Soil Stratigraphy in Geoarchaeological Contexts

Abstract

The various kinds and states of soils, surface and buried, discussed in the previous chapter can be found in an almost infinite variety of combinations, and most can also be found in archaeological contexts. Furthermore, most soil stratigraphic relationships and conditions of soil burial can form a continuum through time or space or both, depending on local and regional variations in rates and depth of burial (i.e., rates and thickness of sedimentation). The most common and most extensive depositional environments with buried soils that illustrate these relationships are alluvial and eolian. These are the settings for much research on buried soils and soil stratigraphy. Alluvial settings likewise have been the loci of considerable archaeological and geoarchaeological research. Tephra—airfall deposits from volcanic eruptions—also commonly contain buried soils because of the episodic nature of eruptions. Though not as extensive as alluvial or other kinds of eolian deposits, tephra stratigraphy is locally important. Archaeological sites are also common in tephra layers from a variety of settings and regions. This chapter illustrates geoarchaeologically significant soil stratigraphic relationships in a variety of alluvial and eolian settings and at various spatial and temporal scales. Alluvial systems probably have been the site of more geoarchaeological research than any other type of depositional environment because they have always attracted occupants who left archaeological sites. A significant amount of archaeological research has also focused on riverine settings owing to “rescue” or “salvage” archaeology. In the United States, for example, this work included the federally funded River Basin Surveys of the 1940s, 1950s, and 1960s, followed by CRM studies beginning in the 1970s and continuing into the 21st century. The importance of alluvial stratigraphy in interpreting the archaeological record of alluvial settings has been recognized throughout most of this work (e.g., Mandel, 2000). Furthermore, the significance of soils in alluvial stratigraphic records has long been recognized; for example, soils were an important component of Haynes’s (1968) classic geoarchaeological model of an “alluvial chronology” for the central and western United States. Alluvial soil stratigraphy per se is more poorly known, however, being underrepresented in the traditional pedology or even traditional soil stratigraphic literature.