Ichnology of a Late Paleozoic (Permo-Carboniferous) Glaciomarine Deltaic Environment, Talchir Formation, Saharjuri Basin, India

摘要

The storm-influenced prodeltaic offshore succession of the Saharjuri Basin sits in a glaciomarine deltaic setting of the Permo-Carboniferous, Talchir Formation, Gondwana Supergroup, India. It offers the opportunity for study of relationships between sedimentation and ichnocoenoses in a glacial sequence. Sandstone/ siltstone-mudstone couplets deposited by storm ebb surges of varying energy levels contain distinct bioturbation patterns formed by suspension-feeders and sediment-eaters. The background sediments contain only the sub-surface sediment eaters. The occurrence of shallow-water and comparatively deep-water ichnoassemblages in alternating layers in the succession records bioturbation of shallow-water forms in an otherwise oxygen and nutrient starved offshore part of the basin during supply of oxygen and nutrients by storm ebb surges. The impoverished marine ichnofaunal assemblage suggests a drop in marine salinity through mixing with glacial meltwater. A near-absence of shelly fossils and a dominance of annelid and other worm traces, attest to a cold climate in an ice-marginal sea.