Sequences in the Sikanni Formation in the frontier Liard Basin of northwestern Canada—evidence for high frequency late Albian relative sea-level changes

Abstract

Listen

Translate article

The frontier Liard Basin is a relatively unexplored basin in northeastern British Columbia, southwestern Northwest Territories and southeastern Yukon Territory. Although it preserves a thick Cretaceous sedimentary succession, the relationships of these strata to those to the south in the Western Canada Sedimentary Basin (WCSB) are poorly understood. Outcrop sedimentary analysis along with foraminiferal micropaleontology and Rock-Eval pyrolysis are used to investigate the relative sea level and palaeoenvironmental changes that accompanied deposition of the upper Albian Sikanni Formation. Analysis of proximal and distal facies from three outcrops of the Sikanni Formation within the Liard Basin indicates that four sequences can be identified in offshore, wave-dominated shoreline, prodeltaic, delta front and delta plain litho- and biofacies. The identification of 10 5 yr cyclicity relative sea level changes that punctuated Sikanni deposition is supported by the presence of chert pebble lag deposits at surfaces interpreted as sequence boundaries. These sequences are regionally correlative in outcrops and well logs of the Sikanni Formation and indicate a previously unrecognized cyclicity in the upper Albian of the WCSB. Among the two causal mechanisms considered to have possibly driven the cycles, high frequency changes in flexural loading is probably responsible for the cyclicity observed, as evidence of basin-wide relative sea level changes necessary to support a eustatic interpretation is lacking in the late Albian of the WCSB.