Volume 9 - 2021 | https://doi.org/10.3389/feart.2021.692895 This article is part of the Research TopicRefining the Interpretation of Nitrogen Isotopes in Deep Time SystemsView all 11 articles The Ediacaran-Cambrian transition is marked by the diversification of metazoans in the marine realm this is not recorded by the Ediacaran-Cambrian Bambuí Group of the São Francisco basin Containing the sedimentary record of a partially confined foreland basin system the Bambuí strata bear rare metazoan remnants and a major carbon isotope positive excursion decoupled from the global record This has been explained by changes in the paleogeography of the basin which became a restricted epicontinental sea in the core of the Gondwana supercontinent promoting episodes of shallow water anoxia we report new δ15Nbulk data from the two lowermost second-order transgressive-regressive sequences of the Bambuí Group The results show a rise of δ15N values from +2 to +5‰ in the transgressive system tract of the basal sequence which was deposited when the basin was connected to other marginal seas Such excursion is interpreted as an oxygenation event in the Bambuí sea δ15N values vary from +2 to +5‰ pointing to instabilities in the N-cyle that are concomitant with the onset of basin restrictions higher sedimentary supply/accommodation ratios the δ15N values stabilise at ∼+3.5‰ pointing to the establishment of an appreciable nitrate pool in shallow waters in spite of the basin full restriction as marked by the onset of a positive carbon isotope excursion our data show that the N-cycle and its fluctuations were associated with variations in sedimentary supply/accommodation ratios induced by tectonically-related paleogeographic changes The instability of the N-cycle and redox conditions plus the scarcity of nitrate along regression episodes might have hindered the development of early benthic metazoans within the Bambuí seawater and probably within other epicontinental seas during the late Ediacaran-Cambrian transition iv) The direct conversion of NO3− to NH4+, known as dissimilatory nitrate reduction to ammonium (DNRA). Although the isotopic effect of this process is not very well known, it can account for fractionations larger than −30‰ (McCready et al., 1983) FIGURE 1. Schematic diagram of the modern marine nitrogen cycle. Oxidation state of nitrogen species is shown on the vertical axis going from −3 (NH4+) to +5 (NO3−). Nitrogen isotopic fractionation of the pathways of the N-cycle are detailed in the text and are expressed in ‰. Modified after Ader et al. (2016) Further knowledge on the interplay between the redox state of Bambuí seawater and the biological metabolic paths could help understanding the limiting conditions for life during the Ediacaran-Cambrian boundary and thus on the comprehension of how life may have progressed to more complex forms at that period we present a new redox proxy on the Bambuí Group sediments: nitrogen isotopic composition (δ15N) The nature of δ15N data have the potential to provide important information on the Bambuí seawater chemistry its redox state and prevailing metabolisms FIGURE 2. The São Francisco Craton geological map and the São Francisco Basin. Studied sections: A, Arcos; W, Well 1; J, Januária. Modified after Caetano-Filho et al. (2019) The SB1 is defined by subaerial features in shallow environments whereas in deeper it is defined by an erosional surface at the base of peritidal channels limestones The samples analyzed here correspond to the two lowermost second-order sequences of the Bambuí Group the terrigenous content is very low and limestones featuring microbial laminations predominate At the segment that goes from 668 to 705 m calcilutite exhibiting microbial structures intercalates with black shaly rocks presenting a crinkled lamination From 718 to 738 m there are oolitic and intraclastic calcarenites The interval between 738 and 761 m is heavily dolomitized featuring oolitic and intraclastic doloarenites The dolomitization is evidence of regression; therefore there is an unconformity that marks the end of the first second-order sequence and the beginning of the second second-order sequence FIGURE 5. Arcos section: Depositional environments, lithologies, structures and sequence stratigraphy framework. δ15N data was obtained in this study and δ13Corg was published by Caetano-Filho et al. (2021). The axis on the Corg/N column is fixed on the Redfield ratio (6.6). Abbreviations here are the same as the ones used in Figure 4 The uppermost 30 m of Well 1 comprises shales with minor intercalations of calcirudites and calcarenites FIGURE 6. Well 1 section: Depositional environments, lithologies, structures and sequence stratigraphy framework. δ15N data was obtained in this study and δ13Corg was published by Caetano-Filho et al. (2021). The axis on the Corg/N column is fixed on the Redfield ratio (6.6). Abbreviations here are the same as the ones used in Figure 4 To acquire δ15Nbulk (N bounded to clays + N bounded to kerogen) data the rocks were crushed into smaller pieces using mortar and pestle and were subsequently pulverized using a tungsten carbide mill The carbonate fraction was removed by adding 25 ml of 5 N HCl to 3–15 g of sample for 12 h at 25°C The reaction proceeded after that at 80°C for 2 h Leachate was centrifuged and discarded and the residue of this procedure was rinsed with distilled water until its pH was neutral and was then dried in an oven at 50°C This allowed to concentrate N in the residue a necessary step given the high carbonate content and very low TOC of most samples quartz tubes were filled with previously purified CuO the tubes were attached to the vacuum line and were degassed under 150°C until high vacuum conditions were obtained the tubes were flame-sealed and proceeded to the combustion step in which the tubes were heated in a furnace at 950°C for 6 h to allow the CuO to decompose into Cu and O as the liberated O causes the combustion of the sample carbon dioxide and nitrogen oxides as products the tubes are cooled down until 600°C for 2 h to allow for the NOx to react with Cu to generate N2 and CuO the generated gas was extracted and purified using the vacuum line CO2 and H2O were separated from N2 using a liquid nitrogen trap the gas was concentrated and pushed into a sample vessel using a Toepler pump which