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In 2004 we published a paper entitled “Calibrated Radiocarbon Chronology for Pinson Mounds and Middle Woodland in the Midsouth” (Mainfort and McNutt 2004). This chapter largely follows that paper with a few differences, including the use of OxCal plots (Bronk Ramsey 1995, 2005) and an explicit assessment of the traditional view of Pinson Mounds chronology (e.g., Mainfort 1986, 1988a, 1988b). As in the earlier paper, we also consider radiocarbon dates from several roughly contemporary mound sites in northern Mississippi. Chronology at Pinson Mounds A long-term research focus at Pinson Mounds has been establishing site chronology. There are presently 39 radiocarbon determinations, including multiple assays for all intensively investigated localities (Mainfort 1980, 1986, 1988a, 1996; Mainfort et al. 1982; Mainfort and McNutt 2004), making Pinson Mounds perhaps the most extensively dated Middle Woodland site in North America (see Greber 2003). All assays are conventional radiocarbon dates. Below we present sample descriptions, calibrated ages of all assays, calibrated average dates for several localities, and some discussion regarding the reliability of certain specific dates. In all cases, we have checked the original sample submission form and/or laboratory report to ensure accuracy in reporting. Initial surveys and limited test excavations at Pinson Mounds (Fischer and McNutt 1962; Morse 1986; Morse and Polhemus 1963) found some evidence of Mississippian occupation, but the researchers correctly inferred that major use of the site occurred during the Middle Woodland period. Excavations in 1974 and 1975 confirmed this interpretation , producing Middle Woodland artifacts and several samples for radiocarbon assays (Broster et al. 1980). More extensive investigations in the 1980s produced compelling evidence, including radiocarbon determinations from mound contexts, that all the earthworks at Pinson Mounds were constructed during Middle Woodland times (Mainfort 1986, 1988a, 1996; Mainfort and Walling 1992; Thunen 1990, 1998). Conventional radiocarbon ages are reported as central tendency values (means) with uncertainty values (standard deviations), which typically are given at 1s. The latter means that 67 percent of the possible dates are accounted for by the value. Uncertainty values reflect limitations of lab procedures and counting errors in specific radiometric dating techniques. The magnitude of the uncertainty values essentially meas- ■ 191 CHAPTER 7 Calibrated Radiocarbon Chronology for Pinson Mounds and Related Sites Robert C. Mainfort Jr. and Charles H. McNutt ures the precision of the associated radiocarbon age; smaller uncertainty means greater precision. Precision and accuracy (whether or not a radiocarbon age encompasses the actual age of the material being dated) clearly are desirable, but are of little bene fit unless the sample being dated clearly is associated with the event that a researcher wishes to date (see Arundale 1981). For example, in dating the summit of a platform mound, carbonized material from a wellde fined feature is more likely to be associated with use of the surface than charcoal collected from mound fill. Most of the dated samples from Pinson Mounds, including all of those collected from 1981 onward, were selected because they could be linked confidently to a specific event. Calibrations, sample testing, and averaging were performed with CALIB 5.0 (Stuiver and Reimer 1993; Stuiver et al. 2005). In instances where there are multiple samples from a given provenience (e.g., the two dates from Ozier Mound, Feature 4), we assessed contemporaneity using the technique developed by Ward and Wilson (1978), which is incorporated into CALIB. If statistically warranted at the 95 percent level, we computed their average. All 39 conventional radiocarbon ages, calibrated dates, and various averages from Pinson Mounds are presented in Table 7.1, with the calibrated averages for key excavated loci shown in Figure 7.1. The accompanying 2s calibrated probability plots (95 percent probability) were generated with OxCal 3.10 (Bronk Ramsey 1995, 2005). In the tables and text, calibrated dates are presented as 2s age ranges. For each calibration, the relative area under the radiocarbon curve for specific date ranges also is given, along with the requisite variation to obtain this area; this measure often provides the likelihood for a more restricted date. Although we present some new material in this chapter, the major conclusion of our 2004 paper (Mainfort and McNutt 2004) remains valid, namely that earthwork construction at Pinson Mounds continued for at least a century longer than initially thought (e.g., Mainfort 1986, 1988a, 1988b). OZIER MOUND Radiometric assays on charcoal samples from Ozier Mound (Mound 5) provided the first unequivocal evidence for the construction of large rectangular platform mounds during Middle Woodland times (Mainfort...

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