Late Glacial Environments and Paleoecology at Blackwater Draw ...

80 CHRISTOPHER L. HILL, FRED WENDORF, PAUL B. SEARS AND EDNA PAPAZIAN
Fig. 2. Image of sedimentary remnant in vicinity of Highway Site and Barrow Pit.
Scale is 10 centimeters = 4 inches. Photo taken in 1998 by C. Hill.
the south of Baseline Road, two localities have been
designated: the Barrow Pit (Locality 7, Haynes 1975)
and the nearby Highway Site (LA 3325, Hester 1972)
(Fig. 1 and 2).
Here, we initially describe the sedimentary sequence
at the Barrow Pit following the stratigraphic terminology
of Haynes (1975; see also Haynes and Agogino
1966:815). Later, we compare the stratigraphic sequence
with other environmental studies that have
used a variety of stratigraphic designations for localities
in and near the draw. The lowest deposit, unit B1,
consists of a speckled sand. It is overlain by unit B2,
a laminated lacustrine mudstone. A sample of carbonate
from the lower part of the mudstone has a radiocarbon
measurement of about 15,770 B.P. (A-669B, Haynes
1975, B.P. = radiocarbon years before present). The
upper part of unit B2 contains a well-developed,
eroded calcic paleosol; Clovis points were recovered
from the deflated surface of this paleosol (Haynes and
Agogino 1966).
The laminated mudstone is overlain by erosional
remnants of sandy silt designated as unit D (Fig. 1
and 2). Unit D contains Anodasta shells with a radiocarbon
age of about 10,600 B.P. (A-493, Haynes 1975).
This is correlated with the “diatomaceous earth” and
“unit D” of Haynes (1995), dated from 10,900–10,200
B.P. and associated with Folsom and Agate Basin artifacts
at the nearby Clovis gravel pit. It could represent
a local manifestation of the Younger Dryas. The uppermost
deposit, designated unit E, is a calcareous silt,
likely equivalent to the “carbonaceous silt” and “unit E”
dated from 10,500/10,000 to 9,000/8,500 B.P. at the
Clovis gravel pit (Haynes 1995).
The stratigraphic sequence at the Barrow Pit was
collected by F. Wendorf in 1965. The samples were collected
from what was then the deepest part of the draw,
in an area of numerous low hummocks (Fig. 1 and 2).
The samples were sent to P. Sears who supervised the
pollen analysis undertaken by E. Papazian. The area of
the Highway Site and the Barrow Pit was visited by Hill
in 1983, 1986, and 1998. A brief visit was conducted in
2006 by Wendorf and Hill with David Batten, Christy
Bednar, and Cheryl Hill. In addition, Hill conducted
a taxonomic study of the paleontological materials from
the Blackwater Draw region stored at the Shuler Museum
at the Institute for the Study of Earth and Man,
Southern Methodist University.
Biostratigraphic Description. Two of the strata at
the Barrow Pit contain biotic materials that can be used
to evaluate Late Pleistocene ecological conditions within
Blackwater Draw. Pollen and molluscs are present in
some of the sediments of unit B2 as well as in unit D.
Twenty-four samples were collected from the unit
B2 and subjected to pollen analysis (Fig. 3). Pollen