Mid-Miocene Palaeofire and Its Complex Relationship With Vegetation Changes in the Wushan Basin, Northeastern Tibetan Plateau, China: Evidence From a High-Resolution Charcoal Record

Fire plays an important role in the Earth system, and is considered an essential control on global vegetation evolution and climate change. However, few Miocene high-resolution fire records have been obtained with which to assess the controls and possible drivers of fire on multiple timescales. Here, we provide a high-resolution charcoal record of the Nanyu section to reconstruct mid-Miocene fire history in the Wushan Basin. Further, we identify and assess the long-term regional fire regime (frequency and intensity) controls and possible drivers by making comparisons with published paleoclimate and paleoenvironmental records (i.e., palynomorphs, magnetic susceptibility, redness, stable isotope, pCO2 and marine delta O-18 data etc.). We also performed spectral analysis of the charcoal records to investigate possible controls of fire activity on orbital time scales. The analysis results indicate that (a) the reconstructed fire regime exhibits an increase from similar to 16 to 13.86 Ma and a significant decrease after similar to 13.86 Ma. (b) The steadily increasing regional fire activity during the period of similar to 16-13.86 Ma may be caused by increased fuel ignitability and drying climate, whereas significantly decreased fire activity after similar to 13.86 Ma is likely attributed to decreased fuel load due to the Mi-3b global cooling event. (c) On orbital time scales, the finding of the Earth's orbital cycles in fire proxy indicates that mid-Miocene fire activity variability in the study area was likely related to Earth's orbital forcing.