Albian foraminiferal biostratigraphy of a key borehole in northeastern British Columbia
Harrison, Shane M.
In the Rocky Mountain foothills of northeastern British Columbia, the thick and widespread Lower Cretaceous Series includes the 1500 m-thick Fort St. John Group of Albian age. This group consists generally of alternating formations of sandstone and shale which record episodes of deltaic sedimentation and more prolonged episodes of marine inundation within the foredeep of the western Interior basin during Albian time. An essentially continuous cored section from a diamond drillhole located in the region of Pine River, northeastern British Columbia, intersects the Goodrich Formation (part), the Hasler Formation (complete), and the Boulder Creek Formation (part) of the Fort St. John Group and provides a section of unusually great stratigraphic extent. Distribution of predominantly agglutinated foraminifers from samples of the core define four faunal divisions and ten faunal subdivisions in the section. Assemblages have close affinities to those of the Trochammina depressa, Trochammina umiatensis, and Reophax troyeri subzones of the Haplophragmoides gigas Zone, and the Verneuilina canadensis and Haplophragmoides postis goodrichi subzones of the Miliammina manitobensis Zone. Regional distribution of these assemblages point to the sediments of part of the Boulder Creek, and those of the Hasler and Goodrich formations being deposited during a major transgressive event which began during late (latest?) Middle Albian and continued until at least middle Late Albian. The faunal assemblages and lithotypes recognized in the cored section, and in the Pine and Peace rivers region, record the oscillatory nature of the transgressing sea.