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| Photograph of the walls of Pueblo Canyon, one of the many canyons that dissect the Pajarito Plateau at the Los Alamos National Laboratory. Cliffs expose the early Pleistocene Bandelier Tuff, a massive sequence of ignimbrites erupted from the Jemez Mountains and associated with development of the Valles caldera. The mountains on the skyline form the eastern rim of the caldera. Striped layers at the bottom of the cliffs in the foreground are part of the Cerro Toledo interval, a sequence of pumice beds, alluvium, and soils formed between 1.61 and 1.22 million years ago, and which record an early Pleistocene drainage network oblique to the modern canyons. The stratigraphy and paleogeography of these units is being investigated as part of hydrogeologic investigations at Los Alamos. |
