The accretion rate of extraterrestrial ³He based on oceanic ²³⁰Th flux and the relation to Os isotope variation over the past 200,000 years in an Indian Ocean core

In the eastern equatorial Indian Ocean, the flux of extraterrestrial ³He, a proxy of interplanetary dust particles (IDPs), has been relatively constant over the past 200 ka. The flux is equal to (1.1 ± 0.4) x 10^-12 cm³ STP cm^-2 ka^-1, a value obtained using the xs²³⁰Th profiling method. Variations in mass accumulation rates (MARs) derived assuming a constant extraterrestrial ³He flux have a 40-ka periodicity similar to that observed in the δ¹⁸O-derived MARs. This frequency is similar to that of the Earth's obliquity. Measured ¹⁸⁷Os/¹⁸⁸Os ratios are less radiogenic than present-day seawater (0.49-0.98), reflecting the mixing of Os derived from extraterrestrial, terrigenous and hydrogenous sources. When coupled with He data measured on the same samples. Os isotope data yield important information about the terrigenous component supplied to the eastern equatorial Indian Ocean. The amount of Os in the sample derived from the extraterrestrial component can be deduced with the help of the helium systematics. Once corrected for the extraterrestrial component of Os, Os isotope signatures, in conjunction with the ⁴He concentrations, suggest a supply of terrigenous material from Indonesian ultramafic and Himalayan crustal sources that clearly varies through time.