The Mesozoic Orpheus rift basin, offshore Nova Scotia and Newfoundland, Canada

• Main Author: Zulfitriadi, Zulfitriadi
• Format: Text
• Language: unknown
• Published: No Publisher Supplied 2011
• Subjects: Canada; Newfoundland; North Atlantic
• Online Access: https://dx.doi.org/10.7282/t3wd404m; https://rucore.libraries.rutgers.edu/rutgers-lib/32011/

The Orpheus rift basin of offshore eastern Canada formed during the Mesozoic breakup of the Pangean supercontinent before the opening of the North Atlantic Ocean. Using a dense grid of 2D seismic data, I have identified four distinct unconformity-bounded packages (A-D) associated with the basin’s early development. Information from nearby wells (albeit limited) and regional stratigraphy suggest that packages A, B, C, and D represent Paleozoic prerift strata and basement, Late Triassic (possibly Middle Triassic or Permian) to early Early Jurassic synrift strata, late Early to Middle Jurassic lower postrift strata, and Middle to Late Jurassic upper postrift strata, respectively. The synrift section contains salt and numerous igneous intrusions of the latest Triassic/earliest Jurassic Central Atlantic Magmatic Province (CAMP). Based on tectonostratigraphic analysis of the seismic data, I propose that the Orpheus and overlying Scotian basins experienced at least four stages of development during the Mesozoic. 1) Continental extension associated with rifting began by Late Triassic time (and possibly during Middle Triassic or Permian time) and continued into early Early Jurassic time, producing a series of E-striking, S-dipping basement-involved faults with normal separation (the Cobequid-Chedabucto border-fault system) that bound the Orpheus basin on the north. During early rifting, the basin was broad with few intrabasin faults. Most intrabasin, basement-involved faulting began during salt deposition, increasing the accommodation space and causing pronounced southward thickening of the salt. Movement on basement-involved faults during rifting produced broad fault-propagation folds in the synrift strata above the salt. 2) Shortening/inversion occurred shortly after rifting, causing widespread uplift and erosion and producing the breakup unconformity. Below the salt, the shortening reactivated many of the basement-involved extensional faults with at least a reverse component of displacement. Above the salt, the shortening produced salt-cored detachment folds and detached thrust faults. 3) Postrift thermal subsidence started likely by the late Early Jurassic, producing the Scotian postrift basin. Postrift salt movement resumed and continued until Late Jurassic, producing fault-parallel salt-cored highs and salt-withdrawal lows. 4) Regional uplift and erosion occurred during the latest Jurassic to Early Cretaceous, producing the widespread Avalon unconformity.