Tectonic and climatic controls on the formation of Neogene red clay in the eastern Ordos Plateau, China: Insights from zircon U-Pb dating and quantitative analysis

The Ordos Plateau in northwest China preserves the world’s most extensive Neogene Red Clay sequence, yet its sediment sources and formation processes remain debated. Here we present detrital zircon U-Pb ages (n = 788) and grain-size distributions (n = 1285) from three representative sections (Xiatianzhuang, Weijiawa, and Mujiawa), integrated with Kolmogorov-Smirnov statistical comparisons. A summary of the detrital zircon age peaks for all samples shows major clusters at approximately 270-290, 430-450, 750-780, 860-950, 1780-1930, and 2400-2515 Ma. The zircon grain sizes across all samples range from 18.4 to 102.2 μm, with most samples showing average lower limits around 26-35 μm and upper limits between 77-98 μm. A dominant Qilian Mountains provenance characterized the Xiatianzhuang section from 11 to 5.5 Ma (KS-D < 0.2), followed by a pronounced transition between 4.9 and 3.4 Ma, during which the northern Ordos Block emerged as the primary sediment source (KS-D = 0.1-0.19). At 4.3 Ma, the Weijiawa section received mixed contributions from the Qilian Mountains, northern Ordos Block, and Gobi region. A consistent pattern of zircon U-Pb age spectra is observed across all three sections at 2.7 Ma, reflecting the renewed dominance of sediment sourced from the Qilian Mountains. Grainsize analysis reveals silt-dominated fractions in western sections (e.g., Chaona, Xifeng) consistent with long-distance aeolian transport, whereas eastern sections (Xiatianzhuang, Weijiawa) contain significantly very fine to coarse sand fractions, pointing to proximal fluvial or aeolian input from the northern Ordos Block. Comparative provenance synthesis indicates that the Qilian Mountains, northern Ordos Block, and Gobi region were the primary sources of Neogene Red Clay across the Ordos Plateau, with negligible contribution from the Taklimakan Desert. We attribute the earlier onset of Red Clay accumulation in the western Ordos Plateau (~29-22 Ma) to limited detrital supply and weak winter monsoon intensity. In contrast, the later and more widespread deposition across the eastern plateau (~11-8 Ma) was driven by enhanced physical weathering in the Qilian Mountains, the establishment of fluvial transfer systems, and an intensified East Asian winter monsoon. This study provides quantitative provenance constraints on the coupled tectonic-climatic controls of Neogene aeolian sedimentation in northwestern China.