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The AAPG/Datapages Combined Publications Database

CSPG Special Publications

Abstract


Sedimentary Basins and Basin-Forming Mechanisms — Memoir 12, 1987
Pages 117-146
Extensional Basins

Tectonic and Structural Framework of the Northeast Newfoundland Continental Margin

M. E. Enachescu

Abstract

The northeastern Newfoundland continental margin off the east coast of Canada is primarily an intracontinental failed rift arm that was subjected to severe extension in the Mesozoic, followed by subsidence in the Late Cretaceous and Tertiary.

The basement, consisting of Precambrian metamorphic rocks, Paleozoic metasediments and pre-rift igneous rocks, underwent extensive block faulting and erosion during the onset of rifting. The complete basinal sedimentary sequence includes: 1) extensional stage sedimentary rocks, represented by an Upper Triassic-Lower Jurassic syn-rift section, overlain by Lower Jurassic-Lower Cretaceous failed rift deposits; 2) thermal subsidence stage sedimentary rocks, represented by uniform Upper Cretaceous and Tertiary marine deposits. The maximum thickness of sediments of over 20 km occurs in the Jeanne d’Arc Basin, immediately east of the Hibernia oil field.

Development of the extensional terrain off northeast Newfoundland, initially took place on an Upper Triassic basement fault, that extends deep into the crust and underlies most of the Grand Banks area. This down-to-the-east fault (Murre/Mercury) and its associated listric synthetic and antithetic faults, are responsible for the creation of half-grabens and ridges on a regional scale, and folds, reverse drag features, rollovers and tilted blocks on a local scale.

The intricate contemporary distribution of the structural provinces and tectonic elements is the result of multiphase lithospheric extension along rotational listric faults, coupled with offsets of crustal blocks across transfer faults. Both phenomena were coeval with various stages of the North Atlantic opening and fragmentation. During the Mesozoic, both basement and sedimentary infill were subjected to successive extensional episodes associated with: a) the Tethyan rift (Late Triassic-Early Jurassic); b) the North Atlantic rift and separation (Late Jurassic-Early Cretaceous); and c) the Labrador- Greenland rifting (Middle-Late Cretaceous). Additional local structural and depositional complications were triggered by the halokinesis and extensional halotectonics of the Argo Formation.

The areas that have the greatest hydrocarbon potential are confined to basins in which the first two Mesozoic rifting events were superimposed and succeeded by a significant thermal subsidence stage. In these areas, several major oil and gas accumulations have been discovered in Upper Jurassic and Lower Cretaceous clastics of the extensional stage sedimentary sequence.


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