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Modeling two sequential coaxial phases of shortening in a foreland thrust belt
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
2014 (English)In: Journal of Structural Geology, ISSN 0191-8141, E-ISSN 1873-1201, Vol. 66, 400-415 p.Article in journal (Refereed) Published
Abstract [en]

Analog sandbox models are used to simulate two sequential coaxial phases of shortening in a foreland thrust belt. A sufficient hiatus is considered so that erosion and sedimentation after the first phase create an angular unconformity that is subsequently deformed. The effect of variation in thickness of post-erosional sediment package and presence of a weak layer at the unconformity level are analyzed. During the second phase, some first phase thrusts are reactivated and new thrusts are also initiated. Thrust reactivation results in a structure spacing that is smaller than the expected spacing for a thicker sediment package. Reactivation of pre-existing structures prevents the weak layer from acting as an intermediate decollement. An increase in thickness ratio tends to weaken reactivation of pre-existing thrusts. Model results also show that total displacement along individual reactivated thrusts generally increases downwards across the unconformity, which could be used to distinguish thrust reactivation in the field. Two regional examples from the northern Eastern Cordillera in Colombia and from the Variscan frontal zone in Western Europe, respectively, where multiphase coaxial shortening occurred, are compared with model results. Both natural cases show features, such as partially eroded first-generation folds and truncated first-generation thrusts that are indicators for two sequential phases of deformation as observed in the models.

Place, publisher, year, edition, pages
2014. Vol. 66, 400-415 p.
Keyword [en]
Coaxial multiple shortening, Deformed unconformity, Sandbox modeling, Thrust reactivation
National Category
Geology
Research subject
Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
Identifiers
URN: urn:nbn:se:uu:diva-232585DOI: 10.1016/j.jsg.2014.06.006ISI: 000340978000026OAI: oai:DiVA.org:uu-232585DiVA: diva2:749569
Available from: 2014-09-24 Created: 2014-09-22 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Superimposition of Contractional Structures in Models and Nature
Open this publication in new window or tab >>Superimposition of Contractional Structures in Models and Nature
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Superimposition of contractional structures is widely observed in different scales in the world. Superimposed structures form due to different processes: change in strain accommodation from one type of structure to another during a single progressive shortening; successive coaxial shortening phases separated by an unconformity; superimposition of different non-coaxial shortening phases. Using results of a series of systematic analogue models and detailed field structural mapping, this thesis focuses on the geometry and kinematics of such superimposed structures that are formed by these three processes. During a single progressive folding, thrusts develop within a fold to accommodate stain variations in different regime of the fold. Limited displacement along these thrusts does not significantly modify the geometry of the fold. However, during multiple shortening phases (coaxial or non-coaxial), early formed structures are modified by the later phase ones. The later thrusts can cut and displace the pre-existing structures. The early folds are tightened or interfered by the later folding phase. Pre-existing thrusts may be reactivated either in dip direction and/or along strike during the later shortening. The pre-existing structures in turn influence development of the later structures, which results in change in structure spacing. An angular unconformity between two shortening phases clearly truncates the early phase structures and separates structures of different levels. Unlike in the post-erosional layers, in the layers below the unconformity, complicated superimposed structures are visible. This thesis shows that geometry and sequence of structures formed during one progressive shortening or multiple shortening phases strongly depend on the mode of the superimposition (coaxial, orthogonal or oblique) and the orientation of pre-existing structures.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 45 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1223
Keyword
superimposition, progressive deformation, multiple phases, coaxial, non-coaxial, analogue modelling, fold-and-thrust belts
National Category
Geology
Research subject
Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
Identifiers
urn:nbn:se:uu:diva-243235 (URN)978-91-554-9160-4 (ISBN)
Public defence
2015-03-27, Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2015-03-04 Created: 2015-02-05 Last updated: 2015-03-12Bibliographically approved

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Deng, HonglingKoyi, Hemin A.

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