Geochemistry and depositional environment of the Losero Formation in the Mesa Central, México
The Losero Formation is exposed in the Guanajuato Mining District, conformably overlying the Guanajuato conglomerate. Most of the up-to-date studies of the Losero Formation have indicated that this formation corresponds to a Cenozoic volcanic sequence. Howe - ver, sedimentological, petrographic and...
| Autores: | , , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2014 |
| País: | México |
| Institución: | Universidad Nacional Autónoma de México |
| Repositorio: | Redalyc-UNAM |
| OAI Identifier: | oai:redalyc.org:94332984001 |
| Acceso en línea: | https://www.redalyc.org/articulo.oa?id=94332984001 |
| Access Level: | acceso abierto |
| Palabra clave: | Ciencias de la Tierra Guanajuato Provenance Geochemistry Losero Formation Tectonic setting |
| Sumario: | The Losero Formation is exposed in the Guanajuato Mining District, conformably overlying the Guanajuato conglomerate. Most of the up-to-date studies of the Losero Formation have indicated that this formation corresponds to a Cenozoic volcanic sequence. Howe - ver, sedimentological, petrographic and geochemical evidence that supports a sedimentary or volcanic origin has not been discussed extensively. We present a comprehensive geological analysis which includes collection of samples and elaboration of eight stratigraphic columns, followed by laboratory studies including petrography, trace element determinations using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and mineralogy by X-ray diffraction and Scanning Electron Microscopy (SEM). The petrographic analysis revealed that the Losero Formation is constituted by litharenite and arkose, mostly derived from granitic and metamorphic basement rocks typical of the interior of a craton. Primary sedimentary structures include ripples, antidunes, Àute and groove casts, cross and parallel lamination, desiccation cracks and soft-sediment deformation structures interpreted as seismites. These ¿ndings demonstrate that the sandstones were deposited by supercritical and subcritical Àows as well as by unidirectional Àows within channels and bars in a river system. Elemental ratios critical of provenance (La/Sc, Th/Sc, La/Cr, Th/Cr and Ba/Sc) are similar to sediments derived from weathering of mostly felsic rocks. Using QmFLt and QtFL ternary diagrams allowed to infer that the sandstones of the Losero Formation were deposited in an active continental margin. Modal analysis of the samples indicates a recycled orogen and dissected arc. Most evidence suggests that the deposit was accumulated in a Àuvial environment with conditions ranging from shallow to deep water. Based on these data and ¿eld observations, the sandstones from the Losero Formation can be considered as part of the distal facies of the Guanajuato Conglomerate. |
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