Low-latitude weathering recorded in magnetic mineral changes across the late Paleozoic glacial–nonglacial transition

The nonglacial interval between the Guadalupian P3 and Lopingian P4 glacial periods represents a critical shift from icehouse to greenhouse conditions in the Late Paleozoic Ice Age, yet how low-latitude regions responded remains debated. Here we present a high-resolution environmental reconstruction across P3–P4 transition based on cyclostratigraphic and environmental magnetic analyses of the Fengshan section (Standard Auxiliary Boundary Stratotype for the Guadalupian–Lopingian boundary) in South China. An astronomical time scale was established using 405-kyr long-eccentricity cycles, and predominant hematite concentration was used to track continental weathering intensity. Integrating these analyses, the weathering evolution can be divided into three stages with boundary at ca. 262.2 Ma and ca. 260.1 Ma. Stage I (the waning of P3 glaciation) is marked by weakening chemical weathering and a slight decline in hematite. Stage II (nonglacial interval) begins with moderate weathering, followed by rapid fluctuations coinciding with marine regression and initial onset of volcanic activity. Stage III (the initial onset of P4 glaciation) records abrupt 3.5- to 4-fold increases in hematite concentration, indicating massive enhancement of weathering driven by erosion of the Emeishan large igneous province basalts. We infer that intensive chemical weathering of the Emeishan basalts, rather than direct volcanic CO₂ emissions, likely amplified CO₂ consumption, which may have contributed to the global cooling that facilitated the onset of the P4 glaciation. These findings favor the weathering fluctuations, ultimately linked to deep Earth processes, serve as an important contributing factor for the glacial−nonglacial transition during the late Paleozoic period.