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A subsurface study of cores and electric well logs from the lower Cretaceous (Albian) Viking reservoir sandstone near Calgary, Alberta, reveals its deposition as a regressive barrier island along the shores of the Haplophragmoides gigas sea.
The barrier island trends northwest-southeast parallel to the paleostrandline for more than 120 km (75 mi) and attained a maximum thickness of more than 30 m (100 ft). Swales characterized by isopach thinning suggest that the island was probably breached by two tidal channels. Bentonite chronostratigraphy indicates that the barrier island prograded in a northeasterly and/or easterly direction for up to 24 km (15 mi). This seaward growth was briefly interrupted by an isostatic transgression. Thus, sandstone depositional pattern is of the imbricate type with younger units successively displaced seaward in the direction of progradation.
The barrier-island facies sequence comprises eleven intergradational facies, i.e., ebb-tidal delta, marginal (spillover) channel, middle shoreface, marine shales, upper shoreface beach, dune, back-barrier mud flat, marshy lagoon and overwash, mixed tidal flat, tidal creek channel, and overbank. This sequence differs slightly from that of the Recent classic regressive Galveston Island, Texas, and the ancient Muddy barrier island, Montana, in the presence of an ebb-tidal delta and marine shelf shales beneath and above the middle shoreface facies, respectively. On this basis the South Carolina Recent barrier islands are considered closer modern analogs.
The writer suggests that this sand body be explored further for oil and/or gas accumulations because of its excellent reservoir properties and the generally low well density.
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