Repositorio Digital Sernageomin
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Remociones en masa por precipitaciones en Vicuña, Paihuano y Río Hurtado, febrero 2023, Región de Coquimbo
No full textInforme Técnico -- Unidad Ejecutora: Unidad de Asistencias Técnicas y Emergencias Geológicas, Santiago19 p
A peculiar specimen of Panochthus (Xenarthra, Glyptodontidae) from the Eastern Cordillera, Bolivia
No full textPanochthus Burmeister is one of the most diversified and widely distributed glyptodonts in the Pleistocene of South America, which includes areas located at high altitudes (>4,000 m a.s.l.). Within the genus, eight species (P. intermedius Lydekker, P. subintermedius Castellanos, P. tuberculatus (Owen), P. frenzelianus Ameghino, P. greslebini Castellanos, P. jaguaribensis Moreira, P. hipsilis Zurita, Zamorano, Scillato-Yané, Fidel, Iriondo and Gillette, and P. florensis Brambilla, López and Parent) are currently recognized. Here, we report a dorsal carapace (UATF-V n/n) from the Pleistocene of the surroundings of Potosí, Bolivia, that shows some morphological particularities when compared to the carapace of P. intermedius, P. frenzelianus, P. subintermedius and P. tuberculatus, including: a) its maximum dorso-ventral diameter is at the anterior half, meanwhile in other species is at mid-point (e.g., Propalaehoplophorus) or at posterior half (e.g., Glyptodon); b) the dorsal profile is different in comparison to other glyptodonts (e.g., Glyptodon, Glyptotherium, Neosclerocalyptus, Propalaehoplophorus); c) the ornamentation pattern of the osteoderms shows a central figure surrounded by small polygonal figures along the most exposed surface of the carapace (except for the mid-dorsal region that shows reticular ornamentation pattern), being different from that of the remaining species: of Panochthus, in which central figures are limited to the caudal/cephalic and most lateral regions of the carapace. In summary, the combination of characters suggests that it could belong to a new species or, alternatively, to P. floriensis or P. jaguaribensis in which the dorsal carapace is not yet known. The phylogenetic analysis confirms its basal position among Panochthus and highlights the importance of these high elevation areas of the Andes in South America in order to understand the complex evolutionary history of glyptodonts.pp.57-7
Remociones en masa : ¿Cuáles son las zonas más sensibles a sufrir estos procesos y cómo podemos minimizar sus consecuencias?
No full textCorresponde a anexo de BSNGM 16319 DVD: Zonificación de áreas expuestas a peligros de remoción en masa en la región de Los Ríos ; Xterrae Geologí
Freshwater bivalves and their environmental conditions in a Jurassic lacustrine system (Cañadón Asfalto Formation) from Patagonia, Argentina
No full textAt the moment, two freshwater bivalve species were described for the continental Jurassic of Patagonia: Diplodon simplex Morton and Diplodon matildensis Morton from La Matilde Formation of the Santa Cruz province. The Cañadón Asfalto Formation located in Chubut province exhibits a high diverse invertebrate fossil fauna preserved mainly in lacustrine facies, which includes clam shrimps, bivalves, gastropods, ostracods and insects. However, few studies have been carried out on freshwater bivalve of this geological unit. In this work, a morphological description of bivalve assemblage and paleoenvironment analysis from the Cañadón Asfalto Formation was performed. Forty samples were collected from three stratigraphic levels at the Cañadón Asfalto locality. These levels are ash fall tuffs rich in glass particles accumulated in a lacustrine system with development of microbial activity. Morphological analyzes of outline and sizes were performed at each level. Our results showing the smallest-sized association of unionids recorded for the Jurassic time with size ranging from 7.6-11.7 mm long and 5.2-7.6 mm high. The environmental influence of pyroclastic falls could have played an important role in the development of the sizes of populations and shells.pp.248-26
Origin of the vanadium-uranium geochemical anomalies in the limestones of the Puyango Formation, La Sota (Ecuador) : Preliminary results
