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ABSTRACT: Cretaceous Paleogeography of Northern Insular Belt, British Columbia, Canada

HAGGART, JAMES W., Geological Survey of Canada, Vancouver, British Columbia, Canada

Recent studies of Cretaceous rocks on Queen Charlotte Islands (QCI) and northern Vancouver Island (NVI) have produced a new interpretation of the regional sedimentation pattern and tectonic setting of this part of the Canadian insular belt. Well-exposed Cretaceous rocks on QCI are shallow-basin deposits that accumulated at shelf to upper slope depths. Younging relationships indicate the Cretaceous strandline transgressed slowly eastward, overlapping numerous Mesozoic basement units including magmatic-arc components. Laterally continuous, northwest-southeast-oriented facies belts can be traced for great distance across QCI; similar facies are known in poorly studied rocks of NVI. No significant hiatus exists in the Cretaceous succession of QCI, although progradation of coarse clastic u its occurred. These observations, plus a lack of syndepositional faulting and volcanism, indicates a tectonically quiescent Cretaceous basin.

The Cretaceous rocks of QCI represent the eastern margin of a fore-arc basin, with active magmatism eastward and subduction westward. Deep-basin equivalents, the accretionary prism deposits, are not present in the QCI, but may be located west of the islands in the downdropped QC Terrace; alternatively, they may have been transported northward along Tertiary faults to the present-day Chugach terrane. Depositional patterns suggest northern Hecate Strait was highland during much of cretaceous time but that a significant basin existed in southern Hecate Strait and northern Queen Charlotte Sound.

The fore-arc basin of the northern insular belt is part of a relatively continuous chain of Cretaceous fore-arc basins paralleling the North American Cordillera from Baja California to southern Alaska.

 

AAPG Search and Discovery Article #91016©1992 AAPG-SEPM-SEG-EMD Pacific Section Meeting, Sacramento, California, April 27-May 1, 1992 (2009)