GEOESPELEOLOGIA
URI permanente para esta coleçãohttps://bdc.icmbio.gov.br/handle/cecav/2
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Resultados da Pesquisa
Item Speleothem in Sandstone: Maranhão as a Geo-Speleological Scenario(2024-06-26) Castro, Cláudio Eduardo de; Silva, Flávia MartinsThe municipality of Carolina, located in the southern region of Maranhão, features a terrain composed of hills and plateaus formed from sandstone lithology originating from the Balsas Group formations. This region houses geological features such as caves and speleothems, which pertain to endokarst, primarily formed through erosive processes. Due to its significant speleological potential, the region has been studied by the Conservation Units Research Group (GEUC) of the Maranhão State University (UEMA) since 2013.Item Obtaining High‐Resolution Magnetic Records From Speleothems Using Magnetic Microscopy(2024) Borlina, C. S.; Lima, E. A.; Feinberg, J. M; Jaqueto, P.; Lascu, I.; Trindade, R. I. F.; et al.Speleothems are mineral deposits capable of recording detrital and/or chemical remanent magnetization at annual timescales. They can offer high‐resolution paleomagnetic records of short‐term variations in Earth's magnetic field, crucial for understanding the evolution of the dynamo. Owing to limitations on the magnetic moment sensitivity of commercial cryogenic rock magnetometers (∼10− 11 Am2 ), paleomagnetic studies of speleothems have been limited to samples with volumes of several hundreds of mm3 , averaging tens to hundreds of years of magnetic variation. Nonetheless, smaller samples (∼1–10 mm3 ) can be measured using superconducting quantum interference device (SQUID) microscopy, with a sensitivity better than ∼10− 15 Am2 . To determine the application of SQUID microscopy for obtaining robust high‐resolution records from small‐volume speleothem samples, we analyzed three different stalagmites collected from Lapa dos Morcegos Cave (Portugal), Pau d'Alho Cave (Brazil), and Crevice Cave (United States). These stalagmites are representative of a range of magnetic properties and have been previously studied with conventional rock magnetometers. We show that by using SQUID microscopy we can achieve a five‐fold improvement in temporal resolution for samples with higher abundances of magnetic carriers (e.g., Pau d'Alho Cave and Lapa dos Morcegos Cave). In contrast, speleothems with low abundances of magnetic carriers (e.g., Crevice Cave) do not benefit from higher resolution analysis and are best analyzed using conventional rock magnetometers. Overall, by targeting speleothem samples with high concentrations of magnetic carriers we can increase the temporal resolution of magnetic records, setting the stage for resolving geomagnetic variations at short time scales.Item A New Attempt to Estimate Underground Soil Leakage through High-Density, Fixed-Point Monitoring in a Typical Karst Rocky Desertification Region(2024-05-01) Dayun Zhu; Qian Yang; Hua Xiao; Yingshan ZhaoUnderstanding soil loss pathways in karst regions is crucial for erosion control. Combining high-density measurements of grid points with runoff plot monitoring, we attempt to use a new indirect method to study the characteristics of soil loss in karst rocky desertification areas of Salaxi Town, Guizhou province. One cycle year monitoring data of 12640 grid points were applied in the soil loss analysis. This study identifies underground leakage as the primary pathway of soil loss, with an mean soil leakage of 21.51 kg in potential areas, accounting for 83.12%, and an average leakage of 22.69 kg in in mild karst rocky desertification areas accounting for 81.48%. Mixed vegetation types (forest, shrub, and grass) were better at preventing surface soil loss but increased underground leakage compared to single vegetation types. The rainy season significantly influences soil erosion, accounting for 67.88% of total loss, with slight variations among different karst rocky desertification grades and vegetation types. Mean underground leakage rates during the rainy and dry seasons are 63.34% and 36.66%, respectively. Although this method still has certain limitations, it plays a positive role in