Provenance of the iron hypothesis: Guidance from multiproxy analysis of surface sediments at the southern margin of the Taklimakan Desert, China 后印本

摘要: The Taklimakan Desert plays an important role in understanding the provenance of the iron hypothesis, which posits that iron availability limits phytoplankton growth in oceans. However, the modern processes governing iron provenance in mountain-desert transition areas remain largely unknown. To address this issue, this study systematically sampled surface sediments along an east–west transect in the Kunlun-Altun piedmont, and analyzed their grain sizes, magnetic susceptibility, total organic carbon (TOC) content, total nitrogen (TN) content, X-ray diffraction (XRD) spectra, and major elements. The grain size distributions (GSDs) at low (<2000 m a.s.l.) and high (>2000 m a.s.l.) altitudes suggested that surface sediments originated from the Kunlun-Altun Mountains, and each exhibited distinct sediment reworking and transport histories. Low chemical index of alteration (CIA) values (<65.00) confirmed that physical weathering was the predominant process and that limited chemical alteration occurred, with the preservation of provenance signatures from the Kunlun-Altun lithologies. Therefore, in the surface sediments, weakly magnetic ferrous ion (Fe2+)-bearing biotite served as the primary iron source. Aeolian transport (relatively fine component), TOC, and the normalized difference vegetation index (NDVI) served as key constraints on iron source dynamics. This study revealed the mineralogical form and influencing constraints of iron sources in the surface sediments derived from the northern Qinghai-Xizang Plateau, providing insights for distinguishing iron sources of the iron hypothesis in paleoclimate proxies.