--> Abstract: Stratigraphic and Sedimentologic Analysis and Hydrocarbon Reservoir Potential of the Lower Cretaceous Jackass Mountain Group, Chilko Lake Area, British Columbia, Canada, by Catherine I. MacLaurin, Brian Mahoney, Peter S. Mustard, James W. Haggart, and J. Russell Goodin; #90078 (2008)

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Stratigraphic and Sedimentologic Analysis and Hydrocarbon Reservoir Potential of the Lower Cretaceous Jackass Mountain Group, Chilko Lake Area, British Columbia, Canada

Catherine I. MacLaurin1, Brian Mahoney2, Peter S. Mustard1, James W. Haggart3, and J. Russell Goodin1
1Department of Earth Sciences, Simon Fraser University, Burnaby, BC, Canada
2Department of Geology, University of Wisconsin- Eau Claire, Eau Claire, WI
3Pacific Division, Geological Survey of Canada, Vancouver, BC, Canada

The Lower Cretaceous Jackass Mountain Group (JMG), near Chilko Lake in south-central British Columbia, is exposed southwest of the dextral Yalakom Fault and has been traditionally considered part of the Jura-Cretaceous Tyaughton Basin. The JMG is over 2 km thick in this area and unconformably overlies Middle Jurassic to Early Cretaceous(?) stata. Preliminary data for the JMG indicate an age range of Hauterivian to Albian. The JMG is exposed in a major northeast-trending synclinorium, which permits detailed examination of the lateral and vertical facies variations. Detailed stratigraphic and sedimentologic analysis documents extensive shallow marine deposition, contrary to previous interpretations that described the bulk of the JMG as a deep submarine fan system. The JMG in the northern limb of the syncline is composed of extensive, moderately well-sorted sandstone bodies, decimeters thick with common trough and hummocky cross-stratification, interpreted to represent high energy shoreface environments. Flaser and lenticular bedded facies also suggest upper shoreface environments were widespread. Classic turbidite sequences overlie the shallow marine strata, suggesting that the basin evolved from shallow marine to outer shelf/slope environments over time. This JMG outcrop belt contains many similarities with Cretaceous strata exposed on the northeast side of the Yalakom Fault, 125 km to the southeast. The strata east of the fault dip northward beneath Tertiary basalts which cover subsurface Mesozoic stratigraphy. If correlative with subsurface Lower Cretaceous Nechako Basin strata, the thick and extensive shoreface sandstones suggest that good reservoir potential may exist in the subsurface of the Nechako Basin. Ongoing geochronologic, geochemical, paleontological, and porosity/permeability analyses will constrain basin evolution and reservoir suitability.

 

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas