Geology Talk

Wed., Mar. 27, 2019 4:00 p.m. - Wed., Mar. 27, 2019 5:00 p.m.

Location: Classroom Building 130

Presenter: Ms. Yuting Zhang, MSc. Student in the Department of Geology at the University of Regina

Topic: Characterising the X-Bentonite of the lower Colorado Group in Southwestern Saskatchewan through petrology and mineralogical analysis

Abstract:Bentonite is the term given to thin, laterally persistent, clay-rich rock, thought to represent altered volcanic ash layers, deposited within sedimentary sequences. Studies of these units may provide an important stratigraphic horizon used to aid correlation of geological strata across large distances.

As a way of expanding upon existing methods of stratigraphy and correlation across a basin or greater distances, our studies of bentonite aim to rigorously test and constrain how bentonite may play an important role in lithostragraphic analysis. Within each ash layer is the potential to date or identify key horizons from single or a series of volcanic eruptions and link various rock units found throughout strata across Saskatchewan, and beyond.

In this research, the X-bentonite is referred to as one of the most widespread bentonite layers accumulated within the Belle Fourche and second White Speck formations in Saskatchewan. It is present across much of Alberta as well. We document and sample the occurrence of fresh-to-altered volcanic ash beds identified as X-bentonite, basing our studies on existing geophysical well log data and cored sedimentary sequences across the southern part of Saskatchewan. To characterise and identify specific eruption horizons, we determine the mineralogy (primary and alteration), as well as unique characteristics of individual bentonite, including those thought to be the X-bentonite units through a combination of petrography, scanning electron microscopy/energy-dispersive spectrometry (SEM-EDS), cathodoluminescence and X-ray diffractometry (XRD). This research will also help us to understand the geological history of Saskatchewan - in strengthening our knowledge of past volcanic eruptions as recorded during the Cretaceous.