Paleoenvironments and regional correlations of Albian-Cenomanian strata in the frontier Liard Basin of northwestern Canada

The frontier Liard Basin is a relatively unexplored basin in northern Canada. A comprehensive outcrop and core study of Albian-Cenomanian strata of the Chinkeh, Garbutt, Scatter, Lepine, Sikanni and Sully formations integrating bio- and sequence stratigraphy, sedimentology, Rock Eval pyrolysis and regional well log correlations details the paleoenvironmental history and response to relative sea level changes. A number of units occur within the Chinkeh and lowermost Garbutt formations and are integrated into a framework of five early Albian sedimentary intervals that provide a high-resolution time control on the paleogeography during Chinkeh deposition. The Chinkeh was deposited by eastwards and westwards prograding shorefaces on opposite margins of a narrow sea and at least one major persistent fluvial/estuarine system situated in the Northwest Territories. Biostratigraphic constraints on deposition of the upper Garbutt and Scatter formations provide ties to events in the Peace River region and Alberta Basin. The Garbutt and Scatter formations were deposited in a high accommodation setting and thin normally eastwards. Unlike correlative strata to the south they do not contain any internal unconformities. The thick Lepine Formation preserves a continuous record of sedimentation although multiple sea level changes produced unconformities elsewhere in the Cretaceous seaway. It is divided into five units in offshore and shelf facies. Events that characterize a low accommodation setting to the south are correlated to the Liard Basin using biostratigraphy and well logs. Analysis of proximal and distal facies from three outcrops of the Upper Albian Sikanni Formation indicates that four sequences can be identified in predominantly wave-dominated deltaic deposits. Fifth-order relative sea level changes are regionally correlative in outcrops and well logs of the Sikanni Formation and indicate that a previously unrecognized cyclicity is present in the Upper Albian of the WCSB that was likely driven by high frequency changes in flexural loading. The base of the Sully Formation is associated with a prominent transgressive ravinement surface. The Fish-Scales Marker, which marks the Albian/Cenomanian boundary, is present within the Sully Formation. The Textularia alcesensis Zone occurs and indicates a continuous record of uppermost Albian and lower Cenomanian sedimentation is present in the Liard Basin.