A New Study of the Gruta de Chac, Yucatán, México

Radiocarbon Dating

Five charcoal samples were submitted to Beta Analytic Inc. for radiocarbon dating services. Only one charcoal sample was recovered from a stratigraphic context associated with the cave ceramics. This sample came from the 2^nd level of the test excavation within the Chac cave. To provide additional indirect dating of the cave ceramics, 2 charcoal specimens from excavated contexts at Chac II with Chemax Slatewares and 2 samples of paint pigments from an Early Classic style molded stucco mask found on the lower south tier of the Great Pyramid were submitted for dating. All samples are associated with early style architecture similar to the one diagnostic building at the Gruta Chac Plaza.

Unfortunately, the Gruta charcoal sample turned out to be intrusive dating to A.D. 1800 (Table 1, Beta-122985). However, two carbon samples from sealed stucco floors contexts containing Chemax Slatewares and early architectural contexts date to A.D. 620 and A.D. 720 (Table 1, Beta-122986 and Beta-122987). These and other dated contexts at Chac II suggest that Chemax ceramics at the Gruta de Chac date to the late Early Classic and Middle Classic periods (A.D. 500-700). This chronological placement accords well with Ball’s (1978:108) estimated dates for Ticumuy Orange Polychrome: Chac Variety to A.D. 300-550 and the suspected chronological overlap between Chac Polychrome and Chemax Slateware suggested by Andrews IV’s. The dates for the paint pigments on the stucco mask are Terminal Classic (A.D. 830 [Beta-122988] and A.D. 850 [Beta-122989]). The Early Classic style of the stucco mask, the associated early style architecture, and the presence of Chemax ceramics, conversely, indicate that these radiocarbon dates are too late and must reflect the last of many re-paintings of a mask that was constructed centuries earlier.

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