Geologic, Geoarchaeologic, and Historical Investigation of the Discovery Site of Ancient Remains in Columbia Park, Kennewick, Washington

Summary

During December 1997, a research team from the U.S. Army Engineer Waterways Experiment Station (WES) conducted geologic investigations at a site in Columbia Park, Kennewick, W A where human remains had been found in the summer of 1996. This study was conducted at the request of the U.S. Army Engineer District, Walla Walla (CENWW), in support of the Corps' resource stewardship responsibilities and to represent the Federal interest in legal issues related to the remains known as Kennewick Man. It was coordinated with concomitant studies of the same site conducted by two separate groups to which permits had been issued by CENWW under the Archaeological Resources Protection Act (ARPA).

The two principal questions addressed by the WES study were:

a. What age is indicated by geologic evidence at the study site? Asked another way, does the geologic evidence at the site support the age indicated by earlier age-dating of the remains at approximately 9,000 years?

b. Are there any indicators of specific cultural affiliation for the remains?

Although the remains were not recovered in place in the sediments, it was important to recognize the possibility that cultural materials related to the remains might be recovered at the site.

Geologic studies to date have been conducted in phases to allow adequate time to coordinate all on-site activities with appropriate interested parties and to assure minimum physical impact to the site itself. Phase One was a preliminary site visit conducted by two WES team members with assistance by two CENWW team members in October 1997. During Phase One, the WES team defined the boundaries of the study site, identified some potentially significant stratigraphic features for establishing the age of the landform, and recommended a phased approach to the study and coordination with team members from the two ARPA permit applicant groups.

Phase Two studies were conducted between 12 and 18 December 1997, and are the principal subject of this report. The focus of Phase Two field investigations was a 350-m exposure of sediments along the south shoreline of Lake Wallula, beginning approximately 50 m east of the location where the skull of the ancient remains was found and extending westward to include a volcanic ash layer found during Phase One. The principal landform at this site is a terrace of the Columbia River, composed of fine-grained sediments that accumulated primarily in quiet water. This terrace may be correlated with terraces of early Holocene age at other locations along the Columbia River and described in published literature.

The volcanic ash or tephra layer at the Kennewick site is Mazama ash. This material originated from the volcanic eruption of Mount Mazama (now Crater Lake) identified by various authors to be at about 6, 700 years before the present. Because it occurs at many widespread locations throughout the Pacific Northwest, and because it is readily identifiable by its chemical signature and is of known age, this tephra is used as a time and stratigraphic marker in geologic and archaeologic studies in the western United States. Its presence as an in situ deposit near the terrace surface at the Kennewick site establishes that the landform associated with the ancient remains is more than 6, 700 years old. Stratigraphic horizons were traceable over the length of the study site, establishing that with the dateable materials that are present, one can interpret the relative ages of the sedimentary units. One important traceable unit includes abundant concretions, which are accumulations principally of calcium carbonate and silica moved downward by groundwater over a long period of time.

Geologic evidence indicates that the remains probably came from this concretion-rich sedimentary unit. Carbon-14 age dates of shells collected from two different locations above the concretion-rich unit indicate ages of greater than 6,000 years, although shells often yield erroneous age dates. However, the layers including volcanic ash and shells all indicate ages between 6,000 and 7,000 yr B.P. and are stratigraphically higher than (i.e., overlie) the sediment layer associated with the ancient remains. Therefore, the geologic features of the site support an age of more than 7,000 yr B.P. for the ancient remains. Age dates of WES-sampled sediments underlying the concretion-rich unit indicate ages of up to 15,000 yr B.P.

Although only a few hundred pounds of sediment were moved and screened, cultural materials were encountered in place in the stratigraphic units along the shoreline during this study. None ofthe cultural materials could be identified as being affiliated with the ancient remains. The materials identified as cultural were similar to known cultural materials from extensive reaches ofthe Columbia River shoreline and suggest repeated human use of this site in prehistory. The teams encountered no evidence of prehistoric burials during this site study. No cultural materials were encountered in sediment or core samples taken for study, and no cultural materials were removed from the site.

The activities of Phase Two confirmed that the landform in Columbia Park is old enough to have held the remains continuously for 9,000 years, and therefore the geologic setting is consistent with the age of the remains reported previously.The work was limited to the exposed reservoir bank and could not answer many research questions about the regional geologic setting and prehistoric land use.

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Contact(s): Francis McManamon

Sponsor(s): Corps of Engineers

Repository(s): Corps of Engineers

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