Sedimentology of the Upper Crataceous (Turonian) Cardium Formation in Outcrop in Southern Alberta

Abstract

<p>Cardium Formation exposures in Alberta consist of vertically juxtaposed thickening- and coarsening-upward cycles. Shallow-marine deposits exhibiting hummocky cross-stratification (HCS) dominate cycles. Locally, cycles record a marine to non-marine transition; they are interpreted as the deposits of a prograding storm-dominated shoreline. Sands were introduced into the basin by storms, and were transported in the proximal offshore region by seostrophically balanced bottom flows. Sharp contacts between cycles represent transgression surfaces; they display erosionally based, laterally extensive marine conglomerates. Locally, erosional transgressions removed non-marine deposits from the cycle tops over extensive distances normal to shoreline. Conglomerates were transported during transgressions, accumulating within a "hydrodynamic shadow" over the drowned shoreface of the preceding regressive episode.</p> <p>A technique for paleohydraulic analysis of conglomeratic symmetrical ripples has been discussed, tested, and applied to Cardium occurrences; results suggest that associated examples of HCS were formed in the oscillatory-flow flat-bed field by previously unrecognized low-amplitude, three-dimensional orbital ripples.</p>