University of SaskatchewanHARVEST
  • Login
  • Submit Your Work
  • About
    • About HARVEST
    • Guidelines
    • Browse
      • All of HARVEST
      • Communities & Collections
      • By Issue Date
      • Authors
      • Titles
      • Subjects
      • This Collection
      • By Issue Date
      • Authors
      • Titles
      • Subjects
    • My Account
      • Login
      JavaScript is disabled for your browser. Some features of this site may not work without it.
      View Item 
      • HARVEST
      • Electronic Theses and Dissertations
      • Graduate Theses and Dissertations
      • View Item
      • HARVEST
      • Electronic Theses and Dissertations
      • Graduate Theses and Dissertations
      • View Item

      Syndepositional tectonic activity in an epicontinental basin revealed by deformation of subaqueous carbonate laminites and evaporites : Red River strata (Upper Ordovician) of Southern Saskatchewan, Canada

      Thumbnail
      View/Open
      M.Sc.Thesis.pdf (3.853Mb)
      ElTakiPratt09Publication.pdf (1.663Mb)
      Date
      2010-10-17
      Author
      El Taki, Hussam
      Type
      Thesis
      Degree Level
      Masters
      Metadata
      Show full item record
      Abstract
      Late Ordovician Red River strata of southeastern Saskatchewan were deposited in a broad epicontinental sea. In the lower part, the Yeoman and Herald formations comprise two cycles of carbonate–evaporite sequences. Although these units possess an overall ‘layer-cake’ aspect, thickness variations especially in the Herald Formation show that accumulation was affected by syndepositional flexure, differential subsidence and displacement of fault-bounded blocks. The mainly laminated dolomudstones and anhydrites of the Lake Alma and Coronach members of the Herald Formation were deposited under relatively tranquil conditions. These units host different kinds of synsedimentary deformation features, interpreted to have been induced by earthquakes generated because of movements along basement faults thought to have been oriented orthogonally NE−SW and NW−SE. The low-energy environmental setting was conducive to preserving these features, referred to as ‘seismites’. The variety of seismites in the Herald Formation is related to the varying rheology of the carbonate or evaporite sediment, as well as shaking intensity. Brittle and quasi-brittle failure is represented by faults, microfaults, shear-vein arrays and pseudo-intraclastic breccias, mostly in dolomudstones which must have been stiff at the time of deformation. Plastic behaviour is recorded by soft-sediment deformation, comprising a family of features that includes loop bedding, folded laminae and convolute bedding. Indeed, these structures in enterolithic anhydrite are more reasonably interpreted as due to deformation than crystal growth, volume expansion and displacement, the more usual explanations. Sediment shrinkage and concomitant fluidization are recorded by dikelets containing injected carbonate mud or granular gypsum, the latter now preserved as anhydrite. Evidence for wholesale liquefaction, however, was not observed. These rheological differences were caused by the primary nature of the sediment plus modifications due to early diagenesis and burial confinement. Shaking intensity is difficult to gauge, but it is presumed that a minimum of VI on the modified Mercalli scale was required to produce these features. Consequently, shaking of lesser magnitude was probably not recorded. The geographic distribution of seismites should reflect the location of basement faults presumed to have been active during deposition, and indeed there is a concentration adjacent to the known location of syndepositonal fault lineaments. In addition, the stratigraphic distribution of seismites records higher frequencies of activity of these same faults. These distributions show that earthquake-induced ground motion was common during deposition of the Lake Alma Member in southeastern Saskatchewan but less so during deposition of the Coronach Member. Seismites serve as proxies for the activity of relatively nearby syndepositional faults making up the tectonic fabric of sedimentary basins. They also point to basement features that, if re-activated, can induce fracture porosity or influence subsurface fluid flow. Syndepositional tectonism undoubtedly had a much more profound influence on many successions than is presently accepted, and its effects are more widespread than currently appreciated.
      Degree
      Master of Science (M.Sc.)
      Department
      Geological Sciences
      Program
      Geological Sciences
      Supervisor
      Pratt, Brian R.
      Committee
      Robertson, Elizabeth; Merriam, Jim; Buatois, Luis
      Copyright Date
      October 2010
      URI
      http://hdl.handle.net/10388/etd-10252010-131133
      Subject
      differential subsidence.
      basement faulting
      seismite
      synsedimentary deformation
      anhydrite
      dolostone
      Red River
      Upper Ordovician
      Williston Basin
      Collections
      • Graduate Theses and Dissertations
      University of Saskatchewan

      University Library

      © University of Saskatchewan
      Contact Us | Disclaimer | Privacy