MICROFACIES AND TRACE ELEMENT VARIATION ACROSS THE FRASNIAN PUNCTATA EVENT WITHIN THE BEAR BILTMORE DRILL CORE (ALBERTA, CANADA)
Microfacies investigation and major and trace element measurement by XRF focused on understanding changes in sedimentation over 150ft of a single Frasnian section from northeastern Alberta. Unlike previously-studied Frasnian sections from western Canada, samples from the Bear Biltmore core (7-11-87-17W4) provide insight into more proximal reef to lower slope environments. Samples cover the middle to upper Frasnian within the Duvernay and Cooking Lake formations, including the globally recognized punctata carbon isotope excursion.
Results show a transition from high reef influence to low reef influence, an increase in terrigenous input, and a deepening trend. In the lower part of the section, rounded to subangular, unlaminated reef-derived bioclastic wackestones to floatstones were deposited in a chaotic ramp environment. The section grades into a calm microbially-dominated ramp environment, concurrent with an increases in terrigenous input, primary productivity, and bottom water anoxia. After a brief change to primarily argillaceous sedimentation, the top of the section consists of largely unlaminated calcareous mudstone. While terrigenous input decreases, it does not return to the same low as at the start of the section.