also allows the quantification of the extracted N2 To assess possible contaminations coming from the vacuum line yielding less than 0.02 μmol of gas within the vacuum line system which is negligible considering the amount of N2 in Bambuí samples The extracted gas was analyzed using a Thermo-Fisher Delta + XP mass spectrometer with a dual inlet introduction system to determine the nitrogen isotope composition Nitrogen isotopes are measured in masses 28 40 (Ar) and 44 (CO2) are tracked to check for possible contaminations The precision of δ15Nbulk values was better than 0.5‰ (2σ) estimated from multiple measurements of a batch of samples Accuracy was monitored by measuring certified materials IAEA-N1(+0.4 ± 0.2‰) and IAEA-N2 (+20.3 ± 0.2‰) and IPGP internal standard MS#5 (+14.9 ± 0.5‰) K and Al contents were measured using a portable XRF device Thermo Scientific Niton XL3t provided by the Geological Survey of Brazil (CPRM) Sample slabs were polished and veins or terrigenous laminations were avoided during measurements A blank (SiO2) and a certified reference material (QC 180-673; Thermo) were run after every batch of 30 samples The blanks present K content that was less than 0.01 ppm and the reproducibility of the standard was better than 0.2% (1σ) The Al blanks were lower than the detection limits and the reproducibility of standards was better than 0.5% (1σ) K and Al content are reported in percentage (%) Januária section samples average δ15Nbulk is +3.1‰ (n = 39), ranging from +1.3 to +4.3‰ (Figure 4) a pronounced positive δ15Nbulk excursion from +1.2 to +3.8‰ occurs on the post-glacial carbonates of this section Januária values form a plateau around +3.0‰ the δ15Nbulk data of Januária oscillate between ∼+2 and ∼+4‰ the average δ15Nbulk of Januária is +3.0‰ (n = 13) Januária average TNbulk and Corg/N is 29 ppm and 20 (n = 39) the low Corg/N interval is present in its 13 lowermost samples which corresponds to the cap carbonates and the upper limit of the EHST interval Considering the three studied sections, Arcos has the heaviest N mean isotopic composition, +3.4‰ (n = 34) with δ15Nbulk going from +1.6 to +5.0‰ (Figure 5) Some excursions are present along Arcos profile The TST interval of this section presents a shift in which δ15Nbulk values go from +3.2 to 5.0‰ δ15Nbulk values are stable (∼+3.0‰) but in the LHST interval they fall to a minimum of +1.6‰ near EHST/LHST boundary and then they return to +3.4‰ the δ15Nbulk values of Arcos section rise and its mean value during this interval is +3.8‰ (n = 3) Arcos section average TNbulk and Corg/N is 37 ppm and 31 (n = 34) the low Corg/N interval ends earlier than in the other sections One sample is an exception in this segment which drives the mean value of this interval to 12 the average value for Arcos low Corg/N interval would be 8 The average K content of samples is 0.4, 0.6 and 2.9%, whilst the average Al content is 1.0, 1.3 and 2.1% in Januária, Arcos and Well 1, respectively. Higher K and Al contents are reported during transgressive tracts, while the regressions show lower values (Table 1) Al and K content average values during the transgressions and regressions The apparently low R2 of Januária is caused by one Nbulk-rich sample present in its second second-order sequence One remarkable feature in all sections is the Corg/N ratio at their base The ratios are low when compared to the modern redfield ratio (6.6) which might indicate that the samples are enriched in N compared to the organic matter from which they were generated when coupled to the fact that some N may be linked to clays and not to organic matter must be investigated since the excess in N can be non-primary excess of N can be a result of N preservation at the expense of C the samples cannot be used for paleoenvironmental reconstruction it is reasonable to consider that δ15Nbulk of the Bambuí Group reflects mainly the primary signals of the organic matter and the data can be used for paleoenvironmental reconstructions Albulk/TOC ratios in low and high Corg/N ratios interval (i) assimilation of NO3− from an ocean where denitrification occurs only in the sediments This would require a fully oxygenated water column to prevent the conversion of NO3− to N2 while the former is transported/sunk (ii) biological N2 fixation using Mo-based nitrogenase as a dominant path of the N cycle; FIGURE 9. Arcos, Well 1 and Januária stratigraphic correlation and their δ15Nbulk and δ13Corg data. δ13Corg was published by Caetano-Filho et al. (2021) As along the TST interval δ15Nbulk values increase another N-assimilation pathway must have competed with N2 direct fixation Two possibilities can be envisaged depending on redox state of the euphotic zone NH4+ is the main dissolved N species) δ15Nbulk >+2‰ can be interpreted as: (i) assimilation of NH4+ from a reservoir in which NH3 dissociated from NH4+ and was volatilized (e.g. Stüeken et al., 2015); (ii) non-quantitative assimilation of upwelled NH4+; (iii) assimilation from an NH4+ pool that faced non-quantitative nitrification while the resultant nitrite and nitrate were completely reduced (e.g. Thomazo et al., 2011) all these paths involving NH4+ as the main nutrient are associated with big fractionation factors and should intuitively lead to significant stratigraphic δ15N variability which does not match the mild and consistent fractionation data reported on the Bambuí rocks we assume in the following that samples from the TST interval which δ15Nbulk values are higher than +2‰ do not reflect ammonium as a main nutrient values of δ15Nbulk >+2‰ is usually interpreted as: (i) non-quantitative assimilation of NO3− (e.g. Sigman et al., 1999) (ii) assimilation from a nitrate reservoir that experienced some degree of denitrification (e.g. Godfrey and Falkowski, 2009; Tesdal et al., 2013); (iii) assimilation from a nitrate reservoir that experienced dissimilatory nitrate reduction (DNRA) (e.g. An and Gardner, 2002; Dong et al., 2011; Jensen et al., 2011); Possible scenario of the N-cycle on the Bambuí Basin during the deposition of its basal sequences a stable nitrate pool was established and the most dominant form of N available was nitrate that went through partial denitrification on zones of low oxygenation the high input of nutrients coming from the continent and P recovery under anoxic bottom water conditions caused