We present a new three-dimensional density model of the Central Andes characterizing the structure and composition of the lithosphere together with a geodynamic simulation subjected to continental ...intraplate shortening. The principal aim of this study is to assess the link between heterogeneities in the lithosphere and different deformation patterns and styles along the orogen-foreland system of the Central Andes. First, we performed a 3D integration of new geological and geophysical data with previous models through forward modelling of Bouguer anomalies. Subsequently, a geodynamic model was set-up and parametrized from the previously obtained 3D structure and composition. We do not find a unambigous correlation between the resulting density configuration and terrane boundaries proposed by other authors. Our models reproduce the observed Bouguer anomaly and deformation patterns in the foreland. We find that thin-skinned deformation in the Subandean fold-and thrust belt is controlled by a thick sedimentary layer and coeval underthrusting of thin crust of the foreland beneath the thick crust of the Andean Plateau. In the adjacent thick-skinned deformation province of the inverted Cretaceous extensional Santa Barbara System sedimentary strata are much thinner and crustal thickness transitions from greater values in the Andean to a more reduced thickness in the foreland. Our results show that deformation processes occur where the highest gradients of lithospheric strength are present between the orogen and the foreland, thus suggesting a spatial correlation between deformation and lithospheric strength.
•Density heterogeneities correlate with different tectonic evolution and processes.•The lithosphere is weak in the orogen and strong in the foreland and forearc.•Deformation localizes in the transition between weak and strong lithosphere.
We present three‐dimensional (3D) models of the present‐day steady‐state conductive thermal field and strength distribution in the lithosphere beneath the Central Andes. Our primary objective was to ...investigate the influence that the structure of the Central Andean lithosphere has on its thermal and rheological state, and the relationship between the latter and the active deformation in the region. We used our previous data‐driven and gravity‐constrained 3D density model as starting point for the calculations. We first assigned lithology‐derived thermal and rheological properties to the different divisions of the density model and defined temperature boundary conditions. We then calculated the 3D steady‐state conductive thermal field and the maximum differential stresses for both brittle and ductile behaviors. We find that the thickness and composition of the crust are the main factors affecting the modeled thermal field, and consequently also the strength distribution. The orogen is characterized by a thick felsic crust with elevated temperatures and a low integrated strength, whereas the foreland and forearc are underlain by a more mafic and thinner crust with lower temperatures and a higher integrated strength. We find that most of the intraplate deformation coincides spatially with the steepest strength gradients and suggest that the high potential energy of the orogen together with the presence of rheological lateral heterogeneities produce high compressional stresses and strong strain localization along the margins of the orogen. We interpret earthquakes within the modeled ductile field to be related to the weakening effect of long‐lived faults and/or the presence of seismic asperities.
Key Points
The thermal and rheological state of the Central Andean lithosphere is mainly controlled by the thickness and composition of the crust
Active intraplate deformation is located along the margins of the orogen and spatially coincides with the highest strength gradients
Earthquakes below the modeled brittle‐ductile transition suggest a possible weakening of the lithosphere by long‐lived deep‐seated faults
The Quaternary infilling of a circular structure located in Bajada del Diablo,Chubut Province,Argentina has been proposed as a crater strewn field in previous studies.Here we report the finding of ...about 65 microspherules collected in a trench excavated in the center of the structure.The majority of handpicked specimens are single,but some of them exhibit compound forms.The single specimens are spherical with a mean size of 137 nm,whereas the more complex samples show peduncles and drop shapes.Dendritic crystal growth is recognized in the internal structure of some broken microspherules.Preliminary chemical composition from the surface and center of microspherules was determined by energy dispersive spectrometry employing EDS.Quantitative EMPA and XRD analysis indicate that the microspherules are mainly composed of Fe and O with magnetite,Fe~0 with subordinate wiistite.Following consideration of possible anthropogenic and volcanic origins,these spherulites are ascribed to an extraterrestrial input.An accumulation rate of 47 microspherules per m~2/yr is estimated for the studied sediments.This value is two orders of magnitude higher than the reference flux for cosmic dust estimated for the last 1 Ma in the Transantarctic Mountains.The microspherules might have been generated as a byproduct of asteroid entry in the atmosphere.
