Depositional Architecture of Confined Meander Belt Deposits, Lower Cretaceous Grand Rapids Formation, east-central Alberta

Abstract

The Cretaceous Grand Rapids Formation in east-central Alberta is comprised ofprograding deltaic to marginal marine deposits incised by fluvial to marine-influenced fluvial bodies at several stratigraphic levels. Facies mapping and a high-resolution allostratigraphic framework are used to map the 3D distribution of marginal marine units and fluvial bodies. A confined fluvial meander belt in the Colony Allomember is studied in detail using a high-resolution data set of densely spaced wells and seismic time slices. Sediment distribution within the meander belt is particularly fine-grained (i.e., siltstone-dominated), despite indications that discharge was substantial due to the large scale of channels and point bars imaged in seismic data. The fine-grained character of the meander belt is likely a result of: (1) a propensity for muddy counter point bar preservation at the expense of sandy point bar deposits; and (2) limited supply of sand to the depositional system.