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Unauthorized fossil trafficking violates national legislation and deprives cultural and natural heritage. This study proposes a pilot method to fingerprint the origin of fossils by characterizing the carbon and oxygen stable isotope signatures of fossil-bearing limestones to provide a non-destructive quantitative tool against illegal fossil trade. This promising approach has been applied to the Crato Formation (NE Brazil), which is a renowned Lower Cretaceous fossiliferous lacustrine limestone. This study aims at establishing the range of isotopic oxygen (δ18O) and carbon (δ13C) values of the Crato Formation’s laminated calci-mudstone by compiling isotopic data from previous studies, conducting new analyses, and comparing with other fossiliferous lacustrine limestones from Brazil (Cretaceous Codó Formation) and the USA (Eocene Green River Formation). This preliminary evaluation determined a distinctive isotopic signature of the Crato Formation fossil-bearing “sete cortes” (“seven cuts”) ethnostratum, with VPDB δ18O and δ13C arithmetic means of −5.94‰ and +0.90‰, standard deviations 0.76‰ and 0.61‰, medians of −5.89‰ and +0.73‰, and interquartile ranges of 1.47‰ and 1.24‰, respectively. This pilot investigation establishes a methodological groundwork for the development of a global database integrating lithofacies and geochemical parameters of fossil-bearing limestones to expedite the identification and restitution of illegally extracted paleontological heritage.

Extreme environments, such as hypersaline habitats, hot springs, deep-sea hydrothermal vents, glaciers, and permafrost, provide diverse ecological niches for studying microbial evolution. However, knowledge of microbial communities in extreme environments at high southern latitudes remains limited, aside from Antarctica. Laguna Timone is a hypersaline crater lake located in a Pleistocene maar of the Pali Aike Volcanic Field, southern Patagonia; the lake was formed during basaltic eruptions in a periglacial setting. Here, we report the first integrative characterization of microbial communities from biofilms and microbial mats in this lake using high-throughput 16S rRNA and ITS gene sequencing, along with mineralogical and hydrochemical analyses of water, sediments, and carbonates. Bacterial communities were dominated by the genera Enterobacterales ASV1, Pseudomonas, Oscillatoria, Nodularia, and Belliella, with site-specific assemblages. Fungal communities included Laetinaevia, Ilyonectria, Thelebolus, Plectosphaerella, and Acrostalagmus, each showing distinct distribution patterns. These baseline data contribute to understanding microbial dynamics in hypersaline maar environments and support future investigations. This integrative approach highlights key microbe–mineral relationships and underscores the potential of Laguna Timone as a natural laboratory for exploring biosignature formation and microbial adaptation in chemically extreme environments, both on early Earth and potentially beyond.

In this study, we present a correlation between δ18OC values of carbonate in tooth enamel samples from the modern Brazilian population and the available δ18ODW data for the meteoric water from the Global Network of Isotopes in Precipitation (GNIP). Tooth enamel from 119 Brazilian individuals from five different regions of the country were analyzed. The δ18OC isoscape obtained is in good agreement with the isoscape based on regional meteoric and drinking water. The regression matrix obtained for the δ18O values of the carbonate tooth enamel and meteoric water was used to build an isoscape using the regression-kriging approach. Our data show that Brazil can be divided in two main regions with respect to the δ18O values of the carbonate tooth enamel: (1) the most easterly part of the northeast region, which is characterized by a warm and dry climate and (2) the remainder of the country, stretching from the Amazon rain forest to the more southernly regions. The data herein reported can be used for forensic purposes related to human identification. •Isoscape based on tooth enamel for the Brazilian population•δ18O isoscape based on tooth enamel for human identification•Isotopic database based on tooth enamel for the modern population in Brazil•Isoscape built using the regression-kriging approach

