Comment on "Significance of first-order faults in folding mechanically isotropic layers: Evidence from the Sudbury Basin, Canada", by Clark and Riller (2017), Journal of Structural Geology, 95, 113-126
Abstract
Fault-slip analysis is a well-established and frequently-used method in structural geology. The implementation of user-friendly software like TectonicsFP (Ortner et al., 2002) has further spread its use, but also bears the risk of misuse, especially in the case when the basics of the method are not known or not adhered to. For this reason, we provided in 2010 guidelines for fault-slip analysis, also highlighting possible pitfalls during data processing and emphasising the importance of data documentation (Sperner and Zweigel, 2010). Clark and Riller (2017; subsequently abbreviated "CR2017") did an adequate documentation in their paper by listing the field measurements as well as the results of all their calculations in their appendix. They used the results from fault-slip analysis to evaluate the kinematics of large-scale fault zones, and to develop a model for the tectonic evolution of the eastern margin of the Sudbury basin. However, in our opinion, the paper is in parts flawed, and we will discuss our critique points in the following and give examples for, in our opinion, inadequate approaches. In doing so, we will use the term "dataset" for the measurements of a single fault plane-lineation assemblage, while the entirety of datasets measured in one outcrop will be termed "station record". For simplification, and as it is not the topic of this comment to discuss the differences between stress and strain, we will use the term "stress" regardless of the applied method; σ1 is defined as the maximum compressive stress (σ1 ≥ σ2 ≥ σ3) and the stress ratio R = (σ2-σ3)/(σ1-σ3) describes the shape of the stress ellipsoid. Additional figures are stored in the appendix.
- Publication:
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Journal of Structural Geology
- Pub Date:
- October 2018
- DOI:
- 10.1016/j.jsg.2017.12.002
- Bibcode:
- 2018JSG...115..263S
- Keywords:
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- Fault-slip analysis;
- Fault geometry;
- Slip vectors;
- Rotation;
- Tectonic model