Source and Depositional Environments of the Moose Channel Formation, Northwest Territories

Abstract

ABSTRACT The Moose Channel Formation of the Fish River area, Northwest Territories, comprises over 8200 ft of clastic rocks. The strata, of Maestrichtian-Paleocene age, are genetically equivalent to much of the thick clastic section underlying the Mackenzie Delta. The sandstones in the Moose Channel Formation are mineralogically and texturally immature. An abundance of feldspars, chert grains, and sedimentary and volcanic rock fragments indicates granitic, sedimentary and volcanic source terranes. The Old Crow granites and the volcanic rocks of the British Mountains are possible sources of the igneous clasts. Many of the sedimentary rock fragments are assumed to have been derived from the Richardson Mountains south of the study area. Paleocurrent measurements show that northerly and easterly transport directions prevailed during deposition of the Moose Channel clastics. Grain-size analyses of 125 sandstone samples indicate that unidirectional current energy and gravitational energy were the two basic kinds of energy responsible for deposition of most of the sandstones. These two energy types are compatible with fluvial depositional processes. The Moose Channel Formation has been divided into five units after Young (1971, 1972). The depositional environment of each unit has been interpreted as follows: Unit 1, the oldest, is a regressive sequence containing prodelta and braided-stream deposits. Unit 2, a transgressive sequence, contains prodelta deposits grading upwards into nearshore marine silty shale and fine-grained sandstone. Unit 3, dominantly sandstone, is interpreted as fluvial deposits. Unit 4 is interpreted as a transitional marine-nonmarine delta-plain complex. The youngest strata, in Unit 5, are interpreted as nearsource channel and overbank deposits. An analogy is drawn between the depositional settings of these units and those of the Wilcox Group of Texas (Fisher and McGowen, 1969).