the limitation of NO3− in superficial waters making N2 fixation the main form of N acquisition by phytoplankton which might have contributed to the maintenance of nitrate on surface waters as δ15Nbulk values are still low when compared to the modern nitrate reservoir pointing to a shallow redoxcline and nitrate loss compensated by N2 Mo-based fixation The δ15Nbulk values from Arcos and Januária sections are slightly higher than in Well 1 indicating that surface waters were more oxygenated in shallow domains than in forebulge grabens which is a plausible scenario in the Bambuí Group geological context Schematic representation of the Sete Lagoas High Domain Well 1 is located inside a forebulge graben and Arcos in a shallower part of the Sete Lagoas Domain if we consider that the chemocline was at the same level Well 1 had a deeper anoxic water column than Arcos Relative sea-level variations seem to exert control in the Bambuí N-Cycle During the first transgression interval (TST) in all the studied sections δ15Nbulk values rise from a minimum of ∼+1.0‰ to a maximum of ∼+5.0‰ which is parsimoniously explained as a rise of the nitrate reservoir and hence oxygen levels in surface waters As the restriction of the Bambuí increases (LHST) the NO3− stability is disturbed which is shown by a negative excursion observed in the transition of Arcos EHST to LHST and by increased variability in the δ15Nbulk values of Januária The low δ15Nbulk observed in the LHST interval of both sections is interpreted as the result of N2 fixation using Mo as cofactor the slightly higher δ15Nbulk values of the second second-order transgressions show that the nitrate pool increased again but not to the level that prevailed during the first transgression N2 fixation still played a significant role maybe due to the restriction of the Bambuí seawater at this stage the δ15Nbulk data shows that the basin operated in periods in which N2 fixation and NO3− assimilation intercalated as the dominant path of nitrogen assimilation by primary producers which can be interpreted in terms of more or less oxygen within superficial waters Nitrate is a very important nutrient for eukaryotes primary producers and eukaryotes are necessary to fuel higher trophic levels its depletion in some intervals might be one of the factors that drove the hostile conditions for metazoans in the Bambuí seawater The raw data supporting the conclusions of this article will be made available by the authors PF-F analyzed the nitrogen isotopic composition of the samples interpreted the data and wrote the manuscript and CB-R obtained K and Al data and also did fieldwork geochemical information regarding the Bambuí Group and also with the conceptualization of this project MK and HR provided samples from the sections of Arcos and Well 1 respectively All the authors collaborated on the final version of the manuscript and assisted with geological interpretations This study was funded by the São Paulo Research Foundation (FAPESP) thematic project The Neoproterozoic Earth System and the rise of biological complexity grant 2016/06114-6 PF-F holds a FAPESP scholarship grant #2019/13228-6 The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher We acknowledge to Lhoist and Petra Energia S.A Brazilian Geological Service (CPRM) for providing the XRF device CAPES for institutional support and Pôle de Spectométrie Océan and Institut de Physique du Globe de Paris staff for the technical support in data acquisition and MK are fellows of the Brazilian Research Council (#307563/2013-8 #206997/2014-0 and #309106/2017-6 Fabricio Caxito for constructive suggestions Graham Shields for the editorial handling of the manuscript The Supplementary Material 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The use distribution or reproduction in other forums is permitted provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited in accordance with accepted academic practice distribution or reproduction is permitted which does not comply with these terms *Correspondence: Paula Luiza Fraga-Ferreira, cGF1bGFmcmFnYUB1c3AuYnI= Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher 94% of researchers rate our articles as excellent or goodLearn more about the work of our research integrity team to safeguard the quality of each article we publish The ad-free version is ready for purchase on iOS mobile app today we couldn't find that page";var n=e.querySelector("h2");return n&&n.remove(),{staticContent:e,title:t}},d=function(e){var t=document.createElement("button");return t.innerText=e,t.classList.add("error-page-button"),t},f=function(e){var t=document.createElement("div");t.id="recirculation-404",t.classList.add("brand-hint-bg");var n="\n \n \n \n \n \n '.concat(e,' Tick here if you would like us to send you the author’s response Unveiling Tomorrow's Cameroon Through Today's News nestled within the conflict-ridden Northwest region of Cameroon and an innocent woman fell victim to violence perpetrated by gunmen believed to be Ambazonian rebels dressed inconspicuously in civilian attire the bar owner offered them a ride on his motorbike The government forces and the bar owner lost their lives instantly struck a woman and her 26-year-old daughter near a junction Her daughter survived but remains hospitalized continues to exact a heavy toll on civilians More than 6,000 lives have been lost during these nearly eight years of conflict communities scarred—the human cost remains immeasurable As the remains of the fallen woman are taken to the mortuary The echoes of violence reverberate through the region leaving questions unanswered and hearts heavy The Anglophone crisis in Cameroon began in 2017 as English-speaking regions in the Northwest and Southwest sought greater autonomy from the predominantly French-speaking government The conflict has led to significant loss of life and displacement with civilians often caught in the crossfire between separatist groups and government forces has been deeply affected by the ongoing conflict The violence disrupts daily life and instills fear within the community highlighting the urgent need for a resolution to the crisis As Bambui and other towns in the region continue to suffer there is an urgent call for dialogue and peace The people of Cameroon yearn for an end to the bloodshed and a return to normalcy This latest incident