On-site plant-wax biomarker analysis for assessing soil-organic-microbial degradation in archaeological contexts: A case study from Southern India

Stable carbon isotope (δ¹³C) analysis of soil organic matter (SOM) from archaeological contexts is widely employed as a proxy for palaeovegetation and palaeoenvironmental reconstruction. However, the reliability of δ¹³C_SOM as a palaeovegetation proxy is influenced by issues of physico-chemical diagenesis and isotopic fractionation, prompting increased interest in source-specific biomarker approaches. In this study, we present a case study from the Palaeolithic site of Jwalapuram (India), where plant-wax biomarker data indicate the degradation of plant-derived lipids, raising concerns about the reliability of δ¹³C_SOM as a palaeovegetation proxy in this context. To further investigate SOM degradation, topsoil samples from central Andhra Pradesh were analyzed, revealing variable levels of SOM preservation across the region, strongly correlated with sedimentary and vegetation contexts. Our research highlights the importance of integrating source-specific proxies, such as plant-wax biomarkers, with bulk proxies such as δ¹³C_SOM to mitigate preservation biases and ensure the integrity of palaeovegetation reconstructions.