Repositorio Digital Sernageomin
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Late Cretaceous mosasaurids of northeastern Brazil : A summary of their record and a paleobiogeographical survey
No full textThe coastal region of northeastern Brazil holds one of the most important records of mosasaurids from the Late Cretaceous of South America. Analysis of these discoveries allowed us to create a picture of the composition of the fauna, as well as the diversity and paleobiogeography of these clades. In the region, the mosasaurid fossils are contained in Cenomanian to Maastrichtian geological units of epicontinental marine origin, in the Cotinguiba (Sergipe-Alagoas Basin), Alcântara (São Luís Basin), Itamaracá (Paraíba Basin), Calumbi (Sergipe-Alagoas Basin), and Gramame (Paraíba Basin) formations. Paleogeographic data corroborate that these deposits represent low-latitude equatorial environments. The Brazilian fauna is represented by fourteen taxa from one family (Mosasauridae), two subfamilies (Mosasaurinae: Prognathodontini, Globidensini and Mosasaurini; Plioplatecarpinae: Plioplatecarpini), and some indeterminate mosasaurid specimens. Mosasaurids from the northeastern region of Brazil resemble Late Cretaceous marine reptiles from western Africa (Angola, Congo, and Morocco), suggesting faunal continuity in the seaway that bridged these areas. The study of this marine fauna is crucial to understanding the evolutionary and paleobiogeographic history of the group during the opening of the South Atlantic Ocean.pp.150-16
Visita Técnica por caída de rocas. Subida Alessandri, comuna de Viña del Mar, Región de Valparaíso
Full text linkInforme Técnico -- Unidad Ejecutora: Unidad de Asistencias Técnicas y Emergencias Geológicas y Unidad de Peligros Geológicos y Ordenamiento Territorial12 p
The orbicular granodiorite of Recoba Hill in the North Patagonian Batholith
Full text linkA small body of orbicular granodiorite crops out on the Recoba Hill, immediately east of the town of Chaitén, in the mainland area called Chiloé continental, in southern Chile. The rock comprises cm-sized igneous cores with a single shell of fine-grained plagioclase-quartz-K-feldspar assemblages. It is hosted in a Miocene granodiorite, and it is crosscut by aplite and mafic dikes. No other mention of orbicular rocks has to date been reported for the >1,000 km long North Patagonian Batholith, suggesting that the conditions necessary for their formation were infrequent. Thermobarometric determinations indicate pressures lower than 2 kbar (less than 6 km depth) for its formation, a level much shallower than the estimated source depth of the older rocks of the batholith.pp.86-10
Resultados de la inspección de remociones en masa ocurridas en cuatro sectores de la localidad de Queule, comuna de Toltén, Región de La Araucanía
No full textInforme Técnico -- Unidad Ejecutora: Dirección Regional de Los Ríos, Valdivia27 p
Driving factors on wetland water area changes in the arid region of central-western Argentina (32° S) during the last two decades
No full textThe wetlands along the Leyes-Tulumaya stream in central-western Argentina (32° S) are part of an old, inactive paleo-stream bed of the Mendoza River. These wetlands have been drastically impacted during the last 20 years, reducing their water areas or even completely drying out. The causes and driving factors of this major environmental impact have yet to be explored. Understanding the interaction of the different natural and/or anthropic factors influencing these wetland area changes in the recent past is imperative to apply proper management and conservation plans. In this contribution, the water areas of three lakes along the Leyes-Tulumaya stream are mapped using a GIS environment from satellite imagery to track variations in the last two decades. Assuming that natural variables have been forcing these environmental changes, annual precipitation, soil moisture, evaporation indexes, and the stream flow of the Mendoza River, are analyzed. Changes in the lake water areas along the Leyes-Tulumaya stream are, however, hardly explained due to these natural variables, so anthropogenic factors might have been key and thus need to be further explored.pp.101-11
The brachiopod Kvania, a biostratigraphic marker across the Cambrian-Ordovician boundary in Andean Gondwana
No full textThe plectorthoid brachiopod Kvania is widely distributed in Upper Cambrian and Lower Ordovician rocks of the Central Andean basin of northwestern Argentina and southwestern Bolivia. In this contribution, Kvania lariensis Benedetto is reported for the first time in the Eastern Cordillera (Quebrada de Humahuaca area) of northwestern Argentina. Studied material comes from the Alfarcito Member of the Santa Rosita Formation (Santa Victoria Group) of well constrained earliest Tremadocian age (Tr1). The presence of Kvania lariensis in different localities of the Altiplano-Puna region and the Eastern Cordillera of Bolivia and Argentina allows proposing this species as a reliable biostratigraphic marker for the lowermost Ordovician of the region. On the basis of the phylogenetic hypothesis supporting the Protorthisina-Kvania-Gondwanorthis lineage, four phylozones are recognized across the Cambrian-Ordovician boundary. The basal member of the lineage is Kvania primigenia, which co-occurs with Parabolina (Neoparabolina) frequens argentina, is proposed here as a biostratigraphic marker for the upper Furongian (Stage 10). The base of the time slice Tr1 is indicated by the first appearance of Kvania lariensis, which is almost time-equivalent to the Jujuyaspis keideli trilobite biozone, whereas the descendent species Kvania azulpampensis is almost coeval with the Kainella andina trilobite biozone. Gondwanorthis calderensis calderensis, a more derived member of the lineage, indicates the upper part of the lower Tremadocian (Tr1), and is equivalent to the Kainella meridionalis trilobite biozone. The specimens of Kvania lariensis from the Alfarcito Member provide additional information about its phenotypic variablity, confirming the trend of increasing costellae number through ontogeny observed in the type material, and also corroborate that the lineage as a whole experienced a defined evolutionary trend to increasing both shell size and costellae number.pp.47-6
Evaluación de caída de rocas en la ruta de ascenso al volcán Villarrica, comuna de Pucón, Región de La Araucanía
No full textInforme Técnico -- Unidad Ejecutora: Dirección Regional de Los Ríos, Valdivia22 p
Visita técnica a sector estero La Sombra, comuna de Linares, región del Maule
Full text linkInforme Técnico -- Unidad Ejecutora: Unidad de Asistencias Técnicas y Emergencias Geológicas, Santiago7 p
Jean-Claude Vicente (1941-2022) Formador de varias generaciones de geólogos y gran explorador andino
Full text linkpp.162-16
Visita técnica a villa El Esfuerzo, comuna de Licantén, región del Maule
No full textInforme Técnico -- Unidad Ejecutora: Unidad de Asistencias Técnicas y Emergencias Geológicas, Santiago8 p