Artifact preservation and post-depositional site-formation processes in an urban setting: a geoarchaeological study of a 19th century neighborhood in Detroit, Michigan, USA

Experimental Order 1 soil survey of vacant urban land, Detroit, Michigan, USA

“…One lot, not discussed further here, was found to have few artifacts and a relatively simple pattern of anthropogenic soils. A second lot from the 19th century with soils containing abundant artifacts of archeological significance is described in a separate paper (Howard et al, 2015). The site described here contained abundant artifacts, a complex pattern of soils, and had supplemental subsurface data obtained with a Geoprobe.…”

Pedogenetic Trends in Soils Formed in Technogenic Parent Materials

“…The oxidation of sulfides, the formation of secondary minerals (sulfates, Fe (hydr)oxides) and sulfate leaching are reported in sulfide-bearing materials when exposed to oxidizing conditions in contact with the atmosphere (e.g., sulfide-rich mine tailings: Néel et al, 2003;Uzarowicz and Skiba, 2011;Uzarowicz, 2013;Hayes et al, 2014;excavated bedrock: Scholtus et al, 2014; dredged sediments: Vandecasteele et al, 2009). Changes in redox conditions related to wetting/drying cycles also contribute to the formation of Fe-Mn concretions and/or coatings (e.g., Huot et al, 2014a;Sokolov et al, 2015) as well as the weathering of iron artefacts (e.g., nails: Howard et al, 2013Howard et al, , 2015. Carbonation, by reaction with atmospheric and microbial CO 2 , may occur during the early stages of weathering of alkaline materials (e.g., Grünewald et al, 2007).…”

“…As in natural soils, organisms are drivers of the development of soils formed in technogenic materials, through the accumulation and decomposition of organic matter at the surface (e.g., Bini and Gaballo, 2006), the pedoturbation and the formation of organo-mineral associations (e.g., burrowing activity of earthworms: Pey et al 2013;Howard et al, 2015) or the rhizosphere effect (e.g., Huot et al, 2013b). Organisms also contribute to changing the conditions for the weathering of technogenic materials.…”

“…Carbonation and decrease in pH in alkaline substrates is partly driven by microbial respiration (Grünewald et al, 2007). Earthworm activity can modify the context of artefacts in urban soils by burying the materials at greater depth or by improving the diffusion of water and air through their vertical burrows, thereby promoting artefact weathering (Howard et al, 2015).…”

“…However, anthropogenic processes also generate recalcitrant technogenic materials and conditions limiting weathering rates. For instance, urban soils may contain high amounts of weathering-stable artefacts (e.g., bricks: Nehls et al, 2013or glass: Howard et al, 2015 or relatively recalcitrant forms of organic carbon due to human activities, Black Carbon (Nehls and Shaw, 2010;Howard et al, 2015). Moreover, fine and microporous technogenic materials (e.g., blast furnace sludge) may favor the retention of water and elements, the preservation of organic matter, and limit fluxes (Huot et al, 2014b.…”