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.