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Large wood (LW, or pieces of dead wood longer than 1m and thicker than 10cm in diameter) is a key element in forested streams, but its abundance has decreased worldwide as a result of snagging and clearing of riparian forests. Therefore, many restoration projects introduce LW into stream channels to enhance geomorphology, biotic communities, and ecosystem functioning. Because LW enhances the retention of organic matter and sediments, its restoration can reduce siltation in receiving reservoirs, although so far little information on this subject is available. We studied the effects of restoring the natural loading of LW in four streams in the Aiako Harria Natural Park (the Basque Country, Spain) in pool abundance, channel form, and storage of organic matter and sediments. In all reaches log jams induced the formation of new geomorphic features and changes in physical habitat, especially an increase in the number and size of pools and in the formation of gravel bars and organic deposits. The storage of organic matter increased 5- to 88-fold and streambed level rose 7±4 to 21±4cm on average, resulting in the storage of 35.2±19.7 to 711±375m3 (733–1400m3ha−1y−1) of sediment per reach. Extrapolation of these results to the entire drainage basin suggests that basinwide restoration of LW loading would enhance the retention potential of stream channels by 66,817±27,804m3 (1075m3ha−1y−1) of sediment and by 361t (5.32Tha−1y−1) of organic matter, which represents 60% of the estimated annual inputs of sediments to the downstream Añarbe Reservoir and almost twice as much as the annual input of organic matter to the entire river network. Therefore, basinwide restoration of LW loading is a potentially important tool to manage catchments that feed reservoirs, where retention of sediments and organic matter can be considered important ecosystem services as they reduce reservoir siltation.
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Spreading from the Near East in the declining Bronze Age from the 2nd millennium BCE onwards, the technique of iron smelting reached Eastern Silesia, Poland, in approximately the 2nd century BCE (pre-Roman Iron Age). At this time the region of the Widawa catchment area was inhabited by the Przeworsk culture. While the older moraine landscape of the study area lacks ores from geological rock formations, bog iron ores were relatively widespread and, due to their comparatively easy accessibility, were commonly exploited for early iron production. This paper investigates the mineralogical and elemental composition of local bog iron ore deposits and iron slag finds, as a by-product of the smelting process, also taking into account the state of the art in research regarding the formation, distribution and utilization of bog iron ores and considering data from comparative studies.
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The extent, basal conditions and retreat history of a Loch Lomond Stadial glacier are reconstructed based on detailed geomorphological and sedimentological assessment. We present new evidence from the vicinity of Coire Ardair that supports the former existence of a warm-based, locally-fed valley glacier, with probable cold-based ice on the surrounding plateau. This is broadly consistent with modelled creep-dominated flow in the upper catchment and sliding-dominated flow throughout much of the valley. A dense suite of moraines, primarily formed in ice-marginal environments, records a multi-phase recessional history: (1) active and oscillatory retreat; (2) a prolonged ice stillstand; (3) partial ice stagnation with occasional minor readvances; (4) increased oscillatory retreat with a substantial readvance event; and (5) rapid and uninterrupted retreat. We propose that a Coire Ardair glacier responded to sub-centennial scale climate fluctuations, possibly associated with the periodic delivery of warmer air masses to the region, rather than to a single, prominent shift in climate.
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Changes in land use related to mining in the north-western mountains of Spain are analysed. We studied 15 representative types of mining activity in the Sil River basin (León province), including three types of mineral resources: gravel, roofing slate and coal. We use colour orthopothos of 2014 to calculate areas occupied by dumps, lagoons, open pits, auxiliary construction and access roads in mines. Also areal photographs of 1956–1957 were used to measure land uses in these years. In all cases the extraction of mineral resources by surface mining has caused the destruction of the former topography, and these alterations are irreversible. The new post-mining topography represents a drastic change in the landscape and land use in these areas. Areas occupied by coal and slate mining (around 1500ha.) are significantly greater than gravel quarries (74ha.). Waste material is greater in slate mining (69%) and coal mining (44%) than in gravel mining (8%). Former agricultural areas now occupied by mining were more extensive in gravel quarries (44%) than in slate quarries (10%) and coal mines (6%) because of the gentler topography in the areas where the gravel quarries are located. In six cases mining are located in natural protected areas and in other cases alter and/or eliminate valuable geological heritage.
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The loess deposits in Iran are a valuable archive of regional paleoclimatic and paleoenvironmental information. Extensive sedimentological and chronological studies have been carried out on the middle to upper Pleistocene loess successions during the past decades, but there is an absence of comparable research in the older loess deposits. Recently, a 19-m-thick loess-paleosol sequence was discovered in the central Iranian Loess Plateau (ILP), which was paleomagnetically-dated to ∼2.4–1.8 Ma and thus represents by far the oldest loess known in northern Iran. Here, we present the results of a detailed micromorphological investigation of these lower Pleistocene loess-paleosol sequences (“red sequence”) from the ILP. Our main findings are as follows: 1) The Agh Band red sequence deposits are an extremely thick soil complex comprising paleosols in different stages of development; 2) the micromorphological index of soil development (MISECA) suggests that the moderately- and well-developed paleosols in the red sequence formed in an environment with mean annual precipitation ranging from around 450 to 650 mm, respectively; and 3) MISECA suggests that the red sequence formed under a semi-arid to sub-humid climate and thus under wetter and more favorable conditions than the overlying late Pleistocene loess and modern soils.
