Caracterización sedimentológica de la formación Guayaquil (Cretácico Medio - Paleoceno Inferior) en el centro-sur del cerro San Eduardo, Guayaquil
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2019
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Facultad de Ciencias Naturales. Universidad de Guayaquil
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Este estudio se realizó con la finalidad de definir las principales características sedimentarias en la Formación Guayaquil, la descripción de las diferentes litologías presentes, el paleo-ambiente y edad relativa de los mismos, así como determinar clasificación y procedencia de los escasos estratos de arenisca que se evidenciaron. En esta formación geológica se determinó que la litología predominante son lutitas silicificadas color gris oscuro intercaladas con limolitas tobáceas, también aparecen estratos de areniscas en la parte media del afloramiento y en la parte final reaparecen las lutitas silicificadas pero con enriquecimiento carbonático. El espesor total de la columna fue de 414 metros donde se levantó parte de la Formación Cayo y la Formación Guayaquil en el afloramiento del cerro San Eduardo dentro de los predios urbanos de la ciudad de Guayaquil. Se tomaron 7 muestras petrográficas, tres para lutitas y cuatro para areniscas, de estas últimas para conocer su clasificación y procedencia. Las areniscas se clasificaron como: Arcosa Lítica, Grauwaca Feldespática y Lítica Feldespática; y se determinó una procedencia de arco disectado, orógeno reciclado y arco transicional. El miembro Inferior de la Formación Guayaquil fue definido por el foraminífero planctónico Abathampholus mayaroensis; el miembro Superior se determinó en base a los foraminíferos planctónicos Eoglobigerina simplicissima y la abundancia de la especie Globigerina triloculinoides. Se determinó un paleo-ambiente de plataforma externa a Batial; de plataforma externa por la asociación de foraminíferos planctónicos y Batial superior por la presencia de foraminíferos aglutinados.
This study was carried out in order to define the main sedimentary characteristics in the Guayaquil formation, the description of the different lithologies, the paleoenvironment and the relative age of the same, as well as the classification and procedure of the strata of the practice. In this geological formation it was determined that the predominant lithology are dark gray silicified shales that are interspersed with tuffaceous siltstones, sandstone strata are also found in the middle part of the outcrop and in the final part it shows silicified shales again but with carbonatic enrichment. The total thickness of the column was 414 meters, where part of the Cayo Formation and the Formation were included in the outcrop of the San Eduardo hill within the urban areas of the city of Guayaquil. Seven petrographic samples were taken, three for shales and four for sandstones, the latter for their classification and provenance. The sandstones were classified as: Arenite Lithic, Feldspath Grauwacke and Lithic Feldspath; and a provenance of dissected arch, regenerated orogen and transitional arch were determined. The lower member of Guayaquil Formation was defined by the planktonic foraminifera Abathampholus mayaroensis; The upper member was determined based in planktonics foraminifera Eoglobigerina simplicissima and abundance of Globigerina triloculinoides specie, A paleoenvironment from external platform to Bathyal was determined; external platform by the association of planktonic foraminifera and upper bathyal by the presence of agglutinated foraminifera.
This study was carried out in order to define the main sedimentary characteristics in the Guayaquil formation, the description of the different lithologies, the paleoenvironment and the relative age of the same, as well as the classification and procedure of the strata of the practice. In this geological formation it was determined that the predominant lithology are dark gray silicified shales that are interspersed with tuffaceous siltstones, sandstone strata are also found in the middle part of the outcrop and in the final part it shows silicified shales again but with carbonatic enrichment. The total thickness of the column was 414 meters, where part of the Cayo Formation and the Formation were included in the outcrop of the San Eduardo hill within the urban areas of the city of Guayaquil. Seven petrographic samples were taken, three for shales and four for sandstones, the latter for their classification and provenance. The sandstones were classified as: Arenite Lithic, Feldspath Grauwacke and Lithic Feldspath; and a provenance of dissected arch, regenerated orogen and transitional arch were determined. The lower member of Guayaquil Formation was defined by the planktonic foraminifera Abathampholus mayaroensis; The upper member was determined based in planktonics foraminifera Eoglobigerina simplicissima and abundance of Globigerina triloculinoides specie, A paleoenvironment from external platform to Bathyal was determined; external platform by the association of planktonic foraminifera and upper bathyal by the presence of agglutinated foraminifera.
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BIOESTRATIGRAFÍA, LUTITAS SILICIFICADAS, ORIGEN TECTÓNICO, PETROGRAFÍA