Tufas are freshwater carbonate rocks that form in continental environments through a combination of physical, chemical, and biological processes. This study investigates the role of microorganisms in the precipitation of Quaternary tufa deposits in the Serra da Bodoquena Formation, in the Bonito region. Two sites along the Mimoso River, named Taíka and Mimosa, characterized by the pool–barrage–cascade depositional subenvironment, were selected for this study. Four distinct facies were identified: stromatolitic boundstones, phytoherm boundstones of algae, phytoherm boundstones of bryophytes, and phytoclastic rudstones. These facies were observed in diverse hydrological settings, including fast-flowing waters, such as waterfalls and cascades, as well as slow-flowing areas, such as pools and dams. The δ18O depletion indicated a meteoric origin for the fluid involved in carbonate precipitation. The low δ13C values were attributed to photosynthetic processes and the contribution of light carbon-enriched groundwater. The presence of Oocardium stratum and calcified organic mucilage from extracellular polymeric substance (EPS) corroborates the significant role of microorganisms in tufa formation, particularly in stromatolitic boundstones and phytoherm boundstones of algae. Rapid CO2 degassing significantly contributes to mineralization in fast-flowing waters. Micro-CT results offer detailed insights into the relationship between mechanical processes and biological influences in shaping porosity characteristics. The findings of this study significantly enhance our understanding of the role of microorganisms in tufa formation, highlighting the complex interplay between biotic and abiotic processes in the development of different tufa facies. Moreover, the insights gained from this study provide valuable implications for interpreting tufa deposits worldwide.

Mg clay minerals are usually associated with carbonates in alkaline-saline environments, precipitated from solution and/or transformation from other minerals. The aim of this research is to identify the mineralogy and geochemistry of clay minerals in different alkaline lakes in the Nhecolândia region, the southernmost region of the Pantanal wetland (Brazil). Sediment samples were analyzed by X-ray diffraction, X-ray fluorescence, scanning electron microscopy and transmission electron microscopy. Water samples were analyzed, determining their main cations and anions, in order to understand their relationship with the clays. The analyses allowed classifying the water bodies as saline, oligosaline and freshwater lakes. The sediments are composed mainly of quartz and a fine-clay fraction, dominated by illite, kaolinite and smectite. The XRD results showed illite and smectite mixed-layered in the saline lakes at Barranco Alto farm, whereas at Nhumirim farm, trioctahedral smectite was only observed in one lake. The smectite minerals were normally identified coupled with calcite at the top of the sequences, associated with exopolymeric substances (EPS) in the lakes, suggesting that these minerals are precipitating due to the physical-chemical and biological conditions of the water bodies.

Quantifying the permeability in karst aquifers often is imprecise and difficult to interpret. Therefore, it is possible to notice the increase and decrease of permeability values related to the known triple porosity within the karstic system. This work analyzed small- and well-scale data from a tubular well situated in a Brazilian Neoproterozoic karst aquifer to show the scale effect and relationships between fractures/channels flow zones and regional tectonic structures of the area. At the micro-scale, 3D micro-Ct images of tubular well core samples and thin sections were used to analyze the aquifer matrix and micro-fractures. In well-scale, data from high-resolution acoustic geophysical logging, borehole video, and drilling reports helped to analyze fractures and channels. Multi-scale lineament mapping with geophysical logging aided to correlate the major tectonic structures in the area to the existing flow zones. The result showed an increase of eleven orders of magnitude in values of permeability and transmissivity from micro- to well-scale, indicating the scale effect, explained by the low permeability of the matrix and the influence of fractures and channels in flow zones in the aquifer. The groundwater flow can be linked regionally to the presence of tectonic structures associated with the anticlinal fold present in the study area, diabase dike intrusions, and the Cenozoic transcurrence. The use of high-resolution methods makes possible the distinction between matrix, fractures, and channels in the calculation of hydraulic parameters allowing a better understanding of the influence of each structure in the groundwater flow.