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The marine gastropod Conomurex fasciatus (Born 1778) is the main component of thousands of shell middens on the Farasan Islands in the southern Red Sea. The middens date from 6500 to 4500 cal BP and cover the period of increased aridification over the region. No general research on C. fasciatus has been carried out before and basic information about the species is mostly speculative. To test if C. fasciatus shells can be used as a recorder of climate variability, we collected living specimens from the Farasan Islands, in Saudi Arabia, over a 1.5 year period. This area receives almost no precipitation and sea surface salinity is extremely high (38–39 psu), and sea surface temperature (SST) ranges from +26.5 °C to +34.9 °C.
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The Longmu–Gozha Co left-lateral strike-slip fault system (LGCF) is located in remote western Tibet, forming a triple junction with both the Altyn Tagh fault (ATF) and the Karakorum fault (KF), the two major strike-slip faults in the region. The Ashikule, Gozha Co and Longmu Co faults are clear and distinct left-stepping en-echelon faults, together forming the LGCF system. Although poorly documented, quantifying its activity remains a key problem to understand the kinematics and the tectonic history of the westernmost Tibetan Plateau. Indeed, the Karakax fault (NW segment of the ATF), LGCF and KF together control the tectonics of western Tibet which itself controls the extrusion of Tibet towards the east, with the LGCF acting as a natural boundary for eastward motion of the Tibetan Plateau due to India's northward impingement. The LGCF system shows clear and impressive morphological indications of left-lateral active shear, that we quantify using field measurements (terrestrial LIDAR) along with 10Be surface-exposure dating. Our data suggest a slip-rate 9 and >8mm/yr, respectively), yielding a few mm/yr of extension accommodated most likely in the Ashikule graben and surroundings, located between the ATF and Karakax faults. Numerous evidences of recent tectonic-related events are present in the vicinity, such as the 1951 volcanic eruption as well as the 2008 and 2014 Ms7.3 Yutian earthquakes, attesting of its high activity. In addition, the LGCF's en-echelon geometry and identical direction with the ATF, as well as smaller geological offsets and lower slip-rate compared to those on the surrounding faults, suggest that this segment of the ATF may be the most recent.
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Commodification of land is at the forefront of the re-casting of rural China by the spread of capitalism. This study examines a market-based program of land development rights trading in Chengdu, China. The program was made possible by a change in the central government’s land-use regulation that shifted the policy goal from ‘no net loss’ of farmland to ‘no net gain’ of construction land. We detail how local governments at multiple levels work together to construct land development rights as a commodity and build market institutions to foster its trading, illustrating land commodification as an inherently political process. A unique combination of innovative local policies and central political concessions created an outcome of ‘commodification without dispossession’ in Chengdu. Land commodification was used to finance rural reconstruction and brought profound changes to rural space, including re-configuring land-use patterns, transforming physical conditions in residential communities, and changing the representation of space.
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(U–Th)/He geochronology of 33 goethite grains from in situ ferruginous duricrusts overlying the Paraná flood basalt in the Guarapuava region, Paraná, Brazil, reveals ages ranging from 3.6±0.4 to 0.4±0.1Ma. Thirty-one grains from detrital fragments of ferruginous duricrust yield ages in the 6.2±0.6 to 0.7±0.1Ma range. The results show that goethites from detrital blocks are generally older than those from the in situ ferruginous layers and that all the goethites from the Guarapuava sites are relatively young (≤6.2±0.6Ma). Goethites show variable U and Th contents depending on the mode of precipitation. Goethite that forms by progressive ferrugization and pseudomorphic replacement of basalts are rich in Th, U-poor, contain various mineral inclusions (e.g., kaolinite, rutile, ilmenite) and display a distinct “checkered” appearance. Colloform goethite precipitated within cavities and desiccation cracks contain higher U, show low Th/U values, and are free of mineral contaminants, suggesting direct precipitation from solution. The geochronological results reveal a dynamic evolution for the soils overlying the Paraná basalt, where recurrent duricrust formation and dismantling lead to the evolution of regional colluvial soil profiles while simultaneously preventing the evolution of chemically stratified lateritic weathering profiles. The modes of formation and U, Th, and He contents of goethite at Guarapuava provide useful constraints on the expected compositions and modes of formation of goethite formed on basaltic soils on Mars.
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In recent decades, the fire regime of the Mediterranean Basin has been disturbed by various factors: climate change; forest management policies; land cover; changed landscape. Size and severity have notably increased, which in turn have increased large fires events with >500ha burned (high severity). In spite of Mediterranean ecosystems' high resilience to fire, these changes have implied more vulnerability and reduced natural recovery with irreparable long-term negative effects. Knowledge of the response of ecosystems to increasing severity, mainly in semiarid areas, is still lacking, which is needed to rehabilitate and restore burned areas.
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