The Cretaceous/Paleogene （K/Pg） Working Group, after many years of studies, voted to define the Global Stratotype Section and Point （GSSP） for the base of the Danian Stage at the base of the boundary clay at a sec...The Cretaceous/Paleogene （K/Pg） Working Group, after many years of studies, voted to define the Global Stratotype Section and Point （GSSP） for the base of the Danian Stage at the base of the boundary clay at a section near El Kef Tunisia. The GSSP was approved by the International Commission on Stratigraphy （ICS） and ratified by the International Union of Geological Sciences （IUGS） in 1991. Nevertheless, the GSSP was not officially published, although some papers dealing with geological aspects of the K/Pg boundary at El Kef have been published and this is quite well known. In April 2006, the GSSP was revisited, a marker was put in place and protection of the site was requested. Many correlation criteria are present at the GSSP of which the most useful are the meteorite impact evidence （iridium anomaly, Ni-rich spinel, etc.） and the mass extinction of planktic micro- and nannofossils. This event coincides with the GSSP, allowing us to propose that the K/Pg boundary is marked exactly by the moment of the meteorite impact, which implies that all the sediments generated by the impact belong to the Danian. This definition solves problems of correlation in the Yucatan peninsula （Mexico） and its surroundings.展开更多
The Central Patagonian Andes is a particular segment of the Andean Cordillera that has been subjected to the subduction of two spreading ridges during Eocene and Neogene times. In order to understand the Cenozoic geol...The Central Patagonian Andes is a particular segment of the Andean Cordillera that has been subjected to the subduction of two spreading ridges during Eocene and Neogene times. In order to understand the Cenozoic geologic evolution of the Central Patagonian Andes, we carried out geochronologic(U-Pb and^(40)Ar/^(39)Ar), provenance, stratigraphic, sedimentologic, and geochemical studies on the sedimentary and volcanic Cenozoic deposits that crop out in the Meseta Guadal and Chile Chico areas(～47°S). Our data indicate the presence of a nearly complete Cenozoic record, which refutes previous interpretations of a hiatus during the middle Eocene-late Oligocene in the Central Patagonian Andes. Our study suggests that the fluvial strata of the Ligorio Marquez Formation and the flood basalts of the Basaltos Inferiores de la Meseta Chile Chico Formation were deposited in an extensional setting related to the subduction of the Aluk-Farallon spreading ridge during the late Paleocene-Eocene. Geochemical data on volcanic rocks interbedded with fluvial strata of the San Jose Formation suggest that this unit was deposited in an extensional setting during the middle Eocene to late Oligocene. Progressive crustal thinning allowed the transgression of marine waters of Atlantic origin and deposition of the upper Oligocene-lower Miocene Guadal Formation. The fluvial synorogenic strata of the Santa Cruz Formation were deposited as a consequence of an important phase of compressive deformation and Andean uplift during the early-middle Miocene. Finally, alkali flood basalts of the late middle to late Miocene Basaltos Superiores de la Meseta Chile Chico Formation were extruded in the area in response to the suduction of the Chile Ridge under an extensional regime. Our studies indicate that the tectonic evolution of the Central Patagonian Andes is similar to that of the North Patagonian Andes and appears to differ from that of the Southern Patagonian Andes, which is thought to have been the subject of continuous compressive deformation since the late Early Cretaceous.展开更多
The fruits and vegetables sector in Ecuador despite its gradual growth in local and international markets has captured the interest of state institutions and academic centers who have focused their studies on agronomi...The fruits and vegetables sector in Ecuador despite its gradual growth in local and international markets has captured the interest of state institutions and academic centers who have focused their studies on agronomic aspects of non-traditional products without considering socioeconomic, productive and performance problems;such is the case of goldenberry value chain. To this extent, the aim of this article was to present an analysis of goldenberry value chain in Ecuador through the identification of stages, agents, flows and activities (primary and support) from the socioeconomic and productive point of view for which a systematic methodology was used involving aspects of the agroeconomic process. As a result, it was determined that goldenberry value chain in the production and postproduction stages requires the diversification of marketing channels, the implementation of refrigerated storage modules located in the supply centers, the strengthening of associative and/or cooperative structures;and the productive planning programs to provide a potential competitive advantage.展开更多
