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We investigated a Plio-Pleistocene alluvial succession in the Albuquerque Basin of the Rio Grande rift in New Mexico using geomorphic, stratigraphic, sedimentologic, geochronologic, and magnetostratigraphic data. New 40Ar/39Ar age determinations and magnetic-polarity stratigraphy refine the ages of the synrift Santa Fe Group. The Pliocene Ceja Formation lies on the distal hanging-wall ramp across much of the Albuquerque Basin. The Ceja onlapped and buried a widespread, Upper Miocene erosional paleosurface by 3.0 Ma. Sediment accumulation rates in the Ceja Formation decreased after 3.0 Ma and the Ceja formed broad sheets of amalgamated channel deposits that prograded into the basin after ca. 2.6 Ma. Ceja deposition ceased shortly after 1.8 Ma, forming the Llano de Albuquerque surface. Deposition of the Sierra Ladrones Formation by the ancestral Rio Grande was focused near the eastern master fault system before piedmont deposits (Sierra Ladrones Formation) began prograding away from the border faults between 1.8 and 1.6 Ma. Widespread basin filling ceased when the Rio Grande began cutting its valley, shortly after 0.78 Ma. Although the Albuquerque Basin is tectonically active, the development of through-going drainage of the ancestral Rio Grande, burial of Miocene unconformities, and coarsening of upper Santa Fe Group synrift basin fill were likely driven by climatic changes. Valley incision was approximately coeval with increased northern- hemisphere climatic cyclicity and magnitude and was also likely related to climatic changes. Asynchronous progradation of coarse-grained, margin-sourced detritus may be a consequence of basin shape, where the basinward tilting of the hanging wall promoted extensive sediment bypass of coarse-grained, margin-sourced sediment across the basin.

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