Late Quaternary Radiocarbon Geochronology and Stratigraphy on the Northern Plains: Silts, Mammoths, and Buried Soils in the Lower Yellowstone Valley, Montana

Summary

Within the Yellowstone River basin, in eastern Montana, upland landscapes contain silts with buried soils. Radiocarbon measurements from bone and the paleosols provide a basis for proposing a regional chronostratigraphic model. At the Lindsay locality, north of the Yellowstone River, mammoth remains were recovered within silts overlain by a buried soil A-horizon. Samples from the mammoth have been analyzed by six laboratories, using beta decay or AMS. If the radiocarbon determinations older than 12,000 RCYBP provide the most accurate age estimates, then the mammoth is older than the Younger Dryas and possibly associated with the Bølling climate event. Radiocarbon measurements of buried soils at OTL Ridge, in the uplands south of the Yellowstone River, suggest the soils may range in age from about 11,415-9,330 years RCYBP. These silt and paleosol sequences are similar to Oahe Formation (the Aggie Brown member within the Leonard Paleosol) as well as sequences associated with the Brady Paleosol. The silts are interpreted as loess that began to accumulate in upland areas prior to 12,000 RCYBP, while intervals of landscape stability and wetter conditions correlated with Younger Dryas age (10,900-9,800 RCYBP) dark layers or "black mats" may be represented by some of the buried soils.

This Resource is Part of the Following Collections

• Society for American Archaeology 82nd Annual Meeting, Vancouver, BC (2017)

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Record Identifiers

Abstract Id(s): 15941