Strain and vorticity analysis using small-scale faults and associated drag folds

Enrique Gomez-Rivas*, Paul D. Bons, Albert Griera, Jordi Carreras, Elena Druguet, Lynn Evans

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

32 Citations (Scopus)
8 Downloads (Pure)

Abstract

Small-scale faults with associated drag folds in brittle-ductile rocks can retain detailed information on the kinematics and amount of deformation the host rock experienced. Measured fault orientation (alpha), drag angle (beta) and the ratio of the thickness of deflected layers at the fault (L) and further away (T) can be compared with alpha, beta and L/T values that are calculated with a simple analytical model. Using graphs or a numerical best-fit routine, one can then determine the kinematic vorticity number and initial fault orientation that best fits the data. The proposed method was successfully tested on both analogue experiments and numerical simulations with BASIL. Using this method, a kinematic vorticity number of one (dextral simple shear) and a minimum finite strain of 2.5-3.8 was obtained for a population of antithetic faults with associated drag folds in a case study area at Mas Rabassers de Dalt on Cap de Creus in the Variscan of the easternmost Pyrenees, Spain. (C) 2007 Elsevier Ltd. All rights reserved.

Original languageEnglish
Pages (from-to)1882-1899
Number of pages18
JournalJournal of Structural Geology
Volume29
Issue number12
Early online date20 Sept 2007
DOIs
Publication statusPublished - Dec 2007

Bibliographical note

This work was financed through the PhD grant BES-2003-0755 to EGR and research project CGL2004-03657, both funded by the Spanish Ministry of Education and Science. We thank Jens Becker and Anne Peschler for their help with the BASIL modelling. We gratefully acknowledge D. Jiang and T. Bell, whose constructive reviews greatly improved the manuscript.

Keywords

  • strain analysis
  • vorticity
  • progressive deformation
  • faults
  • drag folds
  • foliation
  • flanking structures
  • shear zones
  • Eastern Pyrenees
  • non-coaxiality
  • deformation
  • creus
  • cap
  • transition
  • magmatism
  • nonsense

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