Microfossils from volcaniclastic rocks of Serra Geral Group: establishing a background knowledge using Harvard paleontological collections and field sampling

• Grant number: 21/14704-6
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor
• Start date: April 12, 2022
• End date: April 11, 2023
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geology
• Principal Investigator: Valdecir de Assis Janasi
• Grantee: Lucas Del Mouro
• Supervisor: Javier Ortega-Hernández
• Host Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: Harvard University, United States
• Associated to the scholarship: 21/01886-9 - Palynology analyses of sedimentary and volcanoclastic rocks associated to Serra Geral Group, BP.PD

Abstract

The Paraná-Etendeka traps (PELIP), one of the best known Large Igneous Provinces (LIP), comprises the Lower Cretaceous magmatism that covers the central western region of South America and part of modern-day Namibia. Over the last century, this LIP has been intensively studied, and it is now widely acknowledged as the main trigger for the opening of the South Atlantic Ocean and possibly the Valangian Weissert oceanic anoxic event. In Brazil, the PELIP is recognized as the Serra Geral Group (SGG), emplaced over and interdigitated with the aeolian sandstones of the Botucatu Formation (BF). Recently, the investigation of sedimentary and volcaniclastic rocks of the SGG has provided new insights into the paleoenvironmental conditions during the Late Jurassic-Early Cretaceous period in the region. Petrographic indicators, such as vesiculated sediment and sediment-filled fractures, allowed reconstructing lacustrine settings (small ponds) and to hypothesize a paleoclimatic shift to more humid conditions. This emerging picture raises the question of whether evidence of life could be found in such unconventional depositional settings. A positive answer to this question was brought by our recent discovery of rare microfossils within the volcaniclastic succession, but the study of this paleontological material has been severely impeded by a lack of fossils with similarly complex diagenetic histories that could be used for comparison. To overcome these difficulties, we propose to study the extensive Invertebrate Paleontology collections at the Harvard Museum of Comparative Zoology to establish a background understanding of how microfossil assemblages preserved in volcaniclastics are impacted by diagenesis, and how this impact may limit their use in paleoenvironmental and paleoclimatic studies. This work at Harvard University will be complemented by the study of Cambrian soft-bodied fossils from the highly metamorphosed Weeks Formation in Utah and Quaternary peperites from Hawaii. (AU)