Biomarker evidence for deforestation across the Triassic-Jurassic boundary in the high palaeolatitude Junggar Basin, northwest China

Abstract

The end-Triassic mass extinction (ETE), one of the five largest mass extinctions, occurred at 201.6 Ma. It was characterized by dramatic declines in marine and terrestrial ecosystems and was approximately synchronous with the eruption of the Central Atlantic Magmatic Province (CAMP). Loss of marine biodiversity is linked to extreme global warming while the cause of floral destruction in terrestrial ecosystems remains open to debate. In this paper, biomarker records of higher plants are reported from terrestrial facies in the Haojiagou section of the high palaeolatitude Junggar Basin, northwest China. Strata around the ETE interval are marked by sharp increases in the abundances of cadalene, retene, pimanthrene and furans, which are synchronous with “fern spikes”. These results are interpreted as indicating the demise of land vegetation and the enhanced burial of higher plants, consistent with palynological evidence for the loss of floral diversity. The fluctuations in the abundance of n-alkanes series and conversion of n-alkanes peak patterns coincide with wildfires indicated by polycyclic aromatic hydrocarbons. Based on integrated stratigraphic correlation, the increased burial of higher plants, wildfires and CAMP volcanism are synchronous both in the Haojiagou section and other classic Triassic-Jurassic boundary sections globally. We propose that widespread deforestation may be due to CAMP-derived acid rain and the rapid and large-scale demise of vegetation may have provided moisture-free fuels for wildfires.