The Região dos Lagos situated along the coast east of Rio de Janeiro, Brazil, is dominated by a semiarid microclimate attributed to the occurrence of oceanographic upwelling at nearby Cabo Frio. The upwelling is strongly associated with the dominance of NE winds during austral spring/summer and the directional change of the shoreline orientation. Some coastal hypersaline lagoons from this region have been studied intensively over the last 25 yr because they represent relatively rare sites of modern primary dolomite precipitation. Comparison of environmental signals in three lagoons indicates that during the last ~ 3.0 kyr, changes in oceanographic parameters may have influenced biogeochemical processes associated with the production of carbonate-bearing sediments. The timing of a decrease in sea level may have influenced a period of more intense upwelling, which coincides with precipitation of stoichiometric dolomite at ~ 2.3 kyr BP in the lagoons located along the coast directly west of Cabo Frio. The dolomite found in the lower sections of cores from Lagoa Vermelha and Brejo do Espinho contains more positive δ 18O values, indicating greater evaporation with a period of increased semiarid conditions corresponding to greater terrestrial input. The lower δ 13C values indicate re-equilibration with the input of new carbonate ions derived from the decomposition of organic matter during dolomite formation. In contrast, the sediment core from Lagoa Salgada, located northeast of Cabo Frio, contains no dolomite, and very positive δ 13C values recorded in carbonate sediments are attributed to microbially mediated methanogenesis, whereas δ 18O values remain relatively constant throughout the core at around zero.

We conducted a geochemical analysis on three sediment cores collected from soda and freshwater lakes in the Pantanal region, in Brazil. Our objective was to identify the primary sources of organic matter associated with the Pleistocene-Holocene transition, as previously documented in that area. The Nhecolandia region, located in the Pantanal, encompasses over 10,000 lakes, with approximately 10% of them exhibiting alkaline characteristics. Soda lakes became highly saline and alkaline after ~ 910 cal yr BP, which influences biogeochemistry and aquatic ecology. They have high electrical conductivity and pH can reach 10.5. In contrast to freshwater, soda lakes are absent of surrounding vegetation. Literature suggests a strong influence by the Last Glacial Maximum on the region. We hypothesized that periods of aridity and increased precipitation influenced the composition of organic matter present in sediments and preserved within these cores. Our analysis focused on examining the presence and distribution of fatty acids, organic carbon content, and total nitrogen. In general, the cores exhibited two distinct parts in terms of organic matter sources: the upper sections of the cores were primarily composed by terrestrial sources, identified by the presence of long-chain fatty acids, while the deeper sections were dominated by aquatic sources, therefore short-chain fatty acids. We did not find significant difference among fatty acid profile that could distinguish freshwater from soda lakes, the only remarkable difference was the occurrence of saturated fatty acids, which is lower in freshwater lake. These findings suggest the occurrence of humid and arid periods in the region. The C/N ratio displayed a similar trend to the fatty acid’s profiles, exhibiting an abrupt change that was likely induced by climate variations. Although diagenesis can alter the composition of organic matter and, subsequently, the C/N values, it is noteworthy that the abrupt change observed in the Salina da Ponta (soda lake) core corresponds to 3,200 years BP. This coincides with documented climate changes that occurred during the Holocene. Our study revealed the influence of past climatic conditions on the sources and variations of organic matter in sediment cores from the Pantanal’s soda and freshwater lakes. Consideration of diagenesis and climate variations is crucial for interpreting sedimentary records.

Suspended sediments (SSs) were examined regarding the content of fatty acids (FAs) to associate them with sources of soil entry into the river. The source of organic matter was traced through fatty acid distribution, as well as erosion. Also, TOC, TN, and TOC/NT were used to support the results of FAs. For this, a tropical river was chosen to understand the main source of input considering the level of land occupation along the river. The Barigui river, in southern Brazil, was segmented in four distinct areas regarding the soil occupation (P1, P2, P3, and P4). Nine sampling campaigns were conducted from Nov/2014 to Nov/2015 using a time-integrated sampler. Site P1 has the lowest level of urbanization and showed the lowest concentration of FAs (16.35 μg −1 ). In contrast, site P4, the most urbanized, showed the highest content of fatty acids, including those associated with erosion, 378.53 μg g −1 , specifically those with long chains. The mean concentrations of the saturated fatty acids (FAs) was 283.40 μg g −1 , monounsaturated fatty acids (MUFAs) was 79.46 μg g −1 , and polyunsaturated fatty acids (PUFAs) was 15.66 μg g −1 . Twenty-seven fatty acids were examined, nevertheless C15:0, C16:0, C18:0, and C18:1ω9 prevailed in all samples. Generally, those acids indicate sewage inputs. Statics analyses were used to find the relation between the source of organic matter (autochthonous, allochthones, and anthropogenic) and FAs. Finally, the input of organic matter is associated with land occupation, which can be distinguished by FA distribution.