T35 Alluvial Cycles, Climate, and Human Prehistory

Sunday, 28 October 2007
1:30 PM - 5:30 PM

TWO COMPLEMENTARY LATE PALEOINDIAN SITES BURIED IN LAMINATED SILT 9050 14C YR BP ALONG ASH HOLLOW DRAW, WESTERN NEBRASKA

Paper number: T35-11
Program: Technical Sessions
Time: 4:10 PM – 4:25 PM

Authors

Abstract

Four Late-Paleoindian archaeological sites lie along a 1.4 km reach of Ash Hollow Draw in western Nebraska. Of special interest are the multiple-component Clary Ranch and O.V. Clary sites, which represent complementary views of a single, spatially differentiated prehistoric settlement and subsistence system along a major tributary of the North Platte River. The Clary Ranch site served as a secondary processing area for carcasses of bison killed en masse nearby. In contrast, the primary component at the stratified O.V. Clary site is a very rare example of a Paleoindian residential camp, with evidence for occupation during the mid-summer, mid-winter, and late winter/early spring. On-site activities there were organized around an intact hearth, around which is scattered a spectacular variety of organic and non-organic artifacts and discarded food remains.

Late-Holocene incision into the Early- to Middle-Holocene valley fill created the >17 m-high Kersey Terrace and exposed the Clary Ranch and O.V. Clary sites 1.0-1.8 m and 0.2-0.4 m, respectively, above the modern channel. Five lithostratigraphic units (B to F) have been recognized in the lower portion of the fill. Cultural material at both sites occurs within the ripple- or horizontally-laminated silty portion of Unit E. At the Clary Ranch site cultural material is confined to a paleo-channel along the valley margin. At the O.V. Clary site cultural material is scattered over >100 sq m of the paleo-valley floor. Nearly 30 silt laminae (1.4 to 9.6 cm thick) that contain three components can be traced over an even larger area. Frequent, very turbid, low-energy flows in ephemeral Ash Hollow Draw probably account for both rapid burial and excellent preservation of the cultural material at both sites.

Based on 14 AMS radiocarbon ages for Unit E and two for basal Unit F at multiple localities within Ash Hollow basin, deposition of nearly 4 m of laminated silt occurred within 450 years between 9190 yr B.P. (10,400-10,250 cal yr B.P.) and about 8740 yr B.P. (9,890-9,560 cal yr B.P.). Paleo-environmental data indicate that the valley floor was moist and supported a dense gallery forest between 9920 yr B.P. (11,610-11,210 cal yr B.P.) and 9440 yr B.P. (11,070-10,520 cal yr B.P.). By 9100 yr B.P. (10,580-9,910 cal yr B.P.) a tallgrass prairie with wooded areas was present along Ash Hollow Draw and a shortgrass prairie dominated the uplands. Temperatures were cooler, especially in summer, than at present.