underscores the fragile and volatile situation in the Anglophone regions and the dire need for comprehensive peace efforts to bring an end to the ongoing violence Metrics details Age-related cognitive decline (ACD) is the gradual process of decreasing of cognitive function over age Most genetic risk factors for ACD have been identified in European populations and there are no reports in admixed Latin American individuals and fine-mapping to examine genetic factors associated with 15-year cognitive trajectory in 1,407 Brazilian older adults comprising 14,956 Mini-Mental State Examination measures Participants were enrolled as part of the Bambuí-Epigen Cohort Study of Aging Our admixture mapping analysis identified a genomic region (3p24.2) in which increased Native American ancestry was significantly associated with faster ACD Fine-mapping of this region identified a single nucleotide polymorphism (SNP) rs142380904 (β = −0.044 most in genes previously reported to influence cognitive function The top six associated SNPs accounted for 18.5% of the ACD variance in our data our longitudinal study replicated previous GWAS hits for cognitive decline and Alzheimer’s disease Our 15-year longitudinal study identified both ancestry-specific and cosmopolitan genetic variants associated with ACD in Brazilians highlighting the need for more trans-ancestry genomic studies especially in underrepresented ethnic groups Although ACD is not only observed in people with dementia identifying factors associated with changes in cognitive function is fundamental to the understanding of dementia there are no reports of either admixture mapping or genome-wide association studies (GWAS) investigating the association between ancestry-related genomic regions or genetic markers with the trajectory of cognitive function Tri‐hybrid genome‐wide individual proportion of ancestry of 1,407 participants of the Bambuí‐Epigen Cohort Study of Aging Each bar represents one individual and the green and blue colors in the bar plot represent the Native American European and Native American genomic segments of ancestry The Admixture mapping analyses were performed using both (A) RFMix and (B) PCAdmix methods to infer the local ancestry The horizontal red line represents the significance threshold for each admixture mapping test (see methods) LocusZoom plot of fine mapping of the (3p24.2) region using both genotyped and imputed SNPs ± 1 Mb from the target region The SNP rs142380904 with the lowest p-value is color coded in purple and labeled The linkage disequilibrium between this SNP and the remaining nearby SNPs is indicated by the color coding according to r2 values based on admixed Americans (AMR) from 1000 Genomes Project Manhattan plot of the genome-wide association study (GWAS) analysis. The plot represents the −log10 transformed p values for all 10.4 M SNPs analyzed. The horizontal red line represents the standard genome-wide suggestive significance (p = 10-6). The rectangle highlights the hits for the five SNPs in the chromosome 7 (Table S1) We then evaluated selected GWAS Catalog SNPs (Welter et al., 2014) previously associated with “cognitive decline” and/or “Alzheimer’s disease” (reference file “All associations” v1.0). We identified association (p < 0.05) between ACD and the risk allele of 26 of 468 previously reported SNPs (Table S2) Most of these genetic markers were related to lipid metabolism and the strongest association (p = 6 × 10−5) was identified for the SNP rs429358 in APOE we identified a total of 25 SNPs associated (one using admixture mapping and 24 using GWAS) with ACD using the combined approaches of admixture mapping we used a stepwise model selection procedure to select the top SNPs: rs138347004 The set of six SNPs explained 18.5% (SE = 0.082 p = 0.015) of the proportion of phenotypic variance fine-mapping and genome-wide association study (GWAS) revealed a genomic region enriched for Native American ancestry as well as single SNPs associated with age-related cognitive decline (ACD) in the Bambuí-Epigen Cohort Study of Aging Because the study had a longitudinal design our associations analyses allows the identification of genetic determinants of cognitive function over time in addition to neurotransmitter release and neurodegenerative disease consistent with ubiquitous tissue expression and pleiotropy Only 7% of carriers of the rs142380904-T allele had type 2 diabetes (T2D as measured by HbA1c serum levels and/or treatment) it’s unlikely that T2D mediates the association between UBE2E2 and cognitive trajectory in our data Strengths include a large community-based sample of an admixed population followed over a very long period with annual measures of cognitive function there was minimal loss of participants during follow-up resulting in an average of 11 MMSE measures per participant A limitation of our study is inherent to longitudinal studies of aging in which older adults are at greater risk of death which in turn might lead to differential censoring we considered dropouts in our mixed models we did not find differences in the cognitive trajectories estimated by those models An advantage on the use of cognitive trajectory includes the measurement of cognitive changes over time and the examination of individual-specific patterns of decline although the MMSE is among the most widely-used tests of cognitive function in old age it is a global measurement and its total score does not precisely correspond to specific cognitive domains It is important that future analyses use a more detailed assessment of cognitive function that might reveal different patterns of association across cognitive domains We carried out the first admixture mapping and GWAS in Latin America to determine relationships between genetic factors and the trajectory of cognitive decline We found a genomic region at which increased Native American ancestry is associated with faster age-related cognitive decline highlighting the need to increase the availability of Native American-ancestry datasets our GWAS detected new SNP associations and replicated other SNPs associated with cognition-related outcomes Our results lay a foundation to develop a polygenic risk score that can be used as a prognostic marker of cognitive disorders with the potential to be used for prevention The MMSE is evaluated using a score ranging from 