The biogeochemical interaction and alteration of hydrocarbons in shallow sediments of the Scotian Slope, Nova Scotia

Abstract

This thesis presents findings from a study on headspace gas and methane clumped isotopic data obtained from various core samples along the Scotian Slope of Nova Scotia. The research aimed to quantify <i>i</i>) gas loss during sample storage, <i>ii</i>) evaluate the effectiveness of frozen sediment cores in identifying the sulfate methane transition zones, and iii) understand the origins and mechanisms of hydrocarbon gases at deep marine, cold seep sites. Results indicated an average of 75% gas loss for Isojars during the first nine months of storage, emphasizing the importance of proper preservation techniques. Optimal conditions for sample analysis were established, aiding in methane core profile construction for identifying shallow sediment, geochemical transition zones. Methane clumped isotopologue analysis revealed a deep biosphere approximately one kilometer below the seabed, sustained by microbial gas production, supporting seep sites near salt diapirs. This study highlights the significance of direct seep gas samples and provides insights into methane dynamics in marine environments and how deep biosphere methane gas production can impact ocean floor community ecology in diapir controlled cold seep localities.