Structural Styles and Stratigraphy of Terra Nova Oil Field, Grand Banks

J. D. Dwyer, H. J. Welsink

Mesozoic evolution of the Grand Banks involved several episodes of crustal extension that created a suite of northeast-southwest-trending half-grabens. The dominant period of extension was late Callovian to Aptian, when the crust of the central Grand Banks failed along a gently dipping down-to-the-west shear zone. Listric basin-bounding faults sole at this detachment zone.

One of these faults, the Murre fault, bounds the very deep Jeanne d'Arc basin. Cross-basin transfer faults accommodated different amounts and rates of extension and resulted in the conspicuous offset pattern and funnel-shaped geometry of the Jeanne d'Arc basin. The Terra Nova oil field is located where basin-trending faults are intersected by a transfer fault.

The stratigraphy of the Terra Nova oil field is a direct response to this tectonic and structural framework. Subtle faulting associated with incipient rifting resulted in the deposition of oil-prone argillaceous limestones during the Oxfordian-early Kimmeridgian. During the late Kimmeridgian the climax of rifting occurred, which caused floods of coarse clastic material to be shed from the rift shoulders. These sands were deposited in a fan-delta system and form the major reservoir of the Terra Nova oil field. Dispersal patterns were controlled by the structural salient formed by the transfer fault. A depositional limit of the reservoir mirrors the transfer fault and comprises part of the oil-trapping mechanism of the field.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.