Chichinales Formation (original) (raw)

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The Chichinales Formation is a geological formation in Río Negro Province, Argentina which dates from the Late Oligocene to the Early Miocene, around 23 to 17.5 million years ago. It predominantly consists of pyroclastic deposits, which were deposited in a semi-arid environment. It is divided up into a number of members. The diverse fauna of the Chichinales Formation, including a variety of turtles and birds, also includes many mammals such as South American native ungulates (notoungulates and litopterns) as well as armadillos, and caviomorph rodents. It is named after the type locality and extends over a large part of the province of Río Negro. It outcrops in the , in the towns of General Roca, Río Negro and Villa Regina, bordering the southern bank of the Río Negro. Part of the most important outcrops are located within the Paso Córdova Natural Protected Area. The Chichinales Formation, broadly speaking, is made up of grayish sandstones, whitish tuffs, siltstones and greenish claystones with paleo soil levels. It is divided into 3 members: lower, middle and upper. The lower one is composed of grayish brown sandstones with low-angle cross bedding, alternating with light brown tuffs, tuffaceous sandstones, sandstones with carbonate cement and shales. In this member, the presence of "opalized" fossil logs is common. The middle member is formed by paleosols and sequences of siltstones, shales and fine sands that in some sectors form lenses in the form of fluvial channels. Finally, the upper member is represented by more homogeneous levels of tuffs, whitish gray tuffites, siltstones, green claystones and tuffaceous sandstones This member, in some sectors, is laterally interdigitated with marginal marine levels of the , which dates from the Late Oligocene to the Early Pliocene. The Chichinales Formation is correlated with the contemporaneous fluvial and lacustrine tuffaceous Collón Curá Formation of the central Neuquén Basin. The sedimentological and paleontological evidence provided by the Chichinales Formation suggests the existence of open environments with low relief, restricted wooded areas with temporary water bodies and warm temperate climate, in agreement with other Colhuehuapian localities of Chubut Province. In this context, it is possible to interpret, at least tentatively, that the differences between the set of taxa represented in the Cerro Bandera Formation and those of the Chichinales Formation are due to contrasts between the local environmental conditions of each unit rather than to differences in temporal range. It is likely that such differences are the result of the particular conditions that prevailed in the Neuquén region during the Early Miocene, which would be a consequence of its proximity to the Andean zone rather than its latitudinal location. (en)
La Formación Chichinales, es una unidad litoestratigráfica cuya datación se ubica en el Oligoceno superior y Mioceno inferior a medio, presente en gran parte de la Provincia de Río Negro, Argentina. Recibe su nombre de la localidad tipo y se extiende en gran parte de la provincia de Río Negro. Aflora en el valle de Río Negro, en las localidades de General Roca y Villa Regina, bordeando la margen sur del Río Negro. Parte de los más importantes afloramientos se encuentran dentro del área natural protegida Paso Córdova. La Formación Chichinales, a grandes rasgos, está conformada por areniscas grisáceas, tobas blanquecinas, limolitas y arcilitas verdosas con niveles de paleosuelos. Se divide en 3 miembros: inferior, medio y superior. El inferior se compone de areniscas castaño grisáceas con estratificación entrecruzada de bajo ángulo, alternada con tufitas castaño claras, areniscas tobáceas, areniscas con cemento carbonático y lutitas. En este miembro es común la presencia de troncos fósiles "opalizados". El miembro medio está conformado por paleosuelos y secuencias de limolitas, lutitas y arenas finas que en algunos sectores conforman lentes en forma de canales fluviales. Finalmente, el miembro superior está representado por niveles más homogéneos de tobas, tufitas gris blanquecinas, limolitas, arcilitas verdes y areniscas tobáceas (Hugo y Leanza, 2001). Este miembro, en algunos sectores, está interdigitado lateralmente con niveles marinos marginales de la Formación Gran Bajo del Gualicho (Oligoceno superior-Plioceno inferior). (es)

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The Chichinales Formation is a geological formation in Río Negro Province, Argentina which dates from the Late Oligocene to the Early Miocene, around 23 to 17.5 million years ago. It predominantly consists of pyroclastic deposits, which were deposited in a semi-arid environment. It is divided up into a number of members. The diverse fauna of the Chichinales Formation, including a variety of turtles and birds, also includes many mammals such as South American native ungulates (notoungulates and litopterns) as well as armadillos, and caviomorph rodents. (en)
La Formación Chichinales, es una unidad litoestratigráfica cuya datación se ubica en el Oligoceno superior y Mioceno inferior a medio, presente en gran parte de la Provincia de Río Negro, Argentina. Recibe su nombre de la localidad tipo y se extiende en gran parte de la provincia de Río Negro. Aflora en el valle de Río Negro, en las localidades de General Roca y Villa Regina, bordeando la margen sur del Río Negro. Parte de los más importantes afloramientos se encuentran dentro del área natural protegida Paso Córdova. (es)

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Chichinales Formation (en)
Formación Chichinales (es)

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