No full textVanadium (V) and uranium (U) are critical elements for the energy and technology industry. They are characterized by low abundance in the earth crust´s rocks, but can be concentrated and give rise to sedimentary mineral deposits as a result of redox processes during sedimentation and diagenesis. The anomalies of V-U in La Sota, Ecuador, are found in black limestones and black calcareous shales of Cretaceous age. Here we present the results of a geochemical study and a multivariate geostatistical analysis, which enables us to infer four different associations: 1) disseminated organic matter in the limestones that hold V and Zn, probably in the form of organometallic complexes; 2) phosphatic minerals and concentrations of U, HREE and Ni, which may be incorporated as trace elements in the phosphates, compatible with sedimentation in an anoxic environment; 3) Ca in carbonates from a marine environment; and, 4) litophile elements associated with detritic minerals, such as quartz, plagioclase, feldspar, micas, clays and oxyhydroxides of Fe-Mn-Ti, produced by weathering and erosion. Our findings suggest that V is associated mainly with the organic matter of marine origin in the bituminous limestones, while U is associated with P, thereby indicating the formation of uraniferous phosphates during sedimentation.pp.75-9
Garnet composition from the Reflejos de Mar LCT-pegmatite, Ancasti district, Argentina and its implication for exploration of primary deposits of lithium
No full textThe Reflejos de Mar Li-pegmatite, located in northwestern Argentina, is part of the Villismán pegmatite group, Ancasti District, Pampean Pegmatite Province. Four garnet crystals from the outermost part of the pegmatite were analyzed by major and minor elements (SiO2, TiO2, Al2O3, Cr2O3, MgO, CaO, MnO, FeO) using electron microprobe. The pegmatite belongs to the rare-element class, spodumene type, LCT (Li-Cs-Ta) petrogenetic family. Based on their Mn and Fe contents, the analyzed garnet can be assigned to the spessartine-almandine serie. The cores and rims of the analyzed garnets show significant differences for the divalent components in VIII-coordination, especially, Mn and Fe. The average MnO and FeO contents in the cores of the grains is 34.6 and 8.29 wt%, respectively, while in the rims is 29.31 and 12.95 wt%, respectively. The Fe/Mn ratio at the core of the grains is 0.24 while at the rims it is 0.44. Cr2O3 and TiO2 contents are very low (˂0.17 wt%) and the values of SiO2 and Al2O3 are ~36 and ~21 wt%, respectively. The mean chemical and molecular formulas of the core can be expressed: [(Mn2.40 Fe0.57 Ca0.02 Mg0.02)3.01 (Al1.99 Cr0.002)2.00 (Si2.99 Ti0.01)3.00 O12]; {Sps79.8 Alm18.9 Grs0.7 Prp0.5}; and the rim as: [(Mn2.04 Fe0.89 Ca0.05 Mg0.04)3.02 (Al2.00 Cr0.002)2.00 (Si2.98 Ti0.005)3.00 O12]; {Sps67.6 Alm29.5 Grs1.6 Prp1.3}. The chemical composition of garnet from the Reflejos de Mar pegmatite is similar to other worldwide examples in similar rocks, especially LCT pegmatites, which are highly evolved and associated with Li mineralization. Therefore, its composition could be used as an additional tool in the exploration of Li-bearing pegmatites in the Pampean Pegmatite Province. The differences in Fe-Mn contents between core and rim of the crystals would be controlled by variations in composition of the pegmatitic melt and, in addition, by the simultaneous precipitation of other mineral phases, for example, schorl and Mn-Fe-bearing phosphates.pp.150-16
Visita técnica para evaluar estado de conservación de Monumento Histórico Huellas de Dinosaurios, post aluvión enero 2023. Comuna de San Fernando, Región del Libertador General Bernardo O’Higgins
No full textRevisor: Carolina Jara. -- Informe Técnico -- Unidades Ejecutoras: Unidad de Asistencias Técnicas y Emergencias Geológicas, Santiago. Unidad de Geopatrimonio27 p
Evaluación por remoción en masa en sectores Centro, Playa Ancha y Junquillo, comuna de Tortel, región de Aysén del General Carlos Ibáñez del Campo
Get PDFInforme Técnico -- Unidad Ejecutora: Oficina Técnica de Coyhaique, Unidad de Asistencias Técnicas y Emergencias Geológicas13 p
Geología de las áreas Cupo-Toconce y Cerros de Tocorpuri, región de Antofagasta
Get PDFContiene Anexos: Anexo I.Dataciones Radiométricas ; Anexo II.Fósiles ; Anexo III.Análisis Químicos ; Anexo IV.Difractometría de Rayos X ; Anexo V.Microscopía Electrónica de Barrido ; Anexo VI.Depósitos Minerales ; Escala: 1:100.000 ; Coordenadas: 22°00´ y 22°30´ S / 68°30’ y 68°00’ E223 p