La icnofacies teredolites como marcador de condiciones paleoambientales durante el cretácico-paleógeno de la cuenca de Arauco (Chile Central)
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Fecha
2023
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es
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Universidad Andrés Bello
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Licencia CC
Licencia CC
Resumen
Los icnofósiles de Teredolites son empleados con frecuencia como indicador de las condiciones paleoambientales
en sistemas parálicos con influencia marina, ambientes marinos abiertos y secuencias regresivas-transgresivas. En la Cuenca
de Arauco (36°46' a 38°30' S), nuevos registros de restos de troncos con T. longissimus y T. clavatus permiten evaluar las
condiciones paleoambientales de los depósitos en una cuenca con sedimentación principalmente siliciclástica. Estos
depósitos están controlados por procesos tectono-eustáticos los que generan una tendencia transgresiva durante el Cretácico
superior. Esta es sucedida por episodios de alternancias de transgresión-regresión durante el Paleógeno. En este estudio, se
analizaron muestras provenientes la Fm. Quiriquina (Maastrichtiano superior), Fm. Boca Lebu (Eoceno temprano), Fm.
Trihueco (Eoceno medio) y Fm. Millongue (Eoceno medio – superior). Los resultados indican que existe una gran
variabilidad en la preservación, forma y tamaño de las trazas entre las diversas localidades. Las muestras fueron analizadas
en base a criterios morfométricos, a partir de mediciones de diámetros y largos aparentes; tafonómicos, mediante la
identificación de poblaciones y su densidad en el sustrato y; diagenéticos, conforme a la recristalización de las paredes
cálcicas y el relleno de los tubos. Los datos obtenidos permitieron: identificar la polaridad o sentido de crecimiento de T.
longissimus en base a bioglifos, obtener pautas de crecimiento de las diversas poblaciones de T. longissimus, identificar
eventos de invasión del material vegetal y estimar velocidades de enterramiento de las muestras en base a la relación
porcentual de Teredolites y el sustrato leñoso. Se concluye un ambiente transgresivo estuarino con cercanía a selvas o
manglares para Fm.Quiriquina ; para Fm. Boca Lebu, un ambiente transgresivo marino de offshore con eventos específicos
de caída de troncos; y, para Fm. Millongue, un ambiente transgresivo marino de shoreface con un aporte constante de
troncos por cercanía a selvas o manglares que además pasan periodos importantes en la columna de agua.
Teredolites ichnofossils are often used as an indicator of paleoenvironmental conditions in marine-influenced paralic systems, open marine settings, and regressive-transgressive sequences. In the Arauco Basin (36°46' a 38°30' S), newly records of log grounds with T. longissimus and T. clavatus have allowed to assess the paleoenvironmental conditions within a basin primarily characterised by siliciclastic sedimentation. These deposits are controled by tectono-eustatic processes, resulting in a transgressive trend during the Late Cretaceous, followed by alternating episodes of transgressionregression during the Paleogene. In this study, samples from the Quiriquina Fm. (Upper Maastrichtian), Boca Lebu Fm. (Early Eocene), Trihueco Fm. (Middle Eocene) and Millongue Fm. (Middle-Upper Eocene) were analysed. Results reveal substantial variability in the preservation, shape, and size of the traces between the studied localities. Samples were analysed based on the following criteria: Morphometric measurements (diameters and apparent lengths); taphonomy (identifying populations and their density in the substrate); and diagenetic factors (according to recrystallisation of the calcium walls and tube fillings). Data obtained was used to: Determine the polarity or growth direction of T. longissimus based on bioglyphs; establish growth patterns among the various populations of T. longissimus; identify invasion events of vegetal material; and estimate burial velocities of the samples based on the percentage ratio of Teredolites and the woody substrate. The conclussion suggest an estuarine transgressive environment in proximity to forests or mangroves for the Quiriquina Fm.; a offshore marine transgressive environment for the Boca Lebu Fm.; and a shoreface marine transgressive environment with continuous logs influx due to proximity to forests or mangroves, which also experienced extended periods in the water column for the Millongue Fm.
Teredolites ichnofossils are often used as an indicator of paleoenvironmental conditions in marine-influenced paralic systems, open marine settings, and regressive-transgressive sequences. In the Arauco Basin (36°46' a 38°30' S), newly records of log grounds with T. longissimus and T. clavatus have allowed to assess the paleoenvironmental conditions within a basin primarily characterised by siliciclastic sedimentation. These deposits are controled by tectono-eustatic processes, resulting in a transgressive trend during the Late Cretaceous, followed by alternating episodes of transgressionregression during the Paleogene. In this study, samples from the Quiriquina Fm. (Upper Maastrichtian), Boca Lebu Fm. (Early Eocene), Trihueco Fm. (Middle Eocene) and Millongue Fm. (Middle-Upper Eocene) were analysed. Results reveal substantial variability in the preservation, shape, and size of the traces between the studied localities. Samples were analysed based on the following criteria: Morphometric measurements (diameters and apparent lengths); taphonomy (identifying populations and their density in the substrate); and diagenetic factors (according to recrystallisation of the calcium walls and tube fillings). Data obtained was used to: Determine the polarity or growth direction of T. longissimus based on bioglyphs; establish growth patterns among the various populations of T. longissimus; identify invasion events of vegetal material; and estimate burial velocities of the samples based on the percentage ratio of Teredolites and the woody substrate. The conclussion suggest an estuarine transgressive environment in proximity to forests or mangroves for the Quiriquina Fm.; a offshore marine transgressive environment for the Boca Lebu Fm.; and a shoreface marine transgressive environment with continuous logs influx due to proximity to forests or mangroves, which also experienced extended periods in the water column for the Millongue Fm.
Notas
Memoria de título (Geólogo)
Palabras clave
Icnofacies Teredolites, Paleontología, Cretácico Superior, Paléogeno, Chile, Arauco