Clay sources, identification

For the reasons outlined above, outcrops of workable obsidian are relatively few in number and are restricted to areas of geologically recent lava flows. Most sources are therefore reasonably well known, and, because of these constraints, identification of new sources in the eastern Mediterranean region becomes ever more unlikely. This makes the exercise of characterizing archaeological obsidians an attractive proposition, since, unlike potential clay sources for pottery provenance, the existence of completely unknown sources can be (cautiously) ignored. This is, of course, subject to the requirement noted above for more detailed geochemical characterization of existing sources. 

Figure 15 Alternating paleoenvironments of desert CAM shrublands and C3 grasslands represented by a sequence of Quaternary paleosols (0-100 ka) in the Palouse loess near Kahlotus, Washington, USA showing (left to right), field section with thermoluminescence dates and paleosol identification (Moll, is Mollisol, Arid, is Aridisol), paleosol position and development (represented by black boxes), paleosol calcareousness (scale based on acid reaction), Munsell hue (measured dry in field), sand-silt-clay proportion, of pedogenic carbonate, of opal phytoliths, abundance of earthworm pellets, and abundance of cicada burrows (source Retallack, 2001c).

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