Paleomagnetic Secular Variations During the Past 40,000 Years From the Bay of Bengal

Abstract

Paleomagnetic secular variations in South Asia are not well understood due to insufficient records. In this study, we produce a new paleomagnetic secular variation curve covering the past 40,000 years by stacking four marine sediment records from the middle portion of Bay of Bengal. Age models are based on radiocarbon dating and core correlation. Stepwise alternating field demagnetization was used to isolate the primary remanent component. Rock magnetic measurements indicate that the primary magnetic remanence carriers are single domain and pseudo-single domain magnetites with no sign of diagenetic alteration. Our Bengal relative paleointensity stack is broadly consistent with local records and the PISO-1500 relative paleointensity stack (Channell et al., 2009; ). Two geomagnetic excursions presented by paleointensity minima are recognized, which correlate to the Mono Lake (29-32 ka) and Laschamp excursion (38-40 ka), respectively. We conclude that the Mono Lake and Laschamp excursion are two separate events.