Calibration of luminescence sensitivity of quartz as proxy for precipitation

• Grant number: 25/04437-1
• Support Opportunities: Scholarships in Brazil - Master
• Start date: July 01, 2025
• End date: June 30, 2027
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geology
• Principal Investigator: Vinícius Ribau Mendes
• Grantee: Thais Cortez Machado
• Host Institution: Instituto do Mar (IMar). Universidade Federal de São Paulo (UNIFESP). Campus Baixada Santista. Santos , SP, Brazil
• Associated research grant: 22/02957-0 - Effects of the South Atlantic warming over South American precipitation, AP.PNGP.PI

Abstract

The sensitivity of luminescence can be understood as the intensity of light emitted per unit mass of a given luminescent material and per unit of ionizing radiation to which the material has been exposed. In this project, the application is based on optically stimulated luminescence (OSL) and thermoluminescence (TL) of quartz. The use of OSL and TL from quartz as an indicator of precipitation in marine sediment cores was successfully described and tested for the first time by the researcher responsible for this proposal in Mendes et al. (2019), a scientific article resulting from his PhD research (FAPESP 2013/21942-4). OSL/TL sensitivity can be used as a tracer of fluvial discharge, which in turn is directly linked to continental precipitation. Compared to other existing methods, this new approach offers significant advantages, as it is less sensitive to sea level variations, allows for rapid data acquisition, and has lower costs compared to hydrogen isotopes in leaf waxes (Mendes et al., 2019). A high correlation was found between luminescence data and precipitation derived from climate models for the Parnaíba River basin (Mendes et al., 2019). This correlation suggests the possibility of obtaining quantitative precipitation data using the new indicator, which would represent a major advancement in paleoclimatology. However, to test this possibility, it will be necessary to calibrate the method by comparing luminescence sensitivity results with measured precipitation data. For the first attempt at luminescence calibration, we propose collecting sediment cores from reservoirs formed by the Paulo Afonso and Sobradinho dams, inaugurated in 1955 and 1974, respectively. Based on the sediments accumulated in these reservoirs, it will be possible to compare approximately 70 years of luminescence data with meteorological station records from the same basin, establishing the relationship between precipitation variations and luminescence sensitivity values. (AU)