Geological comparison of the south Hopedale and west Orphan Basins, northwest Atlantic Margin

Stead, Jordan Elizabeth (2007) Geological comparison of the south Hopedale and west Orphan Basins, northwest Atlantic Margin. Masters thesis, Memorial University of Newfoundland.

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Abstract

The South Hopedale and West Orphan Basin developed concurrently during the Late Jurassic to Early Cretaceous rifting stage on the northwest Atlantic margin. These basins, and the intervening Paleozoic Cartwright Arch and St. Anthony Basin, were interpreted using 2D reflection seismic, borehole and potential fields data to compare stratigraphic and structural features along the margin, analyze the extension and basin evolution, and examine the petroleum prospectivity of the region. -- Mapping indicates that the Labrador synrift sequence thins seawards but extends past the slope break, and that the West Orphan synrift sequence becomes thicker and more structurally complex towards the east and south of the basin. A thick postrift sequence is evident along the entire Labrador margin and West Orphan Basin. In the South Hopedale Basin, a complex extensional postrift fault system is observed along the shelf break, and complimentary compressional features are observed downslope. This structural system was not evident in the West Orphan Basin, where the postrift sequence thins significantly sea wards. Comparisons of the postift seismic markers and sequences in both basins show many similarities. Arealy extensive, polygonally faulted sequences are present along the entire margin. -- Comparisons of the mapped extensional fault systems to analogue models of orthogonal, oblique and multi-phase rift systems indicate that the Hopedale Basin is characteristic of an orthogonal rift while the West Orphan Basin is typical of an oblique rift. Analysis of the extension along the margin suggests that higher stretching values occur in the West Orphan Basin, where there is significant variation of the postrift-to- synrift ratio across the seismic profiles. The extension values are lower in the South Hopedale Basin, where the postrift-to-synrift ratio is consistently high. -- The petroleum prospectivity of both regions is significant. The established source and reservoir bearing sequences in the Hopedale Basin were mapped onto the outer shelf and slope, where maturation is predicted to increase. The West Orphan Basin has no proven hydrocarbon accumulations, but the similarity of the stratigraphy to that of the Labrador Shelf in the northwest, and that of the producing Jeanne d'Arc Basin in the southeast suggest that the area has considerable potential. Numerous structural and startigraphic traps were mapped throughout both these regions.

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