Shallow site archaeology: Artifact dispersal, stratigraphy, and radiocarbon dating at the Barger Gulch locality B Folsom Site, Middle Park, Colorado

Abstract

Shallowly buried archaeological sites are particularly susceptible to surface and subsurface disturbance processes. Yet, because cultural deposition often operates on short time scales relative to geologic deposition, vertical artifact distributions can be used to clarify questions of site formation. In particular, patterns in artifact distributions that cannot be explained by occupation histories must be explained by natural processes that have affected sites. Buried only 10–50 cm beneath the ground surface for 10,450 14C yr, the Folsom component at Barger Gulch Locality B (Middle Park, Colorado) exhibits many signs of post‐depositional disturbance. Through examination of variation in the vertical distribution of the artifact assemblage, we are able to establish that only a Folsom component is present. Using vertical artifact distributions, stratigraphy, and radiocarbon dating, we are able to reconstruct the series of events that have impacted the site. The Folsom occupation (˜10,450 14C yr B.P.) was likely initially buried in a late‐Pleistocene eolian silt loam. Erosion brought the artifacts to rest on a deflation surface at some time prior to 9400 14C yr B.P. A mollic epipedon formed in sediments that accumulated between 9400 and 7000 14C yr B.P. Some time after 5200 14C yr B.P., this soil was partially truncated, and artifacts that had previously dispersed upward created a secondary lag at its upper contact. This surface was buried again and artifact dispersal continued. © 2005 Wiley Periodicals, Inc.

Comparisons and Interpretations of Charcoal and Organic Matter Radiocarbon Ages from Buried Soils in North-Central Colorado, USA

“…All of the 14 C ages from buried Kremmling surface soil horizons occur between 9000 and 4000 BP, while the buried surface horizon at JCS 05-1 produced entirely late Holocene ages (Table 3; Figures 4 and 5). Surovell et al (2005) c Originally published by Mayer et al (2007) d Originally published by Mayer et al (2005) The HT and HA samples from the Kremmling soil in the main block of the Barger Gulch excavation area show the same relationship as the LT and HA fractions, though they are in closer agreement relative to most SOM pairs (Table 4, Figures 4 and 5). While no charcoal samples were recovered in direct association with the SOM samples, the Kremmling soil A horizon in the Barger Gulch Locality B excavation area produced charcoal ages of ~9500 BP and ~6900 BP from lower and upper samples, respectively Surovell et al 2005).…”

“…Determining the age of the soil is important for understanding landscape evolution and Holocene environmental change, which have archaeological implications. Middle Park contains an abundance of Paleoindian archaeological components (Kornfeld and Frison 2000), some of which occur in buried soils (Kornfeld et al 1999;Mayer et al 2005Mayer et al , 2007Surovell et al 2005). Table 1 The goals of this study are threefold.…”

Paleoindian environmental change and landscape response in Barger Gulch, Middle Park, Colorado

“…Formation of soil III was underway by at least 6000 14 C yr B.P., continuing until at least 5200 14 C yr B.P. Results of particle-size analysis and vertical artifact profiles from excavation units also tend to support this scenario of site-formation history (Surovell et al, 2005).…”

The geoarchaeological and paleoenvironmental context of Paleoindian sites in western Middle Park, Colorado, USA

“…The majority of 14 C ages based on charcoal in association with the Folsom assemblage fall between ϳ9500 and 7000 14 C yr B.P., and SOM ages from the Kremmling A horizon are between ϳ6000 and 5000 14 C yr B.P. (Mayer et al, , 2007Surovell et al, 2005), suggesting two possible scenarios: (1) The Kremmling soil at Locality B represents a relatively stable landscape since Folsom time into the middle Holocene; or (2) the soil represents younger surface and near-surface horizons formed in unit 2 and welded (Ruhe & Olson, 1980) to an older B horizon formed in unit 1, that is, two episodes of soil formation separated by a period of erosion. The fine-grained valley fill in the first-order tributary adjacent to the site ( Table II as well as ages presented by Mayer et al (2007).…”

“…Geoarchaeological investigations at Barger Gulch Locality B concentrated on documenting the soil-stratigraphic context and formation history of an extensive Folsom (ϳ10,500 14 C yr B.P.) assemblage (Daniele, 2003;Laughlin, 2005;Mayer et al, 2005;Surovell et al, 2005; and understanding the geomorphic and environmental histories of the Barger Gulch drainage (Mayer et al, 2007). Work at UTM and Barger Gulch has been useful to reconstructing site-and drainage-specific histories.…”