The effects of reactivating basement structure on the overlying devonian sedimentary cover: selected case examples
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2006
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Abstract
Five effects of reactivated basement structure are proposed for the Devonian strata of the Western Canada Sedimentary Basin: Precambrian topography and structural heredity, modification of systems tracts, synsedimentary deformation structures, modification of preservational geometries and tectonic diagenesis. Significant basement structures have been identified in the Strachan area of west-central Alberta and the Buffalo Lake - Red Deer River area of east-central Alberta, through an integration of drill core data, isotope data, high resolution aeromagnetic data, aerial photographs and reflection seismic data. These structures, which include near-vertical mfaults bounding fault blocks, synforms and antiforms, have been reactivated through time in response to both far-field and intraplate stresses. To substantiate the structural interpretation, a key lithological marker bed has been identified in the cored Devonian units of the Strachan area; this unique chemical laminite unit was originally flat-lying and of broad areal extent. This unit now shows substantial vertical offset (298m) between wells, and has been identified in wells as far apart as 50 km. Brittle deformation features observed in Frasnian and Famennian aged rocks (Leduc to Stettler formations) include shear fractures, tension gashes and brecciation. Fractures have commonly undergone solution-enhancement and contribute substantially to reservoir porosity and permeability. Fracture type and density vary with proximity to the large basement structures, as do the occurrence of brecciated intervals that may function as sealing units. Frasnian subsurface units are compared to the Frasnian Cairn Formation exposed in upper portions of the avalanche chutes south of Canmore, Alberta in the Canadian Rocky Mountains. The Westem Canada Sedimentary Basin is structured; this has affected the rocks through geological time. Many carbonate features previously identified as biologic "reefs" are actually structural preservational remnants. This research will enhance reservoir characterization models as well as contribute to the elucidation of the structural history of the Westem Canada Sedimentary Basin.
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Bibliography: p. 297-326
Some pages are in colour.
Some pages are in colour.
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Greggs, D. H. (2006). The effects of reactivating basement structure on the overlying devonian sedimentary cover: selected case examples (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/315