revealing the mechanism of soil erosion processes in karst regions.Item Karst Hydrological Connections of Lakes and Neoproterozoic Hydrogeological System between the Years 1985–2020, Lagoa Santa—Minas Gerais, Brazil(2024-09-12) Pacheco Neto, Wallace; Paula, Rodrigo de; Galvão, PauloThis study focuses on a complex Brazilian Neoproterozoic karst (hydro)geological and geomorphological area, consisting of metapelitic–carbonate sedimentary rocks of ~740–590 Ma, forming the largest carbonate sequence in the country. At the center of the area lies the Lagoa Santa Karst Environmental Protection Area (LSKEPA), located near the Minas Gerais’ state capital, Belo Horizonte, and presents a series of lakes associated with the large fluvial system of the Velhas river under the influence, locally, of carbonate rocks. The hydrodynamics of carbonate lakes remain enigmatic, and various factors can influence the behavior of these water bodies. This work analyzed the hydrological behavior of 129 lakes within the LSKEPA to understand potential connections with the main karst aquifer, karst-fissure aquifer, and porous aquifer, as well as their evolution patterns in the physical environment. Pluviometric surveys and satellite image analysis were conducted from 1984 to 2020 to observe how the lakes’ shorelines behaved in response to meteorological variations. The temporal assessment for understanding landscape evolution proves to be an effective tool and provides important information about the interaction between groundwater and surface water. The 129 lakes were grouped into eight classes representing the hydrological connection patterns with the aquifers in the region, with classes defined for perennial lakes: (1) constantly connected, (2) seasonally disconnected, and (3) disconnected; for intermittent lakes: (4) disconnected during the analyzed time interval, (5) seasonally connected, (6) disconnected, (7) extremely disconnected, and (8) intermittent lakes that connected and stopped drying up. The patterns observed in the variation of lakes’ shorelines under the influence of different pluviometric moments showed a positive correlation, especially in dry periods, where these water bodies may be functioning as recharge or discharge zones of the karst aquifer. These inputs and outputs are conditioned to the well-developed karst tertiary porosity, where water flow in the epikarst moves according to the direction of enlarged karstified fractures, rock foliation planes, and lithological contacts. Other factors may condition the hydrological behavior of the lakes, such as rates of evapotranspiration, intensity of rainfall during rainy periods, and excessive exploitation of water.Item Investigating speleothem magnetism as a proxy for dust mobilization and rainfall(2024-04-15) Kimberly Hess; Roger R. Fu; Samuel Piascik; Nicolas M. Stríkis; Ricardo I.F. Trindade; Tyler Kukla; Alec R. Brenner; Plinio Jaqueto; Michail I. Petaev; Francisco W. Cruz; Placido Fabricio Silva Melo Buarque; Carlos Pérez-Mejías; Hai ChengCommonly used speleothem-based paleoclimate proxies such as δ18O, δ13C, and trace element ratios are capable of high temporal resolution, but their interpretations are often ambiguous due to the conflated effects of multiple forcings. This complexity motivates the development of targeted proxies that can track specific local hydrological conditions. To this end, the concentration of ferromagnetic Fe-oxide particles in speleothem laminae has been suggested as a potential tracer for local precipitation. Here we use the quantum diamond microscope (QDM) to obtain a sub-annual resolution time series of ferromagnetic content in a Brazilian speleothem from a well-ventilated cave environment covering the period between 1913 and 2016 CE. This high resolution allows us to quantify the correlation between speleothem magnetic properties and an instrumental precipitation record for the first time. We find that ferromagnetic content in the central column displays a modest but significant negative correlation with rainfall ( , while magnetism in the speleothem flanks shows a weaker, statistically insignificant relationship. Rock magnetic analyses of the speleothem further