|Paper No. 81-9|
|Presentation Time: 3:45 PM-4:00 PM|
|EVIDENCE FOR DIFFERING METHODS OF ALKALI-PROCESSING OF MAIZE IN PREHISTORIC MEXICO BASED ON 87SR/86SR IN BEDROCK, BONES AND TEETH|
REID, John B. Jr1, GOODMAN, Alan H.2, BROWNSMITH, Mara2, COLEMAN, Drew3, and WALKER, J. Douglas4, (1) School of Natural Science, Hampshire College, Amherst, MA 01002, email@example.com, (2) School of Natural Science, Hampshire College, Amherst, MA 01002-5001, (3) Department of Geological Sciences, Univ of North Carolina -- Chapel Hill, Campus Box # 3315, Chapel Hill, NC 27599, (4) Department of Geology, Univ of Kansas, Lawrence, KS 66045|
The nutritional value, flavor and texture of cornmeal are enhanced by boiling the corn in a high pH solution before grinding. In modern Mexico, this is achieved with "cal", a mixture of CaO and Ca(OH)2 made from sintered limestone. In some ancient cultures without access to limestone, wood ash was used instead. Aspects of the history of alkali processing can be deciphered from Sr isotopic data on bedrock, teeth and bones from modern and ancient Mexican populations. 87Sr/86Sr values in modern deciduous teeth from six Solis Valley villages in the Trans-Mexican Volcanic Belt, ~150 km NW of Mexico City, do not match the local landscape. Lying between 0.7058 and 0.7077, the isotopic values are higher than the local bedrock, soils, well waters (0.7038-0.7057), reflecting the importance (albeit variable) of the Sr-rich "cal" (0.7074-0.7075) in the diet. The cal data, coupled with the seawater 87Sr/86Sr evolution curve, are consistent with a late Cretaceous (Kr) limestone source for the cal. Published 87Sr/86Sr data (Price et al, 2000) for human bone from burials at Teotihuacan (Mexico City) and Monte Alban (Oaxaca) tell two distinct stories from the view of alkali processing of maize. At Monte Alban where the bedrock includes late-Kr limestone, bones and tooth enamel 87Sr/86Sr match late-Kr seawater (avg: 0.7075), consistent with the use of locally produced cal. At Teotihuacan however, human bone (and modern rabbit bone) 87Sr/86Sr values are surprisingly narrowly restricted at 0.7046, a value far below that of any marine limestone. Maize processing, if practiced, either employed wood ash from local vegetation or caliche produced by weathering of very local basaltic volcanic bedrock (possibly one single flow), but could not have involved the use of limestone.
2002 Denver Annual Meeting (October 27-30, 2002)
|Session No. 81|
Colorado Convention Center: A205
1:30 PM-5:30 PM, Monday, October 28, 2002
© Copyright 2002 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.