Generalized cross section across Mortandad Canyon near the confluence with Ten Site Canyon, showing the subsurface stratigraphy as revealed in drill holes. The 50-60,000 year old El Cajete pumice bed was encountered in one hole, whereas in a nearby hole a 14C date of ca. 7300 years was obtained on charcoal fragments at a depth of 10 m. This canyon and many others in the area have experienced extensive aggradation through the Holocene, deeply burying the late Pleistocene stream channels, and this major change in fluvial processes probably resulted from an increase in sediment supply following the Pleistocene-Holocene climatic transition, coupled with the ineffectiveness of floods to transport all of this sediment to the Rio Grande. This canyon currently receives effluent released from a radioactive liquid waste treatment facility and contains a relatively high inventory of radionuclides in the sediments, and understanding the controls on erosion and deposition would be valuable for predicting the future fate of these contaminants.

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