Print this pageIntegrated Thermal History Analysis of the East MacKay I-77 Well, Central Mackenzie Valley, Northwest Territories, Canada: Insights from Multi-Kinetic Apatite Fission Track Thermochronology, Thermal Maturity, Shale Compaction and Modeling
Dale R. Issler1, Alexander M. Grist2, Laverne D.
Stasiuk1, and Art Stirrett3
1 Geological Survey of Canada (Calgary), Calgary, AB
2 Dalhousie University, Halifax, NS
3 Northrock
Resources Limited, Calgary, AB
The East MacKay I-77 well is located 80 km southeast of Norman Wells, within the Keele Tectonic Zone, a region with multiple phases of anomalous subsidence and uplift during the Phanerozoic. The well penetrates an Upper Cretaceous-Tertiary foreland basin succession that rests unconformably on Devonian strata. This profound unconformity represents 270 My of missing rock record; it developed during pre- and post- Albian time and displays a thermal maturity discontinuity (0.55 to 0.75%Ro). Organic-rich shales occur in the basal Upper Cretaceous Slater River and the Devonian Canol and Hare Indian formations. Two apatite fission track (FT) age populations (222 ± 22.5 Ma, 90 ± 6.1 Ma), defined on Cl content and having different thermal annealing properties, were recovered from an Upper Devonian sandstone.
Geologically-constrained inverse modeling of FT age and length data, incorporating multi-kinetic FT annealing, temperature, %Ro and stratigraphic constraints, yields Monte Carlo solutions that delimit time-temperature ranges for pre-Albian, Albian and post-Albian heating events. Forward burial/thermal modeling of %Ro data provides constraints on eroded sediment thicknesses and paleogeothermal gradients at times of maximum burial. Shale compaction trends are continuous across the unconformity. Data and model results imply that maximum temperatures and source rock maturation at East MacKay I-77 occurred during M. Triassic to E. Jurassic under an elevated geotherm; maximum burial occurred during the Tertiary under a geothermal gradient similar to the present. Although hydrocarbon generation pre-dates trap formation at East MacKay I-77, it is possible that deeper Tertiary burial re-activated Paleozoic source rocks elsewhere in the region.
AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005