An assessment of dip-slip versus strike-slip faulting modes along the Patagonian Andes (39°-50° S) and their related orogenic models

ABSTRACT

The compilation of a database of 225 strain/stress tensors (accounting for ~ 4000 fault-striae data pairs) combined with evidence of syntectonic strata, and a seismotectonic appraisal along the Patagonian Andes (39°-50° S; South America), leads us to assess typical features of Mesozoic to current faulting in this segment of the Andean orogen. At the orogen scale, the fault-slip and focal mechanism database show the prevalence of strike-slip faulting, challenging the classic proposal for the Andean orogen of alternating extensional and contractional deformation phases. However, the wrenching tectonism in Cenozoic times may be explained through a strain partitioning model in the North Patagonian Andes by re-activating a large-scale, inherited anisotropy within the basement (namely the Liquiñe-Ofqui fault system), which is currently the locus of significant seismicity. On the other hand, a non-partitioned context allows explaining the Cenozoic patterns of brittle deformation the South Patagonian Andes. Our results highlight that the classifications of Andean-type orogens should integrate both inherited anisotropies and the heterogeneous distribution of strain across the upper plate in order to address complex patterns of deformation.

KEYWORDS:

• Patagonian Andes
• strike-slip faulting
• dip-slip faulting
• Andean tectonics
• basement anisotropy
• orogenic models

Acknowledgments

This contribution was supported by the bilateral scientific cooperation project between the Argentinian Mincyt - Universidad de Buenos Aires and the BesanÇon University, funded by the Argentinian-French ECOS-SUD under grant project A15U02 directed by C.S. and M.G; CONICET PIP 11220200100307CO assigned to MG; UBACYT GC 20020190100382 BA assigned to MG; and PICT-2020-SERIEA-03277 assigned to MG. RS thanks the institutional support of the IDEAN (UBA-CONICET) allowing the development of Ph.D. studies.

P-T solution from fault-slip data were computed using the Faultkin software, developed by Dr. Richard Allmendinger (http://www.geo.cornell.edu/geology/faculty/RWA/programs/faultkin.html; Marret and Allmendinger 1990). Data treatment of earthquake focal mechanisms was performed with TENSOR software, developed by Damien Delvaux (https://damiendelvaux.be/Tensor/WinTensor/win-tensor.html; Delvaux and Sperner 2003). The background hillshade was downloaded from the Earth data catalog (https://www.earthdata.nasa.gov). We are grateful to the previous authors for producing the data compiled in this contribution and to the Administración de Parques Nacionales de Argentina for granting access to protected zones (Permiso 031-CPA) and providing kind logistical support. Finally, we thank Dr. Robert J. Stern for editorial handling, and Dr. Guido Gianni and two anonymous reviewers for helping us improve the article.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The authors confirm that the data supporting the findings of this study are available within this article and its supplementary materials, as well as in the references, as follow: Diraison et al. (1998) at ”https://doi.org/10.1016/S0895-9811(98)00032-7”, Diraison et al. (2000) at ”https://doi.org/10.1016/S0040-1951(99)00255-3”, Lavenu and Cembrano (1999) at ”https://doi.org/10.1016/S0191-8141(99)00111-X”, Lagabrielle et al. (2004) at ”https://doi.org/10.1016/j.tecto.2004.04.023”, Rosenau et al. (2006) at ”https://doi.org/10.1029/2005TC001943”, Barberón et al. (2018) at ”https://doi.org/10.1111/ter.12339”, and Suárez et al. (2021) at ”https://doi.org/10.1111/ter.12521”.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00206814.2023.2230473

Additional information

Funding

The work was supported by the UBACYT [20020190100382 BA]; CONICET PIP [11220200100307CO]; PICT [2020-SERIEA-03277]; ECOS-SUD [A15U02].