Summary of the Statherian-Calymmian paleogeography of northwestern Laurentia

Abstract

The ca. 1.75 to 1.27 Ga Hornby Bay intracontinental basin, in northwestern Canada, includes the Big Bear, Mountain Lake, and Dismal Lakes groups. This paper investigates the original depositional environments, paleogeography, and architecture of these groups and how they correlate in time and space. The Big Bear group comprises mainly immature clastic rocks deposited by high-energy rivers, the overlying Mountain Lake group was deposited by westerly flowing rivers over a much broader region, and, following tectonic uplift and erosion, basal clastic rocks of the Dismal Lakes Group were deposited in fluvial and then shallow-marine to paralic environments. Detrital zircon geochronology of sandstone units from the Mountain Lake group of Hornby Bay Basin and Wernecke Supergroup in the Wernecke Mountains supports their correlation and the conclusion that they represent the terrestrial and marine components, respectively, of a west-facing, passive-margin clastic wedge that evolved to a stable carbonate platform. These relationships imply further westward extension of a continental drainage system.