The Permian Tiaraju bivalve assemblage, Passa Dois Group, southern Brazil: biostratigraphic and paleobiogeographic significance

Abstract

Permian bivalves of the Paraná Basin evolved in a large inland sea, under conditions of extreme isolation and environmental stress. Although known since 1918, its evolutionary history is still obscure due to the incomplete and biased information on faunal composition and stratigraphic distribution of various assemblages. Hence, the description of the Tiaraju assemblage, the only known bivalve occurrence in the Passa Dois Group from the southernmost Brazil, adds new key information on the composition, biocorrelation and age of this unique molluscan fauna. Terraia falconeri, Cowperesia emerita, Holdhausiella elongata, and Terraia altissima were recorded and described. T. falconeri is the commonest species, followed by C. emerita, H. elongata and T. altissima. The faunule is mainly composed by Terrainae, lacking Pinzonellinae. Assemblage is, thus, poorly diversified, both regarding the faunal composition and guild structure (only infaunal, facultatively motile, unattached, suspension feeders present). Cowperesia emerita and T. altissima strongly indicate biocorrelation with assemblages of the Rio do Rasto and Gai-As formations, Brazil and Namibia, providing an age no younger than the mid-Permian (Wordian-Captianian). On the light of this information, the current geological map of the Tiaraju region, São Gabriel, and the local boundary between the Teresina and Rio do Rasto formations requires reevaluation.

A Permian mixohaline ostracod association of the Teresina Formation, Paraná Basin, Brazil

“…These mixed microfacies, and particularly calcisiltites in the depositional context of the Passa Dois Group, can be accumulated in a wide spectrum of marginal marine paleoenvironments (e.g., lagoons, estuaries, deltas). It is reflected in rich fossil assemblages, which include, for instance, fishes (e.g., Würdig-Maciel, 1975), ostracods (Sohn & Rocha-Campos, 1990;Bergue et al, 2020), temnospondyls (e.g., Dias et al, 2020), conchostraceans (e.g., Ferreira-Oliveira & Rohn, 2010, bivalvia (e.g., Simões et al, 2017) and palynomorphs (e.g., Mori & Souza, 2012).…”

“…The Serra Alta Formation represents its maximum marine influence, and the overlaid Teresina Formation registers pelites with tide influenced structures, which characterizes the inception of new ecological conditions (Milani et al, 2007). According to Simões et al (2017) and Guerrini et al (2020), these processes represent the establishment of a confined epeiric sea, followed by a trend of shallowing and continentalization in the basin. In marginal areas of this epeiric sea, several types of environments with variable salinity gradients might have been established (Ng et al, 2019), such as estuaries, bays, lakes, lakes with occasional marine influence, and lagoons as discussed by Bennett et al (2011).…”

Microbial Landscapes in the Permian Gondwana: Microbialite Beds of the Teresina Formation at the Northeast Border of the Paraná Basin, Brazil

“…There is no radiometric data for the Teresina Formation, but volcanic-ash horizons from the Irati Formation yielded age of 278.4±2.2 Ma (late Cisuralian) (Santos et al, 2006). In turn, the base of the Rio do Rasto Formation is correlated by the Leinzia similis Zone to the Gai-Az Formation, in Namibia (Rohn 1994;Simões et al, 2017), where the shells are associated with volcanic-ash horizons dated in 265.5±2.2 Ma (middle Guadalupian) (Stollhoffen et al, 2000). For the Serra Alta Formation, the Lueckisporites virkkiae Zone indicates a late Cisularian to Guadalupian age (Maranhão & Petri, 1996;Di Pasquo et al, 2018).…”