frequently intruded by volcanic sills and dykes³ giving rise to acoustic features shown in Fig. 1. The presence of these thermogenic hydrocarbons provides the first demonstration of active source rocks in Antarctica.