Evidence of wildfire based on microscopic charcoal, spores and pollen grains from Early Cretaceous sediments of South Rewa and Kachchh basins, India

Abstract

Early Cretaceous sedimentary successions in South Rewa and Kachchh basins of India comprising well–preserved macro–and microscopic biota, are considered to be significant late Gondwanan Lagerstätte of this epoch. Several sedimentary successions of the Bansa Formation in South Rewa and Bhuj Formation in Kachchh basins also contain abundant charcoalified plant fragments and thermally altered spores and pollen grains, indicating effect of fire on the vegetation during the deposition of sediments. Light and scanning electron microscopic images of the fire affected plant remains exhibiting less to severe morphologic distortions, viz. rupturing, shrinkage, curling and perforations due to stress and weight loss. The changes observed in their colour from pale yellow to brown, dark brown and black are most conspicuous and primarily related to the high temperature effect before their burial in the sediments. Botanical affinity of these thermally altered and unaltered spores, pollen grains, charcoalified and non–charcoalified woody fragments indicates their derivation from the vegetation constituted mainly by Pinales, Cycadales, Bennettitales, Ginkgoales, tree ferns and other herbaceous pteridophytes. Record of the charcoalified plant fossils from various sedimentary successions of both the basins provides evidence of the wildfire phenomenon during the Late Gondwanic regimes in India.