A decrease in low-latitude weathering flux facilitated the demise of the Late Paleozoic Ice Age

Abstract

The Late Paleozoic Ice Age (LPIA) was a series of modulated glacial-interglacial pulses that characterized the climate of the late Carboniferous through Permian. Although the ages and durations of the main major episodes of the LPIA have been calibrated from glacial deposits in eastern Australia and elsewhere, the causal factors for the final transition from the oscillating icehouse climate to a continuous hothouse remains uncertain. To aid in unraveling the potential causes for this climatic turnover and its characteristics in the tropical latitudes, we measured the weathering indices and redox proxies recorded by the Lopingian (Late Permian) strata in the Shangsi section of the Upper Yangtze region in South China. The multiple weathering indices derived from the geochemical composition of the acid-insoluble residues in the carbonate rocks exhibit consistent trends. These trends, when combined with published coeval weathering data from other regions, trace four global phases of weathering changes during the late Permian. After the middle Wuchiapingian, the observed increase in the weathering indices and a negative excursion in carbon isotope are apparent responses to gradual warming. The simultaneous increase in ocean oxygenation may have also played a role in the deglaciation. Based on the changes in tropical exposed land area through the late Permian, we quantitatively estimated the low-latitude chemical weathering flux by combining contemporaneous weathering indicators. The curve of that estimated flux support the hypothesis that a sustained decrease in low-latitudes weathering flux, the implied apparent decrease in the amount of exposure and total weathering of silicate rocks, may caused a weakening of the carbon sink and a continuous accumulation of atmospheric CO₂, which in turn facilitate the stepwise deglaciation of LPIA and the onset of a long-term hothouse climate.