NUTRITION AND GEOLOGY OF THE SOLIS VALLEY, MEXICO: LANDSCAPE GEOMORPHOLOGY AND GROUNDWATER CHEMISTRY

In the mid-1980s, a Mexican/US consortium conducted a longitudinal study of mild-to-moderate malnutrition in six villages in the Solis Valley, 160 km NW of Mexico City. We are examining the isotopic and elemental chemistry of the food chain beginning with the landscape through to the food and children's deciduous teeth. The teeth developed during the period of study and were collected once exfoliated. Maize, locally grown, provides 50-70% of dietary energy, mainly as tortillas. The Solis Valley is part of the generally E-W Acambay graben within the Trans-Mexican Volcanic Belt and is traversed by the Rio Lerma. Within late Pliocene/Pleistocene time, the river was dammed about 20 km downvalley by a lava flow sequence at Tepuxtepec, and possibly earlier, 8 km upvalley at El Milagro. The Tepuxtepec barrier has been incised, but a 10m falls at El Milagro, has prevented incision of the lacustrine deposits on which the corn is grown in the upper valley and has allowed for flood-based soil enrichment there. The wells of the three villages on the valley's south side are fed by magmatically enriched waters of the late Pleistocene Altimirano volcano, having Na ~250ppm, Li ~3000 ppb, and high levels of most cations including Zn, Fe, Ca, K, Rb, and Sr. Northside wells in older flow units just SE of the Amealco caldera have much lower dissolved cation concentrations. We are currently examining the possible connections between the water chemistry, dietary data from the 1980s and elemental concentrations of teeth, sensing that the water and tortilla (LaVigne et al, and Goodman et al. this meeting) dominate cation availability in the diet. Supported by NSF C-RUI #DBI-78793.