Beaver dam analogues drive heterogeneous groundwater–surface water interactions     

Jeffrey Wade  Laura Lautz  Christa Kelleher  Philippe Vidon  Julianne Davis  Julio Beltran  Casey Pearce 《水文研究》2020,34(26):5340-5353

Beaver dam analogues (BDAs) are a cost-effective stream restoration approach that leverages the recognized environmental benefits of natural beaver dams on channel stability and local hydrology. Although natural beaver dams are known to exert considerable influence on the hydrologic conditions of a stream system by mediating geomorphic processes, nutrient cycling, and groundwater–surface water interactions, the impacts of beaver-derived restoration methods on groundwater–surface water exchange are poorly characterized. To address this deficit, we monitored hyporheic exchange fluxes and streambed porewater biogeochemistry across a sequence of BDAs installed along a central Wyoming stream during the summer of 2019. Streambed fluxes were quantified by heat tracing methods and vertical hydraulic gradients. Biogeochemical activity was evaluated using major ion porewater chemistry and principal component analysis. Vertical fluxes of approximately 1.0 m/day were observed around the BDAs, as was the development of spatially heterogeneous zones of nitrate production, groundwater upwelling, and anaerobic reduction. Strong contrasts in hyporheic zone processes were observed across BDAs of differing sizes. This suggests that structures may function with size-dependent behaviour, only altering groundwater–surface water interactions after a threshold hydraulic step height is exceeded. Patterns of hyporheic exchange and biogeochemical cycling around the studied BDAs resemble those around natural beaver dams, suggesting that BDAs may provide comparable benefits to channel complexity and near-stream function over a 1-year period.  相似文献   

Character and origin of De Geer moraines in the Seacoast region of New Hampshire,USA          下载免费PDF全文

Samantha N. Sinclair  Joseph M. Licciardi  Seth W. Campbell  Brian M. Madore 《第四纪科学杂志》2018,33(2):225-237

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Pilot Point Optimization of Mining Boundaries for Lateritic Metal Deposits: Finding the Trade-off Between Dilution and Ore Loss     

Dagasan  Yasin  Renard  Philippe  Straubhaar  Julien  Erten  Oktay  Topal  Erkan 《Natural Resources Research》2019,28(1):153-171

Natural Resources Research - Geological contacts in lateritic metal deposits (footwall topographies) often delineate the orebody boundaries. Spatial variations seen in such contacts are frequently...  相似文献   

Secular dynamics of multiplanetary circumbinary systems: stationary solutions and binary-planet secular resonance     

Eduardo Andrade-Ines  Philippe Robutel 《Celestial Mechanics and Dynamical Astronomy》2018,130(1):6

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Meteoric fluid‐rock interaction in Variscan shear zones     

Camille Dussaux  Aude Gbelin  Philippe Boulvais  Vronique Gardien  Stephen Grimes  Andreas Mulch 《地学学报》2019,31(4):366-372

Variscan shear zones in the Armorican Massif represent sites of strong fluid‐rock interaction. The hydrogen isotope composition of muscovite (δD_Ms) from syntectonic leucogranite allows to determine the source of fluids that infiltrated the footwall of three detachment zones and the South Armorican Shear Zone. Using temperatures of hydrogen isotope exchange estimated from microstructural data, we calculate the hydrogen isotope ratios of water (δD_water) present within the shear zones during high‐temperature deformation. A ~40‰ difference in δD_water values from deep to shallow crustal level reveals a mixing relationship between deep crustal fluids with higher δD values that range from ?34 to ?33‰, and meteoric fluids with δD values as low as ?74‰ in the upper part of detachment footwalls.  相似文献   

