Goethite/hematite ratios in synthetic standard samples and natural Luochuan loess-paleosol section

Goethite/hematite ratios in soils are widely used to reconstruct past climatic changes, but their accurate measurements have remained challenging due to the matrix effect. Here we present a new method for measuring soil goethite/hematite ratios by characterizing the band position of electron pair transition (EPT) based on diffuse reflectance spectra using the continuum removal processing. We introduce a ‘half-band-area wavelength’, λ1/2, to characterize the EPT band position and validate the method using synthetic standards made from mixing pure goethite-hematite and four sets of goethite- and hematite-free matrices derived from arid aeolian deposits and tropical saprolite. A consistent λ1/2-goethite/hematite ratios relation is established across the four matrices, demonstrating that our method eliminates the matrix effect. We further validate our method by applying it to quantify goethite/hematite ratios in 180-kyr loess-paleosol sequences and comparing the results to reported convincing paleoclimatic records. This dataset includes a sub-dataset of synthetic standard samples and a sub-dataset of natural Luochuan loess-paleosol section spanning the past 180 kyr.土壤中的针铁矿（Goethite）/赤铁矿（hematite）比值被广泛用于古气候变化重建，但受基质效应影响，其精准测量始终颇具挑战。本研究提出一种全新方法：基于经连续统去除处理的漫反射光谱，通过表征电子对跃迁（EPT）的谱带位置，实现土壤针铁矿/赤铁矿比值的定量测量。我们引入“半峰面积波长λ₁/₂”以表征电子对跃迁的谱带位置，并利用由纯针铁矿-赤铁矿混合物，以及源自干旱风成沉积物与热带风化残积物的4组不含针铁矿与赤铁矿的基质制备的合成标准样品，对该方法进行验证。在4种基质中均建立了一致的λ₁/₂-针铁矿/赤铁矿比值关系，证明本方法可有效消除基质效应。我们进一步将该方法应用于18万年以来的黄土-古土壤序列，量化其中的针铁矿/赤铁矿比值，并将结果与已发表的可靠古气候记录对比，完成方法验证。本数据集包含合成标准样品子数据集，以及覆盖过去18万年的天然洛川黄土-古土壤剖面子数据集。