Western Newfoundland, Canada, a Lower Paleozoic Basin with Hydrocarbon Potential

Abstract

Western Newfoundland hosts an early Paleozoic passive margin that was destroyed by later convergence and is now preserved in a foreland fold and thrust belt. Autochthonous Cambrian-Ordovician carbonate and siliciclastic rift, shelf, and foreland basin cover sequences are structurally overlain by allochthonous comprising of coeval deep-water periplatform and oceanic sedimentary, volcanic, and ophiolitic rocks. Geologic relationships indicate that allochthonous deep-water sediments were partly emplaced above the autochthon by Late Ordovician Taconian orogenesis. Recent mapping of a post-Silurian, pre-Mississippian triangle zone in the offshore, and of an imbricated thrust shelf carbonates in the onshore indicates that the present disposition of lower Paleozoic rocks is the product of Acadian foreshortening of at least 100 km. The stratigraphy, geologic setting, and history of the lower Paleozoic rocks and the presence of oil shows in wells, seeps, and bitumin throughout the area mark western Newfoundland as a potential hydrocarbon basin similar to other lower Paleozoic examples dolomite reservoirs are common in the autochthon and occur locally in the allochthon. Source rocks occur in both the deep-water and foreland basin sequences. Allochthonous deep-water shales have total organic carbon values of up to 8.37%, whereas foreland basin black graptolitic shales range up to 2%. Pyrolysis datamore » and conodont color alteration indices document immature to mature thermal maturation in the southern part of the area and mature to overmature maturation in the northern part of the area.« less