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[en] River basins and water resources management depends on the acquisition and analysis of reliable hydrometeorological data, even more in small mountain basins in semi-arid areas; where they are vulnerable to drastic changes, in relief, elevation, slope aspect, vegetation and soils, which generate high hydrometeorological variability in short distances and times, causing high flood discharges and flash flood events.
[en] Full text: This paper is a case history of the improved characterization of a complex structure in the Azerbaijan offshore achieved by application of advanced seismic tools such as 3 D Pre-Stack Depth Migration and Continuity Depth Cube volumes.The investigation focuses on the Kurdashi Permit and adjacent areas of southern most Azerbaijan, near its boundary with Iran (Fig.1).It considers the techniques used to visualize the subsurface, the resulting subsurface model and implications for its geological history revealed by the more detailed seismic tools.The Kurdashi Permit is operated by AGIP AZERBAIJAN, a subsidiary of the Italian ENI Agip Division.The permit itself encompasses a faulted regional anticlinorium of Neogene series clastic rocks comprising three separate culminations.Seismic imaging in this area is challenged by widespread shallow or near-surface gas, steep dips, and mud volcanoes connected to irregularly shaped mud chambers and associated velocity anomalies.Targets are relatively deep measured in TWT due to both their actual depth and the relatively slow velocities of the sedimentary section.A 3D seismic survey covering about 900 sq km was acquired by Caspian Geophysical over the entire permit.The conventional time processing was executed by Veritas.Subsequently AGIP generated a 3D Pre-Stack Depth Migration and Continuity Cube and the relevant interpretations.
[en] This paper discusses the nature of radioactive occurrence in Chitrial Main Block in terms of distribution of uranium and radium with special emphasis on uranium and its disequilibrium behaviour based on the large number of higher order radioactive borehole core samples. The sample data is from eastern and western parts of the main block of Chitrial, which are close to the unconformity depth. The analytical results show that the radioelemental data of Chitrial area essentially belong to the same population and that there is a continuous influx of uranium into the system with strong disequilibrium in favour of parent uranium. (author)
[en] This study investigates the sedimentary origin of materials deposited by the Amazon River over the last 30 kyr BP and reconstructs the precipitation pattern of the source area at the time of the erosion. For this purpose, fifteen samples of a down-core sediment record from the French Guiana margin have been used to analyse neodymium (Nd) and strontium (Sr) isotope ratios. The sample results (Sr: 0.71385±0.00166; εNd: -11.67±0.55) suggest that the western Amazon basin catchment area is the main source of the terrigenous material, and point to the Solimões river basin as the most probable origin. This study also discusses the strong coherence between the registered millennial events and the atmospheric settings of the region, which indicate humid land conditions for the Heinrich Stadials 1 and 2 compared to the Last Glacial Maximum, and during the Last Glacial Maximum compared to the early Holocene.
[es]Este estudio investiga el origen sedimentario de los materiales depositados por el río Amazonas durante los últimos 30 kyr BP y reconstruye el patrón de precipitación del área fuente. Para ello, se han utilizado quince muestras de un registro sedimentario marino ubicado en el margen de la Guayana Francesa y se han analizado los isótopos de Neodimio (Nd) y de Estroncio (Sr). Los resultados (Sr: 0.71385±0.00166; εNd: -11.67±0.55) sugieren que la zona del Amazonas occidental es la fuente principal del material terrígeno, y apuntan a la cuenca del río Solimões como el origen más probable. Así mismo, el análisis paleoclimático de la zona refuerza esta conclusión, exhibiendo condiciones continentales húmedas para los Heinrich Stadials 1 y 2 en comparación con el Último Máximo Glacial, así como para el Último Máximo Glacial en comparación con el Holoceno temprano.
