Abstract: Regional Lower Mannville Lithofacies Computer Maps

Peter W. Hay

Regional lithofacies and porosity distribution within the lower Mannville Formation are summarized on five maps covering Alberta and northeast British Columbia. The 2,800 data points on each map were derived from the Canstrat digitized lithology file and were extracted and contoured using Amoco's Calgary and Tulsa computers. This information produced five significant maps which provide a regional framework for detailed facies studies and outline numerous porosity pinchouts.

1. The lower Mannville isopach shows thickest values flanking the mountain front and the Precambrian shield, thus identifying two major source areas. A third potential source is indicated by local thickenings along the paleotopographically high Aptian ridge.

2. The net-sandstone plus conglomerate isolith further identifies the mountain and the Precambrian shield sources. The Basal Quartz Bellshill Lake trend from the shield is clearly evident. Sandstone thickenings flanking the Aptian ridge result in part from prolonged erosion of sandy carbonate rocks forming the ridge.

3. A lower Mannville deltaic complex in northeast British Columbia is outlined by the net-coal isolith.

4. Numerous lower Mannville productive fields as well as many nonproductive isolated thickenings of porosity are pinpointed by the porosity isopach. Thick sands along the mountain front are generally tight.

5. The average clastic grain-size map shows increasing average grain size toward four source areas: the mountains, the Precambrian shield, "point sources" within the Aptian ridge, and an early Sweetgrass arch emergence.

AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC