Late Holocene paleosecular variation and relative paleointensity record from Lagoa dos Patos (Rio Grande do Sul, Brazil)
Abstract
Lake sediments are important recorders of the paleomagnetic secular variations and provide information on the mechanisms of the geodynamo. These data provide important information to construct geomagnetic field models and numerical dynamo simulations. Geomagnetic models and paleomagnetic data for the past few millennia are also used to understand important geomagnetic field structures, such as the strong non-dipole field feature in the South Atlantic, the so-called South Atlantic Magnetic Anomaly (SAMA). The southern hemisphere, in particular the South American continent, contributes only with a small fraction of the global paleosecular variation database. Here we present a preliminary paleomagnetic and rock magnetic study from two cores of lake sediment (PT-04 and PT-06) collected at Lagoa dos Patos, Rio Grande do Sul State, South Brazil. Four accelerator mass spectrometer (AMS) radiocarbon data has indicated ages from 4.200 to 3.200 years BP. Hysteresis and isothermal remnant magnetization (IRM) curves were obtained for analysis of magnetic mineralogy. The paleodirectional curves obtained for this region are correlated with each other, as well as the data of the relative paleointensity parameters (NRM / χ, NRM / SIRM, and NRM / ARM). Inclinations vary from -10º and -59º and suggest strong variations between 3800-4000 years for the two cores. Relative paleointensity data show variations that can be interpreted due the persistent presence of SAMA in South America between 4.200 and 3.200 years BP. However, the improvement of age model and new paleomagnetic analysis will be conducted to better constrain the South America paleosecular database.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGP41A0779S
- Keywords:
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- 1513 Geomagnetic excursions;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 1521 Paleointensity;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 1522 Paleomagnetic secular variation;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 1535 Reversals: process;
- timescale;
- magnetostratigraphy;
- GEOMAGNETISM AND PALEOMAGNETISM