Clovis Comet Debate - The Archaeological Conservancy

A miniature Shivwits fingernail incised jar recovered from Site 82.
One of Harry’s goals is to refine the chronology
for the area. Presently, the dating of archaeological sites
on the Shivwits Plateau relies either on ceramic cross-dating
(in which painted pottery styles are dated through comparison
with similar, better-dated pottery styles to the east) or
on the radiocarbon dating of organic matter. However, both
techniques result in a date range of perhaps a hundred years
or so, rather than providing a date of a specific year. “To
understand why the trade network flourished and why it
stopped, we need better dates. We can address more specific
questions if we have a more specific chronology.”
Toward that end, samples of wooden beams recovered
from Site 82 and Lava Ridge Ruin will undergo tree-ring
analysis at the University of Arizona, a technique that can
yield precise dates. Tree-ring dating relies on the fact that,
in certain species of trees, a single growth ring is laid down
each year. The width of the ring is determined by climatic
conditions, and the wetter the year, the wider the ring will
be. Within a given area, variations in ring widths will be patterned
chronologically. In most areas of the northern American
Southwest, regional sequences have been developed
so that the tree-ring patterns can be correlated to specific
calendrical dates. If these sequences are found to apply to
the Shivwits Plateau, then it may be possible to obtain calendrical
dates from the wooden beams recovered from Site 82
and Lava Ridge Ruin.
Allison, however, cautioned that the lack of prior
research on the Shivwits Plateau could make tree-ring dating
difficult. He, too, has some wood samples at the lab from
his sites, but he’s pessimistic: “One issue is whether we’ll
get good dates, because we lack a sequence of this area specifically.
In fact, we have virtually no tree ring dates from
the Shivwits and some lousy ones from southwest Utah. To
get some dates, we’re going to have to hope the climactic
changes there were similar enough to the climactic changes
across the Grand Canyon, where we have very solid data.”
Allison and Harry speculate that the Shivwits Anasazi
may have received salt, turquoise, cotton, and other goods in
return for their pottery. Allison further proposes that they
may have joined their trading partners in the Moapa Valley
during harvest time to assist with the crops in exchange for
a share of the produce.
Harry now awaits the outcome of analyses of pollen to
learn what the people at Site 82 ate and grew as well as of
tree-ring samples. She and Allison are jointly applying for a
National Science Foundation grant to do more extensive treering
testing on older living trees on the Shivwits Plateau that
could provide a baseline. She’s also plans to send samples of
sherds found at Site 82 to the University of Missouri Research
Reactor Center for neutron activation analysis, a process that
reveals the sample’s elemental composition. This, she hopes,
will help pinpoint the place on the Shivwits Plateau where
the pottery found in the Moapa Valley was made.
Yet there is one other somewhat more novel experiment
Harry is excited about. She has been bothered by the
The design of this black and white bowl sherd is similar to the
styles of ceramics found at other Anasazi sites that date from
about 1040 to 1220.
lack of hearths on her sites, but she surmises that the basaltic
clay freezes with moisture from snowfall during the winter
and thaws and dries in the summer, a cycle that obliterated
evidence of hearths. To test this theory, Harry and her students
constructed a room with a hearth, burned items in it,
and then buried it. She’ll return to Site 82 next year to see if
the freeze-thaw cycle results in the hearth’s disappearance.
Before 2006, “nobody had excavated up here at all,” Harry
said. “It helps that there are two of us (Allison and Harry)
because the more work that’s done up here, the more you
have that context. But we still have a very long way to go.”
STEVE FRIESS is a Las Vegas-based freelancer whose work appears
regularly in The New York Times and many other publications.
36 fall • 2010
noelle blair