John Taylor, Department of Geoscience, coauthored an article in the Journal of Sedimentary Research that provides a new, unconventional interpretation of small (1-2m), shale-based and limestone-capped sedimentary cycles in rocks of Cambrian age in the Rocky Mountain and northern mid-continent regions as the products of short-term rises in sea level.
The paper challenges the long-standing and widely accepted view that such mixed “siliciclastic-carbonate” cycles originated in the same way as cycles of similar size and age in pure limestone successions (without shale), which formed by progressive shallowing brought about either by falling sea level or accumulation of sediment upward toward the ocean’s surface over tens of thousands of years. The new model, which attributes the upward change from shale to limestone within a mixed cycle to a reduction in mud supplied to the ocean by rivers affected by rising sea level and/or climate change, is based on data collected over more than a decade by Taylor’s research group in Montana, Wyoming, Minnesota, and Iowa.
Myrow, P.M., Taylor, J.F., Runkel, A.C., and Ripperdan, R.L., 2012, Mixed siliciclastic-carbonate upward-deepening cycles of the upper Cambrian inner detrital belt of Laurentia: Journal of Sedimentary Research, v. 82, p. 216-231. Abstract