ABSTRACT: Paleoflow Directions of a Southern Alberta Fluvial Lobe within the Oldman Member, Upper Judith River Formation

EVANS, CURTIS, Calgary, Alberta, Canada

The Upper Cretaceous Judith River Formation of the Western Canada sedimentary basin is a mostly nonmarine sequence of fluvial sandstones and overbank mudstones deposited on a coastal plain exposed by the regression of the Wapiabi-Lea Park sea. Previous studies have shown the provenance of the sediments in this fluvial system to be in the Omineca Crystalline Belt in northern British Columbia. Paleoflow directions for the formation have been previously documented as being toward the southeast for most of the Alberta basin.

Paleoflow indicators were measured in southern Alberta, and they show northeast paleoflow directions for the Oldman Member in southern Alberta with a possible source in the southern Alberta and/or northern Montana Cordillera. The deposition of feldspathic, immature sandstones indicates a more proximal igneous or metamorphic source in the southern Cordillera, rather than in Northern British Columbia. An antecedent stream that originated in the southern Omineca Crystalline Belt and penetrated the Rockies is highly likely. The Southern Purcell Mountains contain plutonic, volcanic, and metamorphic rocks that have the appropriate mineralogy for the heavy mineral distribution recorded in the southern Alberta Plains.

The development of a large fluvial system with paleoflow toward the northeast, which was not interrupted by a trunk river system originating in the northwest, is postulated for most of the Oldman Member in southern Alberta.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)