Ambiente deposicional, procedencia tectónica y bioestratigrafía de las areniscas de la Formación seca del Grupo Ancón (Eoceno medio), acantilado del área certeza, Ancón, Península de Santa Elena
Fecha
2019
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Facultad de Ciencias Naturales. Universidad de Guayaquil
Resumen
Las rocas de la Formación Seca son parte del Grupo Ancón (Eoceno Medio) y actúan como sellos del yacimiento petrolero Campo Ancón. Se estudiaron diez afloramientos, catorce secciones delgadas y treinta muestras micropaleontológicas para definir litologías, composición mineralógica, petrotectónica, bioestratigrafía y paleoambiente de la Formación Seca en el área Certeza.
Se identificaron secuencias turbidíticas incompletas (Te; Tb – Te y Tc – e), truncadas incompletas (Tb y Tb - c), truncadas (Ta; Ta – b y Ta - c) y completas (Ta - e); litofacies A, B, C, D y F; estructuras sedimentarias (canales y flujos de detritos); y ciclos sedimentarios de engrosamiento y adelgazamiento hacia arriba.
Las areniscas de Seca son sublitarenitas y grauvacas líticas. Los componentes monocristalinos son 84.4% cuarzo monocristalino, 14.5% fragmentos líticos totales y 1.1% feldespato; y los componentes policristalinos corresponden a 38.7% cuarzo policristalino, 37.4% fragmentos líticos volcánicos y 23.9% fragmentos líticos sedimentarios. Desde el sector Sureste disminuyen los cuarzos monocristalinos y fragmentos líticos volcánicos, aumentan los fragmentos líticos totales, cuarzos policristalinos y fragmentos líticos sedimentarios, mientras que los valores de feldespatos son similares. La procedencia tectónica es Orogenia reciclada, Complejo de subducción y tendencia a Orógeno de arco y colisión.
La edad relativa de Seca es Eoceno Medio medio (zona E10 – E11) por la ocurrencia de los foraminíferos planctónicos Globigerina officinalis y radiolarios Eusyringium cf. Lagena y Podocyrtis ampla. El paleoambiente es Marino de Plataforma Externa a Talud Superior por la abundancia de los foraminíferos bentónicos Uvigerina hispida, Uvigerina marksi, Bathysiphon eocénica, Uvigerina rugosa, Nutallides truempyi truempyi, Ellipsonodosaria curvatura, Ellipsonodosaria verneulli, Nodosaria sp., Bulimina uvigerinaformis, Hoeglundina elegans y Uvigerina charapotoensis.
The rocks of the Seca Formation are part of the Ancón Group (Middle Eocene) and act as seals of the Ancón oil field. Ten rocky outcrops, fourteen thin sections and thirty micropaleontological samples were studied to define lithologies, mineralogical composition, petrotectonic, biostratigraphy and paleoenvironment of the Seca Formation in the Certeza area. Incomplete turbiditical sequences (Te; Tb - Te and Tc - e), truncated incomplete (Tb and Tb - c), truncated (Ta; Ta - b and Ta - c) and complete (Ta - e); lithofacies A, B, C, D and F; sedimentary structures (channels and debris flows); and sedimentary cycles of thickening and thinning upwards were identified. The sandstones of Seca are sublitarenites and lithic greywackes. The monocrystalline components are 84.4% monocrystalline quartz, 14.5% total lithic fragments and 1.1% feldspar; and the polycrystalline components correspond to 38.7% polycrystalline quartz, 37.4% volcanic lithic fragments and 23.9% lithic sedimentary fragments. From the Southeast sector, monocrystalline quartz and volcanic lithic fragments decrease, total lithic fragments, polycrystalline quartz and sedimentary lithic fragments increase, while feldspar values are similar. The tectonic provenance is recycled Orogeny, subduction Complex and orogenic tendency of arc and collision. The relative age of Seca is Middle Eocene (zone E10 - E11) due to the occurrence of the planktonic foraminifera Globigerina officinalis and radiolarians Eusyringium cf. Lagena and Podocyrtis ampla. The paleoenvironment is Marine, from External Platform to Upper Slope due to the abundance of the benthic foraminifera Uvigerina hispida, Uvigerina marksi, Bathysiphon eocenica, Uvigerina rugosa, Nutallides truempyi truempyi, Ellipsonodosaria curvature, Ellipsonodosaria verneulli, Nodosaria sp., Bulimina uvigerinaformis, Hoeglundina elegans and Uvigerina charaphotoensis.
The rocks of the Seca Formation are part of the Ancón Group (Middle Eocene) and act as seals of the Ancón oil field. Ten rocky outcrops, fourteen thin sections and thirty micropaleontological samples were studied to define lithologies, mineralogical composition, petrotectonic, biostratigraphy and paleoenvironment of the Seca Formation in the Certeza area. Incomplete turbiditical sequences (Te; Tb - Te and Tc - e), truncated incomplete (Tb and Tb - c), truncated (Ta; Ta - b and Ta - c) and complete (Ta - e); lithofacies A, B, C, D and F; sedimentary structures (channels and debris flows); and sedimentary cycles of thickening and thinning upwards were identified. The sandstones of Seca are sublitarenites and lithic greywackes. The monocrystalline components are 84.4% monocrystalline quartz, 14.5% total lithic fragments and 1.1% feldspar; and the polycrystalline components correspond to 38.7% polycrystalline quartz, 37.4% volcanic lithic fragments and 23.9% lithic sedimentary fragments. From the Southeast sector, monocrystalline quartz and volcanic lithic fragments decrease, total lithic fragments, polycrystalline quartz and sedimentary lithic fragments increase, while feldspar values are similar. The tectonic provenance is recycled Orogeny, subduction Complex and orogenic tendency of arc and collision. The relative age of Seca is Middle Eocene (zone E10 - E11) due to the occurrence of the planktonic foraminifera Globigerina officinalis and radiolarians Eusyringium cf. Lagena and Podocyrtis ampla. The paleoenvironment is Marine, from External Platform to Upper Slope due to the abundance of the benthic foraminifera Uvigerina hispida, Uvigerina marksi, Bathysiphon eocenica, Uvigerina rugosa, Nutallides truempyi truempyi, Ellipsonodosaria curvature, Ellipsonodosaria verneulli, Nodosaria sp., Bulimina uvigerinaformis, Hoeglundina elegans and Uvigerina charaphotoensis.
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SECUENCIAS, CANALES, ARENISCAS, OROGENIA