Cretaceous stratigraphy and basement influences, Peace River Arch region, Western Canada Sedimentary Basin

Geophysical data, including data from well logs (GR, SP,resistivity, sonic), seismic reflection (PRAISE) and aeromagnetic anomaly (Alberta Basement Transects), together with data from the Geological Atlas and SAMS databases (GSC-Calgary), were used to investigate Phanerozoic formations in the Peace River Arch (PRA) region and their possible relationship to basement features. Detailed stratigraphic correlations in the Cretaceous section were made on the southeast flank of the PRA (23 cross sections, 719 wells, 73 surfaces). More than 100 isopach and structural maps were constructed for the defined Cretaceous stratigraphic intervals.; Many formation boundaries in the Cretaceous appear to be time transgressive surfaces. Three major stratal reorientations occurred during Cretaceous time. Repeated, abrupt, ∼90° angle changes in stratal orientation were influenced by PRA collapse and tectonic loading (convergence of plate boundaries and accretion of terranes) on the western margin.; Three different stacking processes of sediments (linear progradation of elongate zones, differential subsidence and aggradation) occurred in the Cretaceous, and appear to have been controlled by changes in the regional stress field during Cretaceous time. Linear shifting of elongate zones is interpreted to have occurred when lateral compression was strong; differential subsidence of blocks is believed to have occurred when lateral compression was weak; and aggradation developed probably when lateral compression was moderate.; Long acting basement faults are developed in the PRA region. These faults either trend NW-SE parallel to the short axis of the PRA or the Rocky Mountain deformation front, or NE-SW (NEE-SWW), parallel to the long axis of the PRA. Throughout Phanerozoic time, these faults are interpreted to have played important roles in relieving intra-plate stresses, shaping subsidence processes, and affecting local sediment accumulations. Reverse motion on faults has been observed in the Arch region.; Five stages of development are recognized during PRA evolution. (1) The Arch remained high from Cambrian to Early Devonian time, and this was related to a much broader regional uplift. (2) The Arch was subsiding from Middle Devonian to Permian time. Subsidence rate was accelerated from the Middle to Late Devonian, reached its peak in Wabamun time, and decreased from the Carboniferous to Permian. (3) The long subsidence history of the PRA was interrupted by Mesozoic convergence events on the western margin. Depositional processes in the Arch region were dominated by convergence events from Jurassic to Early Cretaceous Aptian time. (4) Collapse of the PRA occurred during Early Cretaceous Albian time when the effect from early convergence events waned. (5) Subsequent convergence events dominated the PRA region after the Albian and initiated Arch uplift in late Turonian time (Cardium), and the final uplift began in the latest Cretaceous.