Changes in the morphology and mineralogy of speleothems (flowstones) clearly respond to climate-related phenomena, such as drip rate variability and temperature-modulated cave ventilation. Detailed petrographic observ...Changes in the morphology and mineralogy of speleothems (flowstones) clearly respond to climate-related phenomena, such as drip rate variability and temperature-modulated cave ventilation. Detailed petrographic observations have been coupled with <em><em style="font-family:Verdana;white-space:normal;"><em style="font-family:Verdana;white-space:normal;">δ</em></em></em><sup style="font-family:Verdana;white-space:normal;">18</sup><span style="font-family:Verdana;white-space:normal;">O</span><sup></sup> and <span style="font-size:12px;font-family:Verdana;"><em>δ</em></span><span style="font-size:12px;font-family:Verdana;"><sup>13</sup>C values. Fabrics may show changes related to variations in supersaturation, drip rate or input of detrital particles or organic compounds. Fabrics formed under relatively constant and regular drips (columnar compact, open and elongated) show similar <em>δ</em><sup>18</sup>O and <em>δ</em><sup>13</sup>C values, which are more negative than those of micrite and microsparite. The combination of internal microstratigraphy studies and isotopic data (<em>δ</em><sup>18</sup>O and <em>δ</em><sup>13</sup>C) from two flowstones collected from two caves in the north of Almeria province (SE Spain), suggest a spectrum of environmental conditions ranging from wetter to drier periods. Both records constitute a very useful tool for screening and interpreting high-resolution paleoclimate reconstructions.</span>展开更多
An analytical model is presented for seismic analysis of triple friction pendulum bearings and validated using 81 bearing tests, each subjected to three cycles, with a duration of 12 seconds and using 250, 200 and 100...An analytical model is presented for seismic analysis of triple friction pendulum bearings and validated using 81 bearing tests, each subjected to three cycles, with a duration of 12 seconds and using 250, 200 and 100 tons vertical loads. The main objective is to develop formulas for bilinear behavior using maximum, average and minimum friction coefficients to check which is the closest to the real behavior in the laboratory tests and comparatives curves plotting to observe the standard derivation. Parameters such as friction coefficients, effective stiffness, damping factor and vibration periods are analyzed to understand the structural behavior of the TPF bearings.展开更多
Compositionally zoned plutons, both layered and concentrically arranged, provide granitic exposures where the mechanisms and timing of the magmatic emplacement processes can be studied. The importance of in-situ geoch...Compositionally zoned plutons, both layered and concentrically arranged, provide granitic exposures where the mechanisms and timing of the magmatic emplacement processes can be studied. The importance of in-situ geochemical differentiation and the magma replenishment rates are revealed by geochemistry and field relations, together with the increasingly accurate U-Pb geochronology, which has promoted the knowledge about the pluton incremental assembly theories.The Flamenco pluton, located in the Coastal Range of northern Chile, is part of the Upper Triassic to Early Cretaceous Andean intrusives formed in the western active margin of South America, and present a normal zoned structure with mafic magmatic facies(mostly gabbros and Qtz-diorites) close to the contacts with the host metasediments, and tonalites, granodiorites and granites in the inner areas. A combined study of the field relations, geochemistry and zircon geochronology of the magmatic facies was applied to determine the emplacement sequence of the Flamenco pluton, revealing three distinguishable domains separated by metasedimentary septa. The SW area is constituted by mostly homogeneous leucocratic granodiorites that yielded an age of 213 Ma as the best estimation for their emplacement age. Distinctive geochemical characteristics, such as the absence of an Eu anomaly, the depletion in HREE, or the highest Sr, Sr/Y and Ce/Yb values among the granodioritic facies of the pluton,involve lower T and/or higher P conditions at the magmatic source according to experimental studies.These conditions were established during an early stage of the Andean magmatic arc building that is firstly defined here as Upper Triassic. The NW and E domains of the pluton were sequentially emplaced between 194 Ma and 186 Ma and both the field relations and the detailed geochronological results suggest that the mafic facies intruded latter in the emplacement sequence. To the NW, Qtz-dioritic and gabbroic externally emplaced pulses gave a younger crystallization age of 186.3 ± 1.8 Ma, and promoted the granoblastic textures and metamorphic zircon overgrowths that characterize the granodiorites located in the contact with the intermediate and felsic inner magmas, which yielded a best estimation of their emplacement age of 192 士 1.5 Ma. On the other hand, in the eastern domain, magma-magma relations are observed between gabbros and previously intruded tonalites and granodiorites. Both the mafic and intermediate facies show two main subgroups of ages that yielded 194.7 土 1.5 Ma to188.3 ± 2.1 Ma and 193.1 ± 2.2 Ma to 185.5 ± 1.4 Ma respectively. These differences are related to the variations in the magmatic addition rates, which may