Lower Ordovician calcareous microfossils from the San Juan Formation, Argentina: a new type of calcitarch and its paleoenvironmental implications
Microfósiles carbonáticos del Ordovícico Inferior de la Formación San Juan, Argentina: Un nuevo tipo de calcitarch y sus implicaciones paleoambientales
| dc.contributor | en-US | |
| dc.contributor | es-ES | |
| dc.creator | Moreno, Florencia | |
| dc.creator | Mestre, Ana | |
| dc.creator | Heredia, Susana | |
| dc.date | 2023-06-07 | |
| dc.date.accessioned | 2023-06-16T15:15:07Z | |
| dc.date.available | 2023-06-16T15:15:07Z | |
| dc.identifier | http://www.andeangeology.cl/index.php/revista1/article/view/V50n2-3469 | |
| dc.identifier | 10.5027/andgeoV50n2-3469 | |
| dc.identifier.uri | https://revistaschilenas.uchile.cl/handle/2250/230526 | |
| dc.description | The calcareous microfossils present in the Ordovician and Silurian carbonate successions around the world are limited to few studies and their biological affinities and environmental preferences remain indefinite. In the carbonate Ordovician San Juan Formation from the Cerro La Chilca section, a group of calcareous microfossils was recognized and, based on their size, they are included in the calcitarch classification. Two types of calcitarchs have been recognized, Type-III calcitarch: large spheres with a thin to medium wall (diameter ~250 μm), and Type-0 calcitarch: small spheres with a thin wall (diameter ~80 μm). The carbonate microfacies analysis of the lower part of the San Juan Formation allowed defining five successive microfacies: burrowed bioclastic wackestone (M1), peloidal intraclastic packstone-grainstone (M2), intraclastic floatstone (M3), intraclastic wackestone-packstone (M4) and bioclastic boundstone (M5). These microfacies are interpreted to range from shallow subtidal facies below wave action to shoal and reef facies. It is possible to infer that the recovered calcitarchs show variations in size in relation to the facies that contain them. The calcitarchs recognized in wackestone-type facies are the Type-0 calcitarch and those recovered from the packstone-grainstone facies are the Type-III calcitarch. The calcitarch sizes variation probably is related to a gradual increase of energy within a shallow subtidal environment. Occurrences of calcitarchs within the Floian Oepikodus evae-O. intermedius conodont zone extends their fossil record into the Early Ordovician. | en-US |
| dc.description | Los microfósiles calcáreos presentes en las sucesiones carbonáticas ordovícicas y silúricas están limitados a unos pocos estudios, por lo que sus afinidades biológicas y preferencias ambientales aún están indefinidas. En los niveles carbonáticos de la Formación San Juan en la sección Cerro La Chilca, se reconoció un grupo de microfósiles calcáreos que, en función de su tamaño, se incluyen en la clasificación de calcitarch. Se han reconocido dos tipos de calcitarchs, calcitarchs tipo-III: esferas grandes con una pared delgada a mediana (diámetro ~250 μm) y calcitarchs tipo-0: esferas pequeñas con una pared delgada (diámetro ~80 μm). El análisis de las microfacies carbonáticas de los niveles inferiores de la Formación San Juan permitió definir cinco microfacies sucesivas: wackestone bioclástico bioturbado (M1), packstone-grainstone intraclástico peloidal (M2), floatstone intraclástico (M3), wackestone-packstone intraclástico (M4) y boundstone bioclástico (M5). Se interpreta que estas microfacies van desde facies submareales poco profundas por debajo de la acción de las olas hasta facies de barras y arrecife. Es posible inferir que los calcitarchs recuperados presentan variaciones de tamaño en relación con las facies que las contienen. Los calcitarchs reconocidas en las facies tipo wackestone son las calcitarchs tipo-0 y las recuperadas de las facies packstone-grainstone son las calcitarchs tipo-III. La variación del tamaño de los calcitarchs probablemente esté relacionada con un aumento gradual de energía dentro de un ambiente submareal poco profundo. La ocurrencia de calcitarchs dentro del intervalo comprendido por las zonas de Oepikodus evae-O. intermedius (Floiano) extiende su registro fósil hasta el Ordovícico Inferior. | es-ES |
| dc.format | application/pdf | |
| dc.format | text/html | |
| dc.language | eng | |
| dc.publisher | Servicio Nacional de Geología y Minería | en-US |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/view/V50n2-3469/pdf | |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/view/V50n2-3469/html | |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/downloadSuppFile/V50n2-3469/4034 | |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/downloadSuppFile/V50n2-3469/4035 | |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/downloadSuppFile/V50n2-3469/4036 | |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/downloadSuppFile/V50n2-3469/4037 | |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/downloadSuppFile/V50n2-3469/4038 | |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/downloadSuppFile/V50n2-3469/4044 | |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/downloadSuppFile/V50n2-3469/4045 | |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/downloadSuppFile/V50n2-3469/4046 | |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/downloadSuppFile/V50n2-3469/4047 | |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/downloadSuppFile/V50n2-3469/4048 | |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/downloadSuppFile/V50n2-3469/4049 | |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/downloadSuppFile/V50n2-3469/4050 | |
| dc.rights | Copyright (c) 2023 Andean Geology | en-US |
| dc.source | Andean Geology; Vol 50, No 2 (2023); 302-317 | es-ES |
| dc.source | Andean Geology; Vol 50, No 2 (2023); 302-317 | en-US |
| dc.source | 0718-7106 | |
| dc.source | 0718-7092 | |
| dc.subject | Calcitarch; Floian; Precordillera; San Juan Formation; Ordovician | en-US |
| dc.subject | Calcitarch; Floiano; Precordillera; Formación San Juan; Ordovícico | es-ES |
| dc.title | Lower Ordovician calcareous microfossils from the San Juan Formation, Argentina: a new type of calcitarch and its paleoenvironmental implications | en-US |
| dc.title | Microfósiles carbonáticos del Ordovícico Inferior de la Formación San Juan, Argentina: Un nuevo tipo de calcitarch y sus implicaciones paleoambientales | es-ES |
| dc.type | info:eu-repo/semantics/article | |
| dc.type | info:eu-repo/semantics/publishedVersion | |
| dc.type | es-ES | |
| dc.type | en-US |
This item appears in the following Collection(s)
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Andean Geology
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