Geological evolution and analysis of confirmed or suspected gas hydrate localities: Volume 10, Basin analysis, formation and stability of gas hydrates of the Aleutian Trench and the Bering Sea

• Main Authors: Krason, J., Ciesnik, M.
• Format: Report
• Language: English
• Published: Geoexplorers International, Inc., Denver, CO (USA) 1987
• Subjects: Elements; Lithology; Kerogen; Geology; Geophysical Surveys; Organic Compounds; Geothermal Legacy; Surveys; Sedimentation; Gas Hydrates; Geologic History; Carbon; Organic Matter; Geologic Deposits; Surface Waters; Thermography; Seismic Surveys; Sediments; Materials; Islands; 03 Natural Gas; Geomorphology; Geochemical Surveys; Temperature Gradients Geothermal Legacy; Hydrocarbons; Bering Sea; Seas; Stratigraphy; Stability; Sedimentary Basins; Natural Gas Hydrate Deposits; Geothermal Gradients; Pacific Ocean; Measuring Methods; Geologic Structures; Hydrates; Aleutian Islands; Nonmetals; Bituminous Materials; Carbonaceous Materials; Drill Cores; Atka; Atka Basin; Navarin; Pacific
• Online Access: https://doi.org/10.2172/5699885; https://digital.library.unt.edu/ark:/67531/metadc1090974/

Four major areas with inferred gas hydrates are the subject of this study. Two of these areas, the Navarin and the Norton Basins, are located within the Bering Sea shelf, whereas the remaining areas of the Atka Basin in the central Aleutian Trench system and the eastern Aleutian Trench represent a huge region of the Aleutian Trench-Arc system. All four areas are geologically diverse and complex. Particularly the structural features of the accretionary wedge north of the Aleutian Trench still remain the subjects of scientific debates. Prior to this study, suggested presence of the gas hydrates in the four areas was based on seismic evidence, i.e., presence of bottom simulating reflectors (BSRs). Although the disclosure of the BSRs is often difficult, particularly under the structural conditions of the Navarin and Norton basins, it can be concluded that the identified BSRs are mostly represented by relatively weak and discontinuous reflectors. Under thermal and pressure conditions favorable for gas hydrate formation, the relative scarcity of the BSRs can be attributed to insufficient gas supply to the potential gas hydrate zone. Hydrocarbon gas in sediment may have biogenic, thermogenic or mixed origin. In the four studied areas, basin analysis revealed limited biogenic hydrocarbon generation. The migration of the thermogenically derived gases is probably diminished considerably due to the widespread diagenetic processes in diatomaceous strata. The latter processes resulted in the formation of the diagenetic horizons. The identified gas hydrate-related BSRs seem to be located in the areas of increased biogenic methanogenesis and faults acting as the pathways for thermogenic hydrocarbons.