Good Dates and Bad Dates in Ecuador
Radiocarbon Samples and Archaeological Excavation: a Commentary Based on the "Valdivia Absolute Chronology"
Universidad Autónoma de Barcelona
Departemento de Geologia, Edificio CS
Gliwice Radiocarbon Laboratory
Institute of Physics
Silesian Technical University
ul. Krzywoustego 2
44-100 Gliwice, Poland.
The cultural chronology of Ecuador is based on several hundreds radiocarbon determinations. Most of the dated samples, which come from coastal sites, are charcoal, however a good number were shell and few were the collagen of human bone. Some dates were obtained by other methods. Early in the fifties, obsidian hydration dates served to complete the 14C sequence, and more recent Thermoluminescence assays have not only completed some missing dates for a more refined sequence, but have served to validate some 14C calibrations and to explain some aberrant determinations. In the following commentary, we will refer mostly to Valdivia dates, since they were obtained by the most varied field methods, during the forty years Valdivia sites have been under excavation.
This paper has two parts: firstly, an archaeological discussion of the Valdivia absolute chronology by Jorge Marcos; and secondly, the presentation of the calibration of the Valdivia dates in the Gliwice Radiocarbon Laboratory, by Adam Michczynski. Marcos, discusses the importance of selecting a 14C sample in order to obtain a secure date, and the most common errors that have affected the Valdivia absolute chronology. The necessity to calibrate dates, and the importance of publishing them properly. (1)
The results of calibration of individual 14C dates by Adam Michczynski are presented in Table 1 and Figure 1. Finally, as a corollary, a commentary on the problems presented in the combined presentations is provided by the senior author.