reveal ultrafine, pedogenic grains to be the dominant ferromagnetic carriers. Combining QDM and electron microprobe data, we show that these pedogenic grains were likely developed in surface soils and delivered into the cave as part of airborne, 10–200 μm silicate-carbonate soil agglomerates. Our results show that speleothem magnetism holds strong potential as a targeted proxy for paleorainfall and demonstrate a method for identifying the mechanism of magnetic enhancement, which sets the necessary foundation for any paleoclimatic interpretations.Item Growth rates of Brazilian carbonate speleothems by the 210Pb chronological method(2024-03-14) Figols, A.P.; Bonotto, D.M.Carbonate speleothems contain measurable concentration of 210Pb, which can be used to estimate modern growth rates up to a 150-years timescale. However, data referring to such application of this geochronological method are scarce in the Southern Hemisphere, with most studies based on temperate climate locations in the Asian continent. Such a lack of data makes it difficult to approach an investigative comparison of the main physical parameters that influence the precipitation rate of calcium carbonate in caves. In this context, the present study describes the record of longitudinal growth rates of carbonate speleothems sampled in two different Brazilian regions: Pains municipality (Midwestern Minas Gerais State) and Curitiba Metropolitan Area (CMA, eastern Paraná State), whose climates are subtropical with dry winter (Cwa) and wet temperate (Cfb), respectively. Segments of variable thickness from eight stalactites samples were subjected to HCl dissolution, 210Po deposition onto copper discs, and 210Po analysis by alpha spectrometry for yielding the activity concentration data. 210Po activity concentration data provided the 210Pb values due to radioactive equilibrium condition between these radionuclides. Although all samples exhibited a quantifiable measure of the 210Pb activity concentration in their sectional layers, the longitudinal growth rate could not be estimated by the CF:CS method for three of the eight stalactites. However, the modified CRS method allowed determine growth rates for all speleothems. The mean 210Pb CRS growth rate obtained at Pains and CMA sites is 1.4 ± 0.1 mm/year and 1.5 ± 0.2 mm/year, respectively, indicating coincidence at both sites and suggesting that the approach is reliable for determining modern growth rates.Item DINÂMICAS DA NATUREZA NA REGIÃO DE CARAJÁS COM FOCO NOS ATRIBUTOS CLÁSSICOS DA GEODIVERSIDADE(2024-06) Santos, Railson Luz; Mascarenhas, Abraão Levi dos Santos; Vidal, Maria RitaOs aspectos da geodiversidade têm abarcado discussões teóricas e metodológicas, e na ciência geográfica os estudos de padrões de geodiversidade buscam a identificação e a classificação dos padrões espaciais, sendo cruciais para melhor gestão do geopatromônio. A presente seção elencou a região de Carajás como locus de rica geodiversidade. Partindo da análise dos componentes geodiversos que integram a paisagem, tais como as estruturas litológicas, pedológica e geomorfológica, e posteriormente classificando-os por sua relevância científica, educacional e cultural. Para melhor estruturar os níveis de geodiversidade, os dados foram distribuídos em uma escala de importância de 1 a 5. Espera-se que tais valores possam ser usados como dados técnicos para subsidiar planos de geoconservação da geodiversidade das áreas em tela.Item Preliminary inventory and conservation conditions of speleotems from Gruta da Serra das Cobras, Santa Quitéria, Ceará, Brazil(2024) Paiva, Antonio Victor Rodrigues Sousa de; Carvalho, Bruna Lima; Xinenes, Celso Lira; Fernandes, Nayane Barros Sousa; Sobrinho, José FalcãoNatural underground cavities are environments composed of unique characteristics that house a great complexity of geological formations and lush scenery. The underground environment is considered a true treasure for science and humanity. The main objectiveof this research is to identify and classify the different types of speleothems found in Gruta das Cobras located in the municipality of Santa Quitéria/CE, also highlighting the risks that these structures face in