Structure and kinematics of an extensional growth fold, Hadahid Fault System, Suez Rift, Egypt

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Authors

Christopher Aiden-Lee Jackson , Paul S Whipp, Robert Gawthorpe, Matthew M Lewis

Abstract

Normal faulting drives extensional growth folding of the Earth’s upper crust during continental extension, yet we know little of how fold geometry relates to the structural segmentation of the underlying fault. We use field data from the Hadahid Fault System, Suez Rift, Egypt to investigate the geometry and kinematics of a large (30 km long, up to 2.5 km displacement), exceptionally well exposed normal fault system to test and develop models for extensional growth folding. The Hadahid Fault System comprises eight, up to 5 km long segments that are defined by unbreached or breached monoclines. These segments are soft-linked, hard-linked, or defined by a more subtle along-strike transition in overall structural style. High overlap:separation (O:S) ratios between its segments suggest the Hadahid Fault System comprises a single, now hard-linked structure at-depth. We demonstrate that a progressive loss of at-surface displacement along strike of the Hadahid Fault System results in surface-breaking faults and breached monoclines being replaced by unbreached monoclines developed above blind faults. However, shorter along-strike length-scale variations in structural style also occur, with unbreached monoclines developed between breached monoclines. The origin of this variability is unclear, but might reflect local variations in host rock material properties that drive short length-scale variations in fault propagation-to-slip ratio, and thus the timing and location of fold breaching. We show that folding is a key expression of the strain that accumulates in areas of continental extension, and argue that tectono-sedimentary models for rift development should capture the related structural complexity.

DOI

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

Subjects

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

Keywords

rifting, extensional forced fold, extensional forced folding, extensional growth fold, extensional tectonics, fault-propagation folding, forced folding, Gulf of Suez, normal fault, normal faulting, Suez Rift

Dates

Published: 2020-04-29 21:47

Last Updated: 2020-04-30 12:51

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License

CC BY Attribution 4.0 International

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