Soil Genesis and Site-Formation Processes

Pedogenic processes that produce or alter the soils associated with a landscape (buried or unburied) also modify the archaeological sites and other traces of human activity associated with that landscape and buried landscapes. The wide range of processes that form soils can profoundly affect the archaeological record. Pedogenesis, therefore, is an important component of the processes of archaeological site formation. Archaeological “site-formation processes” are those processes that modify artifacts and archaeological sites from the moment they were formed until they are uncovered by archaeologists (Stein, 2001b, pp. 37–38). Understanding formation processes is crucial in archaeology because archaeologists use the patterns of artifacts in the ground to infer behaviors. Formation processes identify patterns that are created by ancient behaviors and separate those patterns from the ones created by later cultural and natural processes (Stein, 2001b, p. 37). In his influential volume Formation Processes of the Archaeological Record, Schiffer (1987, p. 7) notes that archaeologists try to infer past behavior based on the archaeological record, but the record “must be handled with great care by the investigator seeking to infer past behaviors, for the evidence that survives has been changed in many ways by a variety of processes.” These processes introduce variability and ambiguity into the archaeological record. Schiffer (1987, p. 7) further distinguishes between cultural processes, in which the agency of transformation is human behavior, and noncultural processes, which stem from processes of the natural environment. Natural formation processes are many and varied and include plants, animals, wind, water, ice, and gravity, among others. Soil formation is also identified as an important process of site formation. Schiffer (1987) provides a comprehensive discussion of natural site-formation processes, which are summarized by Stein (2001b). Nash and Petraglia (1987) and Goldberg et al. (1993) also provide a number of case histories of natural formation processes identified at archaeological sites. Because soil formation represents the alteration of rock and sediment (chapter 1), pedogenic processes are important natural processes in the formation of archaeological sites. Other weathering processes that are significant in site formation can be grouped as “diagenetic alterations.”