Abstract

The highly explored Peace River Region and Elmworth Deep Gas Basin have yielded a large database of geophysical wireline well logs and cores. Recent exploration and research within the Trutch, Fort Nelson and the Liard Basin regions are providing a growing database of geological information, allowing for reliable correlations between these two regions, filling the gap between 55.5° N and 58° N. In northeastern British Columbia and northwestern Alberta, four major phases of marine inundation can be traced regionally outlining the geometries resulting from the presence of the foredeep to the west. These phases are referred to paleogeographically in ascending order, as the Moosebar/Clearwater Sea, Hulcross/ Harmon Sea, Joli Fou Seaway, and Mowry Sea. Within the western foredeep, Albian sedimentation to the northwest is preserved as distinct marine shales and mudstones of the Buckinghorse Formation. To the south, this shale package is interrupted by distinct stacked, coarsening-upward sandstone packages.

Along the eastern margin of the foredeep, regional wireline cross-sections are interpreted to show northward extensions of the Falher and Notikewin members, and the preservation of a Notikewin lowstand facies attached to the highstand. The highstand shoreline is interpreted to have been oriented in a southwest to northeast trend, with sandstone progradation occurring in a northwesterly direction. A core located within the lowstand deposit also provides evidence of tidally influenced incised valley fill deposits. The northward extent of the sandstone may be a result of proximity to the eastern flank of the foredeep, transport of sand north during storms over an overall shallow shelf setting and strong basin-wide currents allowing for the northward transport of these coarser deposits. In the southeast, as a result of erosion between the Paddy and Cadotte members, deposits of the Joli Fou Formation are not well preserved. In the north and west, however, an equivalent conformable suite of mudstones is thinning in an easterly direction. The equivalent Viking Formation marker bed in the foredeep can only be detected by a subtle resistivity change.