Bioestratigrafía y ambiente sedimentario de depositación de las calizas de La Formación San Eduardo (Eoceno) al sur del Bosque Protector Cerro Blanco, Provincia del Guayas
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2019
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Facultad de Ciencias Naturales. Universidad de Guayaquil
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La Formación San Eduardo (Eoceno Temprano – Eoceno Medio) es parte de la Cordillera Chongón Colonche, sobreyace a la Formación Guayaquil (Cretácico) y subyase a la Formación Calizas Las Delicias (Eoceno Tardío). El objetivo de este estudio es identificar la edad y el ambiente sedimentario de depositación de las calizas San Eduardo al sur del Bosque Protector Cerro Blanco, Provincia del Guayas. Las cuatro unidades estratigráficas que conforman la Formación San Eduardo se diferencian por el contenido de carbonato de calcio, características litológicas, paleontológicas, petrográficas y bioestratigráficas. Se identificaron tres afloramientos, denominados Ed1, Ed2 y Ed3 en una superficie de cinco hectáreas; las litologías predominantes son calizas brechoides con recristalizaciones de calcita, caliza margosa, seguido de nódulos de chert y escasa arcillolita. Para la interpretación petrográfica y bioestratigráfica se describieron y analizaron siete secciones delgadas. Se utilizó la metodología de Dunham y Folk (1962) para la clasificación de rocas carbonáticas, modelos de microfacies de Flügel (2004) y Wilson (1975) y método de Bernard (1967) para calcimetria. Las rocas calizas tienen entre 55 % a 99 % de carbonato de calcio, petrográficamente las calizas son packstone (caliza granular lodosa) mudstone (lodolita), wackestone (caliza lodosa), grainstone (caliza granular) y crystalline (cristalina). La edad relativa de San Eduardo es Eoceno Medio, pisos Luteciense al Bartoniense, debido al hallazgo de macrofósiles, algas calcáreas, foraminíferos planctónicos y bentónicos. El ambiente sedimentario es Plataforma de Laguna Abierta, rampa interna a media.
The San Eduardo Formation (Early Eocene - Middle Eocene) is part of the Chongón Colonche Cordillera, overlay the Guayaquil Formation (Cretaceous) and subgrade the Las Delicias Limestone Formation (Late Eocene). The objective of this study is to identify the age and sedimentary environment of depositing the limestones. San Eduardo south of Protected Forest Cerro Blanco, Province of Guayas.The four stratigraphic units that make up the San Eduardo Formation are differentiated by the content of calcium carbonate, lithological, paleontological, petrography and biostratigraphy characteristics. Three outcrops were identified, denominated Ed1, Ed2 and Ed3 in a surface of five hectares; the predominant lithology are brechoid limestones with recrystallizations of calcite, marly limestone, followed by chert nodules and sparse arcillolite. For the petrographic and biostratigraphy interpretation, seven thin sections are described and analyzed.This is the methodology of Dunham and Folk (1962) for the classification of carbonate rocks, models of microfacies of Flügel (2004) and Wilson (1975) and Bernard's Method (1967) for calcimetry. Limestone rocks have between 55% and 99% calcium carbonate, petrographically the limestones are packstone (muddy granular limestone) mudstone (mudstone), wackestone (mudstone limestone), grainstone (granular limestone) and crystaline (crystalline). The relative age of San Eduardo is Middle Eocene, Lutecian to Bartonian, due to the finding of macrofossils, calcareous algae, planktonic and benthic foraminifera. The sedimentary environment is the Laguna Open Platform, internal to middle ramp.
The San Eduardo Formation (Early Eocene - Middle Eocene) is part of the Chongón Colonche Cordillera, overlay the Guayaquil Formation (Cretaceous) and subgrade the Las Delicias Limestone Formation (Late Eocene). The objective of this study is to identify the age and sedimentary environment of depositing the limestones. San Eduardo south of Protected Forest Cerro Blanco, Province of Guayas.The four stratigraphic units that make up the San Eduardo Formation are differentiated by the content of calcium carbonate, lithological, paleontological, petrography and biostratigraphy characteristics. Three outcrops were identified, denominated Ed1, Ed2 and Ed3 in a surface of five hectares; the predominant lithology are brechoid limestones with recrystallizations of calcite, marly limestone, followed by chert nodules and sparse arcillolite. For the petrographic and biostratigraphy interpretation, seven thin sections are described and analyzed.This is the methodology of Dunham and Folk (1962) for the classification of carbonate rocks, models of microfacies of Flügel (2004) and Wilson (1975) and Bernard's Method (1967) for calcimetry. Limestone rocks have between 55% and 99% calcium carbonate, petrographically the limestones are packstone (muddy granular limestone) mudstone (mudstone), wackestone (mudstone limestone), grainstone (granular limestone) and crystaline (crystalline). The relative age of San Eduardo is Middle Eocene, Lutecian to Bartonian, due to the finding of macrofossils, calcareous algae, planktonic and benthic foraminifera. The sedimentary environment is the Laguna Open Platform, internal to middle ramp.
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FORMACION SAN EDUARDO, MACROFOSILES, AMBIENTE SEDIMENTARIO, ECOCENO MEDIO