Mechanical Influence of Inherited Folds in Thrust Development: A Case Study from the Variscan Fold-and-Thrust Belt in SW Sardinia (Italy)

Geosciences

Antonio Funedda¹  Fabrizio Cocco¹ 

[1] Department of Chemical and Geological Sciences, University of Cagliari, Cittadella Universitaria-S.S. 554 bivio per Sestu, 09042 Monserrato, CA, Italy;

关键词: back-thrust;    buttressing;    footwall deformation;    inversion tectonics;    mechanical stratigraphy;    pre-existing folds;   

DOI  :  10.3390/geosciences11070276

来源: DOAJ

【 摘 要 】

Fold-and-thrust belts have a high variability of structural styles, whose investigation provides continuous updates of the predictive models that try to better approximate the geometries recognized in the field. The majority of studies are focused on the geometry and development of folds and thrust surfaces and the amount of displacement, taking into account the role played by the involved stratigraphic succession assumed as a layer cake. We present a case study from the external zone of the Variscan fold-and-thrust belt in SW Sardinia, where it was possible to investigate the lateral and vertical variations of the mechanical properties of the involved succession, how they related to previous folding, control thrust geometry, and kinematics. In this case, the superposition of two fold systems acted as a buttress that induced extensive back-thrusting. We found that there is a close connection between the attitude of the bedding and the geometry of back thrust surfaces, shear strength during thrust propagation, and variation in the shortening amount, depending on which part of the folds were cut across. The folding-related mechanical anisotropy also seems to have induced a ductile deformation in the footwall of back-thrusts. Although the case study considers the development of back-thrust, the relations between thrust and not-layer cake geometries could also be applied to fore-thrust development.

【 授权许可】

Unknown