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How Topographic Slopes Control Gravity-spreading in Salt-bearing Passive Margins
  • Zhiyuan Ge,
  • Matthias Rosenau,
  • Michael Warsitzka
Zhiyuan Ge
China University of Petroleum, Beijing, China University of Petroleum, Beijing, China University of Petroleum, Beijing

Corresponding Author:[email protected]

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Matthias Rosenau
Helmholtz Center Potsdam - GFZ German Research Center for Geosciences, Helmholtz Center Potsdam - GFZ German Research Center for Geosciences, Helmholtz Center Potsdam - GFZ German Research Center for Geosciences
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Michael Warsitzka
Institute of Geophysics of the Czech Academy of Sciences, Institute of Geophysics of the Czech Academy of Sciences, Institute of Geophysics of the Czech Academy of Sciences
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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.