Paleoprecipitation reconstitution of Northeast Brazil over the Holocene based on speleothems isotope records from Gruta do Jerônimo

• Grant number: 22/14915-0
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor
• Start date: May 01, 2023
• End date: July 23, 2023
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geology
• Principal Investigator: Francisco William da Cruz Junior
• Grantee: Giselle Utida
• Supervisor: Hai Cheng
• Host Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: Xi'An Jiaotong University, China
• Associated to the scholarship: 20/02737-4 - Teleconections between tropics and extra-tropics of South America, BP.PD

Abstract

The Intertropical Convergence Zone (ITCZ) and the South America Monsoon System (SAMS) are the main responsible for convection over tropical region in South America. According to our previous results, the atmospheric dynamic between ITCZ and SAMS changed throughout the last millennia over Northeastern Brazil (NEB) causing climate fluctuations not expected for some regions. Results from Trapiá Cave and Boqueirão Lake in northern NEB (N-NEB) point to a new ITCZ pattern for the last 2500 years. Comparing this pattern with eastern Amazon it is possible to described a local zonal change in ITCZ during the same period. Previous and recent oxygen isotope results from Gruta do Jerônimo, located in the southern limit of NEB, at Bahia (BA) and under influence of SAMS, suggest that this ITCZ zonal pattern can be related to changes in SAMS in southern NEB (S-NEB). Our hypothesis is that changes in the atmospheric circulation over NEB resulted in different patterns of precipitation in the region between N-NEB and S-NEB, while eastern Amazon could behavior as an axis among these regions, sometimes being in phase with N-NEB and other times in phase with S-NEB. The main goal of the research is better comprehending the dynamic relationship between ITCZ and SAMS by reconstructing precipitation based on the isotope studies covering the last two millennia in NEB. Previous U/Th dates and oxygen isotopes obtained in stalagmites from Gruta do Jerônimo indicate great potential for studies covering the Holocene, specially the last two millennia. A detailed geochronological study of these stalagmites will be essential to continue the paleoprecipitation reconstruction of the region and test our hypothesis. These samples will be dated by U/Th method at the laboratories of Xi'an Jiaotong University (China), using a multi-collector inductively coupled plasma mass spectrometry technique (MC-ICP-MS, Thermo-Finnigan NEPTUNE). The results will refine stalagmite age models for paleoprecipitation reconstructions from Bahia of the last two millennia that will be compared with NEB and other records of South America to better understand the relationship between ITCZ and SAMS through time. Other U/Th results obtained will be essential to complement the stalagmite set covering the Holocene and explore non-dated samples for new potential studies. (AU)