STRATIGRAPHY AND HYDROCARBON POTENTIAL OF CAMBRIAN STRATA, NORTHERN INTERIOR PLAINS, NORTHWEST-TERRITORIES

Detailed correlations within the Lower to Middle Cambrian succession ( Mount Clark, Mount Cap, Saline River and La Martre formations) of the Northern Interior Plains indicate the need to modify the existing stra tigraphic framework. The most important modification is the choice of a consistent and stratigraphically significant base to the Saline Rive r Formation. Correlation of this horizon indicates it is an unconformi ty. Within the Evaporite member of the Saline River Formation, basinwi de, shale-rich horizons are used to divide it into three informal unit s. Several structural and/or paleotopographic elements divide the basi n into a series of depressions and uplifts, the former acting as local depocentres and the latter as sills between the depressions. Early to Middle Cambrian deposition was in a semi-enclosed, epicontinental mar ine basin. Initial transgression resulted in the deposition of a varia bly thick blanket of marine sandstone (Mount Clark Formation) followed by lower energy deposition of clay- and carbonate-muds (Mount Cap For mation). Either uplift or sea-level drop resulted in the development o f an unconformity at the end of Mount Cap deposition. Subsequent depos ition of the Saline River Formation was dominated by more restricted m arine conditions and the development of extensive evaporite deposits. Gas and condensate have been recovered from sandstone reservoirs in th e Mount Clark Formation of the northern part of the basin, and bitumen is a common component of the Cambrian sandstones and along fractures in carbonate beds throughout the basin. Potential source rocks have be en identified in very thin, Gloeocapsomorpha prisca-like alginite-rich layers from the lower Mount Cap Formation of the northern areas of su bcrop. These potential source rocks indicate immature to mature levels of thermal alteration. Late Cretaceous to Early Tertiary compressiona l structures, with underlying precursor structures in Proterozoic rock s, remain the primary exploration target in the Colville Hills area, b ut potential stratigraphic traps in the Mount Clark sandstone are a fe asible alternative play type, especially updip closure against paleohi ghs.