Integrated U-Pb zircon and palynological/palaeofloristic age determinations of a Bashkirian palaeofjord fill, Quebrada Grande (Western Argentina)

Victoria Valdez Buso*, Mercedes di Pasquo, Juan Pablo Milana, Benjamin Kneller, Claus Fallgatter, Farid Chemale Junior, Paulo Sérgio Gomes Paim

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)


This work presents a new age framework for the main Bashkirian glacio-eustatic transgression in Argentina, including the first absolute age for the Jejenes Formation, San Juan Province, based on radiometric dating of a crystal-rich tuff, supported by palynological and palaeofloristic studies, and presented within a revised palaeogeographic setting. The Jejenes Formation represents the glacial to postglacial fill of the Quebrada Grande palaeofjord carved in the Eastern Precordillera. The succession has been subdivided into five stages, the youngest of which suggests a previously unrecognised glacial event for this locality. Six productive levels for palynology were found within proglacial strata, and in the base and top of the succeeding interglacial stage. Palynoassemblages are characterized by poorly preserved trilete spores and monosaccate pollen grains along with a large amount of terrestrial phytoclasts. Main species indicating the Raistrickia densa-Convolutispora muriornata SubZone (DMa SZ) are Vallatisporites ciliaris, Cristatisporites rollerii, C. stellatus, C. chacoparanensis, C. inconstans and monosaccates such as Circumplicatipollis plicatus. This DMa SZ is estimated as Serpukhovian/Bashkirian and characterizes the glacial-related Guandacol Formation and equivalents units of the western Paganzo Basin. A tuffaceous level in the proglacial unit, bearing platyspermic seeds, plant remains and palynomorphs, yielded first-cycle volcanic zircons that were analysed by SHRIMP. An absolute age of 321.3 ± 5.3 Ma confirms a Bashkirian age for the main postglacial transgression in the Paganzo Basin, and offers a novel calibration for the palynoassemblages of DMa SZ that occurs elsewhere in Western Argentina.

Original languageEnglish
Pages (from-to)202-222
Number of pages21
JournalJournal of South American Earth Sciences
Early online date18 Dec 2016
Publication statusPublished - Jan 2017

Bibliographical note

This work is part of a research project supported by BG Brazil E&P Ltda. entitled “Carboniferous deglacial record in the Paran a Basin and its analogue in the Paganzo Basin of Argentina: Impacts on reservoir predictions” undertaken at the Universidade do Vale do Rio dos Sinos (UNISINOS), Brazil, in partnership with Universidad Nacional de San Juan, and University of Aberdeen, United Kingdom; and with funds from Consejo Nacional de Investigaciones Científicas y Tecnicas CONICET PIP 0305 (2011-2013). This contribution is part of the PhD of the senior author funded by BG Brazil E&P Ltda. A special acknowledgment is made to Carla Puigdomenech, Carol Aquino, Deise Silveira, Fabiano Rodrigues and Willian Matsumura, who have collaborated during field work. To Professors Andrea Sander and Wilson Wilder, who helped with the petrographic analysis of the tuffite. Thanks are also given to Lic. Leonardo Silvestri for his help in sample processing at the CICYTTP-CONICET. At last, the authors would like to acknowledge the ANP (Agencia Nacional do Petroleo, Gas Natural e Biocombustível) for their economic assistance.


  • Isotopic age
  • Jejenes formation
  • Late palaeozoic ice age
  • Paganzo basin
  • Palynology
  • Platyspermic seeds


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