Geological Atlas of the Western Canada Sedimentary Basin - Chapter 6

Chapter 6
Protozoic and Lower Cambrian Strata of the Western Canada Sedimentary Basin

Authors:
F.J. Hein - The University of Calgary and Consultant, Calgary
M.E. McMechan - Geological Survey of Canada, Calgary

Additional Contributors:
J.D. Aitken - Retired, Denman Island, B.C.
W.J. Devlin - Exxon Production Research Co., Houston
E.W. Mountjoy - McGill University, Montreal
P.S. Simony - The University of Calgary, Calgary

Introduction

Proterozoic to Lower Cambrian strata of the Western Canada Sedimentary Basin are exposed within the Canadian Cordillera (Fig. 6.1). All exposures have been transported northeastward from their original site of deposition by structures that formed during Late Jurassic to Eocene deformation of the eastern Canadian Cordillera. This chapter deals with three major unconformity-bounded successions: Middle Proterozoic (~1.5 - 1.2 Ga), Upper Proterozoic (~0.78 - 0.54 Ga) and Lower Cambrian (0.54 - 0.53 Ga). Each succession is dominated by clastic strata and is notable for great thicknesses: up to 11 km for the Middle Proterozoic, 9 km for the Upper Proterozoic, and 4 km for the Lower Cambrian. Upper Proterozoic and Lower Cambrian strata form part of a narrow, sinuous belt of correlative rocks that extend for over 4000 km, from Alaska to northern Mexico (Stewart, 1972). Underlying Middle Proterozoic strata lack this longitudinal continuity (Fig. 6.1). These successions record multiple extension events in the early history of the western margin of the North American craton and the Western Canada Sedimentary Basin. In this chapter each succession (Middle Proterozoic, Upper Proterozoic, Lower Cambrian) are discussed separately.