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Sedimentology and Stratigraphy of the Upper Cretaceous Milk River Formation and Alderson Member (Lea Park Formation) in Southeast Alberta, Canada

  • Author / Creator
    Cowper, Anders WS
  • The Upper Cretaceous Milk River Formation-Lower Alderson Member zone in Southeast Alberta records deposition of a fine-grained siliciclastic delta-shoreface on the western margin of the Western Interior Seaway punctuated by significant episodes of shoreline transgression and regression. The variability of the internal stratigraphy of the Alderson-Milk River zone can be attributed to high-frequency transgressive-regressive cycles resulting from accretionary tectonics, which in turn caused fluctuations in available accommodation space. This vertical variability of relative sea level led to large lateral variability of the palaeoshoreline position in the Alderson-Milk River zone, which was exacerbated by a very low angle of subaqueous depositional dip which can be attributed to the fine-grained nature of the shoreline characterized by clay to very fine-grained sand. The goals of this project were: 1) to utilize the high density of wells and well data available in the study area to build a high-resolution sequence stratigraphic interpretation of the Alderson-Milk River zone; 2) to integrate this sequence stratigraphic framework with the ichnology and sedimentology of core in the study area to assess facies variability and 3) to provide a qualitative assessment as to the implications of the findings of this study for the exploration and production of hydrocarbons . In this study, petrophysical well logs and drill core from the study area within Townships 10-21, and Ranges 1-15W4M were used.
    This study’s findings are as follows. 1) The Milk River-Alderson zone contains alternating highstand, lowstand and transgressive systems tracts resulting in net shoreface/deltaic sand deposition focusing in the southwest and northeast regions of the study area with a ~200km-wide bypass region in-between. 2) Four cycles of fall and rise in relative sea level of tens of metres occurred. 3) Lowstand shoreline-proximal facies identified by previous authors in the Alderson Member in Saskatchewan correlate to subaerial unconformities overprinted by transgressive ravinement surfaces within this study area. 4) Sedimentary facies in core display varying degrees of moderate to strong storm influence in prodeltaic settings. 5) Shoreline-proximal sedimentary facies within most of the study area have largely been removed by successive unconformities.

  • Subjects / Keywords
  • Graduation date
    Fall 2023
  • Type of Item
    Thesis
  • Degree
    Master of Science
  • DOI
    https://doi.org/10.7939/r3-rq34-4219
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.