GEOESPELEOLOGIA
URI permanente para esta coleçãohttps://bdc.icmbio.gov.br/handle/cecav/2
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10 resultados
Resultados da Pesquisa
- A hydrogeological conceptual model for the groundwater dynamics in the ferricretes of Capão Xavier, Iron Quadrangle, Southeastern Brazil(2021-12) Dias, Jordania Cristina dos Santos; Bacellar, Luis de Almeida PradoIn the Iron Quadrangle (IQ), southeastern Brazil, ferricretes usually overlie the banded iron formations (BIFs) of the Cauê Formation, rocks that not only host the most important iron ore deposits of this region but are also its major groundwater source. Little is known about the water dynamics in ferricretes and therefore how they influence the recharge of the subjacent aquifer (Cauê aquifer). The objective of this research was to identify ferricrete typologies and investigate their water dynamics in the Capão Xavier region, northwest of IQ. Field work consisted of macroscopic description of ferricretes, infiltration tests and multitemporal electrical resistivity surveys. Two ferricrete typologies were distinguished: structured ferricretes, which are older and occur on top of plateaus, and detrital ferricretes of colluvial-alluvial origin, which were deposited downslope and in topographic lows. The structured ferricretes preserve the medium- to high-angle foliation inherited from the underlying BIFs, whereas the detrital ferricretes constitute thick packs subparallel to the topographic surface and are intercalated with argillaceous layers in areas of karstic depressions. The structured ferricretes are more porous (20.8% to 24.4%) than the detrital ferricretes (14.4% to 17.6%), hence they have higher mean basic infiltration rates (8.3x10-6 m/s) than detrital ferricretes (2.8x10-6 m/s). Despite these low mean basic infiltration rates, infiltration advances thanks to the karstic-fissural porosity (fractures and joints widened by karstification), and superficial cavities that are connected to caves in the interface between the ferricrete and the subjacent, less resistant, transition horizon. Karstification is controlled by the subvertical foliation in the structured ferricretes and subparallel layering in the detrital ferricretes. Some factors that favor infiltration and deep percolation of water are superficial rugosity in structured ferricretes, and karstic depressions in both typologies. The recharge of the Cauê aquifer is diachronic, firstly taking place via the karstic-fissural system and later via the ferricrete matrix.
- Multi-instar descriptions of cave dwelling Erythraeidae (Trombidiformes: Parasitengona) employing an integrative approach(2021-09) Souza, Maysa F. V. R.; Alvarenga, Denizar A.; Souza-Silva, Marconi; Ferreira, Rodrigo L.In the last decade, the scientific community brought to the debate gaps that slow down the advance of knowledge regarding global biodiversity. More recently, this discussion has reached subterranean environments, where these gaps are even more dramatic due to the relict and vulnerable nature of their species. In this context, we tested ecological metrics related to some of these gaps, checking if the biological relevance of the caves would change depending on ecological attributes related to each metric. The study was carried out in caves from southeastern Brazil, located in a region presenting a high richness of troglobitic species restricted to a narrow geographical extent. Thus, we verified: (a) the cave invertebrate communities’ vulnerability with the Vulnerability Index and the Importance Value for Cave Conservation; (b) the distribution and endemicity of the troglobitic species with the Endemicity Index; (c) the phylogenetic diversity of the troglobitic species considering the average taxonomic distinction (∆+), their richness and evenness. We observed a considerable change in the ordering of the caves’ biological relevance according to each tested attribute (index). We discussed how each of these metrics and their attributes indirectly relate to: (a) the preservation and maintenance of the phylogenetic diversity of subterranean communities; (b) the spatial restrictions of different groups, where the greater their restrictions, the greater their vulnerability; (c) the preservation of caves with high biological relevance considering these different attributes together. Thus, we recommend the use of different metrics so that different ecological attributes can be considered, supporting actions that aim to preserve caves in highly altered regions. Finally, we find that the most biologically important cave in the region is not protected (Gruta da Morena Cave). We warn that this cave needs to be contemplated by a conservation unit in the region urgently.
- Natural Hydrogeochemical Background Levels in the Carste Lagoa Santa Protection Unit, Minas Gerais, Brazil(2020-11-05) Aragão, Frederico; Velásquez, Leila Nunes Menegasse; Galvão, Paulo; Vieira, Luísa CostaThe identification of hydrogeochemical anomalies in karst water resources represents a crucial step in Brazil’s water management plans. Accelerated urban and industrial development occurs in the region that includes the Carste Lagoa Santa Protection Unit, State of Minas Gerais, which may negatively impact its water quality. This paper establishes Natural Background Levels (NBL) of waters collected from deep tubular wells and springs for Si4+, Ca2+, Mg2+, Na+, K+, HCO3, SO42, Clto understand sources of possible geogenic and anthropogenic anomalies. Areas with surpassed thresholds were compared with geological, hydrogeochemical, and land use data. Every parameter, except for chloride, showed elevated concentrations due to lithologic origin. The NBLs for waters of wells and springs are, respectively, 17.9 and 12.7 mg/L (silica), 97.0 and 91.5 mg/L (calcium), 4.9 and 2.9 mg/L (magnesium), 6.2 and 3.8 mg/L (sodium), 1.0 and 0.3 mg/L (potassium), 285.5 and 254.6 mg/L (bicarbonate), 9.4 and 13.6 mg/L (sulfate). Chloride, analyzed only in groundwater, presented 6.7 mg/L indi-cating a possible influence of upstream urban areas of Lagoa Santa and Pedro Leopoldo municipalities. Volatile and Semivolatile Organic Compounds were also analyzed, but all of them were below the detection limit. This work is important to comprehend the NBL of major elements, reveal geogenic anomalies, and distinguish car-bonate aquifer units from the impure ones.