A plume tectonics model for the Tharsis province, Mars     

Daniel Mège  Philippe Masson 《Planetary and Space Science》1996,44(12):1499-1546

Morphological and structural data from the whole Tharsis province suggest that a number of shallow grabens radially oriented about the Tharsis bulge on Mars are underlain by dykes, which define giant radiating swarms similar to, e.g. the Mackenzie dyke swarm of the Canadian shield. Mechanisms for graben formation are proposed, and the depth, width, and height of the associated dykes are estimated. Structural mapping leads to define successive stages of dyke emplacement, and provide stress-trajectory maps that indicate a steady source of the regional stress during the whole history of the Tharsis province. A new tectonic model of Tharsis is presented, based on an analogy with dyke swarms on the Earth that form inside hot spots. This model successfully matches the following features: (1) the geometry of the South Tharsis Ridge Belt, which may have been a consequence of the compressional stress field at the boundary between the uplifted and non-uplifted areas in the upper part of the lithosphere at the onset of hot spot activity; (2) extensive lava flooding, interpreted as a consequence of the high thermal anomaly at the onset of plume (hot spot) activity; (3) wrinkle ridge geometry in the Tharsis hemisphere, the formation of which is interpreted as a consequence of buoyant subsidence of the brittle crust in response to the lava load; (4) Valles Marineris limited stretching by preliminary passive rifting, and uplift, viewed as a necessary consequence of adiabatic mantle decompression induced by stretching. The geometrical analysis of dyke swarms suggests the existence of a large, Tharsis-independent extensional state of stress during all the period of tectonic activity, in which the minimum compressive stress is roughly N---S oriented. Although magmatism must have loaded the lithosphere significantly after the plume activity ceased and be responsible for additional surface deformations, there is no requirement for further loading stress to explain surficial features. Comparison with succession of magmatic and tectonic events related to hot spots on the Earth suggests that the total time required to produce all the surface deformation observed in the Tharsis province over the last 3.8 Ga does probably not exceed 10 or 15 Ma.  相似文献   

Ground-based GPS imaging of ionospheric post-seismic signal     

Philippe Lognonné  Juliette Artru  François Crespon  Eric Jeansou  Jérôme Helbert  Pierre-Emmanuel Godet 《Planetary and Space Science》2006,54(5):528-540

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Massive black hole remnants of the first stars in galactic haloes     

Ranty R. Islam  James E. Taylor  Joseph Silk 《Monthly notices of the Royal Astronomical Society》2003,340(2):647-656

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Reconstruction of primordial density fields     

Roya Mohayaee  Hugues Mathis  Stéphane Colombi  Joseph Silk 《Monthly notices of the Royal Astronomical Society》2006,365(3):939-959

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Low‐energy helium ion irradiation‐induced amorphization and chemical changes in olivine: Insights for silicate dust evolution in the interstellar medium     

Philippe CARREZ  Karine DEMYK  Patrick CORDIER  Lon GENGEMBRE  Jean GRIMBLOT  Louis D'HENDECOURT  Anthony P. JONES  Hugues LEROUX 《Meteoritics & planetary science》2002,37(11):1599-1614

Abstract— We present the results of irradiation experiments aimed at understanding the structural and chemical evolution of silicate grains in the interstellar medium. A series of He+ irradiation experiments have been performed on ultra‐thin olivine, (Mg,Fe)₂SiO₄, samples having a high surface/volume (S/V) ratio, comparable to the expected S/V ratio of interstellar dust. The energies and fluences of the helium ions used in this study have been chosen to simulate the irradiation of interstellar dust grains in supernovae shock waves. The samples were mainly studied using analytical transmission electron microscopy. Our results show that olivine is amorphized by low‐energy ion irradiation. Changes in composition are also observed. In particular, irradiation leads to a decrease of the atomic ratios O/Si and Mg/Si as determined by x‐ray photoelectron spectroscopy and by x‐ray energy dispersive spectroscopy. This chemical evolution is due to the differential sputtering of atoms near the surfaces. We also observe a reduction process resulting in the formation of metallic iron. The use of very thin samples emphasizes the role of surface/volume ratio and thus the importance of the particle size in the irradiation‐induced effects. These results allow us to account qualitatively for the observed properties of interstellar grains in different environments, that is, at different stages of their evolution: chemical and structural evolution in the interstellar medium, from olivine to pyroxene‐type and from crystalline to amorphous silicates, porosity of cometary grains as well as the formation of metallic inclusions in silicates.  相似文献