Prof Christopher Ramsey

Abstract:

To create a reliable radiocarbon calibration curve, one needs not only high-quality data but also a robust statistical methodology. The unique aspects of much of the calibration data provide considerable modeling challenges and require a made-to-measure approach to curve construction that accurately represents and adapts to these individualities, bringing the data together into a single curve. For IntCal20, the statistical methodology has undergone a complete redesign, from the random walk used in IntCal04, IntCal09 and IntCal13, to an approach based upon Bayesian splines with errors-in-variables. The new spline approach is still fitted using Markov Chain Monte Carlo (MCMC) but offers considerable advantages over the previous random walk, including faster and more reliable curve construction together with greatly increased flexibility and detail in modeling choices. This paper describes the new methodology together with the tailored modifications required to integrate the various datasets. For an end-user, the key changes include the recognition and estimation of potential over-dispersion in 14C determinations, and its consequences on calibration which we address through the provision of predictive intervals on the curve; improvements to the modeling of rapid 14C excursions and reservoir ages/dead carbon fractions; and modifications made to, hopefully, ensure better mixing of the MCMC which consequently increase confidence in the estimated curve.

Abstract:

The Khao Wong Prachan Valley of central Thailand is one of four known prehistoric loci of copper mining, smelting and casting in Southeast Asia. Many radiocarbon determinations from bronze-consumption sites in north-east Thailand date the earliest copper-base metallurgy there in the late second millennium BC. By applying kernel density estimation analysis to approximately 100 new AMS radiocarbon dates, the authors conclude that the valley's first Neolithic millet farmers had settled there by c. 2000 BC, and initial copper mining and rudimentary smelting began in the late second millennium BC. This overlaps with the established dates for Southeast Asian metal-consumption sites, and provides an important new insight into the development of metallurgy in central Thailand and beyond.

Abstract:

The Khao Wong Prachan Valley of central Thailand is one of four known prehistoric loci of copper mining, smelting and casting in Southeast Asia. Many radiocarbon determinations from bronze-consumption sites in north-east Thailand date the earliest copper-base metallurgy there in the late second millennium BC. By applying kernel density estimation analysis to approximately 100 new AMS radiocarbon dates, the authors conclude that the valley's first Neolithic millet farmers had settled there by c. 2000 BC, and initial copper mining and rudimentary smelting began in the late second millennium BC. This overlaps with the established dates for Southeast Asian metal-consumption sites, and provides an important new insight into the development of metallurgy in central Thailand and beyond.