A synthesis of the Devonian wildfire record: Implications for paleogeography, fossil flora, and paleoclimate

Abstract

The Devonian is known for the earliest dispersal of extensive wildfires, but the spatiotemporal diversification pattern and process have not been studied in detail. We synthesize a total of 65 global wildfire occurrences based on fossil charcoals and geochemical (biomarker) evidence from 10 paleogeographic areas across 10 time bins (Lochkovian–late Famennian). Stratigraphically, the highest number of wildfire occurrences is found in the Late Devonian, especially the late Famennian. Paleogeographically, Devonian wildfire evidence is highly concentrated in the eastern Euramerican region that consists of the Appalachian Basin, Avalonia, and Baltica along the Acadian landmass. These data collectively define a unique diversification pattern, here coined as the ‘Famennian Wildfire Explosion’ (FWE). This possible global wildfire spread, based on our diversity analysis of the plant fossil record in eastern Euramerica, is tightly corresponding to the paleogeographic distribution of lignophytes, but not to other common groups of Late Devonian woody plants (e.g., lycopodiopsids, spermatophytes, pteridophytes-monilophytes). Those lignophyte trees and shrubs include 34 species of Aneurophytales, Archaeopteridales, and Spermatophytes in the eastern Euramerican area that represent the primary forest component as the major fuel source of the FWE. By comparing our wildfire and fossil plant diversity with available paleoclimate data (e.g., global atmospheric oxygen level, paleohumidity), we suggest that the FWE in eastern Euramerica is unique due to a combination of occurrences (i) in a relatively low paleolatitudinal zone and (ii) in arid and warm temperate climate zones, but it shows (iii) a relatively weak correlation with the rapidly increasing atmospheric oxygen level.