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Facies and Paleoenvironments of Campanian Basal Belly River Sands, Southern Alberta, Canada: A Case Study Based on Multidisciplined Approach Using Both Conventional Sedimentology and Palynofacies Synthesis

Hassan Sabry

Basal Belly River sands are not a single, continuous body but are composed of many separate bodies of sand occupying slightly different stratigraphic positions. The shape of the Belly River Formation, its internal geometry, and its lithology fit well with the clastic wedge association of deltaic sediments. The textural and mineralogical immaturity of most of the Belly River sediments indicates rapid deposition, also characteristic of deltaic deposits.

A detailed sedimentologic and palynofacies investigation of over 2,930 ft of core from several wells in southern Alberta has led to the recognition of several distinct lithofacies. The lithofacies of the subaqueous part of the delta are (1) nearshore marine bar and interbar marine facies, (2) pro-delta marine shales and siltstones, and (3) distal and proximal delta front sand facies. The subaerial part of the delta and interdeltaic shoreline sediments consists of 15 lithofacies that can be grouped as follows: estuarine distributary channel; barrier bar; barrier face and back barrier tidal channel; subtidal sand and shale-sand channels and flats; peat swamp; transgressive tidal sand ridges; and upper delta plain/alluvial meandering rivers and overbank complexes.

Best reservoir developments are found in barrier bar, transgressive tidal sand ridges, subtidal channels, and point bar facies. The Basal Belly River sands of prograding deltaic origin experienced episodes of modification from an early river-dominated delta to a tidally dominated one later. This is evident from the paleogeography, geometry, continuity, and internal characteristics of the Basal Belly River sand bodies.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.