Pedogenic Magnetic Minerals and Orbital Cycles in the Equatorial Margin

• Grant number: 25/01156-1
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• Start date: April 01, 2025
• End date: July 31, 2026
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geology
• Principal Investigator: Luigi Jovane
• Grantee: Manoel Damaceno Pereira Neto
• Host Institution: Instituto Oceanográfico (IO). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 16/24946-9 - Sea-level changes and Global Monsoon System: clues from marine cores in Brazil, AP.PFPMCG.TEM

Abstract

The Milankovitch Cycles are well-known for their influence on Earths climate throughout the geological past. Despite the low amplitude of insolation variations at orbital scale, the signal is preserved in the geological record through non-linear climatic response. The orbital cycles strongly influence the South American Monsoon, however, studies identifying these cycles in marine records from the equatorial margin, particularly in elemental ratios, are scarce. Instead, marine cores often show a strong influence of Heinrich Events. Environmental magnetism studies on marine cores from the Brazilian equatorial margin are limited, and the parameters used are frequently dependent on the signal from ferrimagnetic minerals. However, in well-developed soils, intense oxidation of magnetite may occur, leading to the formation of more oxidized mineral phases. To address this issue, proxies based on minerals such as goethite and hematite are used in some studies of marine sediments or soils. Thus, the semi-quantification of goethite and hematite serves as a proxy that potentially records climatic changes associated with hydrological regime. This project aims to understand how variations in the monsoon regime affect the input of terrigenous and magnetic minerals into coastal marine basins of the Brazilian equatorial margin. To achieve this goal, five marine cores are already available and on additional core will be sampled. Furthermore, soil and alluvial sediments samples will be collected over the Rio Parnaíba and Atlântico Nordeste Oriental drainage basins. The samples will be analyzed for mineralogical composition (including magnetic minerals), geochemical properties, textural, and environmental magnetism. Spectral analysis and Dynamic Time Warping techniques will be applied to the marine cores to detect and correlate climatic variability. The results from the characterization of continental samples will be integrated with the marine core data using a source-to-sink approach to understand the processes controlling the transmission of climatic signals to marine deposits. (AU)