Biosphere-geosphere interaction in deep subsurface sediments of the Belgica mound province in the Porcupine basin, offshore Ireland
IODP Leg 307
The investigation of the extent and dynamics of deep microbial ecosystems in sedimentary basins is a new and intriguing topic in today’s geoscience research. In this context the challenging question is, whether abiotic processes such as thermal alteration of sedimentary organic matter or hydrocarbon leakage can form a food source for deep microbial communities by liberating a wide range of biologically amenable compounds. Biosphere-geosphere interactions in deep sedimentary successions are, therefore, of specific interest in the IODP Leg 307 drilling campaign. This project was performed in April to May 2005 in the Porcupine basin area offshore Ireland, and sediment material from three sites on and adjacent to the Challenger mound in the Belgica carbonate mound province was drilled taking strict precautions to avoid microbial surface contamination.
In a previous study (the Geomound project) computer simulations of the basin history, undertaken at GFZ Potsdam (J. Naeth), revealed that below the carbonate mounds in the Belgica mound province specific sandstones from Cretaceous and Tertiary sequences represent important migration pathways for natural gases to the surface. Thus, hydrocarbon gases could have migrated to the mound base stimulating microbial activity at this interval.
Investigation of microbial biomarkers and the isotopic signal of natural gases at the mound base will help to elucidate the microbial processes occurring and the potential biosphere-geosphere interaction at the Challenger mound site.