Holocene evolution of canyons and implications for contaminant transport, Pajarito Plateau
Paul G. Drakos, Jay Lazarus, and Christopher. Inque
The preserved Holocene geologic record in canyons incised into the Pajarito Plateau indicates that sediment is cycled through canyons on time scales of tens to hundreds of years. Canyon stream systems draining the Sierra de los Valles and Pajarito Plateau exhibit episodic sediment transport and deposition during the Holocene, including multiple episodes of incision and aggradation during Holocene and recent (historic) time. Formation of a mid-Holocene fill terrace in Frijoles, Rendija, Los Alamos and Bayo canyons suggests that both the larger canyon systems draining the Sierra de los Valles (e.g., Frijoles and Los Alamos Canyons) and smaller canyons heading on the Pajarito Plateau (e.g., Rendija and Bayo Canyons) are responding synchronously to local or regional climatic changes. Although detailed correlations of the multiple late Holocene and historic surfaces between canyons has not been completed, the presence of Holocene valley floors indicates significant Holocene sediment storage in canyons on the Pajarito Plateau. Canyons examined contain between 3 and 6 ft of sediment less than 50 yrs old in some locations, and also contain one or more inset geomorphic surfaces of historic age. The late Holocene and historic record of multiple cut-and-fill events indicate that the potential exists for remobilization and transport of contaminants through canyon systems. Contaminants discharged into canyons discussed in this paper include (1) 90Sr, natural and depleted uranium dispersed throughout a segment of Bayo Canyon during munitions testing; (2) plutonium discharged into Acid Canyon and transported into Pueblo Canyon; and (3) plutonium released into DP Canyon. Contaminants entrained as part of the sedimentary package have been transported through canyon systems; in Pueblo Canyon contaminants have been transported downstream through Los Alamos Canyon to the Rio Grande.
- Drakos, Paul G.; Lazarus, Jay; Inque, Christopher., 1996, Holocene evolution of canyons and implications for contaminant transport, Pajarito Plateau, in: The Jemez Mountains Region, Goff, Fraser; Kues, Barry S.; Rogers, Margaret Ann; McFadden, Les D.; Gardner, Jamie N., New Mexico Geological Society, Guidebook, 47th Field Conference, pp. 399-406.