Balancing sub- and supra-salt strain in salt-influenced rifts: Implications for extension estimates

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1016/j.jsg.2017.08.006.

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Authors

Alexander James Coleman, Christopher Aiden-Lee Jackson , Oliver Duffy

Abstract

The structural style of salt-influenced rifts may differ from those formed in predominantly brittle crust. Salt can decouple sub- and supra-salt strain, causing sub-salt faults to be geometrically decoupled from, but kinematically coupled to and responsible for, supra-salt forced folding. Salt-influenced rifts thus contain more folds than their brittle counterparts, an observation often ignored in extension estimates. Fundamental to determining whether sub- and supra-salt structures are kinematically coherent, and the relative contributions of thin- (i.e. gravity-driven) and thick-skinned (i.e. whole-plate stretching) deformation to accommodating rift-related strain, is our ability to measure extension at both structural levels. We here use published physical models of salt-influenced extension to show that line-length estimates yield more accurate values of sub- and supra-salt extension compared to fault-heave, before applying these methods to seismic data from the Halten Terrace, offshore Norway. We show that, given the abundance of ductile deformation in salt-influenced rifts, significant amounts of extension may be ignored, leading to the erroneous interpretations of thin-skinned, gravity-gliding. If a system is kinematically coherent, supra-salt structures can help predict the occurrence and kinematics of sub-salt faults that may be poorly imaged and otherwise poorly constrained.

DOI

https://doi.org/10.31223/osf.io/rhcws

Subjects

Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure

Keywords

seismic reflection, structural geology, seismic, normal faulting, Norway, salt, kinematics, folding, Halten Terrace

Dates

Published: 2017-10-28 11:15

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License

CC BY Attribution 4.0 International

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