Diatoms from ancient pots: exploring pottery sherds and palaeoenvironmental insights in the lower Kaveri River Basin archaeological landscape, Tamil Nadu, India

Diatom analysis, despite its existence in archaeological science for over seven decades, remains an underutilized technique. While diatoms are often employed in site-based palaeoenvironmental reconstructions, their application in pottery sourcing and typology is relatively limited. This study focuses on diatom analysis of pottery sherds collected from six Iron Age sites in the lower Kaveri River Basin, Tamil Nadu, India. Scanning Electron Microscopy was utilized to examine the diatoms in 78 samples from 26 pottery sherds across these sites. The analysis revealed the presence of aquatic diatoms, predominantly from freshwater environments, along with desiccation-tolerant taxa belonging to the genera Nitzschia, Hantzschia, Luticola, Stauroneis and Tryblionella. Notably, the dominant genera were Nitzschia (70.73%), Hantzschia (21.95%) and Luticola (4.87%). These findings confirm the presence of a lacustrine environment with mesotrophic to eutrophic conditions and suggest that the clay used in pottery originated from a freshwater source. Moreover, this study highlights the potential of diatom analysis in reconstructing local environments and shedding light on the palaeoenvironmental conditions underlying archaeological sediment deposition in a tropical context