Late Holocene paleosecular variation and relative paleointensity records from Lagoa dos Patos (southern Brazil)

Lake and lagoon sediments are important recorders of the Earth's magnetic field variations. However, the Southern Hemisphere, particularly the South American continent, contributes only a small fraction of the global paleosecular variation (PSV) and relative paleointensity data, which hinders a better understanding of the global PSV. Moreover, the scarcity of information on the geomagnetic field in South Brazil for the past few millennia impedes, for example, a detailed analysis of the evolution of the South Atlantic Magnetic Anomaly (SAMA), which encompasses the weakest geomagnetic field on the Earth's surface. Here, we present high-resolution paleomagnetic and rock magnetic data of two cores collected at the lagoon of Lagoa dos Patos, Rio Grande do Sul State, Brazil. Sediment cores from Lagoa dos Patos represent the period from ∼4540 to 3320 cal years BP. Rock magnetic results show the remanent magnetization resides in pseudo single-domain (PSD) magnetite and/or titanomagnetite. Magnetization inclinations and declinations were isolated after alternating field demagnetization (AFD) and principal component analysis (PCA). Mean inclinations are −39,6° and − 38,4° for cores PT-04 and PT-06, respectively. Relative paleointensity results are compatible with geomagnetic field models, implying very promising results in the reconstruction of a reference curve for the region. As there is no PSV and relative paleointensity data for this region in this period, this study helps to elucidate the past field and the presence of SAMA in South America.