•Tonian to middle Cambrian rocks crop out at the Sauce Chico Complex, Ventania System.•The studied rocks are controlled by paramagnetic phases, largely secondary sericite.•The crystalline basement is ...compartmentalized laterally by tear faults.•Strike-slip movements of such faults generated local rotation of blocks.•Differential displacement of blocks could have generated the curvature of the fold belt.
The tectonic evolution of the Ventania System fold and thrust belt and the origin of its curvature have been the subject of debates for decades. The Gondwanide Orogeny generated the mylonitization of its Tonian–middle Cambrian basement (i.e., Sauce Chico Complex), accompanied by an intense hydrolysis which produced secondary muscovite (i.e., sericite), and the folding of the overlying Paleozoic sedimentary cover. To evaluate the structural and tectonic evolution of the Ventania System as a result of the interaction of its basement with the Río de la Plata Craton, we studied the anisotropy of magnetic susceptibility (AMS) and rock magnetism on samples of the Sauce Chico Complex. Rock magnetic studies suggest that paramagnetic minerals are the main carriers in the entire Sauce Chico Complex. We suggest that our results reflect secondary muscovite generation due to mylonitization. AMS data reveal that the orientation of the magnetic foliation coincides to a large extent with the rock foliation. However, magnetic and rock foliation orientations are not uniform among the different sampled units, displaying strikes between N 320° (NW) and N 345° (NNW) on average. Localities with different orientations are separated by regional strike-slip structures, referred to as tear faults, which have also been reported and interpreted by previous authors. According to this, we suggest that the variations detected between the orientation of the magnetic and rock foliations of the different basement units may be the result of the rotation of crustal blocks bounded by tear faults. We also propose the existence of a new tear fault not previously recognized. Furthermore, a tear fault of regional character, known as the Sauce Chico Tear Fault, juxtaposes two distinct crustal domains. The differential displacement of such domains could have contributed not only to different structural styles between blocks on both sides of the Sauce Chico Tear Fault, but also to the curved shape of the Ventania System during the progression of the Gondwanide deformation.
The evolution of the Paleozoic Claromecó Basin is intimately related to contemporaneous tectonic events in the Sierras Australes and Patagonia (Argentina). These deformation and tectonomagmatic ...processes record, in turn, the evolution of the southwestern margin of Gondwana during the Paleozoic, which is still controversial and has been alternatively interpreted as the result of different subduction-related, extensional or collisional events. The Claromecó Basin, thus, comprises a key area to evaluate possible mechanisms of subsidence, which could have allowed creating the necessary accommodation space for the sedimentary pile. For this purpose, 2D isostatic flexural models, 2.5D magnetic and gravimetric models, 1D backstripping and 3D gravity inversion were carried out in this work. Results suggest that the Claromecó Basin could have initially developed during back-arc extension in a retreating subduction boundary, followed by a period of anomalous subsidence associated with the load exerted by an ancient subducted slab. Dynamic subsidence, thus, played a major role during this period, resulting from subduction processes along the proto-Pacific margin of Gondwana. Later on, the basin evolution was dominated by the load constructed by the deformation that generated the Sierras Australes.
