Orbital-scale Climate Dynamics may Impact Gzhelian Peatland Wildfire Activity in the Ordos Basin

Abstract

The Carboniferous, an important coal-forming period in geological history, was characterized by extensive vegetation and high oxygen levels. Evidence suggests frequent wildfires took place during this time, especially in peatlands. However, the control mechanisms for changes in wildfire activity in peatlands during this period remain unclear. In this study, evidence from the Gzhelian in the Ordos Basin, such as the inertinite/vitrinite (I/V) ratio, indicated varying wildfire frequencies. Climate indicators (CaO/MgO and CaO/MgO·Al₂O₃) revealed that high-frequency wildfires mainly occurred in warm and humid climates. Based on former age constraints, we deduced that orbital cycles (long eccentricity) controlled the climate influence on peatland wildfires during the Gzhelian. Higher eccentricity brought more sunshine and rainfall, creating warmer, wetter peatlands conducive to vegetation growth, which increased fuel loads and led to more wildfires. Global Gzhelian wildfire records show that wildfires occurred mainly in tropical regions with abundant vegetation, reinforcing the idea that fuel loads drove fire activity. While wildfires can release mercury (Hg), the frequent volcanic activity during this period likely contributed significantly to Hg enrichment.