[en] The southwestern part of Cuddapah Basin consists of two distinct types of rocks, i.e. lower arenaceous and upper calcareous, which are termed as Gulcheru quartzite and Vempalle formation. Results of field and subsurface exploration revealed two repeated sedimentary sequences of arenaceous-argillaceous-carbonate units in Papaghni Group. These sequences represent marine transgression and regression cycles in Papaghni Group. Field characteristics of conglomerate (Vempalle Conglomerate), observed above massive dolostone in lower part of Vempalle Formation, show extra-formational and polymictic nature. Subsurface exploration in Tumallapalle and extension areas has also proved continuity of Vempalle conglomerate over 25 km along strike and 3.10 km along downdip direction. Secondly, the gradational contact was observed between Gulcheru shale and massive dolostone in surface exposures, which was also confirmed in one borehole (BH No. TPL-II/83) drilled more than a kilometer vertical depth. The strike and dip continuity (of Vempalle conglomerate) and gradational contact (in Gulcheru) have given a new understanding to the stratigraphic position of rock sequence in Papaghni Group. In the present study, it is proposed to revise the stratigraphic succession by placing carbonate unit of massive dolostone as a part of Gulcheru Formation, and Vempalle Formation would commence with the Vempalle conglomerate. (author)
[en] Different types of uranium mineralisation in the environs of Cuddapah Basin show temporal and spatial association with uraniferous basement granitoids (Closepet Equivalent) exposed in its southern and southwestern margin. Geochemical studies of these granitoids show that these are generally peraluminous and strongly differentiated with uranium concentration from 10 to 90 ppm. Uranium mineralisation (in terms of grade and thickness) in the granite-hosted, fracture- controlled type and in the Cuddapah sediments is pronounced in areas where basement rocks have more volume of these strongly differentiated uraniferous granitoids. In contrast, uranium mineralisation is of low grade and thickness where basement is represented by Peninsular gneisses. (author)
[en] Strata-bound large tonnage uranium deposit hosted by the Grey-impure-dolostone of Vempalle Formation of Cuddapah Basin is known in Tummalapalle-Rachakuntapalle sector. Deposition of rocks of Cuddapah Basin commenced with Papaghni Group, which comprises Clastic - Gulcheru Formation and Chemogenic - Vempalle Formation. The Vempalle Formation is developed over 280 km stretch from south to north along the western margin of Cuddapah Basin with maximum thickness of about 2.1 km. Recent studies helped in classifying the Vempalle Formation into five major lithofacies viz. Massive Dolostone, Conglomerate, Grey-impure-dolostone (host rock for uranium mineralization), Purple shale and Cherty Dolostone. The lithofacies studies along selected traverses from Tummalapalle in south to Dhone in north revealed the development of all five facies upto Narpala near Chitravati River whereas towards its north, the Grey-impure-dolostone and Cherty Dolostone dominate. The study also revealed over lapping nature of Cherty Dolostone in North of Nossam-Peddapaya lineament; where it directly rests above the Gulcheru Formation. Environment of deposition for these facies of Vempalle Formation place this in a Shallowing-upward carbonate depositional system with characteristic tidal flat environment. The Grey-impure-dolostone facies hosting uranium is interpreted to be developed in Supratidal environment with a narrow pH range of 7.0 - 7.5 in a reducing environment along with precipitation of phosphate. Since the tidal flats have later extension over several kilometers, favorable environment of Grey-impure-dolostone may exist over wide area in northern part also. The search for Grey-impure-dolostone hosted uranium, therefore has a bearing an understanding the regional facies variations in Vempalle Formation. The paper presents the studies carried out in this direction and results thereof. (author)
[en] Scaled analog models based on extensional basins with synrift salt show how basement topography exerts a control factor on weld kinematics during the extension and inversion phases. In the case of basement-involved extension, syn-rift salt thickness differences may lead to variable degrees of extensional decoupling between basement topography and overburden, which in turn have a strong impact on the development of salt structures. With ongoing extension and after welding, the basin kinematics evolves toward a coupled deformation style. The basin architecture of our experimental results record the halokinetic activity related to growing diapirs and the timing of weld formationduring extension. Moreover, the structures that result from anysubsequent inversion of these basins strongly depends on the inherited welds and salt structures. While those basins are uplifted,the main contractional deformation during inversion is absorbed by the pre-existing salt structures, whose are squeezed developing secondary welds that often evolve into thrust welds. The analysis of our analog models shows that shortening of diapirs is favored by: i) basement topography changes that induce reactivation of primary welds as thrust welds; ii) reactivation of the salt unit as a contractional detachment and iii) synkinematic sedimentation during basin inversion. Finally, in this article, we also compare two natural examples from the southern North Sea that highlight deformation patterns very similar to those observed in our analog models.
[en] Absolute radiocarbon datings of the sedimentary successions have come to knowledge enabling us to distinguish the Pleistocene deposits from the supra-lying Holocene ones. A palaeo-environmental evolution is proposed considering climatic fluctuations at the time, their relation with the river unloadings of the Andean glaciers and that proposed for the palaeo-lake of Salina del Bebedero. Sediments are described on the basis of a detailed field sampling, textural analysis (sieved and Bouyoucos) and laboratory geo-chemicals. Their interpretation of the geologic evolution is considered to be very important since it is the only river course on this arid-semi-arid region linked to the reduction of glaciers in the Andes. The sedimentary succession is dominated by high percentages of laminated limes and with green-yellowish to greyish-brown-reddish tones deposited in watery environments of low energy such as lacustrine basins and extended plains of flood, which is why the evolution of the deposit is characterized by the contrast of the values of insolubles (clastic sediment and carbonate) versus solubles (insoluble saline). The climatic cycles dominant and proposed for the center-east Argentine region are identified considering the influence of Andean glaciers on the river systems and the water balances in plain semi-arid environments. (author)