Sedimentology and tectonic controls on the preservation of the middle triassic halfway formation, elmworth and wapiti fields, west central Alberta
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2009
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Abstract
The Middle Triassic Halfway Formation in west-central Alberta is interpreted as a series of prograding shoreface facies associations in a ramp setting within a progradational series of parasequence sets. These parasequence sets have been reworked syndepositionally by laterally discontinuous tidal inlet channels cutting perpendicular to the shoreline trend. During the course of this study 131 core from the Middle Triassic Halfway Formation were analyzed which have led to the documentation of ten lithofacies from the Halfway Formation. Depositional environment interpretations range from offshore marine to arid continental. From these ten lithofacies, five genetically related facies associations have been created by grouping together commonly occurring lithofacies. These facies associations include: distal shoreface and proximal shoreface siliciclastics, tidal inlet/channel bioclastic fill, continental evaporates, and biostrome carbonates. Major hydrocarbon exploration targets from this region include tidal inlet/channel fill as well as proximal shoreface sandstone. Evidence gathered in this study suggests a complex geological history to the region including multiple events of deposition, tectonism, and erosion prior to hydrocarbon emplacement. Extensive sedimentary structures indicative of seismic activity are observed in the study area suggesting that the Elmworth and Wapiti field areas were subjected to tectonic activity during or shortly after deposition of the Halfway Formation. This tectonic activity has complicated sequence stratigraphic correlations by creating over-thickened Halfway Formation sandstone intervals. This study has also documented the first Middle Triassic biostrome discovered in the subsurface of the Western Canada Sedimentary Basin. This biostrome consists primarily of terebratulid brachiopods and sedimentological interpretations suggest it was formed within the lower shoreface. If discovered to have undergone the ideal paragenesis, biostrome deposits such as documented in this study could become highly significant hydrocarbon reservoirs within the Western Canada Sedimentary Basin.
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Bibliography: p. 105-114
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Some pages are in colour
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Radomski, M. A. (2009). Sedimentology and tectonic controls on the preservation of the middle triassic halfway formation, elmworth and wapiti fields, west central Alberta (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/2708