Log of part of a trench excavated on Pajarito Mesa, showing a sequence of late Quaternary soils that underlie and overlie the ca. 50-60,000 year old El Cajete pumice bed, in turn overlying the early Pleistocene Bandelier Tuff. A prehistoric Puebloan (Anasazi) archaeological site was exposed in this trench, which was buried by fine-grained sediments that probably have an eolian origin. The timing of the landscape changes recorded by these materials is being investigated using a variety of geochronologic methods, including radiocarbon dating, thermoluminescence dating, tephrochronology, and soil development. Seismic hazard concerns at Los Alamos have motivated much of this work.

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