Abstract

Devonian rocks underlie all of northeastern British Columbia east of the extensive mountain outcrop belt. The thickest development (6000-6500 feet), occurs in the northwest, the thinnest over the Peace River Arch in the southeast (450 feet).

The Devonian unconformably overlies rocks of Precambrian to Silurian age. The Middle and Upper Devonian are well represented; the Lower Devonian is more restricted in distribution and thickness.

Five map units are used to describe the geological history of the Devonian. Map Unit 1 includes Lower Devonian and Eifelian rocks and consists mainly of thick dolomites in the west and thin evaporites and dolomites in the east. Map Unit 2 (approximate Give-tian) shows a gross facies pattern of dolomite with evaporites in the southeast, passing to carbonates with reefs, and thence to shale and carbonate in the west and northwest.

Map Unit 3 consists of the Beaverhill Lake Shale. Map Unit 4 (approximate Frasnian Stage) unconformably overlies Map Units 2 and 3. It consists mainly of shale; a wedge of limestone occurs at the top of the unit in the east. Map Unit 5 (approximate Famennian) comprises a basal silty formation overlain in the east by limestone and in the west by limestone and shale.

Devonian rocks record a prolonged marine transgression reaching a maximum during the early Frasnian followed by a gradual regression during the late Devonian. Important erosional breaks occur near the Middle-Upper Devonian boundary and at the Devonian-Mississippian boundary.

The economic potential of the Devonian in British Columbia is considerable. To date exploration has concentrated on the hydrocarbon resources and has established major reserves of natural gas.