Stratigraphy and palynology of the Cretaceous Colorado Group and Lea Park Formation at Cold Lake, Alberta, Canada

Abstract

ABSTRACT Stratigraphic research of the Colorado Group at Cold Lake, Alberta, has generally been assumed to be of secondary importance to that of the underlying Grand Rapids and Clearwater formations and of their significant volumes of bitumen. However, recent oil field development has required the geomechanical testing of the overlying shales. Using palynology, it has been found that the age of the group ranges from the late middle Albian to Santonian/Campanian and that the uppermost shales are part of the Lea Park Formation. Within the Colorado Group, six formations and an undefined unit can be resolved on logs and, in part, with palynomorphs. The basal contact of the overlying Lea Park Formation can be defined using logs but not the top because the overlying log signatures of the Cenozoic tills are very similar. There are areas within the Cold Lake region that contain evidence of post-Cretaceous erosion of the Lea Park Formation and the top two units of the Colorado Group, but this erosion and subsequent glaciogenic thrusting does not affect lower stratigraphic intervals in the study area.