Geochronology of ferruginous duricrusts from the State of Tocantins

• Grant number: 23/14305-0
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: August 01, 2024
• End date: July 31, 2026
• Field of knowledge: Agronomical Sciences - Agronomy - Soil Science
• Principal Investigator: Pablo Vidal Torrado
• Grantee: Daniela Schievano de Campos
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil

Abstract

The little explored landscapes of the state of Tocantins contain surfaces and soils that are supposedly among the oldest on the planet. Ferruginous duricrusts protect high plateaus with extensive flattened surfaces and they result from long periods of intense chemical weathering associated with recurrent mineral dissolution and reprecipitation. Their highly hardened nature allows them to survive for a long time, making them reliable tools for studying and reconstructing ancient tropical landscapes. This project aims to take advantage of the enormous occurrence of ferruginous duricrusts in Tocantins, particularly those that are more cemented and which favor dating, in order to decipher the evolution of the landscape and correlate it with other occurrencesin the tropical region and in particular in the Brazilian Cerrado. To achieve this, modern geochronological methods specialized in dating chemical weathering events will be used, as well as in determining denudation rates. Dating methods by (U-Th)/He, in iron oxides, and 40Ar/39Ar, in manganese oxides, will be used to identify the main periods of mineral precipitation on different elevation levels surfaces. Furthermore, the use of the cosmogenic isotope ³He will be of fundamental importance in determining the erosion rates that affect different parts of the environment. After fieldwork, laboratory studies will take place partly in Brazil (mineralogy, geochemistry, micromorphology) and later in Australia and the United States (dating and cosmogenic analyses).