Repositorio Digital Sernageomin
Not a member yet
15512 research outputs found
Sort by
Evaluación preliminar de peligro por remoción en masa en dos sitios del borde costero, comuna de Valdivia, Región de los Ríos.
No full textRevisor: Carlos Johnson N.14 p
First Middle Ordovician conodont record related to key graptolites from the western Puna, Argentina: perspectives for an integrated biostratigraphy and correlation of the Central Andean Basin
Get PDFRecent biostratigraphic studies on the western argentine Puna recorded the Middle Ordovician conodont Baltoniodus cf. B. navis (Lindström) for first time, related to key graptolite taxa of the Central Andean Basin. The analyzed material comes from the lower and middle thirds of the turbidite succession exposed at the Huaytiquina section, Salta Province, which was previously assigned to the "Coquena" Formation. The conodont fauna was recovered from the calcareous sandstone beds intercalated in the middle portion of this unit, and it is composed by species of the genera Baltoniodus, Gothodus, Trapezognathus, Drepanoistodus, Drepanodus, and Protopanderodus, among others. The conodont association indicates a middle Dapingian (Dp2) age, linking the conodonts of the Argentine Puna with those from Baltoscandinavia and South China. The conodont productive levels also contain graptolites assignable to Tetragraptus bigsbyi (Hall) and Isograptus sp. They are located overlying strata bearing Azygograptus lapworthi Nicholson and underlying deposits with Xiphograptus lofuensis (Lee). The graptolite associations are indicating a Dapingian age (Dp1-Dp2) for the lower and middle portions of the “Coquena” Formation. The current findings from the western Puna, as well as the record of Azygograptus lapworthi related to the early Dapingian (Dp1) index conodont Baltoniodus triangularis in the Argentine Cordillera Oriental, are suggesting that a high-resolution correlation between both geomorphological regions is possible. This also documents that the Cordillera Oriental as well as the Puna were connected parts of the Central Andean Basin, during the interval from the Lower Ordovician (Floian) to the Middle Ordovician (Dapingian), instead of corresponding to the source and infill sectors of the basin, respectively. Furthermore, the regional and global correlations are discussed, and the potential of the Ordovician successions of the Argentine Puna for future advances on conodont-graptolite high-resolution biostratigraphy is highlighpp.144-16
Evaluación geológica preliminar de quebrada afluente a cauce Philippi en el extremo poniente de la calle Los Peumos, cerro Esperanza, comuna de Valparaíso, región de Valparaíso
No full textRevisor: Alejandro Alfaro S..15 p
Impacto de las remociones en masa de marzo de 2015 en el sistema fluvial del río Salado, Región de Atacama: análisis comparativo de la geoquímica de sedimentos
No full textInforme Registrado IR-20-82 ; Contiene Anexos: Anexo 1. Definiciones de instalaciones mineras ; Anexo 2. Metodología de muestreo ; Anexo 3. Datos ; Anexo 4. Distribución geográfica de muestras pre- y posaluvión (muestras de control) y comparación de las concentraciones de los elementos evaluados ;Anexo 5. Composición química de relaves y sedimentos muestreados en instalaciones antiguas de Codelco División Salvador ; Anexo 6. Decripción de las unidades geológicas de la figura 36108 p
Primer registro de estromatolitos en el Maastrichtiano tardío del Grupo Chubut, Cuenca del Golfo San Jorge, Patagonia central, Argentina
No full textEn este trabajo se reporta por primera vez la presencia de estromatolitos en afloramientos cretácicos en la localidad nacientes del río Chico en la Cuenca del Golfo San Jorge. Los mismos se encuentran en la parte superior de la Formación Lago Colhué Huapi (Coniaciano-Maastrichtiano), unidad correspondiente al Grupo Chubut. La presencia de, hasta el momento, cuatro estructuras interpretadas como estromatolitos en esta localidad, no solo tiene importancia por ser el primer registro en la cuenca, sino porque contribuye al conocimiento de estas bioconstrucciones en los ambientes continentales. Se caracteriza y discute en detalle el estromatolito denominado E1, que se encuentra asociado a un abundante y diverso registro fósil, representado por palinomorfos, fragmentos de troncos silicificados, restos de dinosaurios y cáscaras de huevos de dinosaurios. El estudio, integrado fundamentalmente con el polen y las esporas registradas, es importante para las interpretaciones paleoambientales del sitio y contribuye al entendimiento paleoecológico y paleoclimático del intervalo estratigráfico más moderno del Grupo Chubutpp.162-17
Evaluación de peligro por remoción en masa, sector de Torobayo, comuna de Valdivia, Región de Los Ríos
No full textRevisor: Carlos Johnson N.16 p
Pedogenic and subaerial exposure microfabrics in a late Carboniferous-early Permian carbonate-volcanic lacustrine-palustrine system (San Ignacio Formation, Frontal Cordillera, Argentina)
No full textIn the Argentinian Andes (Frontal Cordillera) the upper part of the late Carboniferous-early Permian San Ignacio Formation is made up of lacustrine-palustrine microbial carbonates and interbedded volcanic deposits. In this lacustrine-palustrine environment a natural monospecific forest was developed. The deposits of this sedimentaryvolcanic succession were repeatedly subjected to subaerial exposure and modified by pedogenesis to varying degrees giving rise to paleosoils development. Diagenetic microfabrics were well preserved in the carbonates and volcanic rocks. The carbonate microfabrics comprise a wide spectrum of features consisting of root marks and stumps-related structures (rhizoliths, alveolar texture, tunnel-like structures and coprolites of arthropods), pisoids, coated grains and pseudomicrokarst, cracking, brecciated and nodular fabrics, and grainification also occur corresponding to different stages in the pedogenic evolution. Meteoric dissolution and cementation processes are observed; examples are well identified by scanning electron microscope showing silica-filled voids in partially dissolved carbonates and growths of inorganic carbonate microcrystals or of microbial origin in voids. Other different types of cements can be seen such as discontinuous carbonate crusts, ribbon spar, cavities with silt infillings and pendant cements. The whole set of these microfabrics are indicative of wetting, desiccation and meteoric conditions (vadose and phreatic). The abundance of plant roots and associated micro-organisms mainly of bacterial origin (micro-rods, short rod-shapes, nano-fibres, filaments and nano-spheres) played an important role in the pedogenic and subaerial diagenetic processes affecting these deposits. The immature character of the paleosoils and absence of calcretes point out to short intervals of subaerial exposure due to oscillating fluctuations in water level, intermittent volcanic supply, tectonic subsidence and oscillating climatic conditions. The whole of the macro and microfabrics reveals that the prevailing weather could correspond to an intermediate between semi-arid to sub-humid, however the alternating wetting and drying conditions in which the fossil forest developed and the abundance and diversity of micro-organisms, suggest a transition to sub-humid climate conditions.pp.275-29