Late Quaternary evolution of alluvial fans in the Playa, El Fresnal region, northern Chihuahua desert, Mexico: Palaeoclimatic implications
The Playa El Fresnal area is a tilted terrane characteristic of an extensional basin. It is a half graben/tilted-block system witha playa-lake on the basin floor flanked by piedmonts covered by alluvial fans. Structural heterogeneities within normal fault zonesinfluenced the geomorphic expression of...
| Autores: | , , , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2004 |
| País: | México |
| Institución: | Universidad Nacional Autónoma de México |
| Repositorio: | Redalyc-UNAM |
| OAI Identifier: | oai:redalyc.org:56843310 |
| Acceso en línea: | https://www.redalyc.org/articulo.oa?id=56843310 |
| Access Level: | acceso abierto |
| Palabra clave: | Ciencias de la Tierra alluvial fans Playa El Fresnal Chihuahuan desert extensional tectonism late Quaternary climate change |
| Sumario: | The Playa El Fresnal area is a tilted terrane characteristic of an extensional basin. It is a half graben/tilted-block system witha playa-lake on the basin floor flanked by piedmonts covered by alluvial fans. Structural heterogeneities within normal fault zonesinfluenced the geomorphic expression of the uplifted footwall blocks of associated volcanism, and the downdropped hangingwall. The footwall area is the main sediment source, but the hanging wall-derived sediments are more extensive. The ancientalluvial fans are in the distal part, whereas the hanging-wall sediments are located in the apex area.A geomorphic analysis of the relative topographic position of the alluvial fans, degree of dissection of the original surfaces,general sedimentology (facies description), and stream channel network type, highlights the importance of climatic change ininterpreting alluvial-fan surfaces. Three generations of alluvial fans were identified on the footwall and hanging wall slopes. Theywere formed during the late Quaternary climatic shift, consistent with the main climatic changes recorded in the paleolake stratigraphyof northern Mexico and the American Southwest. These alluvial fans consist mainly of debris-flow deposits from flashfloods, probably triggered by a change from relatively moist to arid conditions. They contrast with the typically lower-flowregimeof thick-bedded, cross-bedded, and lenticular channel facies, and associated floodplain sequences of rivers. |
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