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Abstract:
Paleomagnetic secular variations in South America are not well understood due to insufficient spatial and temporal records. In this study we present a new paleomagnetic secular variation record from the late Pleistocene (46.15 ka) to the middle Holocene (5.36 ka) by stacking data from two marine sediment cores collected in South Brazil, western South Atlantic. Stepwise alternating field demagnetization was used to isolate the primary remanent component. Relative paleointensity was determined by normalization and by the Pseudo-Thellier approach. Our pseudo-Thellier data were calibrated using detailed selection criteria to better define the uncertainty associated with the paleointensity estimates. Rock magnetic measurements indicate that the primary magnetic remanence carriers are pseudo-single domain or vortex state magnetite with no evidence for diagenetic alteration. Our paleointensity and inclination records are consistent with available South American and Atlantic records, and predictions from global geomagnetic field models. Variations in inclination and relative paleointensity reveal the Laschamp geomagnetic excursion in western South Atlantic. Finally, the recent paleomagnetic findings introduce a valuable tool for refining the chronology of the Pelotas Basin. These new data provide a fresh reference point for developing high-resolution Quaternary age models for South America.
