Observations of Selected Samples Received from Dr. Gary Huckleberry
from Kennewick Site
Department of Archaeology
675 Commonwealth Ave.
Boston, MA 02215
Kennewick 230 [The upper half of the slide is a bit
too thick making it difficult to observe.]
Overall, the material in the slide is comprised of medium to coarse
silt sized grains of predominately quartz and other minerals (e.g.,
biotite, weathered clay aggregates, hornblende and other heavy
minerals) in a calcareous fine silty matrix. A rounded granule
of welded tuff containing quartz and feldspar inclusions was also
The structure of the material is comprised of
sub-parallel plate-like fissures interspersed with irregularly
shaped, millimeter size voids (vughs). The origin of these vughs
appears to be related to biological activity, likely roots. Other
evidence of biological activity is shown by small, millimeter
size burrows and aggregates of the matrix.
Additional postdepositional modification is shown
by localized calcium carbonate cementation of the matrix primarily
in areas encasing voids (called hypocoatings), but these are not
very well developed. In addition, the upper surface of this sample
appears to be slightly more compact and cemented than the material
below; as such, it appears to form a thin crust about 200 Ám thick.
This sample is quite similar to Sample 230, although this is not
completely clear because this is a smaller sample. Nevertheless,
it is somewhat finer grained than Sample 230, having slightly
less quartz silt. Secondary cementation appears slightly better
developed, although certain irregular but sharply defined domains
of non-calcareous silty material can be recognized. These non-calcareous
domains appear to be a result of localized decalcification of
the matrix. The presence of some aggregates also point to biological
activity that affected the sediments.
This sample is different from Sample 230 and 231 in a number of
- Quartz, silt, and other heavy mineral grains
of silt size are noticeably more abundant, with a concomitant
decrease in the fine silt calcareous fraction. Consequently,
this sample is overall less calcareous than the others.
- Remains of hypocoatings are evident, but the
carbonates are clearly being dissolved. In other words, we can
see only remnants of what was once a more calcareous sample.
- The porosity in this sample is much lower,
and the moderately sorted silt fraction is quite compact. The
silt fraction appears to have a higher proportion of heavy minerals,
but this observation could result from the decalcification to
some extent .
- Some irregular vughs and channels can be observed,
but these are much less abundant than in the other samples.
- Aggregation and other evidence for biological
activity are not particularly evident.
This sample is very similar to Sample 245, although vughs are
more abundant. In addition, locally there are a few centimeter
size areas that have a more open and less compact fabric rich
in coarser silt. These areas appear to be burrow infillings. Hypocoatings
are also well represented here, but again these appear to be remnants
of a more calcareous sample. Finally, some of the vughs - including
those with hypocoatings - appear to exhibit thin (~5 Ám) incipient
impregnations of iron/manganese.
Kennewick 250 [Sample is slightly too thick.]
This sample is similar to Samples 245 and 246, but is just ever
so slightly finer grained than they are.
This sample is predominantly silt size mineral material as above,
with some interstitial fine grained carbonate that is in the process
of being dissolved. This dissolution also includes calcium carbonate
that appears to have been precipitated within some of the voids.
In other words, the secondary carbonate here is not in the form
of hypocoatings -which are produced by carbonate solutions which
penetrate from the void into the matrix - but rather these are
carbonates that have been precipitated within the empty space
of the void itself. In any case, the overall makeup of this sample
is not dissimilar from that of Samples 245, 246, and 250. It is
difficult to definitively assess this sample in light of its very
small size and the fact that it is being decalcified.
Similar to Sample 251 but somewhat less decalcified. There is
no evidence for carbonate precipitation in the voids, but again,
this is a very small sample.
In terms of general gross lithological similarity, it is evident
that Samples 230 and 231 are quite similar to each other but are
distinct from the remaining samples, which are coarser grained
and have been subjected to decalcification. It should be pointed
out that all the samples (with the exception of Samples 251 and
251a) exhibit secondary hypocoatings which are a pedogenic feature.
The ultimate textural difference between Samples 230 and 231 and
the others could simply relate to slightly different energies
that one might find in overbank flood deposits, for example. Similarly,
all of them could easily fit within a fluvial or colluvial setting
in which loess-like material could have supplied the basic components.