中晚第四纪豫南地区的古火信息与成因

The evolutionary history of fire serves as a critical indicator for reconstructing paleoclimatic and paleovegetation conditions. To investigate palaeofire activity during the Middle-Late Quaternary in the humid to semi-humid monsoonal region of Eastern China, a systematic analysis was conducted on a 12 m thick sedimentary sequence at the Humiao section (32°57′11″N, 113°51′58″E) in Zhumadian City, Henan Province. The profile consists of two loess-like layers intercalated with two dark red palaeosol layers, topped by a modern cultivated layer. A total of 121 samples were collected at 10-cm intervals. For chronological control, one sample for optically stimulated luminescence (OSL) dating was taken at 2.0 m depth, and four samples for electron spin resonance (ESR) dating were obtained at depths of 4.0 m, 8.0m, 10.0 m, and 12.0 m. All 121 samples were analyzed for organic carbon isotopes, magnetic susceptibility, and Rb/Sr ratios. Additionally, 60 samples at 20 cm intervals were selected for charcoal analysis. Based on multi-proxy data, we reconstructed five distinct phases of palaeofire evolution in southern Henan since the Middle-Late Quaternary: Approximately 875-337 ka, characterized by low fire frequency and intensity; 337-240 ka, showing an increase in wildfire activity; 240-219 ka, a period of stable fire activity; 219-17 ka, a significant enhancement where an increase in herbaceous plants likely served as the primary driver of frequent fires; And finally, 17-5 ka, during which fire activity continued to intensify, reaching its peak. Further analysis indicates that from the Middle-Late Quaternary to the Early Holocene, combustible biomass (i. e., vegetation amount) was the direct controlling factor for palaeofires in the region, while climate exerted an indirect influence primarily by modulating vegetation type and productivity. By the Mid-Holocene, both human activity and combustible biomass emerged as joint dominant drivers of wildfires in southern Henan.