RHX Dating of Archeological Ceramics Via a New Method to Determine Effective Lifetime Temperature

Abstract

Determining the absolute chronology of ceramic artifacts has significant implications for archeological and historical research. Wilson, Hall et al. recently suggested a new technique for direct absolute dating of archeological ceramics based on a moisture‐induced chemical reaction, called rehydroxylation (RHX) dating. RHX dating proceeds by measuring the mass of chemically combined water in the ceramics in the form of OH hydroxyls, and the mass gain rate at the Effective Lifetime Temperature (ELT) that the ceramics experienced over its lifetime. To date, ELT determinations have been based on estimates of the ceramic's lifetime temperature history; taking into account weather and climate data and the depth at which the artifact was found. The uncertainty in determining the ELT can be a major component of the overall dating uncertainty. Here, we propose an alternative method which relies minimally on weather and climate data, and provides more precise determinations of the ELT and the ceramic age. The proposed method (SAS: Same Age Samples) involves a minimum of four measurements of the RHX mass gain rate constant for two ceramic samples of the same age at two temperatures. We show via simulations that the proposed SAS method can determine the ELT with a precision of 0.2 K which is comparable to the best ELT determination based on lifetime temperature history, and also comparable to available microbalance temperature resolutions of around 0.1 K. The corresponding percent age error is then 1.4%, or 43 yr for a 3000‐yr‐old ceramic. The proposed SAS method should be tested with ceramic samples of different ages, whose ELT are well‐known.

Searching for the fundamentals of rehydroxylation dating of archaeological ceramics via NMR and IR microscopy

“…MAS NMR has been extensively used in the past to study the structure of clay compounds. For example, montmorillonite was investigated using 1 H, 27 Al and 29 Si MAS NMR, 57 as were lattice variations of clay minerals such as kaolinite 58 during dehydroxylation. Mantovani et al 59 used 27 Al and 29 Si MAS NMR to study the reaction mechanisms of kaolinite to illite/muscovite transformations.…”

“…For example, montmorillonite was investigated using 1 H, 27 Al and 29 Si MAS NMR, 57 as were lattice variations of clay minerals such as kaolinite 58 during dehydroxylation. Mantovani et al 59 used 27 Al and 29 Si MAS NMR to study the reaction mechanisms of kaolinite to illite/muscovite transformations. Thermal reactions of muscovite up to 1200°C were studied by MacKenzie et al 60 using 27 Al and 29 Si MAS NMR.…”

Theoretical constraints on the precision and age range of rehydroxylation dating

“…It also contains one quantity (effective lifetime temperature, T e ) which at present has to be estimated [ 17 ]. Alternatively, it might be possible to measure T e independently using the same age sample method recently proposed by Moinester et al [ 18 ]. Details of these methods are outside the scope of this paper: for our purposes, T e is treated as known, with normally distributed errors.…”

“…Therefore, σ i are conservative estimates for these measurands. Because uncertainties for T e are not reported in Wilson et al [ 4 ], I follow Moinester et al [ 18 ] by taking σ i for T e as 0.18°C. The MC estimate of rehydroxylation age is , which is in good agreement with the analytical expression from the first-order Taylor series ( u ( t a ), equation ( 4.4 )).…”

Are the intensities and durations of small-scale pottery firings sufficient to completely dehydroxylate clays? Testing a key assumption underlying ceramic rehydroxylation dating

“…Geologists, material scientists, archaeometrists, and archaeologists alike set out to replicate the Wilson et al (2009) experiments with the aim to validate and improve the method, (e.g., Bowen et al, 2013Bowen et al, , 2011Clegg et al, 2012;Hall et al, 2013Hall et al, , 2011Hall and Hoff, 2012;Hamilton and Hall, 2012;Moinester et al, 2015;Wilson et al, 2014) yet many were faced with limited success (Le Goff and Gallet, 2015;Maxime Le Goff and Gallet, 2014;Numrich et al, 2015;Zhao et al, 2015). By now multiple processes have been put forward as potential confounding factors, which we discuss below.…”