Schurr, Mark R. and Sherri L. Hilgeman (Glenn A. Black Laboratory of Archaeology,
Indiana University, Bloomington)
FLUORIDE DATING AND POTTERY CHRONOLOGY AT THE ANGEL SITE
The relative fluoride contents of prehistoric bone can be used to develop fine-scale
relative chronologies for prehistoric human burials and other features that contained
bone. In this paper we report on an attempt to order a series of archaeological
contexts containing faunal material and chronologically diagnostic pottery from
the Angel site.
Bones adsorb fluoride ions from groundwater and, over time, their fluoride content
increases. Under favorable conditions, the fluoride content of prehistoric bone
is a function of age, with more ancient bones having higher fluoride contents
than more recent ones. Earlier applications of fluoride dating to a sample of
human burials from the Angel site showed that the geological conditions at Angel
were suitable for fluoride dating.
A fluoride selective electrode was used to measure the fluoride content of 50
deer metacarpals or metatarsals from 14 different archaeological contexts that
also contained prehistoric pottery. Ten of the contexts were pit features from
the Village Occupation area of the site. These pits all extended into sterile
subsoil. One feature was an artifact concentration identified in the midden of
the Village Occupation area. The remaining three features were located outside
the Village Occupation. Two of these features were defined when Black excavated
Mound 1, a small mound at the foot of the large Mound A. One feature (F23/0- 13-D)
was a semisubterranean house pit. This pit was covered with a layer of sterile
soil which in turn was covered with a layer of midden (F9/0-13-D), which produced
a radiocarbon date of 750 + 50 radiocarbon years (Beta-3924). These contexts provided
an excellent test of fluoride dating because Feature 23 (the house pit) must be
earlier than Feature 9 (the midden) which lies above it.
The distribution of the fluoride contents appeared to have three modes, and the
overall distribution of fluoride specimens matched our expectations about occupations
of the site. The faunal specimens were classified as "early" if they had high
fluoride contents, "middle" if they had moderate fluoride contents, or "late"
if they had very low fluoride contents. The features were then ordered based on
the classified fluoride contents.
In order to evaluate our fluoride chronology, we assigned dates to features based
on associated pottery handles and plate forms, and ranked the features from early
( I ) to late (3). When we compared the ranking (or seriation order) obtained
by fluoride dating with that based on the pottery types present in the features,
we found that we have a good correlation between the two chronological measures
for most of the features. Two features with poor correlations between the magnitude
of the fluoride measures and the pottery chronology were themselves of questionable
context. One was an artifact concentration defined in midden, and this context
may be mixed because the limits of the feature were difficult to define. The other
contained faunal specimens that spanned the full range of fluoride contents and
was apparently a mixed context where earlier material may have been incorporated
into a relatively late pit dug through an earlier midden.
These results indicate that fluoride dating of faunal materials can be used to
develop a chronology for pits and midden features at the Angel site. Fluoride
dating also can be used to identify mixed contexts and to distinguish them from
contexts that span a limited period of time. This potential will be very useful
for fine-scale studies of changes in pottery attributes and in subsistence practices.
Fluoride dates can also be used to assign relative dates to features that do not
contain diagnostic pottery [return to 1990 abstracts menu][continue to next]