Unravelling intrusion-induced forced fold kinematics and ground deformation using 3D seismic reflection data

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.30909/vol.01.01.0117. This is version 2 of this Preprint.

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Authors

Jennifer Reeves, Craig Magee , Christopher Aiden-Lee Jackson 

Abstract

Sills emplaced at shallow-levels are commonly accommodated by overburden uplift, producing forced folds. We examine ancient forced folds developed above saucer-shaped sills using 3D seismic reflection data from the Canterbury Basin, offshore SE New Zealand. Seismic-stratigraphic relationships indicate sill emplacement occurred incrementally over ~31 Myr between the Oligocene (~35–32 Ma) and Early Pliocene (~5–4 Ma). Two folds display flat-topped geometries and amplitudes that decrease upwards, conforming to expected models of forced fold growth. Conversely, two folds display amplitudes that locally increase upwards, coincident with a transition from flat-topped to dome-shaped morphologies and an across-fold thickening of strata. We suggest these discrepancies between observed and expected forced fold geometry reflect uplift and subsidence cycles driven by sill inflation and deflation. Unravelling these forced fold kinematic histories shows complex intrusion geometries can produce relatively simple ground deformation patterns, with magma transgression corresponds to localisation of uplift.

DOI

https://doi.org/10.31223/osf.io/na62q

Subjects

Earth Sciences, Geology, Physical Sciences and Mathematics

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Dates

Published: 2017-11-17 16:09

Last Updated: 2018-01-25 15:52

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License

CC BY Attribution 4.0 International

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