Determinación del origen de las rocas del cerro Las Cabras (Oeste) mediante análisis geoquímico, cantón Durán, provincia del Guayas-Ecuador
Fecha
2020-04
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Facultad de Ciencias Naturales, Universidad de Guayaquil
Resumen
El presente Trabajo de investigación fue realizado con el objetivo de determinar el origen de las rocas volcanoclásticas y sedimentarias en el sector oeste del Cerro Las Cabras del Cantón Durán mediante análisis geoquímico. De esta manera se determinó que las rocas volcanoclásticas corresponden a la Formación Cayo ya que sus elementos de tierras raras tienen un patrón similar a otros que han sido estudiados en localidades asignadas a esta unidad geológica. Los elementos traza y relaciones de tierras raras permitieron reconocer que estos materiales rocosos proceden de una erupción volcánica efusiva que viajaron mayormente en el viento y se depositaron en el mar, exactamente en la pendiente de la plataforma continental. En las cotas superiores del Cerro se reconoció, mediante la geoquímica confirmada por la bioestratigrafía, la presencia del contacto entre las Formaciones geológicas Cayo y el Miembro inferior Guayaquil. En cuanto a la procedencia de los sedimentos que formaron los depósitos de areniscas que están intercaladas con lutitas del miembro Inferior Guayaquil también se reconoce que son de una efusión volcánica, pero estos no se habrían depositado inmediatamente en el océano, sino que habrían tenido contacto con aguas fluviales que los habrían movilizado hasta su zona de deposición final sobreyaciendo a las tobas de la Formación Cayo. El microfósil foraminífero denominado Haplophragmoides sp., permite asignar no solo el ambiente de deposición que es el batial en la pendiente continental sino la asignación de una edad del Campaniano-Maastrichtiano.
This research work was carried out with the objective of determining the origin of volcanoclastic and sedimentary rocks in the western sector of Las Cabras Hill in Durán by geochemical analysis. In this way, it was determined that volcanoclastic rocks correspond to the Cayo Formation since their rare earth elements have a pattern similar to others that have been studied in locations assigned to this geological unit. The trace elements and relations of rare earths allowed to recognize that these rocky materials come from an effusive volcanic eruption that traveled mostly in the wind and deposited in the sea, exactly on the slope of the continental shelf. The presence of the contact between the Cayo geological formations and the lower member Guayaquil was recognized in the upper levels of the Hill by the geochemistry confirmed by biostratigraphy. As for the origin of the sediments that formed the sandstone deposits that are interspersed with shales of the Lower Guayaquil member, it is also recognized that they are of a volcanic effusion, but these would not have been deposited immediately in the ocean, but would have had contact with river waters that would have mobilized them to their zone of final deposition, surpassing the tuffs of the Cayo Formation. The foraminiferous microfossil called Haplophragmoides sp., Allows to assign not only the deposition environment that is the batial on the continental slope but also the assignment of an Campanian-Maastrichtian age.
This research work was carried out with the objective of determining the origin of volcanoclastic and sedimentary rocks in the western sector of Las Cabras Hill in Durán by geochemical analysis. In this way, it was determined that volcanoclastic rocks correspond to the Cayo Formation since their rare earth elements have a pattern similar to others that have been studied in locations assigned to this geological unit. The trace elements and relations of rare earths allowed to recognize that these rocky materials come from an effusive volcanic eruption that traveled mostly in the wind and deposited in the sea, exactly on the slope of the continental shelf. The presence of the contact between the Cayo geological formations and the lower member Guayaquil was recognized in the upper levels of the Hill by the geochemistry confirmed by biostratigraphy. As for the origin of the sediments that formed the sandstone deposits that are interspersed with shales of the Lower Guayaquil member, it is also recognized that they are of a volcanic effusion, but these would not have been deposited immediately in the ocean, but would have had contact with river waters that would have mobilized them to their zone of final deposition, surpassing the tuffs of the Cayo Formation. The foraminiferous microfossil called Haplophragmoides sp., Allows to assign not only the deposition environment that is the batial on the continental slope but also the assignment of an Campanian-Maastrichtian age.