Brassolis astyra Godart is reported for the first time in three localities of Uruguay. This species is found on different native and exotic palm trees causing severe damage.
{"title":"First record for Uruguay of Brassolis astyra Godart (Lepidoptera, Nymphalidae, Brassolinae)","authors":"C. M. Bentancourt, I. Scatoni","doi":"10.31285/agro.26.1118","DOIUrl":"https://doi.org/10.31285/agro.26.1118","url":null,"abstract":"Brassolis astyra Godart is reported for the first time in three localities of Uruguay. This species is found on different native and exotic palm trees causing severe damage.","PeriodicalId":43474,"journal":{"name":"Agrociencia-Uruguay","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73096063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Urioste, R. Ponzoni, M. Aguirrezabala, G. Rovere, D. Saavedra
This study considered the inclusion of carcass attributes in breeding objectives and selection criteria developed for pasture-fed Uruguayan production systems for beef cattle, based on British breeds. Correlated responses in dressing percentage (DP), eye rib area (ERA) and dorsal fat depth (DFD) were determined, when these traits are not formally included in the breeding objective. Addition of DP in the breeding objective, which also included growth, reproduction and feed intake traits, was studied. Genetic change in each trait when using selection indices that included growth (G), growth plus reproduction (GR) and growth plus reproduction plus carcass measures (GRC, where ERA and DFD were obtained by ultrasound techniques) was evaluated. The correlated response in carcass traits when they were not included in the breeding objective was insignificant or very small. When included in the breeding objective, DP showed the lowest economic-genetic importance in relation to other growth, reproduction and feed intake traits. Index GR showed a genetic gain of 94% over that produced by index G, whereas index GRC only showed a superiority of 16% over index GR. Carcass attributes are not expected to deteriorate, even when they were not included in the breeding objective. Inclusion of DP as the only carcass trait in the objective is of secondary importance in beef cattle selection.
{"title":"Carcass attributes in breeding objectives and selection criteria for british breeds in Uruguay","authors":"J. Urioste, R. Ponzoni, M. Aguirrezabala, G. Rovere, D. Saavedra","doi":"10.31285/agro.26.1111","DOIUrl":"https://doi.org/10.31285/agro.26.1111","url":null,"abstract":"This study considered the inclusion of carcass attributes in breeding objectives and selection criteria developed for pasture-fed Uruguayan production systems for beef cattle, based on British breeds. Correlated responses in dressing percentage (DP), eye rib area (ERA) and dorsal fat depth (DFD) were determined, when these traits are not formally included in the breeding objective. Addition of DP in the breeding objective, which also included growth, reproduction and feed intake traits, was studied. Genetic change in each trait when using selection indices that included growth (G), growth plus reproduction (GR) and growth plus reproduction plus carcass measures (GRC, where ERA and DFD were obtained by ultrasound techniques) was evaluated. The correlated response in carcass traits when they were not included in the breeding objective was insignificant or very small. When included in the breeding objective, DP showed the lowest economic-genetic importance in relation to other growth, reproduction and feed intake traits. Index GR showed a genetic gain of 94% over that produced by index G, whereas index GRC only showed a superiority of 16% over index GR. Carcass attributes are not expected to deteriorate, even when they were not included in the breeding objective. Inclusion of DP as the only carcass trait in the objective is of secondary importance in beef cattle selection.","PeriodicalId":43474,"journal":{"name":"Agrociencia-Uruguay","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81553748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The biological characterization of Trifolium polymorphum Poir., a promissory native forage is presented and taken as a model for its amphicarpy between both reproductive modes. Its esteemed productive and biological characteristics, as well as the good adaptation to climatic and edaphic conditions of the region, high persistency in the sward and plasticity, are shown; despite its low vegetative production, the response to phosphoric fertilization is significantly high. Biological, organological, ecological, and productive aspects are also described and discussed. The first of them derived from the reproductive double strategy which develops into high subterranean autogamic seed production, leading to genetical homogeneity of their offspring and the lower aerial seed production with a high impact on population dispersion.