- Late Quaternary episodes of clastic sediment deposition in the Tarimba Cave, Central Brazil(2021-04-10) Caldeira, Dandara; Uagoda, Rogério; Morais Nogueira, Adivane; Garnier, Jeremie; Sawakuchi, André Oliveira; Hussain, YawarThe study presents three sedimentary profiles from Tarimba cave in central Brazil. The data allow constraining the late Quaternary sedimentary evolution of cave systems in the region. A multi-techniques approach was used to characterize sediment texture (grain size and circularity index), mineralogical composition (X-Ray Diffraction), chemical composition (ICP-OES) and deposition ages (Optically Stimulated Luminescence and radiocarbon). Eight sedimentary facies were identified, including a facies formed by autochthonous sediments (Guano) and seven facies formed by allochthonous siliciclastic sediments. The siliciclastic facies range from clayey to gravelly deposits that correspond to high-density gravity flows (Diamicton) and water laid traction process of varied deposition energy (Channel, Backswamp, and Slackwater). The studied deposits reflect an intense cave filing from the Middle to Late Pleistocene in the last 200 Ka. Subsequent depositional events formed three sedimentation phases: the first before 200 Ka corresponding to a larger granulometric interval, clay to gravel, identified through erosive surfaces; the second, after 197 Ka, is composed of sandy sediments and oscillations in the water flow energy. The third phase between 87 and 52 Ka (which covered the other stages) was responsible for the last fluvial deposition.
- Geological and hydrogeological review of a semi-arid region with conflicts to water availability (southeastern Brazil)(2021-11) P.Bhering, Apolo; Antunes, I.M.H.R.; A.G.Marques, EduardoGroundwater consumption has become increasingly relevant for urban development. The city of Montes Claros (Minas Gerais, Brazil) is located in the border region of the Brazilian semi-arid polygon and has registered conflicts of water use for decades ago. The study area contains a complex karst system responsible for the heterogeneous permeability of water recharge and groundwater flow. The urban area of Montes Claros is located in the Vieira River watershed and contains different groundwater wells used to agro-industrial and human consumption. Almost groundwater captions have a low specific capacity with a consequent groundwater depletion. On the region, there are significant areas with a negative water balance concerning to water recharge and groundwater exploitation. Groundwater flow has a regional dominant direction of SW-NE, however locally, groundwater flow varies and could be identified some clusters with high hydrological potential. The contrast between hydrogeological features of the outcropping lithotypes added to the geological structures contribute to variations in the potentiometric level and in the productivity of aquifers. The main aim of this study is a reviewer of the regional hydrogeology of the municipality of Montes Claros to evaluate a potential groundwater availability on the urban area and minimize a groundwater overexploitation and scarcity. A detailed characterization of the local hydrogeology from Montes Claros region will be crucial to a definition of more efficient water supply policies on the management of water resources, particularly in a scenario of climate change and water scarcity in semi-arid areas.
- ANALYSIS OF THE EROSION POTENTIAL AND SEDIMENT YIELD USING THE INTERO MODEL IN AN EXPERIMENTAL WATERSHED DOMINATED BY KARST IN BRAZIL(2021) Silva Tavares, Andre; Uagoda, Rogerio; Spalevic, Velibor; Mincanto, Ronaldo153 Tavares, A.S.; Uagoda, R.E.S.; Spalevic, V.; Mincato, R.L. (2021): Analysis of the erosion potential and sediment yield using the IntErO model in an experimental watershed dominated by karst in Brazil. Agriculture and Forestry, 67 (2): 153-162. SUMMARY Soil losses from water erosion jeopardize agricultural sustainability and food security for current and future generations. The research aimed to evaluate the application of the Erosion Potential Method by the Intensity of Erosion and Outflow-IntErO program in a karst watershed in a region with typical savanna climate in the northeast of the State of Goiás, Brazil. Input data were adapted according to the corresponding characteristics of tropical regions. The results indicated that the Extreme watershed has a value of 0.62 in the index (0 to 1) which defined the strength of the intensity of erosion. The river basin belongs to the category 3 of destruction with moderate erosion intensity, which indicates processes of surface erosion in the largest area of the hydrographic basin, and annual soil loss of 480.60 m³ km² yr-1. According to the IntErO model calculations 16% of the eroded material reaches the outflow of the hydrographic basin, and 84% of these sediments are deposited within the Basin, inside the surface and underground caves and galleries of the karst. Calculations by the IntErO model with the Erosion Potential Method in its algorithm proved to be valuable tool in evaluating the production of sediments in tropical soils, especially in evaluating different scenarios after establishing the inputs database for Brazil and will serve as a good starting point for future evaluations.
