Experimental hearths and the thermal alteration of Caliche on the Southern High Plains

Abstract

Throughout the Holocene, caliche has been a ubiquitous technological resource for the people of the Southern High Plains. Archaeological sites on the Southern High Plains often contain thermal features that appear to utilize caliche nodules in various cultural processes. These processes usually involve some degree of thermal dynamic alteration to the caliche, identified in the archaeological record as fire-scorched or blackened nodules. Previous studies of the pyrodynamic properties of caliche have focused on quantification of color and fracture patterns within a laboratory setting, without direct involvement of cultural processes or problems associated with thermal features. Thermal alteration variables of caliche are examined from an actualistic perspective, utilizing previously excavated basin feature geometry and local caliche outcrops. Results indicate that sustained, intense heating of caliche (above 204°C) causes significant, but variable, structural transformations at the specimen level. The experimental use of shallow basin hearths demonstrates that hearth structures were easily capable of achieving and sustaining temperatures that would result in the physical alteration of individual caliche nodules, defined here as hearthstones. The broader implications of this study suggest that the interpretation of archaeological hearthstone assemblages should reflect variability, as observed during this experiment.

Where were the hearths: an experimental investigation of the archaeological signature of prehistoric fire technology in the alluvial gravels of the Southern Plains

“…With their high potential for preservation, attention is becoming more focused on these ubiquitous artifacts (Petraglia, 2002). Questions, therefore, regarding hearthstone use and performance characteristics have dominated the experimental literature (e.g., Backhouse et al, 2005;Brink and Dawe, 2003;Lintz, 1989;Pagoulatos, 2006). Despite this emphasis on examining hearthstone technology, relatively few studies have attempted to examine the thermal characteristics of hearthstones from a geologic perspective.…”

“…The use of hearthstones in hot-rock technology has been well documented on the neighboring Southern High Plains (Backhouse et al, 2005;Johnson, 1987;Johnson and Holliday, 2004;Ladkin and O'Brien, 1995;Lintz, 1989). Investigations at PLK-Locality 4, a campsite near 41GR146, has resulted in the contextual identification of fractured Ogallala Fm.…”

Rocks of ages: propagation of hot-rock cookery in western North America

“…What cook-stone features have in common, and thus what unites them under that rubric, is macroand microscopic evidencedwidely confirmed via middle range research (e.g., Backhouse et al, 2005;Brink and Dawe, 2003;Clabaugh, 2000;Gose, 2000;House and Smith, 1975;Jackson, 1998;Schalk and Meatte, 1988;Thoms, 1989)dthat the ostensibly oncehot rocks therein served as heating elements. That they were heated sufficiently, typically in excess of 500 C, is evidenced primarily by re-alignment of microscopic magnetic particles, enhanced oxidation that produced a ''reddened'' appearance, and micro-and macrofractures that yielded blocky and curvilinear fragments with sharp edges.…”

“…In areas where stones were unobtainable, objects of baked clay were used for the same purpose''. Only within the last few decades, however, have archaeologists undertaken systematic studies of cook-stone features (e.g., Backhouse et al, 2005;Black and Creel, 1997;Brink and Dawe, 2003;Clabaugh and Thoms, 2007;Hodder and Barfield, 1991;Holdaway et al, 2005;House and Smith, 1975;Jackson, 1998;Latas, 1992;McParland, 1977;Petraglia, 2002;Pierce, 1984;Roll, 1982;Schalk and Meatte, 1988;Thoms, 1986). The extent to which studies pertaining to cook-stone technology have increased is revealed effectively by Doleman's (1996) well-circulated FCR bibliography as well as via a web-based search on ''fire-cracked rock.''…”

By the Campfire: Pyrotechnology and Middle Stone Age Hearths at Sibudu Cave

“…Rocks can fracture, change colour and undergo other changes when exposed to heat (e.g., Backhouse et al, 2005;Domanski et al, 1994;House & Smith, 1975;Lintz, 1989;Mercieca, 2000;Purdy & Brooks, 1971;Schmidt et al, 2012). These changes are important for the identification of cooking with heated rocks (e.g., Ellwood et al, 2013;Thoms, 2009), but the people in the MSA do not appear to have used hot rocks when cooking (see e.g., Chapter 2).…”