Explorando protocolos de luminescência para datar sedimentos mais antigos do oeste da Amazônia

• Processo: 25/19548-3
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Pós-Doutorado
• Data de Início da vigência: 01 de dezembro de 2025
• Data de Término da vigência: 28 de fevereiro de 2026
• Área de conhecimento: Ciências Exatas e da Terra - Geociências - Geologia
• Pesquisador responsável: Fabiano do Nascimento Pupim
• Beneficiário: Priscila Emerich Souza
• Supervisor: Mayank-Jain
• Instituição Sede: Faculdade de Filosofia, Letras e Ciências Humanas (FFLCH). Universidade de São Paulo (USP). São Paulo , SP, Brasil
• Instituição Anfitriã: Technical University of Denmark (DTU), Dinamarca
• Vinculado à bolsa: 21/14022-2 - Reorganização da rede de drenagem do Oeste da Amazônia no Neógeno e Quaternário baseada na proveniência de sedimentos resolvida por técnicas de luminescência, BP.PD
• Assunto(s): Sedimentologia
• Palavra(s)-Chave do Pesquisador: Isothermal TL | Luminescence dating | Pleistocene fluvial terraces | Tadp | Thermally transferred OSL | Sedimentologia

Resumo

This proposal is related to the development of a Research Internship Abroad (BEPE) project to complement the postdoctoral research (FAPESP 2021/14022-2) that the proponent has carried since November 2022. The scope of the original postdoctoral project includes obtaining new optically stimulated luminescence (OSL) ages from older deposits in the western Amazon, which demands pushing the limits of the OSL method. Recently, sediment samples for OSL dating analysis were obtained from the Acre drilling core that was recovered in 2023 under the "Trans Amazon Drilling Project - TADP" (FAPESP 2018/23899-2), which this research is associated with. First analysis on four samples along the top 20 m depth of the TADP-AC core showed that even the shallowest sample of the core (at ~1 m depth) is beyond the limits of conventional quartz OSL dating, because the signal is above saturation. Based on the double of the characteristic dose (2D0) of 135 ± 8 Gy (n=9) and 180 ± 13 Gy (n = 5) and given the dose rates of 1.51 ± 0.09 Gy/ka and 1.91 ± 0.12 Gy/ka for quartz, the samples at 1.3 and 10 m depth would correspond to minimum ages of 89 ka and 94 ka, respectively. Feldspar signals at 4 and 21 m depths were also tested employing the post-infrared infrared stimulated luminescence (pIRIR) protocol at 290 °C. Still, they also proved to be in saturation (2D0 ~600 Gy) and, thus, could only provide minimum ages too. Given a dose rate of 3.19 ± 0.18 Gy/ka for feldspar, the sample at 21 m depth would correspond to a minimum age of 198 ka. Similarly, depositional ages of some samples from older terraces of the Juruá River, western Amazon, which are also part of the scope of this postdoctoral research, remain poorly constrained due to quartz saturated signals. Improving the geochronological framework of these fluvial deposits is crucial for better understanding the reorganization of the western Amazon drainage system. However, this may only be achieved by employing other protocols that are less routinely applied and time-consuming, such as thermal-transferred OSL (TT-OSL) on quartz. Employing protocols that challenge the upper limits of the luminescence dating method is not a trivial task. Specialized assistance and the availability of one or more luminescence readers (for several days) are greatly appreciated to design and optimize measurements, and to ensure data reliability. Thus, we propose to develop this BEPE project over a three-month-stay at the laboratory facilities for luminescence analysis at the Department of Physics, Technical University of Denmark, worldly known as an advanced and well-equipped OSL laboratory, with a highly specialized OSL research team. This project is to be supervised by Dr. Jain Mayank, a renowned researcher on luminescence methods, and associated researcher of both TADP and this postdoctoral project.