With the exception of sample number 3, which has an anomalous date and may have been contaminated by later activity at the historic campground, all the dates from the carbon assays are roughly consistent within the sites and are certaily consistent with the range of dates obtained from other previously investigated Oliver Phase sites. (For a table of site dates from radiocarbon teting, see Redmond 1994: 83, for recently obtained early dates for an Oliver Phase site in Hamilton County, see Plunkett et al. 1995: 53.) All the dates are roughly contemporatneous, although the Sugar Creek site (12 Jo 289) appears somewhat earlier, the dates for the Bundy-Voyles (12 Mg 1) site seem to cluster near the end of the Oliver Phase temporal sequence, and the Crouch site (12 Jo 5) overlaps both.
However, Figure 1 also illustrates some of the problems with radiocarbon assay as a method of making fine temporal distinctions in a two-hundred-to two hundred-and-fifty-year time span. In radiocarbon dating, the greater the probability of accuracy (95 percent at two-sigma results), the wider the range of dates becomes. It is well to remember that a one-sigma calibrated result has only a 68 percent probability, or two chances out of three, of being accurate. Partly this is a result of the time period under study, when unusual sunspot activity and other environmental oscillations in the fourteenth century make current calibrations to dendrochronolgy extermely convoluted, and partly this is result of the method of calibration results.
The figure below, an individual result from Beta Analytic, Inc., for sample Beta-84951, is a case in point. It graphs the calibration curve against the labortory results of the radiocarbon assay, but because the calibration curve is less a true curve than a meander, the dates intercept it at least at two points, even at one sigma (68 percent probabilty), giving two possible time periods separted by decades. At two sigma (95 percent probability), the range of probable dates spans over a century.
From the foregoing, it is apparent that radiocarbon assays, while useful for assigning sites within a broad range of time, cannot provide dates to temporally sequence sites within that broad range with any great certainty. Even within sites known to be single component, and hence of shorter occupation, there can be a disconcertingly broad range of probable dates. To make the fine temporal distinction necessary to establish a sequence to Oliver Phase variation, other methods can be used to supplement the less precise results of radiocarbon dating. For intrasite dating, ceramic refits provide one such method. On a wider level, recent advances in seriational techinques have made seriation an appropriate method for assessing change over time within such a problematic period as the Late Prehistoric. (For good overviews of recent researech, see Duff 1996; Teltser 1995.)
In short, radiocarbon dating remains an important tool both for relative ordering of sites within broad spans of time and for checking relative consistency and placement within this ordering, as it does for the sites reported here, but it must be supplemented with other, often only locally appropriate, methods to make the finer temporal distinctions that are necessary for developing a diachronic picture of the Olver Phase with any degree of certainty.
References Cited
Duff, Andrew I.
1996 Ceramic Micro-Seriation: Types or Attributes? American Antiquity 61(1): 89-101.
O'Brien, Patrick K., and Mary E. Pirkl
1991 Phase II Subsurface Archaeological Investigations at Site 12 Jo 8, Johnson Couty, Indiana. Reports of Investigations 96-35, Glenn A. Black Laboratory of Archaeology, Indiana University, Bloomington.
Plunkett, Jeffrey I., Mary F. Turdeau, and Marnie A. HIlton-Plunkett
1995 Phase II Archaeologica Subsurface Investigations: Sites 12-H-15, 46, 694, 695 and 699, in Hamilton County, Indiana. Landmark Archaeological and Environmental Services, Report 95IN0057. Indiansapolis.
Redmond, Brian G.
1994 The Archaeology of the Clampitt Site: An Oliver Phase Village in Lawrence County, Indiana. Current Research in Indiana Archaeology and Prehistory: 1993 ed. by B. Redmond. Glenn A. Black Laboratory of Archaeology, Research Reports 16.
Teltser, Patrice A.
1995 Culture History, Evolutionary Theory, and Frequency Seriation. In Evoloutinary Archaeology: Methodological Issures, ed. by P.A. Teltser, pp. 51-68. University of Arizona Press.