extend the super-solidus conditions in the eastern domain of the magmatic reservoir as is confirmed by the wider age ranges yielded by these magmatic facies. Zircon overgrowths in the host rocks yield similar ages(around 220 Ma and 205 Ma) than the oldest results obtained in the intrusive facies, indicating that metamorphism correlates with the initial stages of plutonic emplacement.Geochronological results differ between 9 Myr and 41 Myr in the eight studied samples for noninherited ages and gave very close mean ages(within analytical uncertainty) for all the intrusive units. However, we examine other characteristics such as zircon morphology, internal structure,geochemistry and statistical data to assess if the scattering of the geochronological data may be related to the different processes involved in the construction of the Flamenco pluton. We concluded that this detailed study of U-Pb zircon ages, including individual and significative groups of analyses, is useful to determine accurately the emplacement sequence and the genetic relation between the intrusive units,together with the evidences depicted by the geochemistry and field relations.展开更多
The purpose of the research was to obtain the mass wasting hazard map for the state of Vargas, central coast of Venezuela, using GIS technology. The work was developed through the heuristic method with the generation ...The purpose of the research was to obtain the mass wasting hazard map for the state of Vargas, central coast of Venezuela, using GIS technology. The work was developed through the heuristic method with the generation of thematic digital maps, univariate statistical treatment, weighting of each variable and quantifying the relationship of each parameter unit regarding mass wasting processes. The algorithm designed to perform map algebra was designed using the variables: surface geology, slope, slope orientation, terrain curvature, moisture topographic index, power index surface flow rate and capacity sediment transport and the rate normalized difference vegetation. The results show a distribution of landslide hazard with the highest values in the west central part of Vargas state, where the dominant lithology is incompetent, and combined with topographic elements, determining high instability, meanwhile the lower hazard areas were found in specific areas such as the middle watershed areas east of the state. The calibration of this model shows a reliability of 80%, so it is highly advisable to use the information generated in this work by governmental and non-governmental organizations in the planning, management and use of land.展开更多
The accurate identification of dinosaur egg accumulations as nests or clutches is crucial for understanding the reproductive behaviour of these extinct species.However,existing methods often rely on the presence of co...The accurate identification of dinosaur egg accumulations as nests or clutches is crucial for understanding the reproductive behaviour of these extinct species.However,existing methods often rely on the presence of complete eggs and embryo remains,and sedimentological criteria that are only applicable to well-structured sediments.In this study,we introduce an innovative approach to characterize egg accumulations in structureless sediments,where traditional nest structures may not be preserved.Our methodology employs a unique combination of sedimentological,taphonomic,geochemical,and geophysical proxies for the study of egg accumulations.We applied this approach to the egg accumulation from Paimogo(Jurassic,Portugal),traditionally interpreted as a nest.Our findings reveal that the Paimogo egg assemblage is a secondary deposit,resulting from a flooding event in a fluvial plain that dismantled several allosauroid and crocodylomorph clutches.The eggshell vapor conductance results,coupled with sedimentological evidence,suggest that allosauroid dinosaurs buried their eggs in the dry terrain of overbank areas close to a main channel during the breeding season,likely during the dry season to prevent the embryos from drowning.This research underscores the necessity of multidisciplinary approaches in interpreting egg accumulations and offers a novel methodology for studying these accumulations in structureless sediments.Our findings provide new insights into the breeding behaviour and nesting preferences of these extinct organisms,contributing to our understanding of dinosaur ecology.展开更多
Many studies propose a significant shift in the tectonic and paleogeographic evolution of the Andes in south-central Chile and Argentina during the Late Cretaceous.It has been proposed that the preceding Jurassic-Earl...Many studies propose a significant shift in the tectonic and paleogeographic evolution of the Andes in south-central Chile and Argentina during the Late Cretaceous.It has been proposed that the preceding Jurassic-Early Cretaceous extensional regime that resulted in a low-relief volcanic arc and the backarc Neuquén basin came to an end,giving way to shortening and Andean growth from the Late Cretaceous onward.Nevertheless,there are disagreements regarding the timing and nature of this transition to Andean orogenesis.To address these issues,we conducted geochronologic(U-Pb and^(40)Ar/&(39)Ar),sedimentologic,and structural studies on Mesozoic-Cenozoic sedimentary and volcanic rocks in the Río Maule area(Principal Cordillera,Chile,36°S).From our findings and prior analyses,we propose the following tectono-stratigraphic evolution of the region.(1)Marine deposition of the Tithonian-Hauterivian Baños del Flaco Formation took place in an extensional backarc basin.(2)After a~40 Myr hiatus,fluvial deposits of the Colimapu Formation and volcanic rocks of the Plan de los Yeuques Formation accumulated during the Cenomanian-Danian.Whereas the Colimapu Formation displays evidence of syndepositional shortening,the Plan de los Yeuques Formation exhibits synextensional growth strata.Contrary to other studies,our results suggest that the Chilean part of the Principal Cordillera was largely a zone of active deposition rather than an elevated fold-thrust belt during the Late Cretaceous.We propose that sedimentation occurred within a series of relatively stable intermontane subbasins generated by shortening,followed by extension.(3)After a~20 Myr hiatus,middle Eocene to early Miocene(Lutetian-Aquitanian)accumulation of a thick succession of andesitic lavas and minor clastic sediments of the Abanico Formation occurred in an intraarc extensional basin.(4)Finally,major shortening and uplift of previously deposited Mesozoic-Cenozoic rocks took place throughout the Neogene.This phase constituted the primary contractional deformation in the Andes of south-central Chile and Argentina.In terms of the transition to early Andean deformation,we propose that structural deformation did not generate a major,regional-scale fold-thrust belt during the late Albian-Santonian.Modest extension,tectonic quiescence,or low-magnitude shortening seem to have dominated during the early to middle Cenozoic.展开更多
The northern part of the eastern margin of the extensional Neogene Teruel Basin(central-eastern Spain)consists of a non-linear,zigzag fault zone made of alternating ca.2 km long,NNW-SSE trending segments and shorter N...The northern part of the eastern margin of the extensional Neogene Teruel Basin(central-eastern Spain)consists of a non-linear,zigzag fault zone made of alternating ca.2 km long,NNW-SSE trending segments and shorter NNESSW ones.Good outcrop conditions made possible a comprehensive integrated stratigraphic and structural study,especially focused on coarse clastic sediments deposited along the basin margin.Well-exposed stratal relationships with boundary faults,allowed the analysis of tectonic influence on sedimentation.Synsedimentary deformation includes growth faulting,rollover anticlines,and monoclines and associated onlap stratal terminations,angular unconformities,and other complex growth strata geometries.One of them is the onlap-over-rollover bed arrangement described here for the first time,which reveals the competition between tectonic subsidence and sedimentary supply.Both,the structural inheritance(dense Mesozoic fracture grid)and the dominant,nearly‘multidirectional’(σ1 vertical,σ2≈σ3),Pliocene extensional regime withσ3 close to E-W,are considered to have controlled the margin structure and evolution.Tectono-stratigraphic evolution includes:(i)reactivation of inherited NNW-SSE faults and development of W-SW-directed small alluvial fans(SAF)while NNE-SSW segments acted as gentle relay ramp zones;(ii)progressive activation of NNE-SSW faults and development of NW-directed very small alluvial fans(VSAF);during stages i and ii sediments were trapped close to the margin,avoiding widespread progradation;(iii)linking of NNW-SSE and NNE-SSW structural segments,overall basin sinking and widespread alluvial progradation;(iv)fault activity attenuation and alluvial retrogradation.The particular structure and kinematic evolution of this margin controlled alluvial system patterns.Size of alluvial fans,directly set up at the border faults,was conditioned by the narrowness of the margin,small catchment areas,and proximity between faults,which prevented the development of large alluvial fans.The size of the relay zones,only a few hundred meters wide,acted in the same way,avoiding them to act as large sediment transfer areas and large alluvial fans to be established.These features make the Teruel Basin margin different to widely described extensional margins models.展开更多
The terrain reversal effect is a perceptual phenomenon which causes an illusion in various 3D geographic visualizations where landforms appear inverted,e.g.we perceive valleys as ridges and vice versa.Given that such ...The terrain reversal effect is a perceptual phenomenon which causes an illusion in various 3D geographic visualizations where landforms appear inverted,e.g.we perceive valleys as ridges and vice versa.Given that such displays are important for spatio-visual analysis,this illusion can lead to critical mistakes in interpreting the terrain.However,it is currently undocumented how commonly this effect is experienced.In this paper,we study the prevalence of the terrain reversal effect in satellite imagery through a two-stage online user experiment.The experiment was conducted with the participation of a diverse and relatively large population(n=535).Participants were asked to identify landforms(valley or ridge?)or judge a 3D spatial relationship(is A higher than B?).When the images were rotated by 180°,the results were reversed.In a control task with‘illusion-free’original images,people were successful in identifying landforms,yet a very strong illusion occurred when these images were rotated 180°.Our findings demonstrate that the illusion is acutely present;thus,we need a better understanding of the problem and its solutions.Additionally,the results caution us that in an interactive environment where people can rotate the display,we might be introducing a severe perceptual problem.展开更多
