The Lewis Camp Mound: An example of a petrocalcic horizon in Jefferson County, Florida

Soil scientists have described petrocalcic soil horizons, commonly referred to as caliche, from the southwestern United States for quite some time. Caliche normally occurs in semi-arid climates where evapotranspiration (ET) exceeds rainfall. In more arid climates, the repeated process of illuviation and precipitation of CaCO3 forms subsurface accumulations of CaCO3 or other carbonates. To the authors' knowledge, petrocalcic soil horizons have not been reported in the southeastern United States, quite probably because environmental conditions are not normally favorable for such development. While soil scientists may not have been aware of petrocalcic horizons in the southeastern United States, archaeologists have noted their presence for some time. They are usually found within specific sites called middens, which are generally refuse piles, deposited by Native Americans. Many of these middens contain large quantities of shell, in addition to bones of various mammals, birds, fish and turtles, ceramic vessel fragments and lithic tool-making byproducts. The Lewis Camp Mound (08Je00182) is one such midden, composed primarily of apple snail (Flag: italicize Pomacea paludosa) shell, with lesser amounts of banded mystery snail (Flag: italicize Viviparus georgianus), freshwater mussel (e.g., Flag: italicize Elliptio spp.) and several saltwater species including oyster (Flag: italicize Crassostrea virginica) and great ark (Flag: italicize Dinocardum robustus). The site was initially investigated in the summer of 1999, at which time the petrocalcic horizon was thought to have been the underlying bedrock. Subsequent fieldwork, conducted in September 2003 and in June of 2006, have added to our knowledge of the age of the site, as well as provided insights into the formational processes which have occurred. This paper will discuss several explanations archaeologists have suggested for the formation of petrocalcic layers in middens, as well as the age and cultural occupations relating to the Lewis Camp Mound.