Using feldspar luminescence methods for dating Middle Pleistocene fluvial deposits of the Negro River, Amazonia

• Grant number: 24/07848-0
• Support Opportunities: Scholarships abroad - Research Internship - Master's degree
• Start date: August 01, 2024
• End date: October 31, 2024
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Physical Geography
• Principal Investigator: Fabiano do Nascimento Pupim
• Grantee: Renan Cassimiro Brito
• Supervisor: Mayank-Jain
• Host Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: Technical University of Denmark (DTU), Denmark
• Associated to the scholarship: 23/10430-4 - Paleogeographic reconstruction of the middle Negro River during the Quaternary: a geomorphological-geochronological approach, BP.MS

Abstract

The Amazonian watershed is the greatest in the world and the birthplace of one of the most biodiverse ecosystems on Earth. The growing knowledge of the role of the fluvial dynamic in the evolution of the Amazonian landscape contrasts with few available absolute ages for the sedimentary deposits. Enhancing the geochronological dataset of these deposits is crucial as it allows the paleohydrologic reconstruction of the rivers and associated wetlands. Overall, the present project aims at reconstructing the geological evolution of the middle Negro River during the mid-late Quaternary (<500 ka), based on new geomorphological and sedimentary data, and optically stimulated luminescence (OSL) dating. Over 40 samples were collected from terraces and floodplains along the Negro River and its main tributaries. Up to date, we could obtain optically stimulated luminescence (OSL) ages of 16 out of 21 samples due to quartz OSL signal saturation. Geological field knowledge and preliminary screening OSL tests tell that several of the samples remaining to be dated are also above quartz OSL dating limits and, thus, should be dated employing other dating approaches. Then, the objective of this internship project is to overcome the OSL limitations on determining the age of older terraces (~25 samples) employing more sophisticated luminescence protocols designed for feldspar grains, whose luminescence signal saturate at considerably higher doses. Working with feldspars is somehow more complicated than working with quartz and, thus, it is desirable to have more time to perform tests (i.e., to have a dedicated luminescence reader for longer time) and to be accompanied by experts on infrared stimulated luminescence (IRSL) dating. The Nordic Luminescence Laboratory (NLL) in Denmark is a world reference in luminescence dating advances and offers both the necessary infrastructure and specialized team. Our efforts and results will contribute to generate the most detailed geochronological records of the landscape evolution of the Negro River and, thus, allow us refining the interpretations about its evolution and the possible causal correlations with climate changes and tectonics that occurred during the mid-late Quaternary.