Abstract

A new member, the Niton Member, is recognized formally for a distinctive and regionally mappable, unconformity-bounded sandstone unit in the upper Fernie Formation in the subsurface of west-central Alberta. This member is Late Jurassic (Late Oxfordian to Early Kimmeridgian) in age based on terrigenous and marine palynomorph assemblages, and consists predominantly of glauconitic sublitharenites to quartz arenites with rare shale beds. Marine bioturbation of the member is extensive and is dominated by a Cruziana trace fossil assemblage. Concomitant with progradation, the member was overprinted by pedogenic processes. The Niton Member is readily distinguished from the underlying Rock Creek Member (Bajocian to Aalenian) as well as the overlying “Upper Fernie” shale (Kimmeridgian to Tithonian), and serves as a regional marker in a sequence below the Mannville Group that has long been difficult to interpret. The Niton Member accumulated as a prograding, shallow marine sand-body following a 7 Ma (Late Bajocian to Callovian) hiatus. The Niton Member is one of a regional complex of glauconitic clastic rocks that was deposited in a series of prograding events associated with multi-phase transgression initiated in the Late Callovian and Early Oxfordian over much of the southern Canadian and northwest U.S. interior during early orogenic foredeep development.