Volcanic activity drove an increase in the intensity of wildfire events, which in turn disturbed and affected terrestrial ecosystems.

Wildfire is an important part of the Earth’s natural environment. It plays a significant role in many environmental and evolutionary innovations in geological history. The End-Permian mass extinction is the biggest extinction event in Earth’s history, and the response of terrestrial vegetation systems to this event has been highly studied in recent years. Nowadays more and more records of wildfire are reported from the Late Paleozoic, and the investigations focusing on wildfire are of great significance for learning about the collapse of terrestrial ecosystems and the vegetation changeover during the Permian-Triassic transition.

Recently, the Late Paleozoic research group from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (NIGPAS), together with Nanjing University and Yunnan University carried out a systematic study focused on charcoals and δ¹³C_org from the upper Permian of the Dalongkou section in Northwest China’s Xinjiang Uygur Autonomous Region and of the Lengqinggou section in Southwest China’s Guizhou Province. The results were published in Earth-Science Reviews and Frontiers in Earth Science.

SEM images of charcoal from the Dalongkou section in Northwest China’s Xinjiang Uygur Autonomous Region [IMAGE: NIGPAS]

Co-variation diagrams for the δ¹³C_org values, Hg/TOC values, charcoal abundance, reflectance and types of fossil charcoal in the Dalongkou section [IMAGE: NIGPAS]

In the Dalongkou section, charcoals from several stratigraphic horizons in the lower-middle Guodikeng Formation evidenced the frequency of paleo-wildfires during the late Permian. The reflectance values of the charcoals indicate that surface fires were dominant throughout the sequence, with fire regime changing in the upper of the Guodikeng Formation from higher reflectance to extremely low reflectance. It probably hints at vegetation impoverishment and a lack of fuel during that time. The distribution of all categories of the charcoals, the difference of cuticles and the evidence of spore-pollen also support the deforestation stage. In addition, the coupling of the Hg/TOC peaks and the organic carbon isotope (δ¹³C_org) values and the abundance of the charcoals in the sequence indicates that volcanic activity could be the deep-seated driver for wildfires and the δ¹³C_org change.

SEM images of charcoal from the Lengqinggou section in Southwest China’s Guizhou Province [IMAGE: NIGPAS]

Stratigraphic column and δ¹³C_org, charcoal abundance and types of fossil charcoals in the Lengqinggou section, Southwest China’s Guizhou Province [IMAGE: NIGPAS]

The work of the Lengqinggou section shows that charcoals from the Xuanwei Formation occurred more frequently, with higher reflectance and diversity, while those from the Kayitou Formation exhibit low reflectance and diversity. This phenomenon supports the point that the vegetation changed from rainforest to herb land between the two formations. Meanwhile, the fire regime also changed from high temperature crown fire to ground fire with lower temperature. Furthermore, an ash bed in the uppermost coal in the Xuanwei Formation was of interest. Detailed sampling shows that an abrupt excursion of δ¹³C_org and reduction of charcoal abundance occurred immediately above the volcanic ash. It suggests that the intense wildfire associated with volcanism culminated at that time, leading to the eventual vegetation changeover of the terrestrial ecosystems in Southwest China during the Permian-Triassic transition.

For more information, please contact:

Liu Yun, Publicist

Email: yunliu@nigpas.ac.cn

Nanjing Institute of Geology and Palaeontology,

Chinese Academy of Sciences (NIGPAS)

Source: Nanjing Institute of Geology and Palaeontology,

Chinese Academy of Sciences (NIGPAS)