EVIDENCE FOR DEEP ANAEROBIC BIODEGRADATION IN THE BEAUFORT MCKENZIE BASIN

Access to the deep biosphere is extremely expensive and the most readily available samples, obtained from drilling for hydrocarbon resources, are hampered by contamination issues. As an alternative we examine indirect evidence for biologic activity through analyses of its byproducts, CO2 and methane gas, with particular focus on historic Drill Stem Test (DST) data for the Beaufort-Mackenzie Basin (BMB). Our results show evidence for strongly compartmentalized zones of biodegredation within the BMB controlled by thermal history and fluid flow dynamics. We demonstrate that biodegreation is restricted to regions that have not been exposed to temperatures above ~100 oC, whereas regions exposed to higher temperatures during burial history, even with modern active freshwater influx, do not show evidence for biodegredation. These results support recent ‘paleo-pasteurization' models suggesting that biodegredation is driven by microbes originally buried within the sediment. Results also show evidence for biodegreation occurring at higher temperatures than previously recognized, extending the depth of the deep biosphere.