Handheld XRF for Art and Archaeology

13. Handheld XRF analysis of Maya ceramics: a pilot study presenting issues related to quantification and calibration

Jim J. Aimers, Dori J. Farthing and Aaron N. Shugar 424 designed for these purposes to be effective with archaeological ceramics is unreasonable. The desire for quantification, whether it be for provenancing studies or characterization studies, requires the user to create material specific calibrations (see Hein et al. 2002). This paper discusses current investigations of Maya ceramics from Belize. The focus of this study is not to determine the source/provenance of the clay bodies, but to investigate the potential for establishing handheld XRF as an on-site analytical tool for the characterization and potential classification of ceramics based on their chemical signatures. The development of an empirical calibration is presented including the process involved in creating reference materials for that calibration. Overview of Maya chronology and pottery The date of the arrival of people in the Maya lowlands is currently a matter of debate (see Lohse 2010), but lies somewhere in the Archaic period (8000-2000 B.C.) with maize pollen indicating farming by about 3000 B.C. (Pohl et al. 1996). The Preclassic period dates from roughly 2000 B.C. to A.D. 250 with the earliest well-documented Maya pottery about 1100-900 B.C. in the Cunil ceramic complex of the Belize Valley (Sullivan and Awe 2012). By the Late Preclassic period (often dated 250 B.C. to A.D. 250) Maya pottery was very well made and styles were widely spread across the entire Maya lowlands. Although most of the significant cultural aspects of Maya civilization were in place by the Late Preclassic, the subsequent Classic period (A.D. 250-800) is generally considered the height of Maya development. The Classic Maya lived in a literate, highly stratified society which produced monumental art and architecture and elaborate polychrome pictorial pottery. In the Terminal Classic period many sites were abandoned and profound changes swept across the Maya world (Aimers 2007b). Dates vary because different sites were abandoned or transformed at different times from aboutA.D. 750-1050 but the Terminal Classic has traditionally been dated to about A.D. 800-900. Pottery of the Terminal Classic varies across the lowlands but it was still well-made with an emphasis on elaborate modeling and incising over polychromy. The Postclassic period follows the Terminal Classic and ends at the arrival of the Spanish in the Maya area at about A.D. 1540. Postclassic pottery also emphasizes incising and modeling and is typically well-made. The pottery of the Postclassic period is the focus here. Handheld XRF analysis of Maya ceramics 425 The Postclassic period and its pottery Figure 13.1: Map of the Maya region showing key Postclassic and trading sites relevant to this study (After McKillop 2005). In the early years of Maya archaeology the Postclassic period was neglected as a period of cultural decline following the Classic “collapse”, but more recent research at Postclassic sites has revealed population movement, innovative political strategies, increased exchange and commercialization, iconographic innovation, and intense stylistic interaction (Smith and Berdan 2000, 2003). A key characteristic of the Maya Postclassic period is evidence of extensive trade, especially among sites along the Caribbean coasts and on rivers, and involving sites in the northern half of the peninsula such as Mayapán and Chichén Itza (Figure 13.1). A better understanding of the economic and political milieu of the Postclassic would be greatly aided by more detailed documentation of the nature Jim J. Aimers, Dori J. Farthing and Aaron N. Shugar 426 and degree of interaction among Postclassic sites, and one of our most informative artifact classes is pottery. Figure 13.2: Red Payil Group Ceramics. Payil Red is the plain type, Palmul Incised is the incised version (after Sanders 1960: Fig 4, 5). Handheld XRF analysis of Maya ceramics 427 Aimers has been investigating the Postclassic period since his dissertation research on the Maya collapse and its aftermath (Aimers 2003, 2004c, 2004a, 2007b) and particularly with research on the pottery of two sites that were not abandoned in the Terminal Classic: Tipu (Aimers 2004a; Aimers and Graham 2012a) and Lamanai (Aimers 2008, 2009, 2010; Aimers and Graham 2012b). In the summer of 2011 Aimers began a pilot study to investigate the chemical variability of a plain red type (Payil Red) and a related incised type (Palmul Incised) (see Figures 13.2 and 13.3) using XRF with samples from the inland site of Tipu, and the site of San Pedro...