Ambiente sedimentario, bioestratigrafía y condición tectónica deposicional de las Areniscas de la Formación Socorro (Eoceno medio) del acantilado de Ancón, área Cacique, provincia de Santa Elena
Fecha
2019
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Facultad de Ciencias Naturales. Universidad de Guayaquil
Resumen
La formación Socorro es parte del Grupo Ancón (Eoceno Medio), en el sector Cacique, se observaron como afloramientos, se evidenciaron lodolita limosa, limolita y menores areniscas granodecreciente. Los espesores son centimétricos. En la provincia de Santa Elena del sector Cacique, se determinó la bioestratigrafía, composición mineralógica, ambiente sedimentario de depositación y procedencia tectónica de las areniscas de Socorro del Grupo Ancón. En los afloramientos del sector Cacique, se analizaron diez muestras bioestratigráficas y quince láminas delgadas. Se interpretaron tres secuencias: incompletas interrumpidas (e), incompletas truncadas (b) y truncadas (a, b, c, d). La edad relativa de Socorro es Eoceno Medio temprano a Eoceno Medio medio, debido al hallazgo de los radiolarios de orden nassellarios (Thyrosocyrtis triacontha) y el ambiente de depositación es marino de plataforma externa por la abundancia de radiolarios spumellarios (Lithocyclia Ocellus, Periphaena duplus) y foraminífero bentónico (Bolivina). Las areniscas de Socorro son sublitarenitas y litarenitas; y evidencian una procedencia tectónica de Orogenia Reciclado de tipo Cuarzoso, Orógeno de Colisión y tendencia entre Complejo de Subducción y Orógeno de Arco, concuerdan con la propuesta de Jaillard et al. (1995). Jaillard et al. (1995), planteó que durante el Eoceno Medio se produjo el hundimiento extensional del arco insular Cayo. Por lo tanto, los componentes de las areniscas de Socorro procederían: cuarzo monocristalino del margen continental andino, cuarzo policristalino de la formación Santa Elena de edad Cretácico Tardío - Paleoceno Temprano, líticos sedimentarios de la Cordillera Chongón Colonche y líticos volcánicos del remanente arco insular Cayo.
The Socorro Formation is part of the Ancón Group (Middle Eocene), in the Cacique sector, five outcrops were observed, silty mudstone, siltstone and minor fining upward sandstones. the thicknesses are centimetric. In the Province of Santa Elena of the Cacique sector, were determined biostratigraphy, mineralogical composition, depositional sedimentary environment and tectonic provenance of Socorro sandstones. in the outcrops of the Cacique sector, ten biostratigraphy samples and fifteen thin sections were analyzed. Three sequences were interpreted: incomplete interrup (e), incomplete truncated (b) and truncated (a, b, c, d). The relative age of Socorro is early middle eocene to middle Eocene, due to the finding of radiolarians of order nassellarios (Thyrsocyrtis triacontha) and the environment of deposition is marine of external platform by the abundance of radiolarians spumellarios (Lithocyclia Ocellus, Periphaena duplus) and benthic foraminifera (Bolivina). The sandstones of Socorro are sublitharenites and litharenites; and they show a tectonic provenance of quartzose Recycled Orogeny type, Collision orogeny and tendency between the Subduction Complex and Arc Orogeny; and it agree with the proporsal of Jaillard et al. (1995). Jaillard et al. (1995), stated that during the Middle Eocene the extensional subsidence of the Cayo insular arch ocurred. Therefore, the components of the Socorro sandstones would come from: monocrystalline quartz from the Andean continental margin, polycrystalline quartz from the Santa Elena Formation of Late Cretaceous - Early Paleocene, sedimentary lithics from the Chongón Colonche mountain range and volcanic lithics from the remnants of the insular Cayo arc.
The Socorro Formation is part of the Ancón Group (Middle Eocene), in the Cacique sector, five outcrops were observed, silty mudstone, siltstone and minor fining upward sandstones. the thicknesses are centimetric. In the Province of Santa Elena of the Cacique sector, were determined biostratigraphy, mineralogical composition, depositional sedimentary environment and tectonic provenance of Socorro sandstones. in the outcrops of the Cacique sector, ten biostratigraphy samples and fifteen thin sections were analyzed. Three sequences were interpreted: incomplete interrup (e), incomplete truncated (b) and truncated (a, b, c, d). The relative age of Socorro is early middle eocene to middle Eocene, due to the finding of radiolarians of order nassellarios (Thyrsocyrtis triacontha) and the environment of deposition is marine of external platform by the abundance of radiolarians spumellarios (Lithocyclia Ocellus, Periphaena duplus) and benthic foraminifera (Bolivina). The sandstones of Socorro are sublitharenites and litharenites; and they show a tectonic provenance of quartzose Recycled Orogeny type, Collision orogeny and tendency between the Subduction Complex and Arc Orogeny; and it agree with the proporsal of Jaillard et al. (1995). Jaillard et al. (1995), stated that during the Middle Eocene the extensional subsidence of the Cayo insular arch ocurred. Therefore, the components of the Socorro sandstones would come from: monocrystalline quartz from the Andean continental margin, polycrystalline quartz from the Santa Elena Formation of Late Cretaceous - Early Paleocene, sedimentary lithics from the Chongón Colonche mountain range and volcanic lithics from the remnants of the insular Cayo arc.
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AFLORAMIENTO, EOCENO, RADIOLARIO, TECTÓNICA, TURBÍDITAS