10Be depositional flux variation in the central Indian Ocean during the last 43 ka

Abstract

The advent of Accelerator Mass Spectrometer (AMS) enhanced the application of meteoric 10Be (half-life of 1.39 Ma) as a tracer for understanding earth surface processes on thousand to million-year time scales. However, for the majority of applications, an adequate understanding of the 10Be depositional flux is a prerequisite. A number of efforts have been made to understand both spatial and temporal variation of 10Be depositional flux. Yet, due to the limited globally distributed dataset and modulation of the 10Be signal by local processes, a significant offset is observed between model-derived and measured deposition rates of 10Be. In this study, an attempt has been made to determine the 10Be depositional flux from a marine sediment core from the central Indian Ocean chronologically constrained with the AMS radiocarbon dating and 10Be concentration measured with AMS. The 10Be depositional flux estimates using weak leaching method are found to be nearly 44% lower compared to the strong leaching method. The calculated 10Be depositional flux during the Holocene varies between 9.63 and 13.01 � 105 atoms/cm2/yr, which is 2-28% lower compared to the modeled depositional flux for the region. The difference observed in 10Be depositional flux could be due to the local processes (such as boundary scavenging, changing rate of sediment deposition at the location) affecting 10Be deposition into the sediment column or offset associated with the model estimations. The changes in 10Be depositional flux and the 10Be/9Be ratio have been reconstructed up to 43 ka. An increase in the 10Be/9Be ratio during 28 to 43 ka is observed due to the lower geomagnetic field intensity during the period. A high-resolution 10Be/9Be ratio reconstruction shows a peak at 41.2 ka, which can be attributed to the Laschamp event.