SEQUENCE STRATIGRAPHY OF FALLING-STAGE AND LOWSTAND DEPOSITS OF THE LOWER CRETACEOUS (ALBIAN) VIKING FORMATION, JOARCAM FIELD, CENTRAL ALBERTA

The Viking Formation is a sequence stratigraphically complex unit, which was deposited in a low accommodation setting during the Late Albian. Three sequences of Viking deposition have been identified, facilitating the recognition of multiple falling stage and lowstand paleoshoreline positions preserved throughout the subsurface of the Western Canadian Sedimentary Basin. The second sequence lowstand paleoshoreline is preserved at the Joarcam Field in central Alberta. The proposed stratigraphic model characterizes the deposits using the four systems tract nomenclature, allowing recognition of the falling stage systems tract (FSST). The Joarcam Field records the preservation of the second and third sequences of deposition. The base of the succession comprises the remnants of a forced regressive shoreface, which passes across a gradational contact (correlative conformity) with the overlying lowstand systems tract (LST). In proximal positions, the FSST deposits overlie a regressive surface of marine erosion (RSME), which incised into the underlying offshore parasequences of the earlier highstand systems tract. The exhumed mudstone is ideal for colonization with an omission suite, consisting of firmground Skolithos and Diplocraterion. The correlative, non-erosional surface to the RSME is the basal surface of forced regression (BSFR), which occurs as a gradational mud-on-mud contact. The transition from forced regression to normal regression caused the shoreface/deltaic deposits of the lowstand to aggrade over the FSST and prograde seaward. These LST deposits overlie the correlative conformity (CC) of the subaerial unconformity (SU) incised in more proximal positions. A thin transgressive deposit locally caps the second sequence. During deposition of the third sequence, a coarse-grained asymmetric wave-dominated delta of the FSST was erosively incised into the deposits of sequence two. The lowstand of sequence three is preserved at a more distal position in the basin.