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Open AccessShort Note

Twinning Strains in Synfolding Calcite, Proterozoic Sinian System, China

1
Geology Department, Macalester College, St. Paul, MN 55105, USA
2
State Key Laboratory of Geological Processes and Mineral Resources and Key Laboratory of Lithosphere Tectonics, China University of Geosciences, 29 Xueyuan Rd., Beijing 100083, China
*
Author to whom correspondence should be addressed.
Geosciences 2018, 8(4), 131; https://doi.org/10.3390/geosciences8040131
Received: 1 March 2018 / Revised: 2 April 2018 / Accepted: 6 April 2018 / Published: 11 April 2018
Synfolding calcite was precipitated between layers of Neoproterozoic sandy dolomite and striated parallel to the fold axis of an open anticline with a shallow plunge during folding. The fold had limb dips of 45° and plunged 20° to the south. The synfolding calcite had sub-horizontal grooves that trended parallel to the fold. Limb-hinge-limb calcite samples (3 samples; n = 100 grains) preserved a layer-parallel shortening strain that trended at an acute (45°) angle to the trend of the fold axis and fold lineations. Extension axes were vertical and there was no strain overprint (low NEVs). Shortening strain magnitudes were −2.9% and the differential stress responsible for twinning was −38 MPa. The commonly observed structures were layer-parallel slip striations normal to the fold axis: sub-horizontal interlayer slip surfaces parallel to a fold axis (parallel to bedding strike) were unreported; as was a sub-horizontal shortening strain at an acute angle to the axis of a plunging fold. View Full-Text
Keywords: structural geology; folding dynamics; strain analysis structural geology; folding dynamics; strain analysis
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MDPI and ACS Style

Craddock, J.P.; Liu, J.; Zheng, Y. Twinning Strains in Synfolding Calcite, Proterozoic Sinian System, China. Geosciences 2018, 8, 131.

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