Provenance of the Athabasca Oil Sands, Alberta, Canada: Reconstructing an Ancient Source-to-Sink System
Benyon, Christine S.; Leier, Andrew; Leckie, Dale; Webb, Andrew; Hubbard, Stephen M.; Gehrels, George
The Athabasca Oil Sands of northeastern Alberta represent one of the largest reserves of hydrocarbons in the world. Of these deposits, the Lower Cretaceous (Aptian) McMurray Formation is the principal reservoir sandstones in the region. Despite intense investigation, the origin and transport history of the sediment within the McMurray Formation remains poorly understood. Petrographic evidence suggests much of the sand in the McMurray Formation was derived from the nearby Canadian Shield, whereas early paleogeographic maps imply the sand was derived from a large south-to-north drainage network that extended from the southwestern U.S. to northern Alberta. Resolving these issues can help improve our understanding of the depositional history and better predict reservoir characteristics.
Nine sandstone samples from the McMurray Formation were analyzed using detrital zircon U-Pb geochronology to better understand the sandstone provenance of this key hydrocarbon unit. Preliminary results indicate three distinct detrital zircon signatures within the McMurray Formation. The first signature is characterized by zircons of Archean and Early Proterozoic age, which are interpreted as indicating a provenance associated with the nearby Canadian Shield. The second signature is characterized by zircons of Grenville (ca. 1000 Ma) and early Paleozoic age. This latter zircon population suggests an Appalachian source originally; however these zircons may be multi-cyclic, having been reworked from deposits in southern Canada or from the northern U.S. The third signature is dominated by relatively young zircons (<300 Ma) with a lesser population of Early Proterozoic ages, which are interpreted to indicate a Cordilleran provenance. These three signatures suggest a complex provenance history that evolved through time. First-order calculations based on fluvial channel dimensions and deposits provide important constraints on the location and extent of the paleo-watershed. Ongoing analyses will improve provenance reconstructions and provide a more refined sedimentary history.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013