The Karharbari Formation (late Sakmarian–early Artinskian), India: A biostratigraphic, palaeoclimatic, and vegetational framework for Cisuralian Gondwana correlation

Abstract

The Karharbari Formation of Peninsular India, long considered a transitional unit between the Talchir and Barakar formations, is re-evaluated here as a distinct palaeoecological and stratigraphic interval of Late Sakmarian to Early Artinskian age. Integrating megafloral, palynological, petrographic, coal, and lithostratigraphic data, this review synthesizes records from multiple Lower Gondwana coalfields to clarify the formation’s spatial extent, floral composition, and environmental character. Biostratigraphically anchored by the Crucisaccites monoletus Assemblage Zone, the Karharbari strata exhibit strong regional coherence across basins, supported by floral and faunal correlatives in peri-Gondwanan and southern high-latitude Gondwanan settings, including Australia, South Africa, and South America. The vegetation reflects two interrelated ecological domains: a terrestrial forest system dominated by Gangamopteris, Noeggerathiopsis, and early Glossopteris: and a marshy wetland system comprising Schizoneura, Gondwanidium, and lycopsid groundcover. Conceptual models of floral transition, coal petrography, and climatic trajectory illustrate the formation’s role as a post-glacial recovery phase and precursor to widespread Glossopteris-dominated swamps. Collectively, the Karharbari Formation emerges as a regionally mappable, biostratigraphically distinct, and ecologically transitional unit within the Lower Gondwana, offering a valuable reference point for Cisuralian correlations across Gondwana continents.