--> Abstract: Evolution Of A Barred Barrier Island Shoreface Succession: Doig, Halfway &Amp; Basal Charlie Lake Formations (Triassic), British Columbia, Canada, by J-P. Zonneveld, T. F. Moslow, and S. M. Hubbard; #90928 (1999).

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ZONNEVELD, JOHN-PAUL1, THOMAS F. MOSLOW2, and STEPHEN M. HUBBARD3
1Applied Stratigraphy Research Group, Dept. of Geology and Geophysics, Univ. of Calgary, Alberta
2Ulster Petroleums, Calgary, Albeta
3Ichnology Research Grp., Univ. of Alberta, Edmonton

Abstract: Evolution Of A Barred Barrier Island Shoreface Succession: Doig, Halfway & Basal Charlie Lake Formations (Triassic), British Columbia, Canada

Tommy Lakes field is one of the largest Middle Triassic gas reservoirs within the Western Canada Sedimentary Basin. Middle Triassic strata within the study area include an overall progradational succession of fourteen parasequences within two third-order depositional sequences, representing part of a mixed siliciclastic-carbonate depositional system on the northwestern margin of the North American craton.

Within the study area, the basal sequence boundary is characterized by a moderate basinward shift in sedimentary facies, from offshore transition to shoreface sediments and erosional removal of underlying parasequences. Tidal inlet channels, which incised deeply into underlying units during sea-level fall, were abandoned during early transgression. The transgressive systems tract, consisting of a thin retrogradational package of shoreface sandstone (7-12% porosity; 4-25md permeability) and bioclastic tidal inlet channel fill (12-20% porosity; 15-200md permeability), comprises the main reservoir. Hydrocarbon entrapment resulted from the updip pinch-out of tidal inlet channels and upper shoreface sandstones overlain by tight, marginal marine dolomitic mudstones.

As sea-level rise decelerated and sedimentation outpaced creation of accommodation space, back-barrier lagoons were choked with sediment. The system evolved from a barrier island succession with relatively deep, back-barrier lagoons during transgression to a low-gradient, progradational, barred beach-ridge strandplain succession with abundant minor lagoons and shore proximal lakes during highstand.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas