Plio-Pleistocene incision history of the Rio Ojo Caliente, northern EspaƱola Basin, and overview of the Rio Grande system in northern New Mexico
D. L. Newell, D. J. Koning, K. E. Karlstrom, L. J. Crossey, and M. Dillon

Abstract:

The Rio Ojo Caliente, a tributary to the Rio Chama in the Española Basin, exhibits a well-preserved flight of Plio-Pleistocene terrace deposits. Ten terraces identified along the Rio Ojo Caliente consist of several meters of river gravels deposited onto straths cut on Precambrian and Tertiary rock. Strath heights range from 3 to 165 m above the river and correlate to straths beneath dated terraces along the Rio Chama and Rio Grande. River gravels at ~270 m above the Rio Ojo Caliente directly underlie the 3.65 Ma Black Mesa basalt, representing topographic inversion of a southwest-flowing ancestral Rio Grande. Two topographically lower terraces are associated with the ~1.6 Ma Guaje pumice (~160 m) and 0.62 Ma Lava Creek B ash (~110 m). These three surfaces constrain a variable incision history with rates, using basal strath heights, that average 65 m/m.y. from 3.65 to 1.6 Ma, 30 m/m.y from 1.6 to 0.62 Ma, and 175 m/m.y. from 620 ka to present.

New longitudinal profile data support and expand the hypothesis of Wells et al. (1987) that increased incision in the Española Basin since ~600 ka involved piracy of the San Luis Basin drainages by Española Basin drainages in the middle Pleistocene. Likewise, we concur that major knickpoints in the longitudinal profile of the Rio Grande and its tributaries upstream from the Rio Chama represent young transients due to the integration of the two basins. The pattern of knickpoints and convex profiles in the mainstem and tributaries could represent a passing transient wave of incision. South of the mainstem knick-zone, tributary knickpoints occur within convex profiles at progressively higher elevations; north of the mainstem knick-zone, tributaries have simpler concave profiles. Bedrock strength is a strong factor in localizing knickpoints, but does not fully explain this pattern.


Citation:

  1. Newell, D. L.; Koning, D. J.; Karlstrom, K. E.; Crossey, L. J.; Dillon, M., 2004, Plio-Pleistocene incision history of the Rio Ojo Caliente, northern EspaƱola Basin, and overview of the Rio Grande system in northern New Mexico, in: Geology of the Taos Region, Brister, Brian S.; Bauer, Paul W.; Read, AdamS.; Lueth, Virgil W., New Mexico Geological Society, Guidebook, 55th Field Conference, pp. 300-313.

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