Magnetic anisotropy to obtain relative paleointensity in speleothems

• Grant number: 22/05094-2
• Support Opportunities: Scholarships in Brazil - Master
• Start date: September 01, 2022
• End date: September 30, 2023
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geophysics
• Principal Investigator: Ricardo Ivan Ferreira da Trindade
• Grantee: Carolina Silveira de Moraes
• Host Institution: Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The terrestrial magnetic field presents rapid variations, both in its direction and (declination and slope), and in its intensity. These variations are recorded currently in observatories around the globe and also by satellites. For periods prior to the last two centuries, the investigation of the magnetic field is carried out indirectly, from its record in archaeological materials, sediments andvolcanic rocks. More recently, speleothems - which are formations produced by the precipitation of calcium carbonate in caves - have been intensively studied as records of recent field variations. Speleothems have several advantages when compared to other types of records due to their ability to perform continuous records, with good dating by the U-Th method and not showing the effects of post-depositional compaction. The objective of this project is to evaluate the methods of obtaining of the relative paleointensity of the field from speleothems, in particular the use of magnetic anisotropy of these formations. Initially, the anisotropy technique as paleointensity indicator will be tested in artificial speleothems, built in controlled field. Subsequently, magnetic anisotropy measurements will be carried out in speleothems from the collection of the Laboratory of Paleomagnetism at USP (USPmag), which have already been analyzed by other methods. The anisotropy techniques to be used will be: magnetic susceptibility anisotropy (ASM), remanence anisotropy ansteretic magnetic field (AARM), isothermal remanence anisotropy (AIRM). These data will be complemented with analyzes of natural remanent magnetization (NRM), analysis of hysteresis curves, First-Order Reversal Curves (FORC), curves low temperature thermomagnetics and MRI acquisition curves. (AU)