terms of conservation. The materials and methods consisted of bibliographical research, fieldwork, photographic records and analysis and interpretation of information obtained at all stages. In general, the most common speleothem formation present in the study area is of the stalactite and stalagmite type. Speleothems of the column type, Bridal cake and Boxwork type were recorded inside the cave, complex formations that take millions of years to form and which are currently being impacted by the tourism sector, with no regulation or inspection. Impacts on structures, graffiti and breakage of speleothems were identified. In this way, it is concluded that further studies on the site are essential, as well as a preservation intervention by the competent public bodies.Item Uso de traçadores corantes fluorescentes na identificação de rotas de fluxos em sistemas cársticos: panorama de estudos no Brasil(2024) Vieira, Matheus Santiago; Tavares, André Silva; Uagoda, Rogério Elias Soares; Assunção, PedroO transporte de poluentes por condutos cársticos é preocupante, visto que podem ocasionar a perda da biodiversidade aquática na contaminação dos recursos hídricos subterrâneos. Para a identificação e avaliação da origem e destino dos contaminantes e as interações entre fluxos superficiais e subterrâneos os traçadores do tipo corante fluorescente são amplamente usados em todo mundo. Logo, este trabalho teve como objetivo apresentar um panorama sobre a evolução metodológica do uso de traçadores corantes em sistemas cársticos e os principais avanços desses estudos no Brasil. Para isso foi realizada uma pesquisa bibliográfica com o método de análise exploratória quantitativa que contemplou análise de livros, periódicos, teses e dissertações nacionais e internacionais publicadas recentemente nos últimos 10 anos, disponíveis no Portal Periódicos CAPES, Web of Science e Google Scholar. Como resultado, foi possível identificar os avanços de novos instrumentos de campo e laboratoriais, softwares de modelagem específicos e novos traçadores. No Brasil, observou-se um crescimento no número de pesquisas, avanço importante para o melhor entendimento sobre os sistemas cársticos brasileiros. As avaliações sobre as rotas de fluxos subterrâneos permitiram identificar principalmente os limites entre bacias hidrogeológicas cársticas, obter parâmetros mais confiáveis de transporte de contaminantes, e compreender melhor sobre a hidrodinâmica de bacias cársticas no Brasil.Item Avaliação da qualidade da água superficial e subterrânea na Bacia do Rio Peruaçu, Minas Gerais(2024-11) Barros, Bárbara Thaíssa da Silva; Baggio Filho, Hernando; Santos, Matheus Simões; Travassos, Luiz Eduardo Panisset; Carvalho, Frank Alison deAnálises sobre a qualidade geoquímica dos recursos hídricos localizados em Unidades de Conservação,ainda é bastante incipiente, ademais, em áreas cársticas. A amostragem geoquímica é uma ferramenta de extrema utilidade para identificar emensurar os parâmetros físico-químicos e químicos presentes nos corpos hídricos. Neste contexto, a pesquisa teve como objetivo analisar a qualidade da água superficial e subterrânea na bacia hidrográfica do rio Peruaçu, através das análises dos parâmetros físico-químicos, químicos e microbiológicos, comparando os resultadoscom os valores orientadores das resoluções CONAMA357/05 e 396/08.Foram realizadas duas amostragensde campo, totalizando 15 estações de amostragempor período climático.Quanto à sazonalidade, no geral, houve diferença em praticamente todos os parâmetros, com exceção da temperatura e pH.Os teores de LAS, NO2, NO3, em alguns pontos encontram-se em desconformidade com a legislação, apresentado uma poluição de ordem antropogênica. Os elementos metálicos e semimetálicos Ca, Mg, Al, Fe, Mn, Pb e Zn,em alguns dos pontos amostrados, também se encontram em desconformidade com a legislação, sendo sua contaminação de ordem natural,relacionados às litologias do Grupo Bambuí. Do ponto de vista microbiológico, a maioria dos pontos deu positivo paraEscherichia Coli.A poluição de ordem antropogênica e contaminação de ordem natural,foram as identificadas na área de estudo, sendo a influência antrópica bastante expressiva.