Integrated U-Pb zircon and palynological/palaeofloristic age determinations of a Bashkirian palaeofjord fill, Quebrada Grande (Western Argentina). (January 2017)

• Record Type: Journal Article
• Authors: Valdez Buso, Victoria; di Pasquo, Mercedes; Milana, Juan Pablo; Kneller, Benjamin; Fallgatter, Claus; Junior, Farid Chemale; Gomes Paim, Paulo Sérgio
• Is Part Of: Journal of South American earth sciences. Volume 73(2017:Jan.)
• Page Start: 202
• Page End: 222
• Publication Date: 2017-01
• Subjects: Late palaeozoic ice age -- Palynology -- Platyspermic seeds -- Isotopic age -- Jejenes formation -- Paganzo basin; Geology -- Latin America -- Periodicals; Earth sciences -- Latin America -- Periodicals; Geology -- Antarctica -- Periodicals; Earth sciences -- Antarctica -- Periodicals; Geology -- Caribbean Area -- Periodicals; Earth sciences -- Caribbean Area -- Periodicals; Géologie -- Amérique latine -- Périodiques; Sciences de la terre -- Amérique latine -- Périodiques; Géologie -- Antarctique -- Périodiques; Sciences de la terre -- Antarctique -- Périodiques; Géologie -- Caraïbes (Région) -- Périodiques; Sciences de la terre -- Caraïbes (Région) -- Périodiques; Earth sciences; Geology; Antarctica; Caribbean Area; Latin America; Periodicals; 550.5
• DOI: 10.1016/j.jsames.2016.12.009
• Languages: English
• ISSNs: 0895-9811

Abstract

Abstract: 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. Graphical abstract: Highlights: Age framework for the main Bashkirian transgression in Western Argentina. The first isotopic age for the Jejenes Formation. The first platyspermic seed for the region dated as 321.3 ± 5.3 Ma. A new glacial pulse recorded at upper section of Quebrada Grande palaeofjord.