0 to 30 Low measures may indicate cognitive impairment and decreases in measures over time may indicate cognitive decline only markers with an info score of >0.8 were considered for fine-mapping and genome-wide association analysis we excluded SNPs with minor allele frequency <0.01 All remaining genotyped and imputed SNPs were tested for association with the trajectory of cognitive function which was developed especially for admixed populations and global African and Native American proportions as fixed effects we used the kinship matrix estimated by REAP as a random effect We then used the effective number of tests in a partial Bonferroni correction; the significance threshold was 0.05 divided by the effective number of tests We performed fine-mapping analysis for the genomic regions significantly associated in the admixture mapping We used the imputed SNPs ± 1 Mb from the midpoint of significant admixture mapping regions The multiple linear regression models were adjusted for age schooling and the global African and Native American proportions as fixed effects We used the kinship matrix estimated by REAP as a random effect The institutional review board of the Oswaldo Cruz Foundation fully approved the Bambuí Cohort Study of Aging Brazil’s national research ethics committee approved genotyping as part of the Epigen-Brazil protocol (Brazilian National Ethics Research Council (CONEP) All methods were performed in accordance with the CONEP guidelines and regulations Written informed consent was obtained from all participants at baseline and at all follow-up interviews EPIGEN-Brazil data are deposited in the European Nucleotide Archive (PRJEB9080 (ERP010139) under EPIGEN Committee Controlled Access mode The Kwa/Gur datasets are deposited in dbGaP at phs000838.v1.p1 Botswana samples were obtained from dbGaP (phs001396.v1.p1) Genetic Biomarkers on Age-Related Cognitive Decline Frequency and clinical determinants of dementia after ischemic stroke Immune activation in brain aging and neurodegeneration: too much or too little dementia and type 2 diabetes mellitus in the elderly The global prevalence of dementia: a systematic review and metaanalysis Dementia in Latin America: Epidemiological Evidence and Implications for Public Policy Age-related cognitive decline and associations with sex education and apolipoprotein E genotype across ethnocultural groups and geographic regions: a collaborative cohort study Genetic architecture of age-related cognitive decline in African Americans Genomic African and Native American Ancestry and 15-Year Cognitive Trajectory: Bambui Study Origin and dynamics of admixture in Brazilians and its effect on the pattern of deleterious mutations Reconstructing the population genetic history of the Caribbean Power comparison of admixture mapping and direct association analysis in genome-wide association studies Cohort profile: the Bambui (Brazil) Cohort Study of Ageing Admixture in Latin America: geographic structure phenotypic diversity and self-perception of ancestry based on 7,342 individuals Genomic ancestry and ethnoracial self-classification based on 5,871 community-dwelling Brazilians (The Epigen Initiative) Genome-wide association study of atypical psychosis An integrated map of genetic variation from 1,092 human genomes A global reference for human genetic variation HaploReg v4: systematic mining of putative causal variants regulators and target genes for human complex traits and disease Attenuation of neuroinflammation and Alzheimer’s disease pathology by liver x receptors Regulation of Synaptophysin Degradation by Mammalian Homologues of Seven in Absentia Genome-wide association study of shared components of reading disability and language impairment Rare deletions at the neurexin 3 locus in autism spectrum disorder Examining the association of NRXN3 SNPs with borderline personality disorder phenotypes in heroin dependent cases and socio-economically disadvantaged controls Mutations in CNTNAP1 and ADCY6 are responsible for severe arthrogryposis multiplex congenita with axoglial defects Top 10 Replicated Findings From Behavioral Genetics The Mini-Mental State Examination: A Brief Cognitive Assessment In Principles and Practice of Geriatric Psychiatry 145–146 (2010) Dimensions underlying the Mini-Mental State Examination in a sample with low-education levels: the Bambui Health and Aging Study Construct validity of the mini mental state examination across time in a sample with low-education levels: 10-year follow-up of the Bambuí Cohort Study of Ageing Instrumental Variables Regression with Independent Observations A flexible and accurate genotype imputation method for the next generation of genome-wide association studies Fast model-based estimation of ancestry in unrelated individuals A linear complexity phasing method for thousands of genomes RFMix: a discriminative modeling approach for rapid and robust local-ancestry inference PCAdmix: principal components-based assignment of ancestry along each chromosome in individuals with admixed ancestry from two or more populations Loci associated with skin pigmentation identified in African populations Genetic signatures of gene flow and malaria-driven natural selection in sub-Saharan populations of the ‘endemic Burkitt Lymphoma belt’ Evolutionary genomic dynamics of Peruvians before GCTA: a tool for genome-wide complex trait analysis Joint ancestry and association testing in admixed individuals Statistics Complements to Modern Applied Statistics with S ANNOVAR: functional annotation of genetic variants from high-throughput sequencing data dbSNP: the NCBI database of genetic variation HaploReg: a resource for exploring chromatin states and regulatory motif alterations within sets of genetically linked variants EPIGEN-Brazil Initiative resources: a Latin American imputation panel and the Scientific Workflow Admixture/fine-mapping in Brazilians reveals a West African associated potential regulatory variant (rs114066381) with a strong female-specific effect on body mass- and fat mass-indexes Download references We thank Victor Borda for scientific discussions The EPIGEN-Brazil Initiative is funded by the Brazilian Ministry of Health (Department of Science and Technology from the Secretaria de Ciência Tecnologia e Insumos Estratégicos) through Financiadora de Estudos e Projetos The EPIGEN-Brazil