文摘The Cretaceous/Paleogene （K/Pg） Working Group, after many years of studies, voted to define the Global Stratotype Section and Point （GSSP） for the base of the Danian Stage at the base of the boundary clay at a section near El Kef Tunisia. The GSSP was approved by the International Commission on Stratigraphy （ICS） and ratified by the International Union of Geological Sciences （IUGS） in 1991. Nevertheless, the GSSP was not officially published, although some papers dealing with geological aspects of the K/Pg boundary at El Kef have been published and this is quite well known. In April 2006, the GSSP was revisited, a marker was put in place and protection of the site was requested. Many correlation criteria are present at the GSSP of which the most useful are the meteorite impact evidence （iridium anomaly, Ni-rich spinel, etc.） and the mass extinction of planktic micro- and nannofossils. This event coincides with the GSSP, allowing us to propose that the K/Pg boundary is marked exactly by the moment of the meteorite impact, which implies that all the sediments generated by the impact belong to the Danian. This definition solves problems of correlation in the Yucatan peninsula （Mexico） and its surroundings.
基金funded by Fondecyt Projects(Nos. 1151146 and 1110914)Programa de Fomento y Transferencia tecnológica en Exploración Minera, código BIP № 30114940-0, PIP CONICET 2015-2017 No. 11220150100426,UBACYT 2015-2017 No. 20020150100166BA, PICT 2016 No. 2252, NSF EAR-165031the Yale Institute for Biospheric Studies
文摘The Central Patagonian Andes is a particular segment of the Andean Cordillera that has been subjected to the subduction of two spreading ridges during Eocene and Neogene times. In order to understand the Cenozoic geologic evolution of the Central Patagonian Andes, we carried out geochronologic(U-Pb and^(40)Ar/^(39)Ar), provenance, stratigraphic, sedimentologic, and geochemical studies on the sedimentary and volcanic Cenozoic deposits that crop out in the Meseta Guadal and Chile Chico areas(～47°S). Our data indicate the presence of a nearly complete Cenozoic record, which refutes previous interpretations of a hiatus during the middle Eocene-late Oligocene in the Central Patagonian Andes. Our study suggests that the fluvial strata of the Ligorio Marquez Formation and the flood basalts of the Basaltos Inferiores de la Meseta Chile Chico Formation were deposited in an extensional setting related to the subduction of the Aluk-Farallon spreading ridge during the late Paleocene-Eocene. Geochemical data on volcanic rocks interbedded with fluvial strata of the San Jose Formation suggest that this unit was deposited in an extensional setting during the middle Eocene to late Oligocene. Progressive crustal thinning allowed the transgression of marine waters of Atlantic origin and deposition of the upper Oligocene-lower Miocene Guadal Formation. The fluvial synorogenic strata of the Santa Cruz Formation were deposited as a consequence of an important phase of compressive deformation and Andean uplift during the early-middle Miocene. Finally, alkali flood basalts of the late middle to late Miocene Basaltos Superiores de la Meseta Chile Chico Formation were extruded in the area in response to the suduction of the Chile Ridge under an extensional regime. Our studies indicate that the tectonic evolution of the Central Patagonian Andes is similar to that of the North Patagonian Andes and appears to differ from that of the Southern Patagonian Andes, which is thought to have been the subject of continuous compressive deformation since the late Early Cretaceous.
文摘The fruits and vegetables sector in Ecuador despite its gradual growth in local and international markets has captured the interest of state institutions and academic centers who have focused their studies on agronomic aspects of non-traditional products without considering socioeconomic, productive and performance problems;such is the case of goldenberry value chain. To this extent, the aim of this article was to present an analysis of goldenberry value chain in Ecuador through the identification of stages, agents, flows and activities (primary and support) from the socioeconomic and productive point of view for which a systematic methodology was used involving aspects of the agroeconomic process. As a result, it was determined that goldenberry value chain in the production and postproduction stages requires the diversification of marketing channels, the implementation of refrigerated storage modules located in the supply centers, the strengthening of associative and/or cooperative structures;and the productive planning programs to provide a potential competitive advantage.
