A New Bayesian Chronology for Postclassic and Colonial Occupation at Xaltocan, Mexico

Abstract

This article proposes a new four-phase chronology for Postclassic and colonial occupation at Xaltocan, Mexico, using Bayesian statistical modeling of a suite of 54 radiometric dates. Of these, 46 samples come from recent extensive excavations of sealed, stratified household deposits, facilitating improved understanding of sample context and resulting in a more accurate chronology. The timing of the adoption of major ceramic wares at the site and intrasite level is outlined and contextualized within broad, regional phases. These results are particularly valuable given recent research that repudiates a uniform chronological framework for the Basin of Mexico in the Postclassic period, and indicates instead a significant amount of chronological overlap and regional variation in the use of distinct ceramic types.

A New Radiocarbon Sequence from Lamanai, Belize: Two Bayesian Models from One of Mesoamerica’s Most Enduring Sites

“…OxCal uses a Markov chain Monte Carlo (MCMC) sampler to approximate all possible solutions and probability outcomes (Bronk Ramsey 2008, 2009b). 6 Bayesian statistics allow archaeologists to incorporate “prior” information about the samples into the statistical model, including relative stratigraphic and architectural sequences, monument dates, textual dates, ceramic chronologies, and unknown gaps between samples (Bronk Ramsey 2009b; Kennett et al 2011, 2014; Culleton et al 2012; Inomata et al 2013, 2014; Hoggarth et al 2014; Overholtzer 2014; Huster and Smith 2015; Ebert et al 2016). The relative ordering of samples within the stratigraphy of an excavation can therefore verify and constrain the calibrated date ranges.…”

A Multiscalar Approach to Migration and Social Change at Middle Postclassic Xaltocan

“…A midden from the final occupation phase of Structure 129 (Op Z) that contained both Aztec I and Aztec II ceramics yielded a radiocarbon date calibrated at a 95 percent probability to either 1260–1320 (p = .74) or a.d. 1350–1390 (p = .21). We note here that the former range is more likely given that the deposit does not include the Aztec III ceramics that dominate assemblages post-dating 1350 (Overholtzer 2014). This deposit was preceded by Aztec I occupation with a series of eight radiocarbon dates with 95 percent probability ranges of 990 to 1290.…”

“…In the resulting Bayesian model of Xaltocan occupation (Overholtzer 2014) (Table 1), the Dehe phase, from a.d. 900 to 1240, is defined by the use of Aztec I ceramics. This model confirms De Lucia's (2011) findings that Aztec I ceramics were used exclusively until approximately a.d. 1250.…”

A New Archaeological Chronology for Aztec-Period Calixtlahuaca, Mexico

“…Bayesian methods have been rapidly gaining popularity in archaeological chronology building across a wide range of regions and time periods (Beramendi-Orosco et al 2009;Higham and Higham 2009;Overholtzer 2014;Zeidler et al 1998). The methods are uniquely well suited to archaeological dating, which usually includes a mix of absolutely known factors (such as historical dates), relative contextual information, and probability curves (such as radiocarbon or obsidian hydration calibrations).…”