Stratigraphy and provenance of early foreland basin deposits, Minnes Group, British Columbia and Alberta

Subsurface sandstone mapping and age dating of detrital zircons from the Minnes Group of British Columbia and Alberta indicate that Upper Jurassic and earliest Cretaceous sandstones were derived from two distinct source regions. Drainage systems evolved from an orogen-parallel axial drainage network to an orogen-perpendicular, transverse drainage network. Axially transported sandstones are commonly found in basal marine strata, are quartz rich (> 85%) and have detrital zircon age spectra similar to Jurassic and Cretaceous sandstones in the western U.S.A. Axially transported sandstones are increasingly amalgamated towards the distal portion of the foredeep due to lower subsidence rates. Transversely derived sandstones are preferentially found in overlying fluvial successions or on the orogen side of the basin, are characteristically chert-rich (15-70%), and have detrital zircon age spectra similar to Canadian miogeoclinal strata. Long-lived, localized drainage outlets were mapped and imparted a significant influence on sand and ultimately natural gas reservoir distribution.