About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

CSPG Special Publications


The Mesozoic of Middle North America: A Selection of Papers from the Symposium on the Mesozoic of Middle North America, Calgary, Alberta, Canada — Memoir 9, 1984
Pages 568-569
Symposium Abstracts

Structural Controls on Thermal Previous HitMaturationNext Hit as Determined from Coal Rank Studies, Rocky Mountain Foothills North of Grande Cache, Alberta: Abstract

W. D. Kalkreuth1, M. E. McMechan2


Mean maximum vitrinite reflectances (Romax) from Lower and Upper Cretaceous coals outline major variations in thermal Previous HitmaturationNext Hit across the Foothills north of Grande Cache, Alberta. In the west, the rank of coals exposed in the Lower Cretaceous Gething Formation increases from high-volatile A bituminous at their western limit of exposure, to low-volatile bituminous at their eastern limit. In the east, low-volatile bituminous coals and semi-anthracite occur in the Gething Formation in the subsurface, whereas high-volatile A bituminous coals, in the basal part of the Upper Cretaceous Wapiti Formation, are exposed at the surface. Nearly constant coalification gradients for the Gething Formation suggest that a uniform geothermal gradient occurred across the Foothills belt.

Time-depth coalification curves show that the eastward increase in coal rank across the Foothills can be explained by an eastward increase in time and depth of burial beneath Late Cretaceous-Tertiary foredeep deposits. In the west, Lower Cretaceous strata were uplifted 4 to 5 km during Late Cretaceous-Tertiary (Laramide) deformation. This uplift essentially terminated the thermal Previous HitmaturationNext Hit of these sediments. The eastward increase in rank within coals of the Gething Formation can be related to a west to east progression in the movement along the few major thrust faults that underlie the area. In the east, the Lower Cretaceous strata remained deeply buried and thermal Previous HitmaturationTop continued after Laramide deformation.

Gething strata are in the wet and dry gas zones in the east, but are in the oil and wet gas zones where exposed in the westernmost Foothills. Extrapolation of these data suggests that potential Mississippian and Triassic reservoir rocks should be in the wet gas zone beneath the westernmost Foothills and Front Ranges.


Acknowledgments and Associated Footnotes

1 Geological Survey of Canada, 3303 - 33rd Street N.W., Calgary, Alberta T2L 2A7

2 Geological Survey of Canada, 3303 - 33rd Street N.W., Calgary, Alberta T2L 2A7

Copyright © 2009 by the Canadian Society of Petroleum Geologists