Salt tectonics of the Abenaki Graben and central Sable Subbasin: insights from regional seismic interpretation and 4D scaled physical experiments
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The tectono-stratigraphic evolution of the Abenaki graben and central Sable Subbasin of the north-central Scotian margin has been highly influenced by salt deformation. Shimeld (2004) has identified five salt subprovinces defined by varying salt structural styles across the margin. Although it has been hypothesized these varying structural styles are the result of complex salt basin morphologies and variable Mesozoic post-rift sedimentation patterns, there is still a lack of understanding of how these first order controlling factors specifically controlled the tectono-stratigraphic evolution across the margin. Disappointing petroleum exploration results from the last round of deepwater drilling supports the further need to investigate how variable salt basin morphologies, and depositional rates and patterns controlled salt deformation as well as the evolution of the margin. The purpose of this project is to integrate regional 2D seismic reflection data including the ION-GXT NovaSPAN dataset, with 4D scaled physical experiments to better understand the tectono-stratigraphic evolution of the Abenaki Graben and central Sable Subbasin. The study area is located in Shimeld's salt Subprovince III that comprises an extensive salt tongue-canopy system that has spread upwards of 80 km on the secondary detachment level. Seismic interpretation indicates an original salt basin characterized by a landward tapering wedge representing the Abenaki Graben, an intermediate high referred to as the North Sable High (NSH), and a symmetric graben with basin step representing the Sable Subbasin. The geometry of the salt basin floor is composed of rifted basement blocks and syn-rift fill that was originally been infilled with upwards of 2 km of Argo salt. Scaled 4D physical experiments simulating the study area indicate the presence of 4 kinematic domains from the shelf to slope including a: (1) Salt Weld and Pillow, (2) Normal Fault and Reactive Diapir, (3) Passive Diapir and Expulsion Rollover, and (4) Contractional Salt and Allochthonous Salt-Tongue Canopy domain. Experiment results indicate early deposition focused in the Abenaki Graben, later shifting across the NSH into the Sable sub-basin as increased sediment supply and progradation occurred from the Late Jurassic to Early Cretaceous. Experiment evolutions replicated diapir and canopy evolutions with early-inflated salt complexes in the downdip contractional domain focused at changes in the basin-floor and original salt thickness. The inflated salt complexes later evolved into passive diapirs and eventual extensive salt tongue-canopy systems during subsequent sediment progradation. Derived kinematic concepts from the physical experiments successfully explain the regional structural and related depocentre evolution of the margin form the early post-rift stage to the modem margin. Understanding the tectono-stratigraphic evolution, from early salt mobilization to late stage salt tongue-canopy formation, aids in developing new concepts for reservoir distribution and trap formation for the Abenaki Graben and Sable Subbasin area.