Andean Geology ISSN: 0718-7092 [email protected] Servicio Nacional de Geología y Minería Chile Cisterna, Gabriela A.; Sterren, Andrea F.; Gutiérrez, Pedro R. The Carboniferous-Permian boundary in the central western Argentinean basins: paleontological evidences Andean Geology, vol. 38, núm. 2, julio, 2011, pp. 349-370 Servicio Nacional de Geología y Minería Santiago, Chile Available in: http://www.redalyc.org/articulo.oa?id=173919930006 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative Andean Geology 38 (2): 349-370. July, 2011 Andean Geology formerly Revista Geológica de Chile www.andeangeology.cl The Carboniferous-Permian boundary in the central western Argentinean basins: paleontological evidences Gabriela A. Cisterna1, Andrea F. Sterren2, Pedro R. Gutiérrez3 1 CONICET-Fundación Miguel Lillo, Área Geología, Miguel Lillo 251, 4000 San Miguel de Tucumán, Argentina. [email protected] 2 CONICET-CICTERRA-CIPAL Universidad Nacional de Córdoba, Av. Vélez Sársfield 299, X5000JJC Córdoba, Argentina. [email protected] 3 CONICET Museo Argentino de Ciencias Naturales ‘B. Rivadavia’, Av. Ángel Gallardo 470, C1408DJR Buenos Aires, Argentina. [email protected] Ab STRACT. The central western Argentinean basins of Río Blanco, Calingasta-Uspallata and western Paganzo, enclose the most complete marine successions used for examining the Carboniferous-Permian boundary in Gondwana. A detailed review of the key stratigraphical sections has allowed the identification of the latest Carboniferous assemblages; NBG, Interval megafloristic Zone and DM (Raistrickia densa-Convolutispora muriornata) Palynological Zone in the lower part, and the earliest Permian T-S (Tivertonia jachalensis-Streptorhynchus inaequiornatus) invertebrate Zone and FS (Pakhapites fusus-Vittatina subsaccata) Palynological Zone in the upper part. This diagnostic mega/microflora and marine invertebrate paleontological evidence provides a biostratigraphical framework for the definition of the Carboniferous- Permian boundary inside the basins of central western Argentina. Keywords: Late Carboniferous, Early Permian, Biostratigraphy, Gondwana, Argentina. Re Sumen. el límite Carbonífero-Pérmico en las cuencas del centro oeste de Argentina: evidencias paleon- tológicas. Las cuencas del centro oeste de Argentina, Río Blanco, Calingasta-Uspallata y el sector oeste de la cuenca Paganzo, contienen las secuencias marinas más completas para el estudio del límite Carbonífero-Pérmico en Gondwana. Un estudio detallado de secciones estratigráficas claves ha permitido la identificación de las asociaciones megaflo- rísticas NBG y de Intervalo, y de la palinozona DM (Raistrickia densa-Convolutispora muriornata), del Carbonífero Tardío, en la parte inferior de dichas secciones; en tanto, en la parte media superior de las secciones estudiadas, se han identificado la biozona de invertebrados T-S (Tivertonia jachalensis-Streptorhynchus inaequiornatus) y la palinozona FS (Pakhapites fusus-Vittatina subsaccata), ambas asignadas al Pérmico Temprano. El registro de estas asociaciones diagnósticas de mega/microflora e invertebrados marinos provee un esquema bioestratigráfico integrado que permite ubicar el límite Carbonífero-Pérmico en las cuencas del centro oeste de Argentina. Palabras clave: Carbonífero Tardío, Pérmico Temprano, Bioestratigrafía, Gondwana, Argentina. Cisterna296.indd 349 13-07-2011 12:20:47 350 The Carboniferous-Permian boundary in The CenTral wesTern argenTinean basins... 1. Introduction the integrated study of these fossil groups, and the possible correlation with other Gondwan localies, The Carboniferous-Permian (Gzhelian-Asselian) is provided herein. boundary has been biostratigraphically defined in stratotype sections in the latest Carboniferous and 2. The Carboniferous-Permian boundary in the earliest Permian marine sequences from the Uralian marine successions of the Argentine Precordillera Region (Russia and Kazakhstan), by key conodonts and fusulinid foraminiferid species. The beginning of The latest Carboniferous-earliest Permian interval the Asselian stage is indicated by the first appearances in the Argentine Precordillera is associated with a of the conodont Streptognathodus isolatus, the fusu- Paleo-Pacific transgressive event that represents the linid Sphaeroschwagerina aktjubensis (=vulgaris) transition from a glacial to postglacial condition, and the distinctive ammonoid species of the genera with the posterior climatic amelioration in this area Boesites, Daixites, Glaphyrites, Artinskia, Svetla- (López Gamundí, 1989; Limarino et al., 2002). noceras, Prostacheoceras and Prothalassoceras Previous studies of the authors (Cisterna