Crustal structure and formation of the southeast Newfoundland continental margin

Solvason, Krista (2006) Crustal structure and formation of the southeast Newfoundland continental margin. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The discrepancy in the correlation of lithostratigraphy and seismic stratigraphy ofthe B Marker (limestone) Member on the eastem flank ofthe Hibemia oilfield is studied using available 3d seismic profiles and the log data fi-om 16 wells across the Jeanne d'Arc Basin. Unlike the previous studies which suggested that the B Marker was deposited as a time synchronous lithology across basin, detailed seismic stratigraphic and well analysis revealed that the marker was in fact deposited as a mildly diachronous unit. Four seismic traces (S1-S4) are recognized within the stratigraphic range ofthe proposed B Marker seismic event. A Carbonate Ramp Facies Model is proposed, incorporating these traces, for the basin-wide sedimentation ofthe B Marker which explains in a precise manner, the notable lithological variations ofthe marker in various exploration wells across the Jeanne d'Arc Basin. The B Marker was deposited during a relative rise of base level within the basin, coincident with a rise of global sea level during the Valanginian. This deposition is summarized by four discrete events (S1-S4). S1 marks the end of a phase of regression in the basin, and beginning of a transgressive phase of marine deposition. Limestone deposited during S1 was confined to a narrow E-W trending belt in the northem portion ofthe basin. During S2 landward migration ofthe shoreline southward, caused the deposition of shale over a wider E-W trending belt of limestone in the north. During S3 a very broad E-W trending belt of oolitic limestone blanketed the southem shallow shelf, and shingled above thin-bedded limestones (in S1 and S2). This geometry is interpreted as a subtle depositional hinge zone, which migrated south because ofthe stick slip on a master fault and uplift on stmctural culminations in the southem areas ofthe basin. This resulted in the lateral gradation of B Marker limestone into sandstone fiirther north, during ensuing transgression fi*om S1 to S3. S4 marks the peak of transgression within the basin, and in the widest coverage ofthe deeper shelf across basin.

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