Feedback between synrift lithospheric extension, sedimentation and salt tectonics on wide, weak continental margins

Numerical modelling in 2D is used to explore interactions between synrift lithospheric extension, salt deposition and deformation, and pre- and post-salt sedimentation, for wide rifted margins with weak continental crust. Distributed aggrading synrift sedimentation enhances listric normal faulting of the sediments and crust in the mid and distal margin. In contrast, localized prograding sedimentation initiates a positive feedback between sedimentation, faulting and mid- to lower-crustal flow. This feedback causes localized crustal extension at the proximal margin, and leads to thick sediments in deep proximal basins. The feedback is more pronounced when more sediment is deposited, and does not develop in models with stronger, narrower rifted margins. Later initiation of the post-salt prograding sediments leads to a less pronounced feedback with lower-crustal flow and a more significant advancement of the prograding wedge over the salt body. We compare our model results with the rifted Nova Scotia Atlantic margin, contrasting margin evolution and salt tectonics between the northeastern region, which experienced significant post-salt synrift sedimentation, and the central region, where less post-salt sediment was deposited. We show that the northeastern margin may have experienced enhanced proximal graben development owing to prograding synrift sedimentation.