investigators received funding from the Brazilian Ministry of Education (CAPES Agency) ETS and TPL were supported by Brazilian National Research Council (CNPq) Minas Gerais Research Agency (FAPEMIG) and Pró-Reitoria de Pesquisa da Universidade Federal de Minas Gerais Tishkoff laboratory is funded by the National Institutes of Health (1R01DK104339-0 and 1R01GM113657-01) MHG is supported by the Intramural Research Program of the National Institutes of Health in the Center for Research on Genomics and Global Health (CRGGH) The CRGGH is supported by the National Human Genome Research Institute the National Institute of Diabetes and Digestive and Kidney Diseases and the Office of the Director at the National Institutes of Health (1ZIAHG200362) Erico Castro-Costa & Maria Fernanda Lima-Costa Center for Research on Genomics and Global Health Division of Cancer Epidemiology and Genetics All authors read the manuscripts and contributed with suggestions The authors declare no competing interests Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations Download citation DOI: https://doi.org/10.1038/s41598-019-53988-4 Anyone you share the following link with will be able to read this content: a shareable link is not currently available for this article Sign up for the Nature Briefing newsletter — what matters in science An Archaeonassa trace fossil identified in carbonate rocks from the Bambuí Group in Brazil is thought to have been left by an organism during the Late Ediacaran Fossils of a known age have been found for the first time in rocks in Brazil that had previously eluded scientists’ attempts to pinpoint their age The discovery of the marine animals dates the rocks to 550 million years ago offering important insights into the geological evolution and timing of the assembly of the former supercontinent Gondwana Gondwana’s origins date to the breakup of its predecessor starting roughly 850 million years ago in the Early Neoproterozoic India and South America then began slowly reorganizing and fusing together piece-by-piece to form the new supercontinent the assembly of which is thought to have finished in the Middle Cambrian about 510 million years ago Many details of the process along the way remain unclear Lucas Warren, a geologist at Universidade Estadual Paulista in Brazil and lead author of the study and his colleagues studied rock cores collected from a section of the well-known Bambuí Group near the Brazilian town of Januária an area that was part of the São Francisco Craton during the Neoproterozoic The Bambuí Group consists of shallow marine and tidal-zone carbonates thought to have been entirely deposited prior to 600 million years ago as the São Francisco and its neighboring cratons were completing their unification and hence early in the deposition of the Bambuí Group the researchers found the fossilized tube-shaped shells of an organism called Cloudina known from specimens found elsewhere to have lived during a geologically short period between 550 million and 542 million years ago Along with other fossil organisms and trace fossils identified in the core and thought to date to the Late Ediacaran rather than being older than 600 million years the Bambuí Group rocks are likely at least 50 million years younger Cloudina specimens have also been found near the lithified ancient coastlines of other chunks of the proto-Gondwanan supercontinent — of which the São Francisco formed part of the interior — suggesting that a large inland sea wove amid the landmasses and connected them to the ocean at the time This sea “was probably a branch of the Clymene Ocean,” Warren says which “separated the proto-Gondwana supercontinent to the west from the Amazonia and Rio Apa cratons to the east.” (Amazonia and Rio Apa would later collide and merge with the rest of Gondwana.) “This is a very important finding,” says Eric Tohver, a geologist at the University of Western Australia who was not involved in the new study Many researchers have studied and interpreted the history of the Bambuí Group “without any firm notion as to what the age of the rocks actually is” because the age-determination methods used previously have been indirect or less precise “It’s rare to find a paleontological [indicator] in a sequence that has been looked at for decades that so precisely establishes the age,” Tohver says “By establishing that these rocks are much younger than had been supposed … that pushes back the date of formation of [this part of] Gondwana by some 50 million to 100 million years.” The findings raise some new questions about Gondwanan evolution in the area such as why portions of Bambuí Group rock appear to have been folded and deformed by tectonic processes that took place well over 550 million years ago “will lead to many revisions of the geology of central South America.” The page you were trying to reach does not exist. Please check the URL or click here to return to the home page The Cameroon military high command has announced that its soldiers killed ten separatist fighters on Sunday in multiple clashes with the Anglophone combatants in Batibo and Bambui the army announced killing Asenjo Roy Angafor in the Tubah sub-division of the Northwest region According to a statement by the Army General Staff seven suspected separatist combatants were captured and two motorcycles were seized during the Bambui operation the army claims to have killed more than seven separatist fighters during the past week and seized arms and ammunitions from the Anglophone fighters the neutralised Anglophone separatists are responsible for several attacks and abductions in the locality Sources within the military say the killings in Bambui and Batibo were the first successes of General Bouba Dobekreo who took command of the 5th military region in Bamenda on July 18 General Dobekreo is reputed to have been the military officer responsible for the successes of the Cameroon army in the Far North region against the Boko Haram terrorists There are millions of ordinary people affected by conflict in Africa whose stories are missing in the mainstream media HumAngle is determined to tell those challenging and under-reported stories hoping that the people impacted by these conflicts will find the safety and security they deserve To ensure that we continue to provide public service coverage We want you to be part of our journalistic endeavour by contributing a token to us Your donation will further promote a robust Subscribe to our Telegram channel to get the stories on your phone once they arrive Of course, we want our exclusive stories to reach as many people as possible and would appreciate it if you republish them. 