The paleoproterozoic post-tectonic granites of the Gavião Block: the example of Salininha monzogranite, Brumado, Bahia, Brazil

O Bloco Gavião possui como embasamento uma variedade de ortognaisses e greenstone belts intrudidos por um conjunto de granitoides sin-deformacionais e pós-tectônicos cuja idade de colocação é paleoproterozoica. O Monzogranito Salininha é uma intrusão maciça localizada a aproximadamente 50 km a noroeste da cidade de Brumado, centro-sul da Bahia, Brasil. A intrusão é representativa de um conjunto de diversos plútons félsicos pós-tectônicos do Bloco Gavião, cuja petrologia tem sido pouco estudada. O plúton Salininha é irregular e alongado e possui aproximadamente 16 km2, intrudindo ortognaisses e migmatitos fortemente deformados e metamorfisados do Complexo Gavião, de idade arqueana. Em termos modais, o monzogranito Salininha possui biotita como principal mineral acessório ferromagnesiano, além de pouca hornblenda, muscovita, clorita, zircão, opacos e epidoto. Essas rochas são levemente peraluminosas, com alto teor de sílica (71,6 – 75,0 wt%). As rochas possuem altas concentrações de Rb, Sr e Ba (323,88 e 1.155 ppm, respectivamente). O valor médio obtido para a razão La/Yb foi de 18,83. Os padrões de elementos terras raras  ETRs) normalizados pelo condrito mostram variação leve, com enriquecimento leve a moderado em ETRs leves e padrão plano para os ETRs pesados. Todas as amostras possuem anomalias negativas de Eu pronunciadas, o que é consistente com o fracionamento dos feldspatos. Elementos menores e traço possuem trends que indicam a cristalização fracionada de plagioclásio, K-feldspato e biotita. Os dados de elementos traço forneceram evidências para determinar que o monzogranito Salininha é pós-colisional. Uma amostra representativa forneceu idade U-Pb (zircão), via abrasão química-diluição isotópica-espectrometria de massa de ionização térmica (CA-ID-TIMS), de 2003 ± 4 Ma, consistente com o plúton Salininha sendo intrusivo na porção sul doThe Gavião Block is underlain by a variety of Archean orthogneisses and greenstone belts, intruded by a suite of syn-deformational and post-tectonic granitoids which ages of emplacement are poorly constrained between the Paleoand Mesoproterozoic. The Salininha monzogranite is a massive intrusion located approximately 50 km northwest of Brumado, south-central Bahia state, Brazil. The intrusion is representative of several post-tectonic felsic plutons in the Gavião Block. Their petrology, geochemistry and age have been largely unstudied. Salininha pluton is a roughly 16 km2 irregular, elongate body intruding strongly deformed and metamorphosed orthogneisses and migmatites of the Archean Gavião Complex. Modally, the Salininha rocks contain biotite as the major ferromagnesian accessory, besides lesser hornblende, muscovite, chlorite, zircon, opaques and epidote. They are slightly peraluminous rocks with high silica contents (71.6 – 75.0wt%), obtained by lithium tetraborate fusion inductively coupled plasma (ICP). The rocks have high concentration of Rb, Sr and Ba (323,88 and 1,155 ppm, respectively). These values were obtained by lithium tetraborate fusion (mass spectrometer—MS). The average value obtained for the La/Yb ratio was 18.83. Chondrite-normalized rare earth element (REE) patterns show a smooth, restricted range, with moderate light REE enrichment, but flat heavy REE patterns — all samples show pronounced negative Eu anomalies consistent with feldspar fractionation. Major and trace elements have trends, which indicate that crystal fractionation of plagioclase, K-feldspar and biotite — an important process during magmatic evolution of the pluton. The trace element data provided support to the classification of the Salininha monzogranite as a post-collisional intrusion. A representative sample has yielded an early Orosirian U-Pb (zircon) age of 2003 ± 4 Ma, via chemical abrasion-isotope dilution-thermal ionizatio

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

INFLUÊNCIA DOS ASPECTOS HIDROGEOLÓGICOS DE AQUÍFEROS CÁRSTICOS NA EVOLUÇÃO DO RELEVO: PORÇÃO CENTRAL DA CHAPADA DIAMANTINA, BAHIA, BRASIL

