Geologia e paleontologia das formações Tatuí e Irati no centro-leste do Estado de São Paulo [thesis]

Artur Chahud
Petalodontiformes (Itapyrodus punctatus e I. sp.) e Holocephali indeterminados. A fauna de Osteichthyes é a mais abundante em número de espécimes, sendo composta, predominatemente, de dentes e escamas paleoniscóides, raras escamas de Coelacanthimorpha, partes ósseas e dentes labirintodontes, estes atribuídos a Osteolepiformes e a tetrápodes Temnospondyli. Os fósseis estão normalmente dispersos e desarticulados e os elementos ósseos fragmentados e desgastados. O conteúdo fóssil da fácies
more » ... síltico do Membro Taquaral é raro, os mais comuns são crustáceos, principalmente do gênero Clarkecaris, e restos muito fragmentados de Coelacanthimorpha e Palaeonisciformes. ABSTRACT The following Paraná Basin, Late Paleozoic lithoestratigraphic units, the upper part of the Tatuí Formation, located under the lower part of the Irati Formation, Taquaral Member are cropping out at center-eastern State of São Paulo, Brazil, between Rio das Pedras and Leme. The lithologies, fossil contents and taphonomy of these units are studied through stratigraphic sections, allowing the formulations of paleoecological and paleoenvironmental hypothesis. Four facies were recognized at the top of the Tatuí Formation stratigraphic sections which were interpreted as following; the basal an uncertain paleoenvironment of deposition, two paleoenvironmental contexts; mostly continental and one under deposits marine influence. The two facies interpreted as mostly continental are respectively, sandy-siltstones facies with freshwater fossils and coarse to conglomeratic sandstone, Ibicatu facies, locally with log plants. The top facies, interpreted as under a marine influence, is characterized by deposits of fine sandstones, occasionally with large cross beds, hummockies, and, locally, tidal deposits, suited for a large body, of saline water. The fossil content of Tatui Formation include three kinds of trace fossils in three different facies (basal, Ibicatu and top respectively), large stem plants (Pterydophyta and Spermatophyta) in the Ibicatu deposit, with indeterminated fragments of crustaceans and conchostraceans, found out in the siltstone facies and scales, teeth and bone pieces, found out in siltstone and of the top facies. Two facies were recognized at the Taquaral Member. The basal are fine to conglomeratic sandstone with irregularly grain size both horizontal and vertically, with ichthyofossils. It is interpreted as laid down in a salty shallow water dominated by waves. The second are silty shale laid down in low saline water. The fossils of the sandy facies are Chondrichthyes: cladodontes teeth, Euselachii finspines (Amelacanthus and Iratiacanthus santamariaensis), Ctenacanthiformes finspines (Sphenacanthus sanpauloensis and S. sp.), Xenacanthiformes teeth, Diplodoselachidae (Taquarodus albuquerquei) and Xenacanthidae, Orodontiformes: Orodus ipeunaensis, Petalodontiformes (Itapyrodus punctatus and I. sp.) and undetermined Holocephali. The fauna of Osteichthyes, the most abundant in number of specimens are predominantly paleoniscoid teeth and scales, rare Coelacanthimorpha scales, labyrinthodonts bones and teeth, assigned to Osteolepiformes and tetrapods Temnospondyli. The fossils are usually scattered, disorganized, fragmented and worn. The fossil content of the Taquaral silty-shale facies is meager, the most common are crustaceans, mainly of the genus Clarkecaris, and very fragmented remains of Coelacanthimorpha and Palaeonisciformes.
doi:10.11606/t.44.2011.tde-29102012-120319 fatcat:njihvujwnrafvgbsrsa26z5tbm