CARACTERIZACIÓN FÍSICO QUÍMICA, TAFONOMÍA Y ECOLOGÍA DE Orthokarstenia ewaldi (FORAMINIFERIDA: SIPHOGENERINOIDIDAE) DE LA FORMACIÓN LOS PINOS (CRETÁCICO: MAASTRICHTIANO) DE SAMACÁ (BOYACÁ, COLOMBIA)
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Universidad Industrial de Santander
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El género Orthokarstenia se considera un microfósil guía para las edades del periodo Cretácico. La especie característica de la Formación Los Pinos correspondiente al Periodo Cretácico y la edad Maastrichtiana se ajusta a la descripción morfológica de Orthokarstenia ewaldi. De la matriz silícea se extrajeron varios especímenes y se maceraron para realizar pruebas de Espectroscopía de Infrarrojos por la transformada de Fourier (FTIR) utilizando como base KBr. Se colectaron especímenes de tres niveles de una roca. Se tomaron imágenes tridimensionales con un video-microscopio para detallar la forma y organización de los minerales.Un fragmento de la roca se utilizó para llevar a cabo pruebas con Espectroscopia de plasma inducida por laser(LIBS) y determinar la presencia de los elementos Ca, Fe y Mg. También se elaboraron y describieron secciones delgadas. Los espectros de FTIR de los foraminíferos fueron similares en los tres niveles donde se tomaron las muestras aunque presentaron diferencias con el espectro de la matriz de sílice. Los análisis de LIBS confirmaron la presencia de Ca y de Fe en las muestras. En las secciones delgadas se pudo determinar que el relleno de las conchas, está constituido por sílice amorfo apreciándose además una débil traza de la concha original como un sedimento fino. Las trazas de Ca encontradas confirman el reemplazo de aragonito a calcita magnesiana y finalmente a sílice. Utilizando el método de la relación entre la varianza y la media en tres tamaños de cuadrantes se determinó la dispersión de los especímenes. Los valores obtenidos indicaron una distribución de tipo agrupado. Este tipo de distribución es un indicativo de las condiciones de recursos en el hábitat, del modo de reproducción y dispersión. Se puede inferir que el sistema reproductivo dominante de O. ewaldi fue el asexual predominando las formas megalosféricas.
Palabras clave: Bentónico, Cretácico superior, Foraminífera,
The Orthokarstenia genus is considered a microfossil guide to the ages of the Cretaceous period. Thecharacteristic species of Los Pinos Formation corresponding to Cretaceous Period and Maastrichtian age and fitsto the morphological description of Orthokarstenia ewaldi species. From the siliceous matrix several specimenswere taken and macerated for Fourier transform infrared spectroscopy (FTIR) testing with KBr base. Specimenswere collected from three levels of a rock. Three-dimensional images were taken with a video-microscopes to detail the form and structure of minerals. A fragment of rock was used to perform Laser-induced breakdown spectroscopy (LIBS) tests and to establish the presence of the elements Ca, Fe and Mg. Thin sections were also made and described. FTIR spectra of for aminifera were similar in the three levels where the samples were taken but showed differences with the spectrum of the silica matrix. LIBS analysis confirmed the presence of Ca and Fe in the samples. In thin sections, amorphous silica filling the shell was observed, and also a faint. trace of the original shell as a fine sediment. Traces of Ca found with LIBS analysis confirm the replacement of aragonite to magnesian calcite and finally to silica. Using the relationship between the variance and the mean of three sizes of squares was determined the dispersion of the specimens. The values obtained indicated a clustered distribution type. This type of distribution is indicative of the conditions of resources in the habitat, reproduction and dispersal mode. It is possible to infer that the dominant reproductive system of O. ewaldi was megalospheric, being the asexual forms more common. Keywords: Benthic, Foraminifera, FTIR, LIBS, Upper Cretaceous.
The Orthokarstenia genus is considered a microfossil guide to the ages of the Cretaceous period. Thecharacteristic species of Los Pinos Formation corresponding to Cretaceous Period and Maastrichtian age and fitsto the morphological description of Orthokarstenia ewaldi species. From the siliceous matrix several specimenswere taken and macerated for Fourier transform infrared spectroscopy (FTIR) testing with KBr base. Specimenswere collected from three levels of a rock. Three-dimensional images were taken with a video-microscopes to detail the form and structure of minerals. A fragment of rock was used to perform Laser-induced breakdown spectroscopy (LIBS) tests and to establish the presence of the elements Ca, Fe and Mg. Thin sections were also made and described. FTIR spectra of for aminifera were similar in the three levels where the samples were taken but showed differences with the spectrum of the silica matrix. LIBS analysis confirmed the presence of Ca and Fe in the samples. In thin sections, amorphous silica filling the shell was observed, and also a faint. trace of the original shell as a fine sediment. Traces of Ca found with LIBS analysis confirm the replacement of aragonite to magnesian calcite and finally to silica. Using the relationship between the variance and the mean of three sizes of squares was determined the dispersion of the specimens. The values obtained indicated a clustered distribution type. This type of distribution is indicative of the conditions of resources in the habitat, reproduction and dispersal mode. It is possible to infer that the dominant reproductive system of O. ewaldi was megalospheric, being the asexual forms more common. Keywords: Benthic, Foraminifera, FTIR, LIBS, Upper Cretaceous.