文摘Changes in the morphology and mineralogy of speleothems (flowstones) clearly respond to climate-related phenomena, such as drip rate variability and temperature-modulated cave ventilation. Detailed petrographic observations have been coupled with <em><em style="font-family:Verdana;white-space:normal;"><em style="font-family:Verdana;white-space:normal;">δ</em></em></em><sup style="font-family:Verdana;white-space:normal;">18</sup><span style="font-family:Verdana;white-space:normal;">O</span><sup></sup> and <span style="font-size:12px;font-family:Verdana;"><em>δ</em></span><span style="font-size:12px;font-family:Verdana;"><sup>13</sup>C values. Fabrics may show changes related to variations in supersaturation, drip rate or input of detrital particles or organic compounds. Fabrics formed under relatively constant and regular drips (columnar compact, open and elongated) show similar <em>δ</em><sup>18</sup>O and <em>δ</em><sup>13</sup>C values, which are more negative than those of micrite and microsparite. The combination of internal microstratigraphy studies and isotopic data (<em>δ</em><sup>18</sup>O and <em>δ</em><sup>13</sup>C) from two flowstones collected from two caves in the north of Almeria province (SE Spain), suggest a spectrum of environmental conditions ranging from wetter to drier periods. Both records constitute a very useful tool for screening and interpreting high-resolution paleoclimate reconstructions.</span>
文摘An analytical model is presented for seismic analysis of triple friction pendulum bearings and validated using 81 bearing tests, each subjected to three cycles, with a duration of 12 seconds and using 250, 200 and 100 tons vertical loads. The main objective is to develop formulas for bilinear behavior using maximum, average and minimum friction coefficients to check which is the closest to the real behavior in the laboratory tests and comparatives curves plotting to observe the standard derivation. Parameters such as friction coefficients, effective stiffness, damping factor and vibration periods are analyzed to understand the structural behavior of the TPF bearings.
基金funded with FONDECYT Project No. 11140722 of CONICYTthe fund support of DIUDA 2013-22268 and DIUDA 201422273 projects
文摘Compositionally zoned plutons, both layered and concentrically arranged, provide granitic exposures where the mechanisms and timing of the magmatic emplacement processes can be studied. The importance of in-situ geochemical differentiation and the magma replenishment rates are revealed by geochemistry and field relations, together with the increasingly accurate U-Pb geochronology, which has promoted the knowledge about the pluton incremental assembly theories.The Flamenco pluton, located in the Coastal Range of northern Chile, is part of the Upper Triassic to Early Cretaceous Andean intrusives formed in the western active margin of South America, and present a normal zoned structure with mafic magmatic facies(mostly gabbros and Qtz-diorites) close to the contacts with the host metasediments, and tonalites, granodiorites and granites in the inner areas. A combined study of the field relations, geochemistry and zircon geochronology of the magmatic facies was applied to determine the emplacement sequence of the Flamenco pluton, revealing three distinguishable domains separated by metasedimentary septa. The SW area is constituted by mostly homogeneous leucocratic granodiorites that yielded an age of 213 Ma as the best estimation for their emplacement age. Distinctive geochemical characteristics, such as the absence of an Eu anomaly, the depletion in HREE, or the highest Sr, Sr/Y and Ce/Yb values among the granodioritic facies of the pluton,involve lower T and/or higher P conditions at the magmatic source according to experimental studies.These conditions were established during an early stage of the Andean magmatic arc building that is firstly defined here as Upper Triassic. The NW and E domains of the pluton were sequentially emplaced between 194 Ma and 186 Ma and both the field relations and the detailed geochronological results suggest that the mafic facies intruded latter in the emplacement sequence. To the NW, Qtz-dioritic and gabbroic externally emplaced pulses gave a younger crystallization age of 186.3 ± 1.8 Ma, and promoted the granoblastic textures and metamorphic zircon overgrowths that characterize the granodiorites located in the contact with the intermediate and felsic inner magmas, which yielded a best estimation of their emplacement age of 192 士 1.5 Ma. On the other hand, in the eastern domain, magma-magma relations are observed between gabbros and previously intruded tonalites and granodiorites. Both the mafic and intermediate facies show two main subgroups of ages that yielded 194.7 土 1.5 Ma to188.3 ± 2.1 Ma and 193.1 ± 2.2 Ma to 185.5 ± 1.4 Ma respectively. These differences are related to the variations in the magmatic addition rates, which may extend the super-solidus conditions in the eastern domain of the magmatic reservoir as is confirmed by the wider age ranges yielded by these magmatic facies. Zircon overgrowths in the host rocks yield similar ages(around 220 Ma and 205 Ma) than the oldest results obtained in the intrusive facies, indicating that metamorphism correlates with the initial stages of plutonic emplacement.Geochronological results differ between 9 Myr and 41 Myr in the eight studied samples for noninherited ages and gave very close mean ages(within analytical uncertainty) for all the intrusive units. However, we examine other characteristics such as zircon morphology, internal structure,geochemistry and statistical data to assess if the scattering of the geochronological data may be related to the different processes involved in the construction of the Flamenco pluton. We concluded that this detailed study of U-Pb zircon ages, including individual and significative groups of analyses, is useful to determine accurately the emplacement sequence and the genetic relation between the intrusive units,together with the evidences depicted by the geochemistry and field relations.
