Sedimentology,
Ichnology, and Depositional History of the Falher D Member,
Hoffman, Trevor1,
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.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California