Cenozoic seismites and soft-sediment deformation structures in the Losero Formation, southern Sierra de Guanajuato, Mexico
Siliciclastic deposits of the Eocene-Oligocene Losero Formation,which crop out in the Sierra de Guanajuato in central Mexico,show several types of soft-sediment deformation structures that areinterpreted as seismites. The Sierra de Guanajuato is a complex tectonicpile of thrust sheets composed of Me...
| Autores: | , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2015 |
| País: | México |
| Institución: | Universidad de Guanajuato |
| Repositorio: | Redalyc-UG |
| OAI Identifier: | oai:redalyc.org:57240685003 |
| Acceso en línea: | https://www.redalyc.org/articulo.oa?id=57240685003 |
| Access Level: | acceso abierto |
| Palabra clave: | Ciencias de la Tierra Soft Mexico seismites Losero Formation sediment deformation |
| Sumario: | Siliciclastic deposits of the Eocene-Oligocene Losero Formation,which crop out in the Sierra de Guanajuato in central Mexico,show several types of soft-sediment deformation structures that areinterpreted as seismites. The Sierra de Guanajuato is a complex tectonicpile of thrust sheets composed of Mesozoic lithostratigraphicsuccessions. During the Paleogene, the Sierra de Guanajuato wasaffected by extensional tectonism that occurred in a short timeinterval, which was contemporary with clastic sedimentary depositionalprocesses. Eocene-Oligocene deposits are characterized bya red bed sequence represented by the “Guanajuato Conglomerate”and the Losero Formation, which has many syn-sedimentary faultsand microfaults oriented NE 35°– 45°SW, with a dip of 70°–87°SE.These sediments are the result of a braided fluvial system characterizedby plane parallel laminae, desiccation cracks, ripples, and crossbed sets, antidunes, groove and flute casts. In the study area, twostratigraphic sections (Caídos y Socavón) were measured in detail(facies distributions, primary structures and stacking patterns).Several types of soft-sediment deformation structures were recordedin Losero deposits and these occur interbedded with undeformedstrata throughout the entire stratigraphic interval. The lateral extentof the deformation is of several hundred meters long and thedeformed bed involves the mid-upper part of the 30 meter thicksuccession. Deformation affects about two meters of coarse-grainedsandstone, fine-grained sandstones, and mudstones. This deformationis represented by layers with asymmetric and symmetric folds,dish structures, pseudonodules, sandstone dikes, flame structures,syn-sedimentary normal microfaults and convolute laminae. Itcan be described as a gradient system of unstable density layers.Soft-sedimentary deformation structures observed in the LoseroFormation are interpreted as seismites, developed as a result of increasedpore pressure and vertical or horizontal stresses induced byseismic activity. |
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