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Contact us for enquiries or requests and website in this browser for the next time I comment Cloudina and Corumbella fossils found in northern Minas Gerais indicate that a shallow sea covered parts of South America and Africa some 550 million years ago in northern Minas Gerais: fossils of tiny marine animals have been found in the Sete Lagoas Formation part of the geological unit known as the Bambuí GroupPEDRO STRIKIS owes its virtues to the climate and the natural moisture in the local soil which are favorable for growing the sugarcane that is used to make it The area’s strategic geographic location on the left bank of what becomes the huge São Francisco River called opará (sea river) in ancient times by the local Indians made Januária a major port and commercial hub during the colonial era nearly forgotten but marked by an intimate connection to the water have just come to light in still-active stone quarries on the outskirts of the city A team of geologists and paleontologists from the University of São Paulo (USP) and the São Paulo State University (Unesp) has found a special type of fossil there: tiny fragments of marine animals of the genus Cloudina tubular creatures consisting of a series of calcareous cones nested within one another which lived on Earth around 550 million years ago were embedded in a steep wall and in other outcrops of rocks of the Sete Lagoas Formation A sedimentary unit of the São Francisco watershed the Bambuí stretches over approximately 300,000 square kilometers and includes vast portions of the states of Minas Gerais and Bahia extending as well into the states of Goiás PEDRO STRIKISOutcrop in a stone quarry in the Januária regionPEDRO STRIKIS ILLUSTRATION SANDRO CASTELLIIn the new study the researchers support the hypothesis that this shallow seaway covered not just the part of Brazilian territory having rocks of the Bambuí Group but vast portions of eastern South America western Africa and southern Antarctica (see map) “This sea linked the three continents and connected to the ocean,” says biologist Pedro Strikis of the Geosciences Institute at USP (IGc-USP) the shape of the reasonably stable rocky blocks that form the continental crust—which geologists call cratons—differed from their present-day configuration Africa and Antarctica were interconnected and formed part of Gondwana the southern supercontinent that held most of the landmasses now situated in the Southern Hemisphere Although there is still intense debate among Brazilian researchers as to precisely how and when all the pieces of Gondwana came together—whether it occurred 520 million or 620 million years ago—there is consensus on the view that most of South America was already connected to Africa and Antarctica around 550 million years ago The idea that there was a shallow sea that flooded large sections of Gondwana is principally based on the geographic distribution of the Cloudinas found in various parts of the world Fossil specimens have been obtained in places such as Namibia prior to the discovery of the specimens in northern Minas Gerais traces of these marine creatures had been recovered in Corumbá Measuring up to three centimeters in length Cloudinas are one of the first macroscopic marine animals to have a calcium carbonate-based exoskeleton they were initially thought to be annelids are usually classified as members of the Cnidaria Their habitat was the carbon dioxide-rich floor of shallow seas at a depth where light can pass through the water which are fine layers of cyanobacteria that derive their energy from photosynthesis In some cases these mats are associated with the formation of calcareous rocks that can produce formations called stromatolites (if their layers are visible) or thrombolites (when the layers have a clotted appearance) LUCAS WARRENFossil fragments of Cloudinas: vestiges of marine life from 550 million years ago in Januária LUCAS WARREN The fragments of Cloudina specimens are considered guide fossils this means that they are a type of record found in several places on Earth but whose occurrence is limited to a well-defined period of time guide fossils are used throughout the world to correlate and date geological layers and the depositional environment associated with them Cloudinas occur only in sedimentary rocks of marine origin that were deposited onto the Earth’s crust between 550 million and 542 million years ago at the end of the geological period known as the Ediacaran immediately prior to the beginning of the Cambrian when marine invertebrates with biomineralized carapaces diversified over a short period of time Cloudinas have a fragile carapace that contains a small amount of calcium carbonate and wouldn’t be able to “survive” vigorous transport or the continuous action of running water,” says paleontologist Marcello Guimarães Simões of the Botucatu Biosciences Institute (IB) at Unesp they were autochthonous or parautocthonous.” For this reason the fossils of these animals are thought to have originated at the sites where they were found That particular feature reinforces the idea that a shallow sea did indeed once cover the places where these fossils were found Since the Cloudina sites were part of cratons roughly contiguous with what is believed to be Gondwana some 550 million years ago it is reasonable to assume that this ancient shallow sea connected South America and Africa LUCAS WARRENTraces of a soft-bodied animalLUCAS WARREN “Finding animal fossils in Januária was a pleasant surprise and it virtually ends the debate about the age of the Bambuí Group,” Pimentel says Geologist Claudio Riccomini of IGc-USP thinks along the same lines “The discovery of Cloudinas as well as fragments of Corumbellas definitively answers the question of the age of the Bambuí Group at least with the current state of knowledge,” says Riccomini another co-author of the article on the new marine fossils it is important to confirm whether the Bambuí Group shows the same age in different parts