- Multi-criteria analysis for mapping susceptibility to iron formation caves development in the Gandarela mountain range (MG), southeast Brazil(2021-05) T.S. Nola, Iraydes; A.P. Bacellar, Luisn tropical regions, abundant in iron-rich geological materials, caves that are genetically and geographically associated with exploitable mineral deposits may develop. These caves have speleological relevance and are environmentally and legally protected in Brazil. Thus, for better planning of exploitation and environmental licensing, it is necessary to study the genesis and development of the iron formation caves seeking to preserve them without impeding the advancement of mining. This subject is complex, rarely studied, and few are the knowledges on alternatives to predict the occurrence of these caves. This gap justifies the development of research and products capable of assisting decision-makers, planners, and competent authorities in supporting the definition of target sites for speleological prospecting in the field. In this study, the prediction of the factors involved in the development of iron formation caves was evaluated producing a map of susceptibility in a GIS environment using fuzzy logic and an analytical hierarchic process (AHP). Therefore, the variables: iron oxide ratio, slope gradient, normalised difference vegetation index (NDVI), plan curvature, profile curvature, lineament intensity, and height above the nearest drainage (HAND) were selected. These variables were obtained by processing of geospatial data from a region of the Gandarela Range (Minas Gerais, Brazil). The fuzzy logic and AHP techniques were applied, and for the validation of the results, a previously surveyed cave inventory was used. The results showed satisfactory performance of the map produced in predicting areas favourable to the occurrence of iron formation caves, presenting an area under the receiver operating characteristic (ROC) curve of approximately 0.85, which indicates a high prediction rate and validates the proposed method. Such results demonstrate that this susceptibility map was reliable and that the set of criteria and weights used were suitable for mapping areas favorable for speleological prospecting.
- Origin of spring waters employing a multiparametric approach with special focus on stable isotopes 2H and 18O in the Lagoa Santa Karst region, Southern Brazil*(2020-01-19) Ribeiro, Carolina; Velásquez, Leila; Fleming, PeterKarst environments have an inherent complexity that interferes with their hydrogeology comprehension. Hence, isotope hydrology can be a valuable tool to assess trajectory of subsurface flows in an unexplored setting. The study area is located in the Lagoa Santa Karst, an environmental protection area of great economic, cultural and ecological importance, where Neoproterozoic metalimestones accommodate karst-fractured aquifers, characterized by complex water dynamics, essential vulnerability and high productivity. The purpose of this study was to investigate groundwater flow origins of springs using principally environmental stable isotopes 2H and 18O. Rainwater and spring water were sampled and analysed. The LMWL presents angular and linear coefficients strongly similar to those of the GMWL. Spring isotopic signatures, which represent the base flow and present wide-ranging of 2H and 18O, were separated into two groups. The first group can be associated with recent rainwater major contributions, while the second group shows significant evaporated water contributions, largely represented by resurgences. Tritium concentration and physico-chemical parameter data supported this interpretation, pointing that waters of the second group remained more time on the surface and subsurface. Therefore, using isotope tracers to evaluate upper groundwater zone in this tropical karst system is a powerful instrument for water resources management.
- Natural Hydrogeochemical Background Levels in the Carste Lagoa Santa Protection Unit, Minas Gerais, Brazil(2021-01) Aragão, Frederico; Velásquez, Leila Nunes Menegasse; Galvão, Paulo; Vieira, Luísa CostaThe identification of hydrogeochemical anomalies in karst water resources represents a crucial step in Brazil's water management plans. Accelerated urban and industrial development occurs in the region that includes the Carste Lagoa Santa Protection Unit, State of Minas Gerais, which may negatively impact its water quality. This paper establishes Natural Background Levels (NBL) of waters collected from deep tubular wells and springs for Si4+, Ca2+, Mg2+, Na+, K+, HCO3−, SO42, Cl− to understand sources of possible geogenic and anthropogenic anomalies. Areas with surpassed thresholds were compared with geological, hydrogeochemical, and land use data. Every parameter, except for chloride, showed elevated concentrations due to lithologic origin. The NBLs for waters of wells and springs are, respectively, 17.9 and 12.7 mg/L (silica), 97.0 and 91.5 mg/L (calcium), 4.9 and 2.9 mg/L (magnesium), 6.2 and 3.8 mg/L (sodium), 1.0 and 0.3 mg/L (potassium), 285.5 and 254.6 mg/L (bicarbonate), 9.4 and 13.6 mg/L (sulfate). Chloride, analyzed only in groundwater, presented 6.7 mg/L indicating a possible influence of upstream urban areas of Lagoa Santa and Pedro Leopoldo municipalities. Volatile and Semivolatile Organic Compounds were also analyzed, but all of them were below the detection limit. This work is important to comprehend the NBL of major elements, reveal geogenic anomalies, and distinguish carbonate aquifer units from the impure ones.