Magnetostratigraphic and palynostratigraphic correlation of late Campanian to early Maastrichtian strata of the Bearpaw and Horseshoe Canyon formations between the CPOG Strathmore corehole and the Red Deer Valley section, Alberta, Canada

Abstract

Abstract The Horseshoe Canyon and Bearpaw formations in the Canadian Pacific Oil and Gas Strathmore (CPOG) cored well (7-12-25-25W4M) in southern Alberta were sampled for magnetostratigraphy and palynostratigraphy. The studied interval begins in the continental upper Horseshoe Canyon Formation (early Maastrichtian) and continues to the base of the marine Bearpaw Shale (late Campanian) encompassing 358 m. A total of 152 horizons were sampled for magnetostratigraphy, and 48 horizons for palynostratigraphy. Four magnetozones (31r, 32n, 32r and 33n), 26 magnetosubzones and 8 cryptozones, a subdivision of a subzone, were identified. Most of the subzones had been previously identified in the Red Deer Valley outcrops. Magnetozone 32n in the CPOG core is only 70 per cent as thick as in the Red Deer Valley. Most of this difference occurs within the interval of coals 1 to 9 of the Red Deer Valley. The palynomorphs provide important information on the ranges of a number of key species that allow comparisons to other equivalent age sites in southern Alberta. These ranges indicate that the top of the CPOG Strathmore well is considerably younger than the top of Castor well as documented in Lerbekmo et al. (2003). The palynological results support the conclusions arrived at during the paleomagnetostratigraphic studies. The paleoecological inferences show similar oscillating marine and nonmarine conditions within the core developed by previous studies of the cored interval between the top of the Dinosaur Park and basal Horseshoe Canyon formations (Wall et al., 1971; Hills & Levinson, 1975).