4 research outputs found
Diamictites and sturtian Cap Dolomites Covering the jacobina group - Araras, North of Campo Formoso - Bahia
Occurrences of diamictites with a probable glacial origin underlying limestones north of Campo Formoso - BA around Araras village, had already been described by some authors during the 60´s and 70´s. Some of these occurrences have been recorded in some geological maps of 1/100,000 scales and even in others of smaller scales. The importance of these occurrences which have been studied in greater detail is increased because of the now identified litho-structural similarities (and probable stratigraphic correlation) with those of Ituaçu, América Dourada, Morro do Chapéu (all of which overlie the Chapada Diamantina Group), as well as with those in the northern part of the São Francisco Craton (Patamuté, Bendegó etc. overlying TTG rock units of the basement). For all these cases there is evidence of foreland tectonics associated to the centripetal vergence of the Neoproterozoic fold belts, marginal to the craton. There are some additional observations of these rock units occurring in the level of the "Sul-americana Surface", thus demonstrating deep levels of erosion, which may be partially responsible for the present geographic separation of the whole original litho-stratigraphic context. Nevertheless it seems very clear that these records have somehow been sparsely distributed in the Cryogenian paleogeographic scenery, which may be an additional argument to contest the Snow Ball Earth theory. Some selected geological sections were undertaken in the surroundings of Araras which made it possible to discriminate 4 types of litho-structural relationships between the Jacobina Group (Orosirian) and the overlying diamictites of the São Francisco (Bebedouro Fm. Cryogenian).A ocorrência de diamictitos - provavelmente glaciais -, sotopostos a calcários no norte de Campo Formoso-BA, adjacências da vila de Araras, já havia sido observado"en passant" por alguns autores nas décadas de 60 e 70, e inclusive chega a fazer parte de alguns mapas geológicos de escala 1/100.000 e inferiores. A importância destas ocorrências, agora examinadas com mais detalhes, amplia-se com as similaridades lito-estruturais identificadas e a provável correlação com outras ocorrências conhecidas de Ituaçú, América Dourada, Morro do Chapéu (estas sobre o Grupo Chapada Diamantina) e do nordeste do Craton do São Francisco (Bendegó, Serra da Borracha, Patamuté), neste caso sobre o embasamento TTG deste craton. Em todos os casos, a tectônica de"foreland" associada com a vergência centripetal das faixas móveis neoproterozóicas marginais do norte e sul-sudeste do craton (respectivamente) se faz ostensivamente presente. Componente adicional de importância desta ocorrência aqui descrita é: a presença dessas unidades em cotas da superfície Sul-americana (a demonstrar níveis de dissecação erosiva considerável), que não é a única responsável pela atual separação dos contextos acima mencionados. Fica claro que esses registros lito-estratigráficos acima mencionados foram esparsados espacialmente já no Criogeniano, o que constitui argumento expressivo, que pode vir a ser usado para contestar a hipótese do"Snow Ball Earth". Secções geológicas foram realizadas nas adjacências de Araras, discriminando-se quatro diferentes tipos de secções lito-estruturais da discordância (erosiva e angular) entre os (meta-) sedimentos do Supergrupo São Francisco (F. Bebedouro, Criogeniano) sobre o Grupo Jacobina (Orosiriano)
Diamictites and Sturtian Cap Dolomites Covering the Jacobina Group - Araras, North of Campo Formoso - Bahia
Occurrences of diamictites with a probable glacial origin underlying limestones north of Campo Formoso – BA around Araras village, had already been described by some authors during the 60´s and 70´s. Some of these occurrences have been recorded in some geological maps of 1/100,000 scales and even in others of smaller scales. The importance of these occurrences which have been studied in greater detail is increased because of the now identified litho-structural similarities (and probable stratigraphic correlation) with those of Ituaçu, América Dourada, Morro do Chapéu (all of which overlie the ChapadaDiamantina Group), as well as with those in the northern part of the São Francisco Craton (Patamuté, Bendegó etc. overlying TTG rock units of the basement). For all these cases there is evidence of foreland tectonics associated to the centripetal vergence of the Neoproterozoic fold belts, marginal to the craton. There are some additional observations of these rock units occurring in the level of the “Sul-americana Surface”, thus demonstrating deep levels of erosion, which may be partially responsible for the present geographic separation of the whole original litho-stratigraphic context. Nevertheless it seems very clear that these records have somehow been sparsely distributed in the Cryogenian paleogeographic scenery, which may be an additional argument to contest the Snow Ball Earth theory. Some selected geological sections were undertaken in thesurroundings of Araras which made it possible to discriminate 4 types of litho-structural relationships between the Jacobina Group (Orosirian) and the overlying diamictites of the São Francisco (Bebedouro Fm. Cryogenian)
Stratigraphic review of the parecis basin - Amazonian region.