{"title":"Biological characteristics of the promissory forage native legume Trifolium polymorphum poir. (fabaceae, faboideae)","authors":"G. Speroni, P. Izaguirre","doi":"10.31285/agro.26.1076","DOIUrl":"https://doi.org/10.31285/agro.26.1076","url":null,"abstract":"The biological characterization of Trifolium polymorphum Poir., a promissory native forage is presented and taken as a model for its amphicarpy between both reproductive modes. Its esteemed productive and biological characteristics, as well as the good adaptation to climatic and edaphic conditions of the region, high persistency in the sward and plasticity, are shown; despite its low vegetative production, the response to phosphoric fertilization is significantly high. Biological, organological, ecological, and productive aspects are also described and discussed. The first of them derived from the reproductive double strategy which develops into high subterranean autogamic seed production, leading to genetical homogeneity of their offspring and the lower aerial seed production with a high impact on population dispersion.","PeriodicalId":43474,"journal":{"name":"Agrociencia-Uruguay","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89255721","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dominant soils of the mapping units of the Reconnaissance Soil Map of Uruguay were tentatively classified in hydrologic groups (GH) following the procedure developed by the U.S. Soil Conservation Service (SCS). Since information on the relationship between precipitation and runoff is not available yet, the classification is mostly based on soil morphology: horizons sequence, their texture and structure, soil matrix color, mottling and presence of Fe-Mn concretions as indications of redoximorphic phenomena. Estimates of soil permeability and drainage on the basis of profile morphology and the knowledge of the hydric regime support the classification in GH. The results show that only very few soils are included in Group A, mainly Arenosols (Psamments) or very gravelly soils. Group B (24 profiles) includes mainly moderately well to well drained Subeutric Brunosols (Udolls). Group C (68 profiles) includes Subeutric and Eutric Brunosols (Udolls) and Argisols (Udolls and Udalfs), mostly moderately well to somewhat poorly drained, with a fine textured subsoil. Group D (63 profiles) includes all Vertisols, Planosols (Albolls and Aqualfs), Gleysols (mostly Aquolls and Udolls) and solonetzic soils (Aqualfs), most Litosols (Lithic Orthents and Udolls) and a few Brunosols (Udolls); drainage range from somewhat excessive to poor. the classification achieved is razonably consistent with available information on infiltration rate and hydraulic conductivity measurements for some soils. The comparison with known soils of USA, classified in GH with a more scientific basis, has not shown any evident contradiction between the classification criteria used both in US and Uruguay to assign each soil to the correct GH.
{"title":"Classification in hydrologic groups of soil of Uruguay","authors":"A. Duran","doi":"10.31285/agro.26.1073","DOIUrl":"https://doi.org/10.31285/agro.26.1073","url":null,"abstract":"Dominant soils of the mapping units of the Reconnaissance Soil Map of Uruguay were tentatively classified in hydrologic groups (GH) following the procedure developed by the U.S. Soil Conservation Service (SCS). Since information on the relationship between precipitation and runoff is not available yet, the classification is mostly based on soil morphology: horizons sequence, their texture and structure, soil matrix color, mottling and presence of Fe-Mn concretions as indications of redoximorphic phenomena. Estimates of soil permeability and drainage on the basis of profile morphology and the knowledge of the hydric regime support the classification in GH. The results show that only very few soils are included in Group A, mainly Arenosols (Psamments) or very gravelly soils. Group B (24 profiles) includes mainly moderately well to well drained Subeutric Brunosols (Udolls). Group C (68 profiles) includes Subeutric and Eutric Brunosols (Udolls) and Argisols (Udolls and Udalfs), mostly moderately well to somewhat poorly drained, with a fine textured subsoil. Group D (63 profiles) includes all Vertisols, Planosols (Albolls and Aqualfs), Gleysols (mostly Aquolls and Udolls) and solonetzic soils (Aqualfs), most Litosols (Lithic Orthents and Udolls) and a few Brunosols (Udolls); drainage range from somewhat excessive to poor. the classification achieved is razonably consistent with available information on infiltration rate and hydraulic conductivity measurements for some soils. The comparison with known soils of USA, classified in GH with a more scientific basis, has not shown any evident contradiction between the classification criteria used both in US and Uruguay to assign each soil to the correct GH.","PeriodicalId":43474,"journal":{"name":"Agrociencia-Uruguay","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90769713","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
V. Aguerre, P. Chilibroste, M. Casagrande, S. Dogliotti
Sustainability of most vegetable family farms in Southern Uruguay is threatened by low income and the deterioration of natural resources. This study quantified the effect of the inclusion of different alternatives of livestock production in the structure, and economic and environmental performance of different types of vegetable farms. Based on two farms as case studies, we conducted a model based exploratory study at farm scale. The results suggested that the inclusion of livestock production in vegetable family farms is a key factor in reducing erosion of the cultivated area. To reduce erosion, the model reduced the area of vegetables per farm, while expanding the area of forage production. As a consequence, family farm income (IF) was reduced between 12 % and 31 % depending on the case studied. However, we could design production systems with erosion lower than the tolerance limit for the soil type and higher IF, relative to the target, in both farms. From the livestock production alternatives evaluated, the most appropriate ones to include in vegetable production systems are fattening steers or heifers in cycles of 14 to 18 months, due to lower cost for restocking and less use of concentrates, reducing capital requirements and dependence on external inputs.
