Applications of Dendrochronology in Northwestern Mexico

Abstract

Although dendrochronological methods have the potential to provide precise calendar dates, they are virtually absent in Mesoamerican archaeological research. This absence is due to several long-standing, but erroneous, assumptions: that tree rings in this region do not reflect annual growth and environmental variability, that an adequate number of samples do not exist, and that tree-ring measurements cannot be useful without modern trees to link prehispanic chronologies. In this article we present data from the sites of La Quemada and Los Pilarillos, located in the Malpaso Valley, Zacatecas, to demonstrate that suitable archaeologically derived samples of dendrochronologically useful species do exist, that the samples from these sites are measurable and cross-datable, and that the tree rings can yield precise calendar dates using a method that “wiggle-matches” radiocarbon dates on tree-ring sequences. The work demonstrates the potential of these methods to address chronological, and, in the future, climatic questions, which have so far eluded archaeological work in the region.

Refinement of the Chronology of La Quemada, Zacatecas, Mexico, Using Ceramic Seriation

“…Although Turkon and colleagues’ (2018) results are preliminary, they provide information relevant to our discussion of the seriation results presented in the next section. A set of three roof beam supports was analyzed from the Cuartel area of La Quemada's monumental core, suggesting a series of two felling episodes that date after AD 639 ± 4 and AD 726 ± 4 based on the calibration of established cutting dates (Turkon et al 2018:117).…”

“…Although Turkon and colleagues’ (2018) results are preliminary, they provide information relevant to our discussion of the seriation results presented in the next section. A set of three roof beam supports was analyzed from the Cuartel area of La Quemada's monumental core, suggesting a series of two felling episodes that date after AD 639 ± 4 and AD 726 ± 4 based on the calibration of established cutting dates (Turkon et al 2018:117). An additional sample was analyzed from the Temple on Terrace 18, placing the initial construction of this feature at AD 661 ± 4 (calibrated), which suggests that the Cuartel and Terrace 18 were built around the same time (Turkon et al 2018:117).…”

“…Second, new dates have since been published from excavations in the Cuartel (Jimenez and Darling 2000; Santos Ramírez 2014) and Ciudadela (Lelgemann 2000) areas of the site. Third, recent efforts to build a dendrochronological sequence for the northern frontier involve a reexamination of the La Quemada radiocarbon dates and propose a considerable shortening of the site's occupation (Turkon et al 2018). Nelson (1997) concluded that the main occupation of La Quemada was between 500 and 900 CE.…”

“…Recent research on the development of a dendrochronological sequence for the northern frontier region has found sufficient samples for the creation of a 305-year tree-ring sequence for the Malpaso Valley (Turkon et al 2018). A sample of 25 wood and charcoal fragments, recovered primarily from the Cuartel area of La Quemada and the monumental architecture at Los Pilarillos, a secondary center located in the Malpaso Valley, was subjected to established methods of tree-ring measurement and cross-dating within cultural contexts and across the two sites to create “floating chronologies” based on a relative dating scale (Turkon et al 2018:108–109, Table 1). A series of radiocarbon-dated tree-ring samples selected from the chronologies provided absolute date anchors (using a “wiggle-matching” technique; Bronk Ramsey et al 2001) for the entire sequence, which resulted in a calibrated date range of AD 466–770 ± 4 for tree harvesting in the Malpaso Valley sites.…”

“…A set of three roof beam supports was analyzed from the Cuartel area of La Quemada's monumental core, suggesting a series of two felling episodes that date after AD 639 ± 4 and AD 726 ± 4 based on the calibration of established cutting dates (Turkon et al 2018:117). An additional sample was analyzed from the Temple on Terrace 18, placing the initial construction of this feature at AD 661 ± 4 (calibrated), which suggests that the Cuartel and Terrace 18 were built around the same time (Turkon et al 2018:117). Their analysis also involved a reevaluation of Nelson's (1997:107, Figure 3) radiocarbon dates using a corn cob recovered from a hearth below Terrace 18 (Sample no.…”