Inversion of extensional basins parallel and oblique to their boundaries: inferences from analogue models and field observations from the Dolomites Indenter, European eastern Southern Alps
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Published:2023-07-04
Issue:7
Volume:14
Page:647-681
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ISSN:1869-9529
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Container-title:Solid Earth
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language:en
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Short-container-title:Solid Earth
Author:
Sieberer Anna-KatharinaORCID, Willingshofer Ernst, Klotz Thomas, Ortner HugoORCID, Pomella HannahORCID
Abstract
Abstract. Polyphase deformation of continental crust is analysed
through physical analogue models for settings wherein platform–basin
geometries at passive continental margins are subject to subsequent
shortening and orogenesis. In a first stage, segmentation of the brittle and
brittle–ductile models into basins and platforms is achieved by extension.
Basins are partly filled with brittle material to allow for a strength
difference between basin and platform realms, simulating relatively weaker,
incompetent deposits of grabens surrounded by competent pre-rift basement or
carbonate platform rock, respectively. In a second stage of deformation,
contraction parallel and oblique (10 to 20∘) to the basin axes has
been applied, leading to the inversion of basins formed earlier. The
experiments show that strength contrasts across platform–basin transitions
control the localisation and overall style of compressional deformation,
irrespective of the nature of the basal décollement (frictional versus
viscous), the rheology of the basin fill, or changing platform–basin
thickness ratios. Orientations of thrust faults change laterally across
inherited platform–basin transitions throughout all experiments; higher
obliquity of basin inversion leads to stronger alignment of thrust curvature
with the orientation of pre-existing rift axes. At individual thrust faults,
variations in the strike of thrust fronts are accompanied by changes in
the shortening direction during incremental phases of deformation.
Reactivation of normal faults occurs in oblique basin inversion settings
only, favourably at platform–basin transitions where the normal faults face
the shortening direction. The amount and style of fault reactivation depend
on the material used. Our experiments are relevant for natural cases such as
the Dolomites Indenter of the eastern Southern Alps, underlining the
importance of inherited geologic features for the subsequent shortening
geometries. Field structural data from the western segment of the Belluno
thrust of the Valsugana fault system support predicted variations of thrust
fault orientation and a lateral change in shortening direction (from SSW to
SSE along-strike) along one single fault. Based on our modelling results, we
suggest that this variability of thrust fault orientation and shortening
directions, controlled by inherited structures, is consistent with strain
partitioning during a single phase of deformation and does not necessarily
reflect different deformation phases.
Funder
Austrian Science Fund
Publisher
Copernicus GmbH
Subject
Paleontology,Stratigraphy,Earth-Surface Processes,Geochemistry and Petrology,Geology,Geophysics,Soil Science
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