M.A. Cosca and colleagues investigated mafic rock samples from a small volcanic field near Yampa, Colorado, using geochemical and isotopic techniques. Their results indicate that these volcanic rocks are melt products of the subcontinental lithospheric mantle that ascended rapidly to the surface between 4.5 and 6 million years ago. The ages of the volcanic rocks become younger toward the southwest and form part of a regional pattern of volcanism closely associated with late Cenozoic extension that is migrating toward the northeast margin of the Colorado Plateau. The youngest (Quaternary) volcanic rocks within this migrating sequence of volcanism coincide with the western margin of the Rio Grande rift in Colorado, and projection of this volcanism defines the incipient northern segment of the rift that includes the Leucite Hills, Wyoming.
U-series geochronology of large-volume Quaternary travertine deposits of the southeastern Colorado Plateau: Evaluating episodicity and tectonic and paleohydrologic controls
A. Priewisch et al., Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA. Published online 21 Feb. 2014, http://dx.doi.org/10.1130/GES00946.1
Large-volume travertine deposits in the southeastern Colorado Plateau of New Mexico and Arizona, USA, occur along the Jemez lineament and Rio Grande rift. These freshwater carbonates reflect locations where mantle-derived carbon dioxide and deeply sourced groundwater were conveyed to the surface along faults and discharged through springs. U-series dating shows that large-volume (2.5 cubic kilometers) deposition took place episodically 700� thousand years ago, 350� thousand years ago, and 100 thousand years ago. These pulses of travertine formation coincide with regional basaltic volcanism, which s
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