About This Item
Share This Item
The Peace River arch is a pre-Devonian structure 250 miles long which was modified by post-Devonian tectonic events. It is situated in the west-central part of the Alberta basin in Western Canada.
The structure consists of Precambrian and Cambrian rocks which were tectonically elevated and formed an island in the Devonian seas. The island was enveloped in sedimentary rock by the close of Devonian time or very soon thereafter.
The arched area became slightly negative during Mississippian time and failure in the crestal part resulted in a horst and graben complex. The configurations oi deeply buried horizons were altered by these tectonic movements which depressed the pre-Devonian surface. A very moderate negative condition prevailed fn the area of the arch until about Middle Cretaceous time, after which the rate of subsidence was common to most of the Alberta basin.
The Laramide orogeny resulted in uplift and differential warping. The Alberta basin tilted westward and the arch formed a westward-plunging nose on the basement surface.
The present westward dip results in a number of large stratigraphic and structural traps along the east (updip) side of the arch. Major hydrocarbon accumulations were anticipated but only small pools have been found despite intensive search. The lack of major accumulations may be due to one of three factors or combinations of them: (1) a lack of source rocks surrounding the most important reservoir systems; (2) a loss of hydrocarbons up the slope of the island during a lengthy period of non-deposition, and (3) a lateral and vertical dispersal of hydrocarbons into numerous small pools in many reservoir systems and structural complexes.
End_of_Article - Last_Page 523------------