Permian brachiopods from the Tupe formation, San Juan Province, Precordillera, Argentina

The brachiopod fauna from the Tupe Formation at La Herradura Creek, located on the west flank of Perico Hill, San Juan Province, Argentina, palaeogeographically belongs to the western sector of the Paganzo basin ('Guandacol embayment'). The stratigraphical section of the Tupe Formation at La Herradura Creek is the stratotype of the Tivertonia jachalensis-Streptorhynchus inaequiornatus biozone, was previously regarded as being of Late Carboniferous age but here is assigned to the earliest Permian (Asselian). We describe and review the biozone assemblage, which consists of Streptorhynchus inaequiornatus, Tivertonia jachalensis, Kochiproductus sp., Costatumulus sp., Coronalosia argentinensis, Tupelosia paganzoensis, Trigonotreta pericoensis, Septosyringothyris sp. aff. Septosyringothyris jaguelensis and Crurithyris? sp. This brachiopod assemblage is related to Indian and Australian Early Permian faunas and its presence in the La Herradura Creek section provides new evidence in support of an Asselian (Early Permian) age for the Tivertonia jachalensis-Streptorhynchus inaequiornatus biozone. This assemblage is also important for intra- and inter-basinal correlation because several of its characteristic species have been identified from other sections of the Paganzo basin and the Riacuteo Blanco basin. The proposed age for this biozone is consistent with the age of palynological data from slightly above the marine faunas from the stratotype locality.

Carboniferous brachiopods from the "Levipustula Fauna" in central-western Argentina : biostratigraphic, palaeoclimatic, and palaeobiogeographic implications

The “Levipustula fauna” is a relatively diverse fossil assemblage composed of brachiopods, bivalves, bryozoans, gastropods and crinoids that appears in glaciomarine sequences related to the Carboniferous glacial event that affected the central-western Argentinean basins. Brachiopods that characterize this fauna have been studied in some of the classical localities of the Argentine Precordillera in San Juan province.

In the Hoyada Verde Formation, the “Levipustula fauna” is usually located immediately above the glacial diamictite horizons and appears to be associated with the mudstones facies of the postglacial transgression. From a palaeoecological study, three brachiopod subfaunas are distinguished in this formation: the lower “Neospirifer” (“Trigonotretidae” gen. nov.) subfauna, above which the more diversified Kitakamithyris subfauna occurs, and the upper Levipustula subfauna, with the dominant species being attributed to Levipustula levis Maxwell. The Hoyada Verde fauna, as well those identified in the La Capilla Formation (Cerro El Morado locality), have been proposed as the typical “Levipustula fauna”. However, in the Leoncito Formation, the “Levipustula fauna” occurs in sandstones horizons located below the glacial diamictite beds. This fauna is poorly diversified and the brachiopods are characterized by “Neospirifer” (“Trigonotretidae” gen. nov.)-Septosyringothyris assemblage and Levipustula is not abundant. This fauna has been considered a colder “pre-interglacial fauna”.

The significant taxonomic, palaeoecologic and taphonomic variations of the “Levipustula fauna”, as well as its position in the glacial sequences, suggest an important palaeoenvironmental control related to Carboniferous glacial dynamics. From the palaeobiogeographic viewpoint, this fauna shows the highest affinity with the Eastern Australian basins from where it was previously described.

An early Permian brachiopod–gastropod fauna from the Calytrix Formation, Barbwire Terrace, Canning Basin, Western Australia

A small brachiopod–gastropod fauna from a core close to the base of the Calytrix Formation within the Grant Group includes the brachiopods Altiplecus decipiens (Hosking), Myodelthyrium dickinsi (Thomas), Brachythyrinella narsarhensis (Reed), Neochonetes (Sommeriella) obrieni Archbold, Tivertonia barbwirensis sp. nov. and the gastropod Peruvispira canningensis sp. nov. The fauna has affinities with that of the late Sakmarian‒early Artinskian Nura Nura Member directly overlying the Grant Group in other parts of the basin but, as with all lower Cisuralian (and Pennsylvanian) glacial strata in Western Australia, its precise age remains poorly constrained, especially in terms of correlation to international stages. Although the Calytrix fauna lies within the Pseudoreticulatispora confluens Palynozone, the only real constraint on its age (and that of the associated glacially influenced strata) is from Sakmarian (Sterlitamakian) and stratigraphically younger faunas. A brief review of radiometric ages from correlative strata elsewhere in Gondwana shows that those ages need to be updated. The presence of Asselian strata and the position of the Carboniferous‒Permian boundary remain unclear in Western Australia.Arturo César Taboada [ataboada@unpata.edu.ar], CONICET-Laboratorio de Investigaciones en Evolución y Biodiversidad (LIEB), Facultad de Ciencias Naturales, Sede Esquel, Universidad Nacional de la Patagonia ‘San Juan Bosco’, Edificio de Aulas, Ruta Nacional 259, km. 16,5, Esquel U9200, Chubut, Argentina; Arthur Mory [arthur.mory@dmp.wa.gov.au], Geological Survey of Western Australia, 100 Plain Street, East Perth, WA 6004, School of Earth and Environment, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia; Guang R. Shi [grshi@deakin.edu.au], School of Life and Environmental Sciences, Deakin University, Melbourne Burwood Campus, 221 Burwood Highway, Burwood, Victoria 3125, Australia; David W. Haig [david.haig@uwa.edu.au], School of Earth and Environment (M004), The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia; María Karina Pinilla [mkpinilla@fcnym.unlp.edu.ar], División Paleozoología Invertebrados, Museo de Ciencias Naturales de La Plata, Paseo del Bosque s/n, 1900 La Plata, Buenos Aires, Argentina.