Structural Impact of the Yarmouth Arch in the Central Atlantic Opening and on the SW Nova Scotian Margin Architecture (SW Nova Scotia 2011 PFA Expansion)

Abstract

This study on the Shelburne Subbasin is an extension of the Play Fairway Analysis done in 2011 on the Scotian margin. It is located on an under-explored area of the Scotian margin, which is a producing hydrocarbon region. This passive margin results of a complex tectonic evolution since Proterozoic time and the breakup of the Pangea at the end of Trias (225-220Ma). It follows the Central Atlantic opening with the rifting between the Nova Scotia and Morocco, the conjugate margin. The Shelburne Subbasin is bounded to the NE by the Georges Banks area which comprises the Yarmouth Subbasin and the Yarmouth Arch. The Yarmouth Arch is the structural high of the Georges Banks area and is a buried complex of approximately N-NE trending basement elements that are probably composed of Paleozoic metamorphic and plutonic rocks. It is bounded by a zigzag pattern of faults with two dominant directions: N-S and NE-SW. Moreover the Arch is oblique to the main extensional direction suggesting a possible right lateral transtensional structure along the East side. The Yarmouth Arch appears to have played an important role during rifting of the Shelburne Subbasin. Two trends of faults are recorded in the Yarmouth subbasin: NS oriented and NE-SW oriented. From Early to Late Trias, rifting of the Central Atlantic may have begun in the Yarmouth Subbasin, with the arch acting as a ‘locked zone’ forcing later periods of rifting to propagate across it. A layer of salt is deposited above the basement and is overlain by a thick carbonate layer. During the Mid-Triassic, the rifting propagates NE of the Yarmouth Arch. Thus, the Arch is segmented during the Trias as a subaerial horst. From Mid-Trias to Early Jurassic, the rifting propagates to the Shelburne subbasin with a NE-SW tilted-blocks trend. Synrift sediments are deposited (Eurydice Fm) followed by a thick layer of salt (Argo Fm). At 200Ma (Early Jurassic) the rifting decreases and the drifting stage begins. This transition, corresponding to the Breakup Unconformity, is associated with a strong volcanic episode (CAMP volcanics). The passive margin stage begins. The salt starts to creep during the Early to Mid-Jurassic due to sediment load over the entire subbbasin. From Early to Late Jurassic, a new set of NW-SE strike-slip faults appear and accommodate the oceanic accretion. These faults will create the NE corner observed between the Yarmouth Arch and the Shelburne Subbasin which will be the Argos salt boundary

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016