Successive Pediments and Terraces of the Upper Rio Puerco in New Mexico
1936; University of Chicago Press; Volume: 44; Issue: 2, Part 1 Linguagem: Inglês
10.1086/624414
ISSN1537-5269
AutoresKirk Bryan, Franklin T. McCann,
Tópico(s)Archaeology and Natural History
ResumoIn the area drained by the Upper Rio Puerco and its tributaries, erosion has been marked by the development of a series of successively lowered, stabilized, local base-levels whose existence is recorded by multiple pediments and terraces. The early geo-morphologic history is obscure. Some indications of a hypothetical early and widespread erosion surface exist. There are more definite traces of a later high-level surface of coalescing pediments. The detailed history began in the Pleistocene with the dissection of this second surface and involved formation of the Upper Rio Puerco by adjustment to structure with accompanying piracy. Thereafter, the La Jara pediment was formed to a stabilized grade 180-200 feet above that of the present stream. Renewed incision and adjustment to structure occurred and the Rito Leche pediment was formed to a stabilized grade 75-85 feet above the present stream. Two minor cycles produced terraces about 30 and 10 feet high, respectively, but on rock. Finally, the inner valley of the river was cut and alternately filled and eroded in the minor epicycles characteristic of the region.
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