Abstract: Stratigraphic Correlations and Analogues Between the East Georges Bank Basin, Offshore Nova Scotia, and the Triassic and Jurassic Outcrops in the High Atlas Mountains, Morocco
Koning, Tako - Texaco Angola Inc.
Nova Scotia's offshore East Georges Bank Basin is located between the West Georges Bank Basin, located on the NE USA continental shelf, and the Scotian Shelf. Although the East Georges Bank Basin covers a large area (2.5 million acres) and offers promising hydrocarbon potential, the basin is undrilled due to a long term oil and gas exploration moratorium covering the entire basin. Pertinent regional well control is limited to two COST stratigraphic wells and eight oil and gas exploration wells drilled in the USA portion of the West Georges Bank Basin and two wells located on the Scotian Shelf. Since well control is absent within this basin, the geological interpretations are entirely based on regional geology and seismic-stratigraphic analysis of 16,000 km of seismic data covering the basin.
The East Georges Bank Basin formed during the Triassic concurrent with the opening of the North Atlantic. A prominent Paleozoic basement high, the Yarmouth Arch, separated the East Georges Bank Basin from the West Georges Bank Basin and had a dominant influence on sedimentation until it was buried by sediments during the Middle Jurassic. The seismic data provides evidence of alluvial fan deposits and lacustrine sediments similar to those which outcrop in the onshore Triassic rift basins extending from South Carolina to Nova Scotia. During the late Triassic, marine incursions into the basin resulted in extensive salt deposits in response to the restricted nature of the basin and climate. Further continental spreading during the early Jurassic was marked by the deposition of carbonates and evaporites followed by the deposition of Middle Jurassic shelf carbonates and deltaic sands. The carbonates include a trend of seismically-defined possible algal mounds or pinnacles reefs located on the seaward edge of the Yarmouth subplatform.
Seismic data including seismic interval velocities suggests that the structural and stratigraphic evolution of the East Georges Bank Basin is significantly different than the West Georges Bank Basin. Well data in the West Georges Bank Basin indicates that the Jurassic section is primarily carbonates. However, the Jurassic interval velocities in the East Georges Bank Basin are suggestive of a primarily clastic section.
Reconstruction of the Pangea landmass places the East Georges Bank Basin in juxtaposition to Morocco. In order to gain a better insight into the East Georges Bank Basin's stratigraphy, Triassic and Jurassic outcrop sections were visited via an AAPG sponsored field trip in the High Atlas Mountains of Central Morocco. Superbly exposed sections of Triassic red beds and Jurassic carbonates and turbidites were studied. Of special significance to the East Georges Bank Basin is an exhumed atoll with a rim of Jurassic patch and pinnacle reefs extending over a distance of some 30 km. This reef trend is similar to the interpreted reef trend along the Yarmouth subplatform of the East Georges Bank Basin which covers about 80 km.
AAPG Search and Discovery Article #90933©1998 ABGP/AAPG International Conference and Exhibition, Rio de Janeiro, Brazil