O presente trabalho discute como o funcionamento hidrogeológico do aquífero cárstico condiciona e interage com a evolução morfológica do relevo. O sistema cárstico situado na porção central da Chapada Diamantina, Bahia, Brasil abriga um conjunto de sítios espeleológicos de relevância no país. A região é palco de importantes descobertas científicas, particularmente relacionados à espeleologia e evolução dos terrenos cársticos. Entretanto, a compreensão das relações existentes entre a morfologia e a hidráulica subterrânea ainda estão pouco exploradas. Com esse intuito, foram realizados estudos comparativos entre as feições morfológicas do terreno e dados de capacidade específica de poços tubulares, apoiados por dados hidrogeoquímicos e de isótopos estáveis (δ13C). As feições superficiais do terreno mostraram correlação com os dados de capacidade específica, principalmente levando em consideração a distribuição de dolinas. Já quando comparados com a profundidade, os dados de capacidade específica apresentaram dois intervalos de maior produtividade: o primeiro para poços com menos de 60 metros de profundidade, e o segundo para poços com profundidade variando entre 91 e 120, sugerindo uma maior conexão hidráulica nesses intervalos de classe. A evolução morfológica da área estudo é, provavelmente, intrínseca a coalescência de dois processos de carstificação distintos: a carstificação hipogênica e a epigênica, que conotam ao sistema características distintas

Ecological landscape explains aquifers microbial structure

10 pages, 5 figures, 1 table, supplementary information https://doi.org/10.1016/j.scitotenv.2022.160822.-- Code availability: The bioinformatics pipeline and statistical analysis are available at https://github.com/MeirellesLab/aquifer_metagenomes.-- Data availability: I have shared the link to the data/codes within the manuscript fileAquifers have significant social, economic, and ecological importance. They supply 30 % of the freshwater for human consumption worldwide, including agricultural and industrial use. Despite aquifers' importance, the relationships between aquifer categories and their inhabiting microbial communities are still unknown. Characterizing variations within microbial communities' function and taxonomy structure at different aquifers could give a panoramic view of patterns that may enable the detection and prediction of environmental impact caused by multiple sources. Using publicly available shotgun metagenomic datasets, we examined whether soil properties, land use, and climate variables would have a more significant influence on the taxonomy and functional structure of the microbial communities than the ecological landscapes of the aquifer (i.e., Karst, Porous, Saline, Geyser, and Porous Contaminated). We found that these categories are stronger predictors of microbial communities' structure than geographical localization. In addition, our results show that microbial richness and dominance patterns are the opposite of those found in multicellular life, where extreme habitats harbour richer functional and taxonomic microbial communities. We found that low-abundant and recently described candidate taxa, such as the chemolithoautotrophic genus Candidatus Altiarcheum and the Candidate phylum Parcubacteria, are the main contributors to aquifer microbial communities' dissimilarities. Genes related to gram-negative bacteria proteins, cell wall structures, and phage activity were the primary contributors to aquifer microbial communities' dissimilarities among the aquifers' ecological landscapes. The results reported in the present study highlight the utility of using ecological landscapes for investigating aquifer microbial communities. In addition, we suggest that functions played by recently described and low abundant bacterial groups need further investigation once they might affect water quality, geochemical cycles, and the effects of anthropogenic disturbances such as pollution and climatic events on aquifersThis work was primarily supported by the PROPESQ-UFBA (11268). FASB was supported by Programa Institucional de Bolsas de Iniciação Científica and Fundação de Amparo a Pesquisa da Bahia (4102/2019); CMF was supported by CAPES (88887-468244-2019-00). PMM thanks Serrapilheira Institute (grant number Serra-1709-17818). [...] FHC was supported by a Juan de la Cierva - Incoporación fellowship (Grant IJC2019-039859-I)With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)Peer reviewe

Evaluation of susceptibility for terrain collapse and subsidence in karst areas, municipality of Iraquara, Chapada Diamantina (BA), Brazil.

The morphological evolution of the karstic systems is associated with a set of physical and chemical processes, triggered by the dissolution of the rocks, related to percolation of groundwater and surface water, which consequently open underground voids and carve out peculiar forms of relief. Due to environmental and geotechnical aspects, this system is naturally more fragile and vulnerable than other natural systems and, therefore, has increasingly received the attention of the scientific community over the past decades. The objective of the study was to delimit zones with varying degrees of susceptibility for collapses and subsidence of sinkholes in the municipality of Iraquara, Chapada Diamantina (BA), Brazil, and to understand their geological and morphological determinant factors. Geological data, karst phenomenon map, and visual analysis in the field were used to categorize zones with different types of susceptibilities to the nucleation of new sinkholes based on a Hazard Index. This index was defined from the sum of geological hazard factors, lineament density, and sinkhole density. The areas that presented the highest susceptibility for terrain collapse and subsidence corresponded to regions where carbonate rocks outcrop, with high density of photolineaments and 2.62 sinkholes/km2. Processes associated with terrain collapse and subsidence in karst areas consisted of a combination of various factors, hindering precise predictions. However, zones of different types of susceptibilities to terrain collapse and subsidence can be delimited when the relationships between these processes and their factors are understood. The Hazard Index proposed does not provide quantitative values for the probability of hazard susceptibility, but rather indicates areas that are more susceptible to terrain subsidence and collapse