The stratigraphy of the Pennsylvanian and Lower Permian Tobermory, Kananaskis and Johnston Canyon formations of the front ranges of the southern Canadian Rocky Mountains, Alberta and British Columbia, Canada.

摘要

Pennsylvanian and Permian rocks of the southern Canadian Rocky Mountains (Tyrwhitt, Storelk, Tobermory, Kananaskis, Johnston Canyon, and Ranger Canyon Formations) are composed of thin, mixed carbonate-siliciclastic units bounded by erosional unconformities that subdivide the succession into six sequences. These sequence-bounding unconformities are recognized in equivalent units of the Pennsylvanian to Permian Belloy Formation in the subsurface of the Peace River Basin. Deposition in both regions appears to have been influenced by an arid climate and occasional tectonic events. However, the environments of deposition and resultant lithofacies differ between chronologically equivalent outcrop and subsurface units impeding high resolution correlation. Nevertheless, the proposed stratigraphic model for the Pennsylvanian and Permian rocks of the southern Rocky Mountains assists in illuminating stratigraphic relationships within the Belloy Formation.; This study examines outcrop from four Pennsylvanian and Permian sequences which are exposed between Banff, Alberta and Fernie, British Columbia. Numerous exposures of these rocks occur in the Kananaskis Valley where they overlie Mississippian rocks and are overlain by siliciclastic deposits of the Triassic Sulphur Mountain Formation. Individual outcrop exposures of the Pennsylvanian and Permian in this study are up to 230 m thick and thin to the East. Based on these outcrop sections a model for and climate cyclothems is presented. These cyclothems are composed of a succession of marginal and shallow marine siliciclastic and carbonate sediment. Cyclicity is of a similar periodicity and scale as classic cyclothems of the American mid-continent.; Conodont biostratigraphy allowed for age assignment of individual formations. The Tobermory Formation is Bashkirian to Moscovian in age. The overlying Kananaskis Formation (Moscovian to Sakmarian) is here divided informally into upper and lower units, which are separated by an unconformity that spans the Pennsylvanian-Permian boundary. The Artinskian Johnston Canyon Formation overlies the upper Kananaskis, and the Roadian-Wordian Ranger Canyon Formation represents the youngest Permian rocks in the study area.