Geochronology of reworked ash and its implications for accommodation space variations in distal foreland basins, McMurray Formation, Alberta, Canada

A bentonite bed consisting of reworked volcanic ash from the Barremian to Aptian lower McMurray Formation is dated using chemical abrasion thermal ionization mass spectrometry (CA-TIMS) on zircon. The bentonite bed is from a cored interval in the McKay Paleovalley in the northern Athabasca Oil Sands Region of Alberta, Canada. Deposition of the lower McMurray Formation took place in the distal portion of the Western Canada Sedimentary Basin early in the Cretaceous-to-Paleocene phase of widespread contractional deformation in the Canadian Cordillera. A 30 g sample of volcanic ash yielded >10,000 very small (