Depositional Architecture of a Slope Channel Complex Set (Isaac Formation, Neoproterozoic, Canadian Cordillera): Implications for Reservoir Characterization

Ernesto Schwarz¹, R. William C. Arnott¹, and Gerry Ross^2
1 University of Ottawa, Ottawa, ON
² Geological Survey of Canada, Calgary, AB

A detailed architectural analysis was conducted in slope Channel 5 of the Isaac Formation (Neoproterozoic), in the Castle Creek area (east-central B.C., Canada). Channel 5 (75-100 m thick) occurs toward the top of a well exposed 4 km-wide by 1km-thick section that constitutes an ideal area for examining the depositional architecture of deep-marine slope systems.

Channel 5 consists of three stacked channel complexes (8-30 m thick) separated by fine-grained deposits (<11 m thick). Each channel complex was initiated by an episode of incision (high-relief erosion surfaces), followed by an infill phase. This depositional phase consists of several nested (3-12 m thick) channel fills associated with accumulation by mostly sand-rich flows (amalgamated Bouma Ta divisions). Cessation of flows (updip avulsion?) led to local channel/channel complex deactivation and accumulation of laterally extensive (> 2.5 km), thin-bedded units interpreted to indicate low-energy overbank deposition. Subsequent reincision led to the development of a new channel complex. Based on this stacking pattern, slope Channel 5 forms a channel complex set.

Four channel-fill architectural elements were recognized within the Channel 5, each with different reservoir-type sandstone units that highlight the potential complexity in slope channel reservoirs. The uppermost channel-fill unit, for example, exhibits inclined depositional surfaces (lateral accretion) and a mixed sand-mud fill. This channel body is interpreted to have been deposited by a migrating, sinuous channel that recorded the last stage of Channel 5 development, just prior to backstepping and consequent abandonment of the entire turbidite system.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005