HR: 0800h
AN: T11D-0417    [Abstracts]
TI: The Bowser and Sustut Basins, Northern British Columbia, Canada: Insights From Analysis of Magnetic Anomaly Data.
AU: Baker, J
EM: jubaker@nrcan.gc.ca
AF: Natural Resources Canada, PO Box 6000, 9860 West Saanich Road, Sidney, BC V8L 4B2 Canada
AU: * Lowe, C
EM: clowe@nrcan.gc.ca
AF: Natural Resources Canada, PO Box 6000, 9860 West Saanich Road, Sidney, BC V8L 4B2 Canada
AB: The Bowser and Sustut basins occupy an area of more than 60,000 km² in northern British Columbia, Canada. They comprise three, dominantly sedimentary, stratigraphic successions, in part overlapping in age: the Bowser Lake Group, the Skeena Group, and the Sustut Group. These three successions overlie arc volcanic and volcaniclastic strata of Stikinia, an allochtonous island arc terrane that accreted to the western margin of North America in the Early Jurassic to early Middle Jurassic. All three basin successions and underlying Stikinia were deformed during development of a thin-skinned fold and thrust belt (the Skeena Fold and Thrust Belt) in Cretaceous and possibly into earliest Tertiary time. Recently, the basins have been the focus of intense geological studies which have resulted in major revisions to the stratigraphic and structural framework of the basins and demonstrated that they have significantly higher petroleum potential than had been previously recognized. To advance these new findings further requires better imaging of the three-dimensional geometry and architecture of the basins. In this study we harness existing magnetic anomaly data to provide the first quantitative estimates of sedimentary thickness across the entire extents of both basins. Our results, which are in general in accord with geological interpretations, indicate that basin-fill is relatively thin and fairly uniform in the Sustut Basin (2.5-3 km), but highly variable in the Bowser Basin, ranging from less than 2 km to more than 6 km. Overall, sedimentary fill is thicker in the northern half of Bowser Basin compared to the south and is typically less than 2 km near the basins northern, western and southern margins. In addition, we demonstrate how a large, buried intrusion beneath the northeast part of Bowser Basin can account for an observed magnetic anomaly and explain the high coalification gradients and localized high maturation levels of the overlying sedimentary rocks. Neither of the latter can be adequately explained by the estimated burial depths. We delineate at least one regionally extensive fault that is more than 150 km long and that cuts basement of Bowser Basin. The fault may have facilitated migration of hydrocarbons sourced in the basement into Bowser Basin. We show how magnetic data can be used to refine isotopically-determined ages of the late Tertiary Maitland Volcanics that overlap the sedimentary fill and to demonstrate that the volcanism must have been episodic and not the result of a single eruptive event. Collectively, these findings provide new insights into the crustal architecture of northern British Columbia and important constraints for geodynamic models of the basins evolution and their resource potential.
DE: 0903 Computational methods: potential fields (1214)
DE: 0925 Magnetic and electrical methods (5109)
DE: 0933 Remote sensing
DE: 1517 Magnetic anomalies: modeling and interpretation
DE: 8108 Continental tectonics: compressional
SC: Tectonophysics [T]
MN: Fall Meeting 2005