High-precision U-Pb CA-ID-TIMS calibration of the Permian Lueckisporites-dominated assemblages in westernmost Gondwana: inferences for correlations

Abstract

Palynology is one of the most useful tools for constructing biostratigraphic charts in the late Paleozoic basins of South America, but the lack of radiometric ages often makes it difficult to establish the precise age of the biozones. This paper focuses on two points: (i) the description of new Argentinian palynological assemblages referred to the Lueckisporites/Weylandites (LW) Biozone and (ii) the application of a new isotopic age that enables more confident large-scale correlations with the neighboring Paraná Basin of Brazil. The palynofloras were recovered from the upper part of the De La Cuesta Formation that crops out in the retroarc basin of the Paganzo Basin, more specifically obtained from mudstones intercalated with limestones, cherts, and tuffs interpreted as being deposited in a shallow water body. The assemblages are characterized by an abundance of bi-taeniate pollen grains of the Lueckisporites complex and multitaeniate pollen grains such as Lunatisporites, Protohaploxypinus, Striatopodocarpidites, Tornopollenites, and Vittatina. Colpate pollen grains are also represented by Marsupipollenites and Pakhapites. A U-Pb CA-ID-TIMS age of 278.84 ± 0.22 Ma, obtained from a tuff level interstratified with the fossiliferous strata, allows the age of the LW Biozone in the Paganzo Basin to be constrained for the first time and the adjustment of the record Lueckisporites virkkiae in Gondwana. Moreover, this date enables precise correlations with other basins, such as the San Rafael Basin (Yacimiento Los Reyunos Formation) in Argentina and the Brazilian Paraná Basin (Iratí Formation).

Keywords:

• Permian
• Argentina
• palynostratigraphy
• isotopic ages

Acknowledgements

The authors are grateful to Daniel Mantle and two other, anonymous, reviewers for their constructive and valuable suggestions that improved the manuscript, as well as for their meticulous review of the English style. Thanks also to Dr. Ian Millar for his comments on isotopic dating.

Disclosure statement

No potential conflict of interest is reported by the authors.

Additional information

Funding

This work was supported by the Agencia de Promoción Científica y Tecnológica under Grant PICT 2016-1312.

Notes on contributors

Silvia N. Césari

SILVIA N. CÉSARI is a Researcher Scientist with the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). In 2003 she moved from the University of Buenos Aires to the Museo Argentino de Ciencias Naturales B. Rivadavia. Silvia was President of the Asociación Paleontológica Argentina and Editor-in-Chief of Ameghiniana and Revista del Museo de Ciencias Naturales. Her research, since her doctoral thesis, has been focused on late Paleozoic palynofloras and megafloras. Recently new contributions on late Triassic assemblages were added to her studies. The main goal of the investigations, with her husband Limarino and collaborators, is to improve the late Paleozoic biostratigrapy of western Gondwana.

Carlos O. Limarino

CARLOS O. LIMARINO is a Researcher Scientist with the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Professor of Sedimentology at Buenos Aires University, and Member of the Academia Nacional de Ciencias. His research focuses in the reconstruction of the paleoenvironmental evolution of the western basins of Argentina during the late Paleozoic. He was President of the Asociación Sedimentológica Argentina, co-author of the book Petrología y diagénesis de rocas clásticas, and editor of several special publications.

Sergio Marenssi

SERGIO MARENSSI is a Researcher Scientist with the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Professor of Sedimentary Basins at Buenos Aires University. Sergio was director of the Argentinian Antarctic Institute for ten years. At present his is focused on sedimentological studies of late Paleozoic and Tertiary sequences from western Argentina.

Patricia L. Ciccioli

PATRICIA CICCIOLI is a Researcher Scientist with the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Assistant Teacher at Buenos Aires University. At present Patricia is Academic Secretary of the Department of Geology and she received the Stimulus in Earth Sciences Award of the Academia Nacional de Ciencias Exactas, Físicas y Naturales in 2017. Her research is focused on Cenozoic stratigraphy and sedimentology of the foreland basins of Argentina and late Paleozoic ecosystems of Argentina.

Fanny C. Bello

FANNY CARINA BELLO is Chief of the Division of Uranium Geology in the CNEA (Comisión Nacional de Energía Atómica), Córdoba, Argentina. She is in charge of geological exploration in uranium-bearing stratigraphic units.

Luis C. Ferreira

LUIS C. FERREIRA works in the Exploration Section of the CNEA (Comisión Nacional de Energía Atómica) in the Northwest Regional Management. He conducts stratigraphic field studies on late Paleozoic uranium-bearing sequences, proposing metallogenetic models.

Leonardo R. Scarlatta

LEONARDO R. SCARLATTA received his Bachelor’s Degree in 2007 from the Universidad Nacional de Córdoba, Argentina. He works for National Atomic Energy Commission (CNEA) as an exploration geologist. He is in charge of applying different exploration techniques in order to understand the geology in different environments and thus be able to find new uranium deposits.

Richard Friedman

RICHARD M. FRIEDMAN was, at the time that this research was conducted, a research scientist and laboratory manager at the Pacific Centre for Isotopic and Geochemical Research at the Department of Earth, Ocean and Atmospheric Sciences at the University of British Columbia (UBC) in Vancouver, BC, Canada. He has worked in the field of U-Pb geochronology at UBC for more than 30 years and retired in April, 2021.