The characterization of uranium-bearing minerals by different remote sensing technologies is a challenging task due to the implications for the exploration or the protection of uranium deposits. In nature, uranium-rich mineral ores are often associated with phosphates. Fossil bones may contain almost 1% of uranium as a result of interaction with ground water or other uranyl-bearing mineralizing fluids during fossil diagenesis. Sediments in the Lower Miocene fossil site of Córcoles (Guadalajara, Spain), in the Tajo Basin, host uranyl-vanadate metatyuyamunite associated with mammal fossils, constituting a remarkable example of the relationship between uranium ores and phosphates. The mineralogical composition and the spectral response of different phosphates (geological fluorapatite, fossil fluorapatite from Paracuellos III fossil site, and Recent hydroxyapatite) and uranyl-bearing minerals (metatorbernite, metautunite, metauranocircite and fossils from Córcoles Fm with metatyuyamunite) were studied through laboratory reflectance spectroscopy. Spectral features of the different samples were compared with XRD, XRF and FTIR-ATR to determine the relationships between reflectance spectral curves, mineralogy and chemical composition. It should be highlighted that reflectance signatures of uranyl micas and Ca-phosphates allow for the mineral identification. Fluorapatite samples show absorption bands at 586, 737, 750, 805 nm related to the phosphate anion, not always present in uranyl-phosphate micas and a characteristic chemical heterogeneity probably caused by REE content. Uranyl-bearing minerals show absorption features at 1100, 1330 and 1672 nm attributed to uranyl anions (UO22+). Although further research is needed this study highlights the use of laboratory reflectance spectroscopy in uranium detection.
Paleoseismological studies are related to the analysis of past earthquakes. One of the most common methods in paleoseismological studies is the excavation of trenches across the faults, or parallel to them in the case of strike-slip. Accurate stratigraphic correlation of sedimentary layers cropping out in different trenches is key to detect and quantify fault movements with precision. Very often, this correlation is a difficult task, plagued with uncertainties owing to the homogeneous appearance and composition of the deposits. Laboratory and field reflectance spectroscopy are applied to 11 samples corresponding to two paleochannels in two parallel trenches excavated in the left-lateral Carboneras fault (Tostana site, Almeria, southeastern Iberian Peninsula). Each sample was sieved into four fractions (<4mm, 4-2 mm, 2-1 mm and <1mm) and together with the total sample, the spectral response was measured with an ASD FieldSpec4 Spectroradiometer. The results show: a) the highest similarity values usually appear between samples of the same fraction size; b) the “total fraction” analysis shows the lowest similarity values between samples; c) the results also confirm the previous characterization of the paleochannels based on field characteristics, with the highest similarity values between samples of the same paleochannel in each trench, and the lowest similarity values between samples of different paleochannels; d) a similar mineralogical composition (presence of dolomite) in all the samples suggests the same source area for the alluvial fan sediments. These results allow to assess the plausibility of correlations based on macroscopic observation in the field, and to help reduce uncertainties in the future quantification of the lateral slip rate for this segment of the Carboneras fault.
Irrigation enterprises who manage the irrigated water distribution need to anticipate farmer’s demands to minimize the evaporation amounts from irrigation pools, as well as storing enough water to accomplish crop’s water needs at any time and farmer’s management approach. Crop coefficient Kc has proved to be essential when estimating evapotranspiration with FAO56 procedure, but it varies locally. The purpose of this study is to estimate the local corn crop coefficient with remote sensing to estimate the water crop needs in 164 plots in an area of the northwest of the Iberian Peninsula and to identify different farmer’s ways to manage the land. For this purpose, 25 images from Sentinel-2 were analyzed to create their NDVI images. Therefore, the temporal Kc values were estimated and a Kc-curve for each corn field was calculated. Results allowed to differentiate the four crop growth stages and their corresponding Kc values for the study area. Besides, the 164 corn fields were clustered into 31 groups according to their different Kc curves as a result of farmer’s management. Therefore, the method has proved to help in the future to anticipate the local irrigation needs of the corn crops and to improve the farmer’s assessment to reduce their water demands without diminishing their crop production.
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