A Bacia dos Parecis está localizada na região centro-oeste do Brasil, na porção sudoeste do Cráton Amazônico, entre
os cinturões de cisalhamento Rondônia e Guaporé. Está dividida, de oeste para leste, em três domínios tectono-sedimentares:o extremo oeste é uma depressão tectônica, a porção central é um baixo gravimétrico e o extremo leste é uma bacia interior tipo “sag”. Durante Paleozóico (do Ordoviciano ao Eo-Permiano) a região Amazônica foi afetada por um evento extensional, quando foram depositados, na Bacia dos Parecis, as formações Cacoal, Furnas, Ponta Grossa, Pimenta Bueno e Fazenda da Casa Branca. A Formação Cacoal é composta de conglomerados, rochas sedimentares líticas, folhelhos e dolomitos, interpretados como depositados em leques aluviais, deltas e lagos. Os ambientes deposicionais das formações Furnas e Ponta Grossa, compostas respectivamente de arenito com seixos e folhelho, são interpretados como de planície de maré e marinho, respectivamente. Os conglomerados, folhelhos e arenitos da Formação Pimenta Bueno, e conglomerados, arcóseos e folhelhos da Formação Fazenda da Casa Branca
são interpretados como glacial ou periglacial. Desde o Permiano ao Triássico existe um “gap” no registro estratigráfico da Bacia dos Parecis. Sucessão de rochas vulcânicas e sedimentares mesozóica registra outro evento extensional na região Amazônica. Este evento está representado na Bacia dos Parecis pelos arenitos eólicos jurássicos da Formação Rio Ávila e basaltos das formações Anarí e Tapirapuã. No Cretáceo os arenitos e conglomerados do Grupo Parecis, foram depositados em ambientes fluvial e eólico. Corpos kimberlíticos do Cretáceo cortam os sedimentos nas porções noroeste e sudeste da bacia. Areia, silte e argila cenozóicos cobrem discordantemente os depósitos da Bacia dos Parecis.The Parecis basin is located in central-western Brazil, on the southwestern part of the Amazon Craton, between the Rondônia and Guaporé fold belts. From West to east, the Parecis basin can be divided into three tectono-sedimentary domains: a tectonic low to the west, a central compartment characterized by a negative gravimetric anomaly, and a interior sag to the east. During the Paleozoic (Ordovician to Early
Permian), the Amazon region was affected by an extensional event, when the Cacoal, Furnas, Ponta Grossa, Pimenta Bueno e Fazenda da Casa Branca formations were deposited in the Parecis basin. The Coacal Formation is composed of conglomerates, wackes, shales and dolomites, interpreted as deposited in alluvial fans, deltas and lakes. The pebbly sandstones and shales of the Furnas and Ponta Grossa formations are interpreted as deposited, respectively, in tidal flats and marine environments. Glacial or glacial-influenced environments are suggested for the conglomerates, sandstones and shales of the Pimenta Bueno and Fazenda da Casa Branca formations. The sedimentary record of Parecis basin shows a stratigraphic gap from Permian to Triassic. Mesozoic volcanic and sedimentary successions record another extensional event in the Amazon region. This event is represented in the Parecis basin by the eolian sandstones of the Jurassic Rio Ávila Formation and the basalts of the Anarí and Tapirapuã formations. The sandstones of the Parecis Group have been deposited during the Cretaceous in fluvial and eolian environments. Cretaceous kimberlite bodies cut the sediments in the northeastern and southeastern parts of the Parecis basin. Cenozoic sandstones and mudstones cover unconformably the deposits of the Parecis basin
NEOTROPICAL ALIEN MAMMALS: a data set of occurrence and abundance of alien mammals in the Neotropics
Biological invasion is one of the main threats to native biodiversity. For a species to become invasive, it must be voluntarily or involuntarily introduced by humans into a nonnative habitat. Mammals were among first taxa to be introduced worldwide for game, meat, and labor, yet the number of species introduced in the Neotropics remains unknown. In this data set, we make available occurrence and abundance data on mammal species that (1) transposed a geographical barrier and (2) were voluntarily or involuntarily introduced by humans into the Neotropics. Our data set is composed of 73,738 historical and current georeferenced records on alien mammal species of which around 96% correspond to occurrence data on 77 species belonging to eight orders and 26 families. Data cover 26 continental countries in the Neotropics, ranging from Mexico and its frontier regions (southern Florida and coastal-central Florida in the southeast United States) to Argentina, Paraguay, Chile, and Uruguay, and the 13 countries of Caribbean islands. Our data set also includes neotropical species (e.g., Callithrix sp., Myocastor coypus, Nasua nasua) considered alien in particular areas of Neotropics. The most numerous species in terms of records are from Bos sp. (n = 37,782), Sus scrofa (n = 6,730), and Canis familiaris (n = 10,084); 17 species were represented by only one record (e.g., Syncerus caffer, Cervus timorensis, Cervus unicolor, Canis latrans). Primates have the highest number of species in the data set (n = 20 species), partly because of uncertainties regarding taxonomic identification of the genera Callithrix, which includes the species Callithrix aurita, Callithrix flaviceps, Callithrix geoffroyi, Callithrix jacchus, Callithrix kuhlii, Callithrix penicillata, and their hybrids. This unique data set will be a valuable source of information on invasion risk assessments, biodiversity redistribution and conservation-related research. There are no copyright restrictions. Please cite this data paper when using the data in publications. We also request that researchers and teachers inform us on how they are using the data