Sedimentology, Ichnology, and Depositional History of the Falher D Member, West-Central Alberta, Canada – Presence of a Wave-dominated Delta

Hoffman, Trevor¹, Murray Gingras¹, S. George Pemberton² (1) University of Alberta, Edmonton, AB (2) Alberta University, Edmonton, AB

The lower Cretaceous Falher Member within the Wapiti field area consists of five stacked successions of coarsening-upward storm-dominated sandstones and conglomerates. The Falher “D” member is one such succession and is subdivided into five facies associations: lower shoreface (FA1), upper shoreface and foreshore (FA2), channelized/convoluted deposits (FA3), brackish water deposits (FA4), and non-marine fluvial and coastal plain deposits (FA5). A number of significant stratigraphic surfaces have been utilized to sub-divide the Falher “D” into two parasequences termed D1 and D2.

A detailed investigation of the D1 and D2 sandbodies reveal a number of interesting along-strike trends. The basal Falher “D” sandbody (D1) is extremely irregular in terms of thickness and lithology. Thickness varies from zero to roughly 11m within the study area. The upper Falher “D” sandbody (D2) has a more uniform thickness compared to the basal Falher D, ranging from 8m to 25m. However, significant variations in sedimentology, ichnology, and character indicate the presence of a number of different depositional environments. Typical strandplain shoreface deposits are present in the eastern and western portions of the study area while wave-dominated deltaic deposits are present within the central region. Specific evidence for the presence of a wave-dominated delta include the presence of stacked fluvial deposits within non-marine deposits directly perpendicular to the shoreline trend, depressed ichnological intensities and diversities, presence of specific sedimentary structures, and the distribution of conglomerate within the upper shoreface and foreshore. This conclusion is strengthened through comparison with recognized wave-dominated deltas.