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Upper-crustal architecture and record of Famatinian arc activity in the Sierra de Narváez and Sierra de Las Planchadas, NW Argentina

Lusk, Alexander D. and Ratschbacher, Barbara C. and Larrovere, Mariano A. and Alasino, Pablo H. and Memeti, Valbone and Paterson, Scott R. (2021) Upper-crustal architecture and record of Famatinian arc activity in the Sierra de Narváez and Sierra de Las Planchadas, NW Argentina. Journal of South American Earth Sciences, 105 . Art. No. 102895. ISSN 0895-9811.

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The 495 to 450 Ma Famatinian orogen, exposed throughout central and northwestern Argentina, formed from east-directed subduction under the Gondwanan margin. The Sierra de Narváez and Sierra de Las Planchadas preserve a rare upper-crustal section of the Famatinian arc. New mapping, structural analysis, detrital U–Pb zircon geochronology, as well as major and trace element geochemistry in the Sierra de Narváez – Las Planchadas are presented to give a comprehensive geodynamic portrait of the volcano-sedimentary, igneous, and deformational processes acting within the top of the Famatinian arc in the Ordovician. Field observations and bulk rock geochemistry agree with previous work indicating that the top of the Famatinian arc consisted of volcanic centers, mafic and felsic feeders, and plutons built into continental crust in a shallow marine arc setting, characterized by fossil-bearing, fine-grained marine sediments interbedded with coarse-grained volcanic-clastic material. Trace element chemistry is consistent with the Sierra de Narváez – Las Planchadas region being a continuation along the main arc axis from the more southerly Sierra de Famatina, not a back arc setting as previously interpreted. Detrital zircon geochronology in Permian and Carboniferous sedimentary units unconformably overlying Ordovician units adds further constraints to the duration of Famatinian arc activity and the source of sedimentary material. Two peaks in detrital zircon ages within Carboniferous and Permian strata at 481 Ma and from 474 to 469 Ma, record periods of enhanced magma addition during Famatinian arc activity. Structural analysis establishes both Famatinian and post-Famatinian (largely Andean) deformation; contractional deformation in the Ordovician, although small relative to middle- to lower-crustal levels of the Famatinian orogen, caused crustal thickening and likely initiated surface uplift. Unlike the Famatinian middle to lower crust, however, where widespread ductile deformation is ubiquitous, shortening here is accommodated by open folding, pressure solution, and likely localized brittle faulting. We briefly speculate on the implications of variable shortening recorded at different crustal levels.

Item Type:Article
Related URLs:
URLURL TypeDescription
Lusk, Alexander D.0000-0002-4660-0648
Ratschbacher, Barbara C.0000-0002-2112-7225
Larrovere, Mariano A.0000-0001-7550-5474
Alasino, Pablo H.0000-0002-3871-4119
Memeti, Valbone0000-0001-7373-4126
Paterson, Scott R.0000-0003-0370-9528
Additional Information:© 2020 Published by Elsevier. Received 19 May 2020, Revised 1 September 2020, Accepted 9 September 2020, Available online 25 September 2020. We thank Fernando Hongn and Alina Tibaldi for their thorough and thoughtful reviews that helped to improve this manuscript, as well as Andres Folguera for handling editorial duties. Mapping and analytical work presented in this study is a combined effort stemming from two international field research classes which included students from the University of Southern California, California State University – Fullerton, National University of La Rioja, and National University of Salta. This work was funded by the respective universities. The authors wish to thank the students for their good spirits and enthusiasm. A special thanks to Robert Hernandez for his assistance with data organization and drafting. We would also like to thank researchers and staff at CRILAR for their hospitality. Lastly, B. Ratschbacher acknowledges a USC Enhancement Fellowship grant, which paid for parts of the U–Pb zircon geochronology. Author statement: All authors were involved in the following: Conceptualization, Methodology, Formal analysis, Investigation, Writing - original draft, review & editing. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Funding AgencyGrant Number
University of Southern CaliforniaUNSPECIFIED
California State University, FullertonUNSPECIFIED
National University of La RiojaUNSPECIFIED
National University of SaltaUNSPECIFIED
Subject Keywords:Famatinian arc; Argentina; Upper arc; Deformation; Flare-up; Volcanics
Record Number:CaltechAUTHORS:20200925-091914513
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Official Citation:Alexander D. Lusk, Barbara C. Ratschbacher, Mariano A. Larrovere, Pablo H. Alasino, Valbone Memeti, Scott R. Paterson, Upper-crustal architecture and record of Famatinian arc activity in the Sierra de Narváez and Sierra de Las Planchadas, NW Argentina, Journal of South American Earth Sciences, Volume 105, 2021, 102895, ISSN 0895-9811, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105540
Deposited By: George Porter
Deposited On:25 Sep 2020 17:44
Last Modified:08 Jan 2021 17:33

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