and (Bogoslovkaya et al., 1995; Davydov et al., 1997; Sabattini, 1998; Cisterna and Simanauskas, 2000; Mei et al., 1999; Lucas et al., 2001). However in Cisterna and Sterren, 2007; Cisterna et al., 2002, Gondwana and the peripheral gondwanan regions, 2005, 2006b, 2006c; Coturel and Gutiérrez, 2005; these faunal groups, considered the principal tools Gutiérrez et al., 2005; Sterren, 2000, 2004), indicate for correlation, are absent or more often, extremely that the most complete and fossiliferous gondwanan rare. The marine faunas and terrestrial microflora data successions identified for this interval of time have from the early Permian (Asselian-Early Artinskian) been documented in the central western Argentinian interval of these regions (Australia, Afghanistan- basins, i.e. the Río Blanco basin (Río del Peñón and Pakistan, Himalaya, China, Southeast Asia, India, Quebrada Larga Formations) and in the west part Africa, Arabia, Antarctica and South America), has of the Paganzo basin (Tupe Formation) (Fig. 1B). been compiled by Archbold (2001). This author has Paleontological evidence, located throughout each also suggested the importance of using palynological stratigraphical section of these units, have allowed for data to link the marine successions in the definition integrated studies of the marine faunal data with the of the Carboniferous-Permian boundary. Recently associated palynological and megafloristic records. early Permian faunal and palynological records from A diversified marine faunal assemblage composed eastern Australia and the Argentine Precordillera of brachiopods, bivalves, gastropods and ostracods, have been discussed by Archbold et al. (2004). with brachiopods clearly exhibiting Permian gond- The authors concluded that integrating the studies wanan affinities (Cisterna and Simanauskas, 2000; of marine faunas with the palynological record is Cisterna et al., 2002, 2006a; Cisterna, 2010), is required to both date the record and to strengthen typically related to the marine horizons of a trans- Gondwanan wide correlations. gressive event. This fauna belongs to the Tivertonia The central western Argentinean basins (Fig. jachalensis-Streptorhynchus inaequiornatus Zone 1A) examined here, appear to enclose one of the (Sabattini et al., 1991), considered to be early more complete successions for the study of the Permian by Cisterna et al. (2002) and Archbold et Carboniferous-Permian boundary in this part of al. (2004). Detailed studies conducted in the strati- Gondwana. Because more precise biostratigraphical graphical sections of the Tupe Formation inside the elements, such as conodonts and fusulinids that western Paganzo Basin (i.e., La Herradura Creek, would define the boundary in the type section of La Delfina Creek and Mina La Ciénaga) (Fig. 1B), the Uralian region are absent, this paper attempts have allowed to understand the compositional varia- to match the marine faunal data (primarily bra- tions of the Tivertonia jachalensis-Streptorhynchus chiopods, the most biostratigraphically important inaequiornatus fauna and its relationship with the group available and the conspicuous bivalve fauna), new palynological and paleofloristic records from with the extensive megafloristic and palynological the associated horizons (Cisterna et al., 2002, 2005, records in different key sections inside the Argen- 2006b; Gutiérrez et al., 2005). The latest Carboniferous tine Precordillera. A biostratigraphic local scheme (NBG and Interval megafloristic zones; Raistrickia of the Carboniferous-Permian boundary, based in densa-Convolutispora muriornata Palynological Cisterna296.indd 350 13-07-2011 12:20:47 Cisterna et al./ Andean Geology 38 (2): 349-370, 2011 351 Zone) and earliest Permian assemblages (Pakhapites fusus-Vittatina subsaccata Palynological Zone and Tivertonia jachalensis-Streptorhynchus inaequior- natus Zone), recognized in these studies in the Tupe Formation, restricts the timing of the paleo-Pacific transgression into the western Paganzo basin to the latest Carboniferous-earliest Permian interval (Cisterna et al., 2005). Recent field work in the Agua del Jagüel Forma- tion (Calingasta-Uspallata basin), in the southernmost part of the Argentine Precordillera, allows suggesting a probable new key section to define the Carboniferous- Permian boundary. This stratigraphical unit is charac- terized by a sedimentary succession grading upwards from a deglaciation facies to a fluvial and shallow marine facies (Henry et al., 2008). The lower part of this unit (deglaciation phase) includes the diagnostic late Carboniferous Rhipidomella-Micraphelia faunal assemblage, located immediately