Rethinking the fourth of July Valley site: A study in glacial and periglacial geoarchaeology

Abstract

AbstractThe Fourth of July Valley site (5BL120) occupies the crest and inner slope of a Satanta Peak (latest Pleistocene) terminal moraine above timberline in the Indian Peaks Wilderness Area, Colorado Front Range. Excavations in 1971 suggested that a Late Paleo‐Indian lithic tradition marked by lanceolate and stemmed projectile points with parallel‐oblique flaking persisted at high altitude during the Altithermal, long after its disappearance from drought‐susceptible lowlands. Analysis of a sediment column collected in 2001 casts doubt on this interpretation. Large charred sclerotia (the resting stages of mycorrhizal fungi) show that tree islands colonized the moraine soon after deglaciation, fueling Early and Middle Holocene wildfires. Conditions became increasingly periglacial ca. 3340 yr B.P., when a lobate rock glacier advanced to the south margin of the site, altering snow‐accumulation patterns, eliminating trees, supplying meltwater that fueled ice‐lens formation, and initiating deposition of humus‐rich, snowbed loess. Large waste flakes and artifacts were frost‐sorted to the existing ground surface, where they became mixed with 6240‐year‐old wildfire charcoal in a pseudo‐occupation layer. Microflakes were too small to participate in vertical frost sorting, so remained in their original stratigraphic locations. The association of thermally altered microflakes with 8920‐year‐old charcoal in a deeply buried stratigraphic context suggests that the site was occupied during the Early Holocene and is irrelevant to the Altithermal refugium hypothesis. © 2005 Wiley Periodicals, Inc.