of its watershed and to ascertain the relationships between the rocks of the Sete Lagoas Formation and the glacial deposits that lie beneath them.” PEDRO STRIKISCalcareous formations in a cave in the Januária regionPEDRO STRIKIS Experts generally agree on the importance of the Januária fossils for establishing a more precise chronology of the Bambuí Group and developing the hypothesis that significant portions of South America Africa and Antarctica were covered by a shallow sea about 550 million years ago But discovery of the Cloudinas in northern Minas Gerais intensifies the debate around a fundamental question: a little over half a billion years ago had the southern supercontinent Gondwana already been completely formed have aligned into two groups with different views Each current of thought is based on different types of data such as rock dating and information on paleomagnetism which help determine where the cratons of Gondwana must have been during a given period and how they moved and interacted on the earthly globe over time The authors of the paper on the Januária fossils support the hypothesis that Gondwana particularly its western section (which today includes South America) was not yet fully formed at the time when Cloudinas and Corumbellas lived that formed the supercontinent were already joined but one of them—the large Amazonia craton—was already separate from the others around 550 million years ago given the name Clymene in 2006 by geologist Ricardo Trindade of the Institute of Astronomy Geophysics and Atmospheric Sciences of USP (IAG-USP) is thought to have separated most of Gondwana from the Amazonia craton the Clymene was likely the source of the saltwater that created the shallow sea over a significant portion of the land masses of the nascent Gondwana in the time of the Cloudinas Only around 520 million years ago did the ocean close completing the assembly of the jigsaw puzzle of the southern supercontinent “The formation of western Gondwana is more complex and it happened later than was thought,” Trindade says LUCAS WARRENMarks from small waves: evidence of an ancient shallow sea in northern Minas GeraisLUCAS WARREN In the opinion of geologist Umberto Cordani of IGc-USP the waters of the shallow sea that probably covered part of South America and Africa in the late Ediacaran cannot have come from the Clymene Márcio Pimentel of UnB and other researchers hold the more classic view on the establishment of Gondwana came together around 620 million years ago through the closing of a large ocean that separated the Congo and Saara cratons from the continental blocks of Amazonia and western Africa South America and Africa had no internal oceans The small marine animals that have now been found in Minas Gerais and in other Gondwana sites are thought to have populated a vast shallow interior sea that stretched over a continental lithosphere (crust) “There is no geological evidence of an oceanic lithosphere in central Brazil during the Ediacaran or Cambrian period that could be associated with the possible existence of the Clymene,” Cordani says The two groups with differing views on the formation of Gondwana have amicably published articles and comments questioning data and interpretations of colleagues who do not share their position The discovery of the marine fossils in northern Minas Gerais—which for some serves as evidence that the Clymene Ocean covered South America and Africa—is one more ingredient to fuel the debate Scientific article WARREN, L.V et al. The puzzle assembled: Ediacaran guide fossil Cloudina reveals an old proto-Gondwana seaway © Revista Pesquisa FAPESP - All rights reserved Two Imperial Horizons teams presented their work at the Engineers Without Borders (EWB) UK Challenge Finals on June 20th Over 4,600 students had taken part in the competition to design ‘real sustainable cross-cultural development projects’ for the community of Bambui in Cameroon  The Finals showcased the best work from across the UK and As a Teaching Fellow in the Global Challenges field within Imperial Horizons I accompanied our teams along with their tutor The event was held at the Siemens Crystal building at the Royal Victoria Dock in East London appropriately dubbed as ‘one of the world’s most sustainable buildings’.  However there was little sun for the solar panels as we arrived in pouring rain at 9am.  Nonetheless by 10am the venue was full of posters and buzzing with students ready to be judged by industry professionals ranging from water filters to mapping protocols for Bambui Representing Imperial College were Claudia Caravello Christopher Parsonson and Jonathan Risley with their proposal for ‘Waste for Power’.  Their ‘Biodigester and Biobox Scheme’ used waste to create methane and fertilizer Jaime Fernandez de Santaella presented his group’s design for a ‘Healthy Public Toilet’ in the farmers’ market of Bambui.   The format of the competition was certainly challenging but the students were prepared and ready to share and defend their ideas praised by the judges for their rigorous analysis and thorough outline of their scheme the ‘Waste for Power’ team qualified for the final assessment and presented to the entire competition  Again the team spoke very professionally using an animation to explain their design that palpably grabbed the attention of the room.  It was therefore no surprise that they stimulated the most questions from the judges students from Sheffield Hallam were awarded first prize for their Efficient Modular Stove Burner – potentially of great benefit to the people of Bambui.  However the Imperial Horizons teams had acquitted themselves exceptionally well such was the interest in ‘Waste for Power’ that Imperial students were answering questions from students and academics until the end of the day celebrating the work of students and promoting the importance of social economic and environmental context when designing development and engineering projects  Thanks go to Dan Craddock and the team at Engineers Without Borders UK for organizing a great event that was a fitting end to this year’s challenge.  Personally I am already looking forward to next year’s Article text (excluding photos or graphics) available under an Attribution-NonCommercial-ShareAlike Creative Commons license. 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