Paleobiology of Itajaí Basin (Ediacaran? Santa Catarina): evolutionary and paleoecological implications

Abstract

In the Ediacaran, soft-body organisms and animals with biocalcifiedskeletons became part of the biosphere that stated some forms and ecologicalstructures that enunciated and evolved in the Phanerozoic ecosystems. The EdiacaranBiota has representatives compiled in diverse parts of the world, temporally stratified inthe Avalon, White Sea and Nama assemblages, each one with intrinsic evolutionaryand paleoecological and, sometimes, paleoenvironmental peculiarities. Earth'sgeological history has shown deep relationships between the patterns of evolution anddiversification of life and environmental changes. These issues can be investigated inthe depositional environments of Ediacaran fossils, being able to reveal synergisticeffects between paleoautoecology, paleosinecololy and paleoenvironment in theseassemblages. In this context, the Itajaí Basin, Santa Catarina, seems to be animportant geologic unit of South America, with paleontological implications that cancompose the synthesis of knowledge about the dawn of animal life and thestructuration of marine ecosystems. Its record presents fossils of megascopicorganisms compatible with the typical Ediacara Biota, besides fossils already attributedto the Cambrian, such as Choia and Chancelloria. If the presence of Cambrian fossilsin Ediacaran rocks were corroborated in the Itajaí Basin, this would imply in abiostratigraphic set back of ca. 40-50 Ma. for these taxons. The paleobiologicalimplications of sponges in the Ediacaran, for example, would be revealed in ecosystemengineering and possible environmental rearrangements arising from the activity ofthese organisms. Therefore, this project aims to: a) investigate the taxonomicalcomposition, as well as its variation in the Itajaí Basin; b) verify the evolutionary andpaleoecological moments of this unit; c) model the paleoenvironments of the fossils bymeans of taphonomical aspects and MISS morphology; and d) establish comparisonswith correlate unities and chronologies in Australia, England and Newfoundland, tobetter interpretation of the evolutionary context of Itajaí Biota. Therefore, in addition tothe classic observation analysis, we will use paleometrical techniques such, as Micro-CT, Raman Spectroscopy, X-ray Fluorescence (XRF), Scanning Electron Microscopycoupled with Energy Dispersive Spectroscopy (EDS), and SHRIMP zircon dating. Thedating will be realized by SHRIMP U/Pb radiometric analysis.