HR: 08:15h
AN: T41C-02    [Abstracts]
TI: Detailed Provenance Analysis Constrains Variations in Basin-Wide Deposition Trends And Source Area Uplift: The Late Cretaceous Nanaimo Basin, Southwest British Columbia, Canada
AU: * Mustard, P
EM: pmustard@sfu.ca
AF: Simon Fraser University, Earth Sciences , Burnaby, BC V5A 1S6, Canada
AU: Mahoney, B
EM: mahonej@uwec.edu
AF: Univ Wisconsin - Eau Claire, Dept of Geology , Eau Claire, WI 54701, United States
AU: Haggart, J
EM: Jim.Haggart@nrcan-rncan.gc.ca
AF: Geological Survey of Canada, 625 Robson St. , Vancouver, BC V6B 5J3, Canada
AU: Kimbrough, D
EM: dkimbrough@geology.sdsu.edu
AF: San Diego State University, Dept of Geological Sciences , San Diego, CA 92182, United States
AU: Grove, M
EM: marty@ess.ucla.edu
AF: Univ of California - Los Angeles, Earth and Space Sciences , Los Angeles, CA 90095, United States
AU: Fanning, M
EM: Mark.Fanning@anu.edu.au
AF: Australian National University, Research School of Earth Sciences , Canberra, ACT , Australia
AB: The Upper Cretaceous Nanaimo Group accumulated in a peripheral foreland basin on the Insular Superterrane in southwestern British Columbia. Detailed facies studies, paleontologic control and regional provenance analysis facilitate reconstruction of basin depositional architecture. Basin subsidence began in Turonian time in response to contractional crustal thickening in the southern Coast Belt and Cascade Range to the east and southeast. Initial sedimentation was diachronous, with non-marine, marginal marine, and shallow marine deposition on a complex paleotopography having local relief >100m. Most clastic detritus was locally derived, but the presence of syndepositional Late Cretaceous zircon indicates rapid unroofing of the arc system on the eastern basin margin. Subsidence dramatically increased in late Santonian -early Campanian time, resulting in progradation of submarine fan lobes west across the basin. Santonian to Maastrichtian sedimentation produced thick successions (>3 km) of complexly intertonguing fan lobes resulting from episodic sediment flux. Predominance of volcanoplutonic debris and paleocurrent data indicate derivation from the Coast Plutonic Complex to the east. Syndepositional detrital zircon throughout the section suggests strong coupling between rapid orogenic exhumation and basin subsidence. By early Campanian time, however, the main continental arc system was locally breached by one or more large rivers, and extraregional sediment from distal back arc regions prograded westward into the basin. Significant (locally >50%) Precambrian detrital zircon from uplift of the Belt Supergroup to the east are mixed with Jura-Cretaceous grains of the Coast Plutonic Complex. Contribution from eastern sources peaked in late Campanian time, reflected by conspicuous quartzite pebbles and cobbles. By Maastrichtian time, the Precambrian component was significantly diluted due to a major pulse of plutonic detritus from final unroofing of the Cretaceous arc system.
DE: 8110 Continental tectonics: general (0905)
DE: 8169 Sedimentary basin processes
DE: 8178 Tectonics and magmatism
SC: Tectonophysics [T]
MN: 2007 Joint Assembly