PERMIAN BIVALVES OF THE CAPIVARI FORMATION, ITARARÉ GROUP (STATE OF SÃO PAULO): STRATIGRAPHIC AND BIOSTRATIGRAPHIC IMPLICATIONS

SIMOES MARCELLO; NEVES JACQUELINE; TABOADA, ARTURO CÉSAR

Crato

Congreso; XXIV Congresso Brasileiro de Paleontologia; 2015

Within the glaciomarine succession of the Itararé Group (late Carboniferous to early Permian) sea-level rise following ice retreats was often accompanied by widespread deposition of ice-rafted debris free shales with rare shelly benthos (bivalves and brachiopods). At least five marine shale beds are recognized in this unit, which are known by their local geographic names, as follow: Araçoiaba (Late Carboniferous), Mafra-Ortigueira, Lontras, Capivari, and Passinho (Early Permian) shales. These are associated to trangressive events and are widespread in the Parana basin. Hence, these are useful as sequence boundary markers. However, in the outcrop belt area those mudstones are very difficult to correlate. This is the case of the ?Capivari shale? at the mid portion of the homonymous unit, which is mapped in the central-eastern region of the State of São Paulo. Some authors have correlated this unique marine bed with the Lontras shale in the upper third of the glaciogenic succession of the Itararé Group. However, others have correlated the Capivari shale with the Passinho shale and associated fossil-rich beds of the uppermost portion of the Taciba Formation. Ongoing taxonomic revision of the Permian bivalve fauna of the Capivari Formation, on the basis of the type material studied by J.C. Mendes in 1952 and newly found fossils, allowed us to better constrain the biocorrelation of the Capivari shale. The fauna includes Phestia sp. (=Nuculana? sp.), Streblopteria? sp., Praeundulomya cf. subelongata Dickins, 1963 and Limipecten capivariensis (=Aviculopecten capivariensis Mendes, 1952). All these genera occur in the uppermost portion of the Taciba Formation, in Teixeira Soares, PR. Particularly noteworthy is the record of P. cf. subelonagata that also occurs not only in marine assemblage of Teixeira Soares, but also in the Fossil Cliff Formation, Carnavon Basin, Western Australia. Hence, the Capivari bivalve fauna closely resembles that one of the uppermost portion of the Taciba Formation of the southern Brazil, suggesting biocorrelation with the Passinho shale. Deposition of this shale is linked to the widespread Early Permian (Asselian-early Sakmarian) demise of Gondwana ice sheets. This is also supported by the bivalve biocorrelation between the Capivari and Australian molluscan faunas. Thus, the Capivari shale and associated marine fauna might be younger than previously realized. [FAPESP 2009/17555-0]