Abstract

The Falher C lithostratigraphic sub-Member of the Spirit River Formation in northeastern British Columbia is a product of deposition by wave- and storm-processes along a gravelly, wave-dominated strandplain. The oldest and southernmost outcropping stratigraphic unit (C1) is sandstone dominated and marks the onset of the prograding shoreface facies association. To the south, the C1 stratal unit consists of coal, shale and interbedded sandstone that make up the Coastal Plain Facies Association. The C2 stratal unit is a conglomerate shoreface facies association deposited during the relative falling of sea level. The C2 shoreface trend erosionally overlies the C1 stratal unit. Internal erosional surfaces within C2 are source diastems that amalgamate basinward to form a regressive surface of erosion. The source diastems vary across the outcrop in scale and orientation and are interpreted to be the product of shoreface ravinement due to high magnitude storms. The geometry and architecture of the outcrop exposures suggest that shoreface sandstone and conglomerate were deposited episodically by waves and longshore currents during phases of coastal progradation. Channel deposits, observed in outcrop, control the orientation of the shoreface facies depocentres. During this time, gravel is introduced to the C2 depositional package as bedload from narrow, deeply incised channels during a falling relative sea level. Conglomerate with the highest porosity and permeability occurs along the southern edge of the C2 stratal unit, adjacent to coevally deposited channels. This study provides a template for interpreting and predicting the architectural framework of shoreface reservoirs in the Deep Basin of northeastern British Columbia and Alberta.

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