This first comprehensive geochemical investigation of vertebrate fossils from India focuses on mass death assemblages recovered from four contemporaneous bonebeds in the Upper Triassic Tiki Formation, India. The study encompasses three extinct tetrapod taxonomic groups, namely the metoposaurids, phytosaurs and rhynchosaurs that co-existed, occupied different life habits and proliferated on the Tiki landscape. Geochemical signals including high crystallinity indices with low variability, similar patterns of Post-Archean Australian Shale-normalised mean rare earth element concentrations, considerable overlapping of convex hull polygons, and consistent enrichment in middle rare earth elements suggest similar early diagenetic palaeoenvironments for the four Tiki bonebeds. Such enrichment in middle rare earth elements is seen because of the presence of iron oxide within a terrestrial well-oxygenated fluvial setting that prevailed during fossilisation. The burial was a single-phase event, likely caused by a major flooding event, irrespective of whether the fossil accumulation was time-averaged, attritional or catastrophic. Differences in mean rare earth element concentrations in the taxonomic groups may have resulted from variation in their infiltration that was influenced by bone density which in-turn was influenced by contrasts in lifestyle. A positive europium anomaly in all specimens suggests localised reducing or anaerobic conditions resulting from autolytic degradation of the tissues at the time of early diagenesis. Studied specimens exhibited both positive and negative cerium anomalies that signify variations in the duration of subaerial exposure prior to burial, weathering stages and burial depth. The study helped in delineating the early diagenetic palaeoenvironments and reconstructing fossilisation pathways of the four Late Triassic bonebeds and highlights the significance of understanding geochemical signals in fossil bones.
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