Radiocarbon dating of lipids preserved in pottery vessels: guidelines for best-practice in compound-specific 14C analyses

Pottery vessels played a central role in the processing, storage and transport of animal and plant products by prehistoric and historic peoples with their chemical residues surviving for thousands of years. Accurate radiocarbon dating of archaeological pottery vessels by isolating reliable sources of carbon relating to the use of pots has long been a major challenge, but is now possible using compound-specific radiocarbon analysis of absorbed organic residues preserved in the ceramic fabric of the vessel wall. This method involves the radiocarbon dating of single fatty acids most commonly derived from degraded animal fats. These compounds are extracted from the ceramic matrix and isolated from potentially interfering compounds using preparative capillary gas chromatography. When coupled with lipid biomarker and compound-specific stable carbon isotope analyses, this method enables the palaeodietary and chronological information contained in archaeological lipids preserved in ceramic vessels to be interpreted together. From a practical perspective the methodology is challenging and for successful application must adhere to rigorous protocols. We present here guidelines which include (i) consideration of pottery selection, (ii) technical parameters for the isolation of fatty acids then their 14C dating and calibration, and (iii) case studies selected to illustrate the best use of this method.