{"title":"Exploring Alternatives for Sustainable Development of Mixed Vegetable Beef-cattle Family Farm Systems in Southern Uruguay","authors":"V. Aguerre, P. Chilibroste, M. Casagrande, S. Dogliotti","doi":"10.31285/agro.26.1098","DOIUrl":"https://doi.org/10.31285/agro.26.1098","url":null,"abstract":"Sustainability of most vegetable family farms in Southern Uruguay is threatened by low income and the deterioration of natural resources. This study quantified the effect of the inclusion of different alternatives of livestock production in the structure, and economic and environmental performance of different types of vegetable farms. Based on two farms as case studies, we conducted a model based exploratory study at farm scale. The results suggested that the inclusion of livestock production in vegetable family farms is a key factor in reducing erosion of the cultivated area. To reduce erosion, the model reduced the area of vegetables per farm, while expanding the area of forage production. As a consequence, family farm income (IF) was reduced between 12 % and 31 % depending on the case studied. However, we could design production systems with erosion lower than the tolerance limit for the soil type and higher IF, relative to the target, in both farms. From the livestock production alternatives evaluated, the most appropriate ones to include in vegetable production systems are fattening steers or heifers in cycles of 14 to 18 months, due to lower cost for restocking and less use of concentrates, reducing capital requirements and dependence on external inputs.","PeriodicalId":43474,"journal":{"name":"Agrociencia-Uruguay","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85626076","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Forty-six malting barley genotypes, including five commercial varieties, were evaluated in two years in order to characterize the genetic variability in breeding use in Uruguay, and its potential to over yield the varieties currently in use. The two analyzed years presented highly contrasting climatic characteristics. The genotypes were grouped according to their relative performance in the two years for a group of fourteen agronomic and grain quality traits. A cluster analysis was carried out, and the traits responsible for each cluster separation, were studied. The checks showed the ability to maintain a good grain yield and quality level in stressing climatic conditions. In the high yield year, several introduced genotypes exceeded the best checks, but they failed to maintain that superior performance in stressing climatic conditions. This performance was associated to longer cycles to anthesis and shorter grain-filling periods, which hinder the adaptation to national conditions. The use of introduced germplasm resulted in an inefficient way of reaching high yield potentials with high and stable grain quality.
{"title":"Barley germoplasm characterization using agronomic and quality traits","authors":"A. Castro, O. Ernst, E. Hoffman, O. Bentancur","doi":"10.31285/agro.26.1102","DOIUrl":"https://doi.org/10.31285/agro.26.1102","url":null,"abstract":"Forty-six malting barley genotypes, including five commercial varieties, were evaluated in two years in order to characterize the genetic variability in breeding use in Uruguay, and its potential to over yield the varieties currently in use. The two analyzed years presented highly contrasting climatic characteristics. The genotypes were grouped according to their relative performance in the two years for a group of fourteen agronomic and grain quality traits. A cluster analysis was carried out, and the traits responsible for each cluster separation, were studied. The checks showed the ability to maintain a good grain yield and quality level in stressing climatic conditions. In the high yield year, several introduced genotypes exceeded the best checks, but they failed to maintain that superior performance in stressing climatic conditions. This performance was associated to longer cycles to anthesis and shorter grain-filling periods, which hinder the adaptation to national conditions. The use of introduced germplasm resulted in an inefficient way of reaching high yield potentials with high and stable grain quality.","PeriodicalId":43474,"journal":{"name":"Agrociencia-Uruguay","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88555829","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Gaucher, C. Cingolani, G. Blanco, D. Piñeyro, A. Celio, A. Ribot
A synthesis of the academic and scientific activity developed by Prof. Dr. Jorge Bossi, during more than 60 years dedicated to the study of the geology of Uruguay, is offered. This work is a review of his university teaching work and a tribute to his fruitful academic and scientific work on the geology of Uruguay and the region. His contributions have decisively influenced the current understanding of the tectonic evolution, stratigraphy and mineral resources of an important part of South America and southern Africa.
