Long eccentricity forcing of the Late Pliensbachian to Early Toarcian (Jurassic) terrestrial wildfire activities in the Tarim Basin, northwestern China

Abstract

Wildfires are an important disturbance driver for terrestrial ecosystems and even Earth systems, which reflect crucial information about the interactions between the atmosphere and the biosphere. However, the relatively long-term secular evolution controlled by climate change in the Early Jurassic wildfires are poorly understood. Here, we conduct cyclostratigraphic, chemostratigraphic, and molecular compound analyses on the Late Pliensbachian to Early Toarcian terrestrial stratigraphy of the Kuqa River section in the Tarim Basin, northwestern China, in order to obtain a holistic understanding the evolutionary processes of wildfire on long time scales during a past warming event, the Pliensbachian-Toarcian event (Pl-To). Based on the long eccentricity cycle identified in the time series analysis, we establish a ∼ 1.8 Ma high-resolution floating astronomical timescale (FATS) and reconstruct the variable lake level by using the sedimentary noise model. The Pl-To warming event associated with the Karoo-Ferrar Large Igneous Province (K-F LIP) may have led to a shift in climate from warm and wet to dry and hot, with a significant decrease in lake levels in the Tarim Basin. Besides, polycyclic aromatic hydrocarbons (PAHs), C29 sterane and dibenzofuran evidence indicates that the global warming event (Pl-To event) also may regulate the wildfires by affecting the fuel abundance (vegetation). Notably, the astrochronology and PAHs suggest that the periodically enhanced wildfires correspond to the long eccentricity cycles, indicating that astronomical forcing plays a key role in triggering the wildfires. Our results report the first documentation of multiple full long eccentricity cycles forced wildfires during the Late Pliensbachian to Early Toarcian and reveal orbital forcing as a driving mechanism for periodically enhanced wildfires superimposed on a long-time gradual weakening trend associated with Pl-To warming event.