Postrift deformation of the Scotian basin, offshore Nova Scotia and Newfoundland, Canada

The Scotian basin is a postrift basin on the passive margin of eastern North America. Using 2D and 3D seismic data, located in the Laurentian and Penobscot study areas, respectively, I have identified three types of deformation affecting Cretaceous through Recent strata: reactivation of basement-involved faults during both extensional and contractional deformation, detached extension and shortening, and deformation associated with lithological changes; salt movement accompanied the first two types of deformation. Two angular unconformities bound the section, indicating two notable episodes of uplift and erosion first during the earliest Cretaceous and second during the late Cenozoic. An anomalous NW-trending anticline beneath the eastern Laurentian Channel resulted from reactivation of deep-seated faults. Faults with reverse separation formed beneath the anticline. Miocene channels are deflected from the anticline, whereas Pliocene-Pleistocene channels directly overlie the anticline, suggesting that the anticline was active during Miocene time. The anticline and subsidiary structures are subparallel to modeled seafloor displacement from the 1929 Grand Banks earthquake. The faults and folds indicate widespread, long-lived deformation. Extensional reactivation of deep-seated faults resulted in shallow faults with normal separation that were active from Cretaceous through middle Cenozoic time. During late Cenozoic time, deformation changed and was dominated by shortening that coincided with the formation of the late Cenozoic angular unconformity. The most recent phase of deformation, which produced the 1929 Grand Banks earthquake, involves NE-SW to NNW-SSE shortening. Faults associated with detached extension were active during the Early Cretaceous and again during the late Cenozoic (Miocene). Detached shortening, at least locally, occurred during Late Cretaceous time. In the Penobscot study area, faults have reverse separation at depth and normal separation at shallow levels. The faults had reverse separation during early Early Cretaceous time. An offset channel suggests that one fault had normal slip during Late Cretaceous through early Cenozoic time. Episodic normal faulting during Late Cretaceous time and polygonal faults with a preferred orientation indicate NW-SE extension during Late Cretaceous to early Cenozoic time. Polygonal faults, present in both study areas, resulted from deformation associated with lithological changes. They were active during Late Cretaceous to early Cenozoic time.

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