the stratigraphy and structural history of the mesozoic and cenozoic ...

Abstract
The continental shelf and slope of Nova Scotia is underlain by a number of
interconnected rift sub-basins that collectively form the Scotian Basin. Petroleum
exploration companies have been moderately successful on the shelf region of the basin,
close to Sable Island, where several significant hydrocarbon discoveries have lead to the
development of the Sable Project. This success has sparked interest in exploration of the
adjacent frontier slope region within water depths between 200 and 2500m. However, the
Scotian Slope Basin has been the focus of only limited regional geologic studies. Present
accounts of the slope are largely extrapolated from shelf descriptions and/or modeled
after play types and depositional systems typically associated with deep water exploration
in other Atlantic margin areas. A discrete study area was defined for this project within
the central slope region approximately 125 kilometres southwest of Sable Island. The
area is approximately 120 square kilometres and contains five of the ten Scotian Slope
exploration wells, three shelf wells and 4 500 kilometres of 2D seismic data.
Scotian Basin development commenced in the Late Triassic - Early Jurassic with
rifting of the Pangean Supercontinent and opening of the Atlantic Ocean. Red bed and
evaporate deposition characterized the rift phase, while the drift phase was characterized
by clastic progradational with periods of carbonate deposition. A prominent carbonate
bank developed in the western part of the basin during the Late Jurassic, the eastern
extent of which was limited by a Late Jurassic - Early Cretaceous Sable Delta. As relative
sea level rose throughout the Late Cretaceous and Tertiary major transgressive sequences
were deposited. This overall transgression was punctuated by major sea level drops
resulting in the deposition of regressive lowstand sequences partially comprising turbidite
deposits.
Seismic stratigraphic analysis of the study area identified ten major sequence
boundaries on the basis of reflection character and termination patterns. The sequence
boundaries divide the Mesozoic through Cenozoic Scotian Slope Basin fill into nine
depositional sequences. There are major changes in depositional style and thickness
distribution patterns of the depositional sequence through time. Depositional patterns are
closely linked to the tectonic, structural and halotectonic evolution of the basin.
Five fault families were defined within the study on the basis of their regionality,
duration of movement and depths of detachment; the Slope Basin-Bounding Fault
Family, the Basement-Involved Fault Family, the Listric Growth Fault Family, the Major
and Minor Sedimentary Fault Family and the Halokinetically Induced Fault Family. The
existence of a sixth fault family, the Transfer Fault Family, is implied by local structural
and stratigraphic architecture, however, the signature of this potential transfer fault is not
clear enough on the available seismic data to allow for confident mapping.
The complete spectrum of salt structures typical of passive margins has been
identified and mapped within the study area. Five halotectonic structural associations
with variable areal distributions have been identified. These associations are: the Trough
and Swell Association, the Intra-Salt Detachment Association, the Diapiric Association,
the Secondary Weld Association, and the Allochthonous Salt Association.
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