Bulletin of the Texas Archeological Society, Volume 84, 2013 Page: 50
270 p. : ill.View a full description of this periodical.
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Group 15
Grpur u6
Group 3
GGro7p92
gr up7 G ou
Group 6
Group 30
Group 14 + + ."m
+Group 9
Group 5 ++ A0
Group 4
Group 8
1 903 4 5 6 7 8 9 102
Cr (ppm)2
Figure 4. Bivariate plot of chromium and terbium showing the small compositional groups. Ellipses represent 90 percent
confidence intervals for membership in the group.due to very unique chemistries. These samples have
been classified as outliers. Some of these samples
may only be unique in the concentration of one or
two elements, but it is enough to skew some of the
multivariate statistics if they were not removed.
While the specific sources for the outliers' unique
chemistries are not known, it is not safe to assume
that they represent imported ceramics.
An additional 186 samples remain unassigned.
The vast majority of the unassigned samples are
part of the large mass of samples that was divided
to form Groups 10, 11, and 12. The groups repre-
sent very conservative clusters, and thus the groups
exclude many more potential members than other
approaches. Many of the unassigned samples are
either not quite similar enough to any of the large
groups or potentially belong to more than one
group. Figure 8 is a plot of the unassigned samples
relative to the three large groups.INTERPRETATION OF CHEMICAL
COMPOSITIONAL GROUPS
Statistical analysis of the dataset resulted in
the identification of 15 compositional groups, five
of which contain only historic mission period ce-
ramics and are not discussed further here. Of the
10 groups containing native-made, non-mission
pottery, three (Groups 1, 10, and 12) have been
split into three subgroups each. In effect, this
yields 16 separate groups that include native-made,
non-mission ceramics (Table 4). It is important
to note, however, that 317 (53 percent) of the
ceramic samples are either outliers or, much more
frequently, are currently unassigned to a composi-
tional group. Slightly less than one-third of these
are Caddo pottery samples that have no probability
of membership in any of the Central Texas compo-
sitional groups.50 Texas Archeological Society
2
10o
CL 9
8
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6
5
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32
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Texas Archeological Society. Bulletin of the Texas Archeological Society, Volume 84, 2013, periodical, 2013; Abilene, Texas. (https://texashistory.unt.edu/ark:/67531/metapth1222741/m1/54/: accessed July 18, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu; crediting Texas Archeological Society.