Mesozoic tectonic and stratigraphic evolution of the Orphan Basin, with special emphasis on regional correlations with Flemish Pass and Northern Jeanne d'Arc Basins, Grand Banks of Newfoundland

Gacal-İs̨ler,, Burcu (2009) Mesozoic tectonic and stratigraphic evolution of the Orphan Basin, with special emphasis on regional correlations with Flemish Pass and Northern Jeanne d'Arc Basins, Grand Banks of Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

The tectonic framework and depositional settings of the Orphan Basin are studied using ~25,000 km of 2-D seismic reflection profiles and stratigraphic data from nine key exploration wells. The evolution of the region is recorded in five seismic distinct stratigraphic units (Z, A, B, C, X), each separated from one another by widespread regional markers U1-U4, representing prominent unconformities. Exploration well data showed that Units Z, A, B, C and X are correlated with the Pre-Cambrian/Paleozoic basement, ?Triassic/Jurassic, Early Cretaceous, Late Cretaceous and Tertiary successions, respectively. Similarly, the well data showed that U1, U2, U3 and U4 markers are correlated with the Top Paleozoic, Top Jurassic, Mid-Cretaceous and Base Tertiary Unconformities, respectively. The well data further showed that the seismic Units A, B+C, and X are broadly correlated with three regional tectonic episodes, where each episode includes a period of extension, followed by a period of protracted uplift associated with sectoral break-up, and a period of sustained thermally-driven subsidence. -- On the basis of stratigraphic and structural architecture of the successions imaged between the Top Paleozoic Unconformity and the Base Tertiary Unconformity, the study area is divided into five tectonic provinces: the Western and Southwestern Basin Margin, the Eastern Basin Margin, the White Sail Fault Zone, the West Basin and Ridge Province, and the East Basin. The Bonavista and White Sail Fault Zones were developed during the ?Jurassic (may be as early as Triassic if evaporates are present in the Orphan Basin), as prominent basin-bounding faults. Several large faults paralleling the White Sail Fault Zone also developed during this time. The extensional tectonic activity continued in the study area throughout the Cretaceous, but slowly culminated in the late Cretaceous / Early Tertiary as indicated by the absence of growth strata within the Tertiary succession associated with the faults, and tip points of these faults being situated in the Early Tertiary successions. -- The seismic data documents that faults in the northern and northeastern segment of the Orphan Basin display greater growth, rotation and tilting of the mid-Late Cretaceous successions than those observed in the western and southern segment of the basin. These observations together with the large fan-shaped fault splays of the White Sail Fault Zone collectively suggest that the Flemish Cap probably experienced a progressive clockwise rotation of 25°-35° during the Late Jurassic - Late Cretaceous. This rotation and extrusion of the Flemish Cap is largely accommodated by the Cumberland Belt Fault Zone in the south and the Charlie Gibbs Transfer Zone in the north.

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