Late Paleozoic marine faunal succession in the Itararé Group, Paraná Basin, Brazil: toward an integrated brachiopod and bivalve biocorrelation scheme

NEVES, JACQUELINE P.; TABOADA, A. C.; PAGANI, M.A.; WEINSCHÜTZ, L.C.; SIMOES, MARCELLO

Madrid

Congreso; 15th Gondwana Conference; 2014

During the Late Paleozoic, the Paraná Basin was a huge intracratonic basin mainly filled bycontinental, marine and fluvial deposits. In this context, the basal portion of the Carboniferous?Permian sequence corresponds to the Itararé Group. This records one of the most continuous and thickest glacio-marine successions in South American Gondwana, including glacial diamictites, sandstones and shales. The succession is capped by coal-bearing sandstones of the Sakmarian? Artinskian Rio Bonito Formation. Marine invertebrates are rare and sparsely distributed in the Itararé succession. However, in the eastern border of the basin, at least nine marine assemblages were recorded in the Mafra and Rio do Sul (=Taciba) formations. Ongoing taxonomic analyses indicate that 10 brachiopod and 19 bivalve species can be recognized. Low diverse, linguliform dominated brachiopod assemblages are recorded in the mid portion of the Mafra Formation (late Carboniferous) and in the basal portion of the Rio do Sul Formation (Lontras shale, Carboniferous?Permian boundary), and are associated with marine intercalations generated by transgressive events. At the top of the Rio do Sul/Taciba Formation, above the last diamictite beds, at least seven bivalve-dominated assemblages were recorded. The unique exception is the Butiá assemblage, Mafra county, Santa Catarina state, which is dominated by productidbrachiopods. The older fauna, the Heteropecten paranaensis-Pleurophorella sp. assemblage, is recorded in sandstones deposited in shallow water conditions. This is stratigraphically succeeded by the following assemblages: Praeundolomya cf. subelongata-H. paranaensis; Exochorhynchus itararensis- Cosmomya (Paleocosmomya) baitaquensis-H. paranaensis (plus Tomiopsis cf. harringtoni and Streptorhynchus? sp.); Atomodesma (Aphanaia) orbirugata-H. paranaensis (plus Sulciplica? sp.); and Myonia argentinensis-H.paranaensis assemblages, which were found in siltstones deposited in shelf conditions. Theyoungest fauna is represented by the Phestia aff. sabattiniae-Palaeoneilo sp. (plus Chonetes? rionegrensis, Crurithyris roxoi, Langella? imbituvensis and Orbiculoidea guaraunensis) assemblage and is recorded in massive or well-laminated shales, deposited under anoxic to dysaerobic offshore conditions. Within the studied assemblages key bivalve species for biocorrelations are: A. (Aphanaia) orbirugata, H. paranaensis and M. argentinensis, which indicate correlations with the Eurydesma Fauna of the Bonete Formation, Sauce Grande?Colorado basin, Argentina. The probable occurrences of Tomiopsis cf. harringtoni in the E. itararensis-C. (Paleocosmomya) baitaquensis-H. paranaensis assemblage would also support this correlation. The presence of the productid brachiopod Lyonia and pectinid bivalves (=Heteropecten) in the Butiá assemblage, Taciba Formation, is also noteworthy, suggesting a possible late Asselian?early Sakmarian age, and biocorrelation with Gondwanandeposits of the Carnarvon and Perth basins, Western Australia. In summary, the taxonomiccomposition of the faunal succession of the Itararé Group, mainly of the Rio do Sul/TacibaFormation, suggests the presence of endemic species in association with marine, cosmopolitan and Gondwanan brachiopod and bivalve species. This offers valuable clues to better constrain these faunas to the late Asselian?early Sakmarian lapse, linking them to faunas of eastern Argentina and, to a lesser extent, Western Australi.