Ambiente sedimentario, tectónica deposicional y bioestratigrafía de la formación punta Ancón (eoceno medio) acantilados al sur de Anconcito, Provincia de Santa Elena
Fecha
2021-10
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Facultad de Ciencias Naturales. Universidad de Guayaquil
Resumen
La Formación Punta Ancón es una de las unidades que conforman el Grupo Ancón (Eoceno Medio). El objetivo de este estudio es determinar el ambiente sedimentario deposicional, tectónico y bioestratigrafía en el sector Acantilados al sur de Anconcito, Provincia de Santa Elena. Se describieron e interpretaron cinco afloramientos, siete láminas delgadas y ocho muestras micropaleontológicas; y se usaron diagramas ternarios para establecer la procedencia tectónica. Los afloramientos litológicamente están compuestos por intercalaciones de areniscas arcillosas, areniscas laminadas, areniscas tobáceas, areniscas ferruginosas, areniscas masivas, arcillolitas y limolitas arenáceas. Se definieron ocho ciclos sedimentarios con secuencia granodecreciente y granocreciente. El ambiente sedimentario de depositación es Supralitoral, Litoral y Costa Afuera Superior. La edad relativa es Eoceno Medio medio por la presencia del radiolario Nassellario Podocyrtis ampla y el paleoambiente es marino de plataforma externa por la ocurrencia de los radiolarios Spumellarios Lithocyclia ocellus y Spongatractus pachystylus. Las areniscas son Líticas Feldespáticas y Grauwaca Lítica, con porcentajes promedios de componentes esenciales: 64.97% cuarzo, 11.55% feldespatos, 23.48% fragmentos líticos, 60.48%. En dirección suroeste el cuarzo monocristalino disminuye de 63.11% a 61.61%, el cuarzo policristalino aumenta 30.77% a 32.98%, los fragmentos líticos volcánicos disminuyen 53.90% a 44.01% y los fragmentos líticos sedimentarios aumentan 15.33% a 23.01%. La procedencia tectónica es Orogenia Reciclada, Orogenia Reciclada tipo cuarzosa con tendencia a Orógeno de Arco.
The Punta Ancón Formation is one of the units that make up the Ancón Group (Middle Eocene). The objective of this study is to determine the depositional, tectonic and biostratigraphic sedimentary environment in the Cliffs sector south of Anconcito, Santa Elena Province. Five outcrops, seven thin sections and eight micropaleontological samples were described and interpreted; and ternary diagrams were used to establish tectonic provenance. Lithologically outcrops are composed of intercalations of clayey sandstones, laminated sandstones, tobaceous sandstones, ferruginous sandstones, massive sandstones, claystones and sandstone siltstones. Eight sedimentary cycles were defined with decreasing grain and increasing grain sequences. The sedimentary environment of deposition is Backshore, Foreshore and Upper Offshore. The relative age is middle Middle Eocene due to the presence of radiolaria Nassellario Podocyrtis ampla and the paleoenvironment is marine with an external platform due to the occurrence of the radiolaria Spumellarios Lithocyclia ocellus and Spongatractus pachystylus. The sandstones are Lithic Feldspathic and Grauwaca Lithic, with average percentages of essential components: 64.97% quartz, 11.55% feldspars, 23.48% lithic fragments, 60.48%. In the southwest direction, monocrystalline quartz decreases from 63.11% to 61.61%, polycrystalline quartz increases 30.77% to 32.98%, volcanic lithic fragments decrease 53.90% to 44.01% and sedimentary lithic fragments increase 15.33% to 23.01%. The tectonic origin is Recycled Orogeny, Quartz type Recycled Orogeny with a tendency to Arc Orogeny.
The Punta Ancón Formation is one of the units that make up the Ancón Group (Middle Eocene). The objective of this study is to determine the depositional, tectonic and biostratigraphic sedimentary environment in the Cliffs sector south of Anconcito, Santa Elena Province. Five outcrops, seven thin sections and eight micropaleontological samples were described and interpreted; and ternary diagrams were used to establish tectonic provenance. Lithologically outcrops are composed of intercalations of clayey sandstones, laminated sandstones, tobaceous sandstones, ferruginous sandstones, massive sandstones, claystones and sandstone siltstones. Eight sedimentary cycles were defined with decreasing grain and increasing grain sequences. The sedimentary environment of deposition is Backshore, Foreshore and Upper Offshore. The relative age is middle Middle Eocene due to the presence of radiolaria Nassellario Podocyrtis ampla and the paleoenvironment is marine with an external platform due to the occurrence of the radiolaria Spumellarios Lithocyclia ocellus and Spongatractus pachystylus. The sandstones are Lithic Feldspathic and Grauwaca Lithic, with average percentages of essential components: 64.97% quartz, 11.55% feldspars, 23.48% lithic fragments, 60.48%. In the southwest direction, monocrystalline quartz decreases from 63.11% to 61.61%, polycrystalline quartz increases 30.77% to 32.98%, volcanic lithic fragments decrease 53.90% to 44.01% and sedimentary lithic fragments increase 15.33% to 23.01%. The tectonic origin is Recycled Orogeny, Quartz type Recycled Orogeny with a tendency to Arc Orogeny.
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EOCENO, CICLOS, FORMACIÓN, RADIOLARIOS, PALEOAMBIENTE