End-Permian terrestrial ecosystem collapse in North China: Evidence from palynology and geochemistry

The Permian-Triassic Mass Extinction (ca. 252 Ma; PTME) is the most severe biocrisis of the Phanerozoic in both the oceans and on land. The crisis saw the collapse of terrestrial ecosystems in low, mid and high latitudes. Although terrestrial plant losses have been implicated as a driver of concurrent changes in terrestrial sedimentary environments and facies (e.g., fluvial style and/or grain size), the relationship between extinction and environmental change in the North China Plate (NCP) remains uncertain due to a paucity of plant macrofossils. We explore the relationship between terrestrial environments and changes in plant communities using a combination of sedimentology, palynology, geochemistry, mineralogy and charcoal data from a terrestrial succession in the Yiyang Coalfield located in the southern NCP. Our multiproxy approach places the end-Permian Terrestrial Collapse (EPTC) at the base of bed 20, below the level of the main (marine) PTME at the top of bed 21. The EPTC manifested as a rapid loss of vegetation accompanied by climatic warming and frequent wildfires. The main
PTME was accompanied by warming, spikes in the Chemical Index of Alteration (corrected CIA, CIA*) and sedimentary Ni (Ni/Al) concentrations, and a transition from arid floodplain to fluvial facies in the sedimentary record. Our results reveal a rapid increase in charcoal content, rapid decline of spore-pollen content, disappearance of plant macro-fossils, rapid decline in TOC content, the onset of a negative δ13Corg excursion, and a shift in lithology from grayish-green sandstone and mudstone to purplish-red mudstone, suggesting that wildfires induced by global warming during the early eruption phase of the Siberian Traps Large Igneous Province triggered terrestrial ecosystem collapse in the NCP prior to the PTME. Plant extinctions during the EPTC were accompanied by changes in sedimentology and environment, but there was no abrupt change in fluvial styles. Temporal coincidence suggests that shifts in end-Permian terrestrial ecosystems toward those tolerant of warmer and more environmentally stressed environments were driven by concurrent Siberian Traps volcanism.