Abstract
Sediment spreading is a key process during gravity-driven deformation in
salt-bearing passive margins. Whether and how progradational sedimentary
wedges control gravity-spreading is still under debate. We use analogue
modelling to compare two endmember configurations constrained by
critical wedge theory, where the initial depositional slopes are: a 5°
critical (stable) slope and a 27° unstable slope. In both
configurations, differential loading initiates spreading characterized
by a basinward migrating system of proximal extension and distal
contraction. With a critical frontal slope, the translational domain
expands as the contractional domain migrates forward with viscous flow
evenly distributed. With a steep frontal slope, both extensional and
contractional domains migrate due to more localized viscous flow under
the wedge toe producing diagnostic structures of late extension
overprinting early contraction. In both cases, salt flow is dominated by
Poiseuille flow. Our study highlights that geometric variations of
sedimentary wedges result in variable responses in gravity-spreading
systems.