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Trace fossils from Tamengo and Guaicurus formations (Ediacaran-Cambrian), Corumbá Group: paleoenvironmental and paleoecological implications

Grant number: 17/25433-8
Support type:Scholarships in Brazil - Doctorate
Effective date (Start): April 01, 2018
Effective date (End): February 12, 2021
Field of knowledge:Physical Sciences and Mathematics - Geosciences
Principal Investigator:Juliana de Moraes Leme Basso
Grantee:Cleber Quidute Clemente Diniz
Home Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil
Associated research grant:16/06114-6 - The Neoproterozoic Earth System and the rise of biological complexity, AP.TEM
Associated scholarship(s):18/21995-4 - Analisys of Precambrian trace fossils of Corumbá Group in a global context , University of Saskatchewan, Saskatoo - Canada, BE.EP.DR

Abstract

The Cambrian Explosion represents one of the most critical events in Earth's history. This increase in the diversity and complexity of fossils and ichnofossils is marked by the expansion of sediment exploitation, which has caused a drastic change in the environment and allowed the formation of new habitats. In the Neoproterozoic, the ichnofossils are simpler mirroring their producers, but they are of paramount importance, because describe the characteristics of these activities in a moment which the organisms would be differentiating and specializing, helps in the evolutionary understanding of then. Used in an integrated way with the sedimentological and stratigraphic analysis, the study of ichnofossils is applied as an additional tool to paleoenvironmental and stratigraphic analysis of sedimentary deposits. In Brazil, the pre-Cambrian-Cambrian ichnofossils register is scarce, both due to the lack of geological units and the difficulty of preservation. In the Bambuí Group, Sete Lagoas Formation, are found ichnofossils attributed to Palaeophycus and Archaeonassa. Ichnofossils of Cambrian age were described in the Northern part of the Paraguayan belt in the Upper Paraguay Group of Skolithos linearis. Diplocraterion parallelum, Arenicolites sp. In the South Paraguay belt, in Mato Grosso do Sul, the Corumbá Group is located, in which the Guaicurus Formation corresponds to the top and has gradational contact with the Tamengo Formation of age 542 M.a. In the Guaicurus Formation, macroalga named Eoholynia corumbensis and icnofossils with sinuous tube, forming sub-horizontal tunnels and an irregular network with multiple layers, and bilobed-like trace fossils are found. This project will be based around paleontological issues related to the morphological description and taxonomic identification of the ichnofossils through equipment such as stereomicroscope, scanning electron microscope, microtomography, chemical analysis by EDS and Raman spectroscopy. Paleoenvironmental, paleoecological and biostratigraphic issues related to the impact that bioturbatory organisms would cause to the environment, such as oxygenation rate and substrate revolving through the analysis of trace elements that react according to paleoenvironmental conditions. These elements are useful as paleoredox proxies because their presence / absence and oxidation are directly linked to the redox condition of the depositional environment.