Sprecher
Beschreibung
The traditional interpretation of Gondwana sediments as exclusively fluvio-lacustrine has been increasingly challenged by evidence supporting Permian marine incursions following the Late Palaeozoic Ice Age. Both peninsular and extra-peninsular Gondwana successions in India preserve indications of marine influence within predominantly non-marine sequences, reflected in fossil occurrences and sedimentological signatures. However, many fossil-bearing horizons have been degraded or lost due to mining, erosion, weathering, fossil collection, and limited accessibility.
This study employs a multiproxy approach integrating biotic and abiotic datasets to reassess marine-influenced strata from several sub-basins of the Damodar Valley Basin and Gondwana-equivalent successions in Sikkim. Samples from opencast mines and outcrop sections were analyzed using organic and inorganic geochemical techniques. Fourier Transform Infrared Spectroscopy (FTIR) identified carbonate absorption bands at 1460 cm⁻¹ and 880 cm⁻¹, suggesting marine influence. Biomarker analyses revealed abundant C29 regular steranes and 4-methylsteranes, indicating predominantly terrestrial organic matter deposited under brackish conditions. Trace-element geochemistry from the Giridih Basin, particularly Th/U and Sr/Ba ratios, points to deposition in brackish to shallow-marine environments. Elevated sulphur concentrations and the occurrence of framboidal pyrite in the Ashoka coal seams further support episodes of marine incursion. Palynological assemblages from Sikkim contain leiospherids, indicating affinity with brackish to marine settings, while ichnological evidence from the Ramgarh Basin, including burrows such as Diplocraterion and Skolithos, is consistent with marine depositional conditions.
Together, these independent lines of evidence provide strong support for marine influence during Barakar sedimentation and suggest a persistent marine connection across multiple Gondwana basins during the Permian.