Evidências de vida no ediacarano inferior da Bacia do Itajaí, SC

Abstract

In Brazil, the occurrences of macrofossils become scarcer as increase the age of the sediments and the intensity of the processes of diagenesis and/or metamorphism, being extremely rare the pre-ordovician fossil record. In the valley of the Itajaí river (east of the Santa Catarina State, southern Brazil), occur, with relative profusion and easy access, well preserved outcrops of the Itajaí Basin. This is filled by related siliciclastic sedimentary Neo-proterozoic strata of the amalgamation of the west of the Gondwana. In diverse related outcrops of prodeltaic deposits had been found life registers, the majority represented for biogenic constructions such as microbial mat. Also occur great outcrops whit impressions of macrocospic organisms, some of typically ediacaran age (Parvancorina sp, Charniodiscus? sp. and Ciclomedusa), other internationally attributed to the Cambrian period (Choia sp.), and others, described in this work, still with uncertain affinity. In the studied sediments, also occurs microfossil (acritarchs) of ediacaran age. Volcanoclastic félsico layer collected in fossiliferous outcrops, and the zircon was dated by SHRIMP method, points 642+12 My as maximum age with respect to the beginning of the fulfilling of the basin, and 606+8 My as age of the volcanogenic episode. This geocronologic interval corresponds to the end of the great Neo-proterozoic glaciations, and this work presents the second register of metazoan found in this period until the moment.