文摘The purpose of the research was to obtain the mass wasting hazard map for the state of Vargas, central coast of Venezuela, using GIS technology. The work was developed through the heuristic method with the generation of thematic digital maps, univariate statistical treatment, weighting of each variable and quantifying the relationship of each parameter unit regarding mass wasting processes. The algorithm designed to perform map algebra was designed using the variables: surface geology, slope, slope orientation, terrain curvature, moisture topographic index, power index surface flow rate and capacity sediment transport and the rate normalized difference vegetation. The results show a distribution of landslide hazard with the highest values in the west central part of Vargas state, where the dominant lithology is incompetent, and combined with topographic elements, determining high instability, meanwhile the lower hazard areas were found in specific areas such as the middle watershed areas east of the state. The calibration of this model shows a reliability of 80%, so it is highly advisable to use the information generated in this work by governmental and non-governmental organizations in the planning, management and use of land.
基金supported the PLEC2021-008203 project and RYC2021-034473-Ifunded by MCIN/AEI/10.13039/501100011033+4 种基金by the European Union"NextGenerationEU"/PRTRFundação para a Ciência e Tecnologia(FCT-MCTES)of Portugal(projects PTDC/CTA-PAL/31656/2017 and PTDC/CTA-PAL/2217/2021)Research Unit GeoBioTec UIDB/04035/2020Also,the work is part of the Carmen Nunez-Lahuerta is supported by FJC2020-044561-I-MCIN,co-financed by the NextGeneration EU/PRTR.
文摘The accurate identification of dinosaur egg accumulations as nests or clutches is crucial for understanding the reproductive behaviour of these extinct species.However,existing methods often rely on the presence of complete eggs and embryo remains,and sedimentological criteria that are only applicable to well-structured sediments.In this study,we introduce an innovative approach to characterize egg accumulations in structureless sediments,where traditional nest structures may not be preserved.Our methodology employs a unique combination of sedimentological,taphonomic,geochemical,and geophysical proxies for the study of egg accumulations.We applied this approach to the egg accumulation from Paimogo(Jurassic,Portugal),traditionally interpreted as a nest.Our findings reveal that the Paimogo egg assemblage is a secondary deposit,resulting from a flooding event in a fluvial plain that dismantled several allosauroid and crocodylomorph clutches.The eggshell vapor conductance results,coupled with sedimentological evidence,suggest that allosauroid dinosaurs buried their eggs in the dry terrain of overbank areas close to a main channel during the breeding season,likely during the dry season to prevent the embryos from drowning.This research underscores the necessity of multidisciplinary approaches in interpreting egg accumulations and offers a novel methodology for studying these accumulations in structureless sediments.Our findings provide new insights into the breeding behaviour and nesting preferences of these extinct organisms,contributing to our understanding of dinosaur ecology.
基金founded by ANID,Fondecyt Regular projects 1151146,and 1200428founded by ANID,National Doctoral Scholarship.
