Alexander M. Grist
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M. Sc. Thesis
Provenance and Thermal History of Detrital Sandstones of the Scotian Basin, Offshore Nova Scotia, using the Apatite Fission Track and 40Ar/39Ar Methods
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Apatite fission track analysis and 40Ar/39Ar age spectrum analysis have been carried out on sandstone drillcores taken at depths of 2 to 5 km from 9 hydrocarbon exploration wells in the Scotian Basin. K-feldspar argon spectra from the Early Cretaceous Missisauga and Logan Canyon Formations, which are unaffected by present-day burial heating at depths of less than 4 km, give mainly Precambrian ages (800-1000 Ma), and are similar to spectra from the Grenville Province of the Canadian Shield. K-feldspar and muscovite argon spectra from the Jurassic Mohican Formation give mainly late Paleozoic ages (250-350 Ma), and are similar to spectra from plutons on the Nova Scotian mainland. Muscovite argon spectra from the Missisauga Formation give Cambrian-Carboniferous ages, indicating that the sources of K-feldspar and muscovite had quite different thermal histories. At depths of greater than 4 km K-feldspar argon diffusion is apparent, and estimates of argon loss range from 1 or 2 to over 30 percent.
Apatite fission track ages are generally younger than stratigraphic ages, and tend to zero at a depth of 4 km (corresponding to formation temperatures of approximately 125oC). Fission tracks in samples from the Mic Mac J-77 and Erie D-26 wells are more annealed than present-day formation temperatures would predict, and are interpreted to have been affected by warm convecting fluids subsequent to deposition.
The provenance data are used to explain the deposition of the Mohican Formation in terms of a model of simple flank uplift and erosion of Acadian-age sources on the Nova Scotian mainland. The deposition of the Missisauga Formation can be approximated by a more complex model of an extensive fluviodeltaic system that combines sediments from at least two sources. K-feldspars are dominantly derived from the Canadian Shield, but the micas are derived from the Avalon Uplift, south of Newfoundland.
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Pages: 213
Supervisor: Peter Reynolds