{"title":"Prof. Dr. Jorge Bossi (1934-2020): father of modern Uruguayan geology","authors":"C. Gaucher, C. Cingolani, G. Blanco, D. Piñeyro, A. Celio, A. Ribot","doi":"10.31285/agro.26.554","DOIUrl":"https://doi.org/10.31285/agro.26.554","url":null,"abstract":"A synthesis of the academic and scientific activity developed by Prof. Dr. Jorge Bossi, during more than 60 years dedicated to the study of the geology of Uruguay, is offered. This work is a review of his university teaching work and a tribute to his fruitful academic and scientific work on the geology of Uruguay and the region. His contributions have decisively influenced the current understanding of the tectonic evolution, stratigraphy and mineral resources of an important part of South America and southern Africa.","PeriodicalId":43474,"journal":{"name":"Agrociencia-Uruguay","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84088947","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Raquel Caggiano, J. Bossi, Gonzalo Blanco, D. Poiré
El objetivo de este trabajo es determinar el material generador de suelos para el área de Carlos Reyles, Durazno, y su relación con la geología local. Para ello se estudiaron cuatro sectores donde se realizó relevamiento geológico y muestreo de horizontes C. Para los horizontes C se estimó el tamaño de partículas minerales por el método Bouyoucos y la Difracción de Rayos X para cuantificar la composición mineral y el tipo de mineral arcilloso dominante. Para las litologías más representativas (areniscas ferrificadas, silicificadas) se realizaron láminas delgadas para su visualización en microscopio petrográfico. Estas indican que la composición y la distribución de minerales son similares, teniendo como diferencias entre ellas que fueron afectadas por procesos diagenéticos posteriores. Con respecto a una de las zonas que mostraba microrrelieve gilgai, el material corresponde a una arenisca fina de matriz arcillo limosa, que no había sido reportada en la zona como material geológico, asociándosela a los niveles arenosos de la Formación Fray Bentos. Los restantes horizontes C relevados mostraron características similares a las litologías aflorantes muestreadas, tanto para la zona E como W del área de estudio. En la zona este, los suelos resultantes son arenosos, de colores pardo grisáceo, con profundidades variables (70-100 cm), con mineralogía dominante compuesta por cuarzo, plagioclasa, feldespato potásico y proporciones de arcilla que van de muy escasa a escasa, donde el mineral arcilloso dominante es caolinita. Para la zona oeste, donde aparece el microrrelieve gilgai, los suelos resultantes son más profundos (>100 cm), oscuros, con alto contenido de arcilla con respecto a los de la zona este. La mineralogía dominante en el C está compuesta por cuarzo y plagioclasa, con una proporción de arcilla media. En las zonas de estos sitios donde no se reconoce microrrelieve la mineralogía de los horizontes C es similar a los observados para el sur de la zona oeste. Los minerales arcillosos dominantes de la fracción arcilla de todos los horizontes C en esta zona corresponden principalmente a esmectitas.