•Southwestern margin of Gondwana, Paleozoic Claromecó Basin evolution•Backstripping; flexural, magnetic and gravimetric forward models; gravity inversion•Initial back-arc extension, possibly in a retreating subduction boundary•~3 km of tectonic/dynamic subsidence, possibly related to a fossil slab•Foreland basin, in response to Sierras Australes load, since Middle-Late Permian
The evolution of the Paleozoic Claromecó Basin is intimately related to contemporaneous tectonic events in the Sierras Australes and Patagonia (Argentina). These deformation and tectonomagmatic ...processes record, in turn, the evolution of the southwestern margin of Gondwana during the Paleozoic, which is still controversial and has been alternatively interpreted as the result of different subduction-related, extensional or collisional events. The Claromecó Basin, thus, comprises a key area to evaluate possible mechanisms of subsidence, which could have allowed creating the necessary accommodation space for the sedimentary pile. For this purpose, 2D isostatic flexural models, 2.5D magnetic and gravimetric models, 1D backstripping and 3D gravity inversion were carried out in this work. Results suggest that the Claromecó Basin could have initially developed during back-arc extension in a retreating subduction boundary, followed by a period of anomalous subsidence associated with the load exerted by an ancient subducted slab. Dynamic subsidence, thus, played a major role during this period, resulting from subduction processes along the proto-Pacific margin of Gondwana. Later on, the basin evolution was dominated by the load constructed by the deformation that generated the Sierras Australes.
Along the central Andes a pattern of vertical axis rotations (CARP) has been paleomagnetically identified. These rotations, which are counterclockwise north of Arica and clockwise to the south, have ...been detected in Mesozoic and Cenozoic rocks cropping out in the Andean forearc and the Altiplano‐Puna. Different models have been proposed to explain the geodynamic evolution of the central Andes, but the origin of these rotations remains controversial. Such models involve oroclinal bending and/or local block rotations. This lack of agreement is partly due to the scarce paleomagnetic database, particularly for the Argentine Puna. Here we report new paleomagnetic data obtained in the northern Argentine Puna from 57 sites drilled from Miocene volcaniclastic rocks and 12 sites from the Cretaceous‐Eocene Salta Group. It was determined that (1) the Morro Blanco area did not undergo significant vertical axis rotation since at least the middle Miocene; (2) the Loma Blanca mine area underwent a clockwise vertical axis rotation of ∼10° later than the late Miocene; and (3) the Coranzulí area underwent a clockwise vertical axis rotation of ∼40° later than the Cretaceous‐Eocene. The central Andes database was analyzed, and some features of the CARP were determined. These features were explained considering “domino”‐style models for the forearc and a local block rotation model in response to penetrative shear for the Altiplano‐Puna. Penetrative shear would occur along a high electrical conductivity zone. However, the possibility of the existence of an oroclinal bending of <5° cannot be discarded.
Objectives
Globalization and migration are increasing the demand for reports in different languages. We aimed to examine if structured reports created by non-German-speaking radiologists with ...multilingual templates show significant differences in quality to structured reports and free-text reports by German native speakers.
Methods
We used structured templates that allow radiologists to report in their mother tongue and then switch the report language to German or English automatically using proprietary software. German- and English-speaking radiology residents created structured reports in both German and English with these templates. Reports for three different exam types were created (intensive care chest x-ray, shoulder x-ray specifically for degenerative processes, and CT pulmonary angiogram for pulmonary embolism). The report quality of automatically translated German structured reports by English-speaking radiologists and German structured reports by German radiologists was then evaluated by German clinicians with a standardized questionnaire. The questionnaire was designed to assess attributes including content, comprehensibility, clinical consequences, and overall quality.
Results
Structured reports by English-speaking radiologists that were automatically translated into German and German structured reports by German radiologists both received very high or high overall quality ratings in the majority of cases, showing no significant differences in quality. Likewise, no significant differences were observed between the two report types regarding comprehensibility and clinical consequences. Structured reports by German radiologists received significantly better ratings for overall quality and comprehensibility compared to free-text reports by German radiologists.
Conclusions
Multilingual structured reporting templates may serve as a feasible tool for creating high-quality radiology reports in foreign languages.
Key Points
• Multilingualism in structured reporting templates can be a useful tool for creating high-quality radiology reports in foreign languages.
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German reports created with multilingual structured reporting templates by English-speaking radiologists and German structured reports by German radiologists exhibit no significant differences in overall report quality.
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Multilingual structured reporting templates can help radiologists overcome communication barriers and facilitate teleradiology.
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