文摘Many studies propose a significant shift in the tectonic and paleogeographic evolution of the Andes in south-central Chile and Argentina during the Late Cretaceous.It has been proposed that the preceding Jurassic-Early Cretaceous extensional regime that resulted in a low-relief volcanic arc and the backarc Neuquén basin came to an end,giving way to shortening and Andean growth from the Late Cretaceous onward.Nevertheless,there are disagreements regarding the timing and nature of this transition to Andean orogenesis.To address these issues,we conducted geochronologic(U-Pb and^(40)Ar/&(39)Ar),sedimentologic,and structural studies on Mesozoic-Cenozoic sedimentary and volcanic rocks in the Río Maule area(Principal Cordillera,Chile,36°S).From our findings and prior analyses,we propose the following tectono-stratigraphic evolution of the region.(1)Marine deposition of the Tithonian-Hauterivian Baños del Flaco Formation took place in an extensional backarc basin.(2)After a~40 Myr hiatus,fluvial deposits of the Colimapu Formation and volcanic rocks of the Plan de los Yeuques Formation accumulated during the Cenomanian-Danian.Whereas the Colimapu Formation displays evidence of syndepositional shortening,the Plan de los Yeuques Formation exhibits synextensional growth strata.Contrary to other studies,our results suggest that the Chilean part of the Principal Cordillera was largely a zone of active deposition rather than an elevated fold-thrust belt during the Late Cretaceous.We propose that sedimentation occurred within a series of relatively stable intermontane subbasins generated by shortening,followed by extension.(3)After a~20 Myr hiatus,middle Eocene to early Miocene(Lutetian-Aquitanian)accumulation of a thick succession of andesitic lavas and minor clastic sediments of the Abanico Formation occurred in an intraarc extensional basin.(4)Finally,major shortening and uplift of previously deposited Mesozoic-Cenozoic rocks took place throughout the Neogene.This phase constituted the primary contractional deformation in the Andes of south-central Chile and Argentina.In terms of the transition to early Andean deformation,we propose that structural deformation did not generate a major,regional-scale fold-thrust belt during the late Albian-Santonian.Modest extension,tectonic quiescence,or low-magnitude shortening seem to have dominated during the early to middle Cenozoic.
基金supported by project number CGL2012–35662 of Spanish Ministerio de Economía y Competitividad-FEDER.co-financed by the Aragón Government and the PO FEDER-Aragón 2014–2020
文摘The northern part of the eastern margin of the extensional Neogene Teruel Basin(central-eastern Spain)consists of a non-linear,zigzag fault zone made of alternating ca.2 km long,NNW-SSE trending segments and shorter NNESSW ones.Good outcrop conditions made possible a comprehensive integrated stratigraphic and structural study,especially focused on coarse clastic sediments deposited along the basin margin.Well-exposed stratal relationships with boundary faults,allowed the analysis of tectonic influence on sedimentation.Synsedimentary deformation includes growth faulting,rollover anticlines,and monoclines and associated onlap stratal terminations,angular unconformities,and other complex growth strata geometries.One of them is the onlap-over-rollover bed arrangement described here for the first time,which reveals the competition between tectonic subsidence and sedimentary supply.Both,the structural inheritance(dense Mesozoic fracture grid)and the dominant,nearly‘multidirectional’(σ1 vertical,σ2≈σ3),Pliocene extensional regime withσ3 close to E-W,are considered to have controlled the margin structure and evolution.Tectono-stratigraphic evolution includes:(i)reactivation of inherited NNW-SSE faults and development of W-SW-directed small alluvial fans(SAF)while NNE-SSW segments acted as gentle relay ramp zones;(ii)progressive activation of NNE-SSW faults and development of NW-directed very small alluvial fans(VSAF);during stages i and ii sediments were trapped close to the margin,avoiding widespread progradation;(iii)linking of NNW-SSE and NNE-SSW structural segments,overall basin sinking and widespread alluvial progradation;(iv)fault activity attenuation and alluvial retrogradation.The particular structure and kinematic evolution of this margin controlled alluvial system patterns.Size of alluvial fans,directly set up at the border faults,was conditioned by the narrowness of the margin,small catchment areas,and proximity between faults,which prevented the development of large alluvial fans.The size of the relay zones,only a few hundred meters wide,acted in the same way,avoiding them to act as large sediment transfer areas and large alluvial fans to be established.These features make the Teruel Basin margin different to widely described extensional margins models.
文摘The terrain reversal effect is a perceptual phenomenon which causes an illusion in various 3D geographic visualizations where landforms appear inverted,e.g.we perceive valleys as ridges and vice versa.Given that such displays are important for spatio-visual analysis,this illusion can lead to critical mistakes in interpreting the terrain.However,it is currently undocumented how commonly this effect is experienced.In this paper,we study the prevalence of the terrain reversal effect in satellite imagery through a two-stage online user experiment.The experiment was conducted with the participation of a diverse and relatively large population(n=535).Participants were asked to identify landforms(valley or ridge?)or judge a 3D spatial relationship(is A higher than B?).When the images were rotated by 180°,the results were reversed.In a control task with‘illusion-free’original images,people were successful in identifying landforms,yet a very strong illusion occurred when these images were rotated 180°.Our findings demonstrate that the illusion is acutely present;thus,we need a better understanding of the problem and its solutions.Additionally,the results caution us that in an interactive environment where people can rotate the display,we might be introducing a severe perceptual problem.