{"title":"Caracterización de los materiales generadores de suelos agrícolas en la zona de Carlos Reyles, Durazno","authors":"Raquel Caggiano, J. Bossi, Gonzalo Blanco, D. Poiré","doi":"10.31285/agro.26.503","DOIUrl":"https://doi.org/10.31285/agro.26.503","url":null,"abstract":"El objetivo de este trabajo es determinar el material generador de suelos para el área de Carlos Reyles, Durazno, y su relación con la geología local. Para ello se estudiaron cuatro sectores donde se realizó relevamiento geológico y muestreo de horizontes C. Para los horizontes C se estimó el tamaño de partículas minerales por el método Bouyoucos y la Difracción de Rayos X para cuantificar la composición mineral y el tipo de mineral arcilloso dominante. Para las litologías más representativas (areniscas ferrificadas, silicificadas) se realizaron láminas delgadas para su visualización en microscopio petrográfico. Estas indican que la composición y la distribución de minerales son similares, teniendo como diferencias entre ellas que fueron afectadas por procesos diagenéticos posteriores. Con respecto a una de las zonas que mostraba microrrelieve gilgai, el material corresponde a una arenisca fina de matriz arcillo limosa, que no había sido reportada en la zona como material geológico, asociándosela a los niveles arenosos de la Formación Fray Bentos. Los restantes horizontes C relevados mostraron características similares a las litologías aflorantes muestreadas, tanto para la zona E como W del área de estudio. En la zona este, los suelos resultantes son arenosos, de colores pardo grisáceo, con profundidades variables (70-100 cm), con mineralogía dominante compuesta por cuarzo, plagioclasa, feldespato potásico y proporciones de arcilla que van de muy escasa a escasa, donde el mineral arcilloso dominante es caolinita. Para la zona oeste, donde aparece el microrrelieve gilgai, los suelos resultantes son más profundos (>100 cm), oscuros, con alto contenido de arcilla con respecto a los de la zona este. La mineralogía dominante en el C está compuesta por cuarzo y plagioclasa, con una proporción de arcilla media. En las zonas de estos sitios donde no se reconoce microrrelieve la mineralogía de los horizontes C es similar a los observados para el sur de la zona oeste. Los minerales arcillosos dominantes de la fracción arcilla de todos los horizontes C en esta zona corresponden principalmente a esmectitas.","PeriodicalId":43474,"journal":{"name":"Agrociencia-Uruguay","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76109055","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
G. Piñeiro, Lorenzo Marchetti, Sebastián Marmol, A. Celio, Pedro Luis Xavier, M. Francia, C. Schultz
This article describes an intriguing fossil material recently found in the fine-grained sandstone levels from the upper section of the Yaguarí Formation of Uruguay. The nature of this specimen and its relationships were, initially, not easy to determine with confidence although it was subjected to several analyses, such as morphological and comparative examination complemented with preparation of thin sections and microanatomical and chemical studies under SEM. However, the anatomical structure shown in the performed transversal thin sections allowed solving the issue on the different animal or plant interpretations of the fossil specimen, which was finally discerned in favor of the latter. Therefore, after a detailed comparative study of the thin sections, we concluded that the specimen is a wood fragment related to the Dadoxylon-Araucarioxylon complex. Moreover, in order to provide a better biostratigraphic calibration for these deposits until now devoid of fossils, we include a preliminary description of recently found fossil footprints, which represent the first evidence of the presence of tetrapods in levels of the Yaguarí Formation (sensu Elizalde et al., 1970), below the conglomerates that have yielded the Colonia Orozco Fauna. The footprints were preliminary assigned to the ichnotaxa cf. Karoopes isp, cf. Capitosauroides isp., and cf. Pachypes isp., suggesting the presence of gorgonopsids and therocephalian therapsids and pareiasauromorphs, respectively. The Middle-Late Permian age recently suggested for the Yaguarí Formation based on paleomagnetic and radioisotopic studies is here supported by the described fossils, which thus constitute preliminary but nonetheless relevant discoveries for deposits whose fossiliferous potential has yet to be explored.
{"title":"Enigmatic wood and first evidence of tetrapods in the Yaguarí Formation (Middle-Late Permian), Uruguay","authors":"G. Piñeiro, Lorenzo Marchetti, Sebastián Marmol, A. Celio, Pedro Luis Xavier, M. Francia, C. Schultz","doi":"10.31285/agro.26.504","DOIUrl":"https://doi.org/10.31285/agro.26.504","url":null,"abstract":"This article describes an intriguing fossil material recently found in the fine-grained sandstone levels from the upper section of the Yaguarí Formation of Uruguay. The nature of this specimen and its relationships were, initially, not easy to determine with confidence although it was subjected to several analyses, such as morphological and comparative examination complemented with preparation of thin sections and microanatomical and chemical studies under SEM. However, the anatomical structure shown in the performed transversal thin sections allowed solving the issue on the different animal or plant interpretations of the fossil specimen, which was finally discerned in favor of the latter. Therefore, after a detailed comparative study of the thin sections, we concluded that the specimen is a wood fragment related to the Dadoxylon-Araucarioxylon complex. Moreover, in order to provide a better biostratigraphic calibration for these deposits until now devoid of fossils, we include a preliminary description of recently found fossil footprints, which represent the first evidence of the presence of tetrapods in levels of the Yaguarí Formation (sensu Elizalde et al., 1970), below the conglomerates that have yielded the Colonia Orozco Fauna. The footprints were preliminary assigned to the ichnotaxa cf. Karoopes isp, cf. Capitosauroides isp., and cf. Pachypes isp., suggesting the presence of gorgonopsids and therocephalian therapsids and pareiasauromorphs, respectively. The Middle-Late Permian age recently suggested for the Yaguarí Formation based on paleomagnetic and radioisotopic studies is here supported by the described fossils, which thus constitute preliminary but nonetheless relevant discoveries for deposits whose fossiliferous potential has yet to be explored.","PeriodicalId":43474,"journal":{"name":"Agrociencia-Uruguay","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79439130","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
G. Blanco, P. Abre, M. Lanfranchini, C. Cingolani, H. Ferrizo, D. Piñeyro, N. Uriz, M. Benítez
The geochemistry of two metavolcano-sedimentary sequences deposited in the Piedra Alta Terrane is compared, and their geotectonic evolution is discussed. The Ojosmín Unit (OU) comprises MORB-like basic rocks at the base and a fine-grained siliciclastic sequence interpreted as marine turbidites towards the top. The succession was later obducted during the Orosirian. Whole-rock geochemistry of the metasedimentary rocks of the OU indicates the lack of source rock alteration during deposition (Chemical Index of Alteration, CIA ca. 40-53), implying ice-house climatic conditions in correlation with the worldwide Rhyacian glaciations. Recycling of zircon fractionates the Rare Earth Elements (REE) increasing the amount of HREE, Y, and Hf. Variation ranges of Th/Sc (0.4-4.9), Zr/Sc (30-410), Th/U (2.5-4.3), and of the Eu/Eu * negative anomaly (0.4-0.7) approximate Upper Continental Crust (UCC) values. A new clastic metasedimentary, gently folded unit, the Cerro de la Figurita Formation (CFFm), is erected. The CFFm clastic sedimentation (3,000 m in thickness) represents a deepening upward sequence, starting with polymictic conglomerates deposited in an alluvial fan-dominated environment that evolves to marine turbidites. The CFFm is probably related to a foreland geotectonic setting developed during the Orosirian. The geochemistry of the CFFm reveals similarities to unrecycled UCC, and weathering of the source rocks increases up section (CIA 45-92). Low ratios of Th/Sc (0.3-1.5), Zr/Sc (6-20), Th/U (3-6), high Cr/V (1.1-12.2), and a less pronounced Eu/Eu* negative anomaly of certain samples (0.5-0.9) suggest a contribution from mafic source rocks (probably ophiolitic).
比较了彼德拉-阿尔塔地体中两个变质火山-沉积层序的地球化学特征，并讨论了它们的大地构造演化。Ojosmín单元(OU)包括底部类似morb的基性岩石和顶部被解释为海相浊积岩的细粒硅屑层序。这种继承后来在奥罗西亚时期中断了。OU变质沉积岩的全岩地球化学特征表明，沉积过程中缺乏烃源岩蚀变(Chemical Index of蚀变，CIA ca. 40-53)，表明其冰窖气候条件与世界范围内的rhyasian冰期有关。锆石的回收使稀土元素(REE)分馏，增加了稀土、钇和铪的含量。Th/Sc(0.4 ~ 4.9)、Zr/Sc(30 ~ 410)、Th/U(2.5 ~ 4.3)和Eu/Eu *负异常(0.4 ~ 0.7)近似上陆壳(UCC)值的变化范围。一个新的碎屑变质沉积层，轻轻折叠的单元，Cerro de la figita Formation (CFFm)，被竖立起来。CFFm碎屑沉积(厚度为3000 m)代表了一个不断加深的向上序列，从冲积扇主导的多聚砾岩沉积到海相浊积岩。CFFm可能与奥罗世发育的前陆大地构造环境有关。CFFm的地球化学特征与未循环的UCC相似，烃源岩的风化作用在剖面上增加(CIA 45-92)。低Th/Sc(0.3 ~ 1.5)、Zr/Sc(6 ~ 20)、Th/U(3 ~ 6)、高Cr/V(1.1 ~ 12.2)，部分样品Eu/Eu*负异常不明显(0.5 ~ 0.9)，提示烃源岩可能为基性烃源岩(蛇绿岩)。
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