Unraveling the roles of asymmetric uplift,normal faulting and groundwater flow to drainage rearrangement in an emerging karstic landscape          下载免费PDF全文

Christine Authemayou  Gilles Brocard  Bernard Delcaillau  Stéphane Molliex  Kevin Pedoja  Laurent Husson  Sonny Aribowo  Sri Yudawati Cahyarini 《地球表面变化过程与地形》2018,43(9):1885-1898

Landscape adjustment to tectonic, lithologic and climatic forcing leads to drainage reorganization and migration of divides. The respective contribution of these forcings, especially on carbonate landscapes is not well defined. Here, we have addressed this issue by combining field observations, satellite image interpretation and digital elevation model (DEM) quantitative analysis to assess drainage response to spatially heterogeneous rainfall, asymmetric uplift, and normal faulting on an emerging carbonated platform (Sumba Island, Indonesia). We map geomorphic markers of fluvial dynamics and drainage rearrangement and compute a χ parameter that incorporates the contributions of unevenly distributed precipitation and asymmetric uplift to estimate erosional disequilibrium across drainage divides. We find that asymmetric emergence of Sumba Island created an initial parallel drainage, asymmetric across a divide that propagates landwards. Soon after establishing itself on the emerging slopes this drainage was disturbed by normal faulting, which has become the main force driving drainage rearrangement. Vertical offsets across normal fault scarps first triggered aggradation within valleys over the hanging walls, and then disconnected upstream reaches from downstream reaches, leading to the formation of wind gaps atop the fault scarps and upstream perched sedimentary basins. The defeat of rivers by growing fault scarps was catalysed by the possibility for surface water to be rerouted near the fault scarps into underground water networks inside the underlying carbonates. At the end of the process, the opposite drainage across the main water divide captured the struggling drainage. Capture mechanisms include initial groundwater capture of the perched alluvial aquifers, followed by ground sapping at the head of the opposite drainage and surface stream diversion by avulsion. Finally, normal faulting is the main driving force of drainage rearrangement allowing avulsion and karstic rerouting whereas asymmetric uplift and climate forcings have shown a low efficiency. The role of karstification is more ambiguous, catalysing or inhibiting drainage rearrangement. Copyright © 2018 John Wiley & Sons, Ltd.  相似文献   

New Tabu Algorithm for Positioning Mining Drillholes with Blocks Uncertainty     

Zagré  Gilles Eric  Marcotte  Denis  Gamache  Michel  Guibault  François 《Natural Resources Research》2019,28(3):609-629

This paper proposes a new approach to the mining exploration drillholes positioning problem (DPP) that incorporates both geostatistical and optimization techniques. A metaheuristic was developed to solve the DPP taking into account an uncertainty index that quantifies the reliability of the current interpretation of the mineral deposit. The uncertainty index was calculated from multiple deposit realizations obtained by truncated Gaussian simulations conditional to the available drillholes samplings. A linear programming model was defined to select the subset of future drillholes that maximizes coverage of the uncertainty. A Tabu Search algorithm was developed to solve large instances of this set partitioning problem. The proposed Tabu Search algorithm is shown to provide good quality solutions approaching 95% of the optimal solution in a reasonable computing time, allowing close to optimal coverage of uncertainty for a fixed investment in drilling.

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Seismic properties of gabbroic sections in oceanic core complexes: constraints from seafloor drilling     

Blackman  Donna K.  Abe  Natsue  Carlson  Richard L.  Guerin  Gilles  Ildefonse  Benoit  Kumpf  Amber 《Marine Geophysical Researches》2019,40(4):557-569

Marine Geophysical Research - The physical properties of rock within Oceanic Core Complexes (OCC) provide information about the history of magmatism, deformation and alteration associated with...  相似文献   

Occurrence of gas hydrate in Oligocene Frio sand: Alaminos Canyon Block 818: Northern Gulf of Mexico   总被引：1，自引：0，他引：1  

Ray Boswell  Dianna Shelander  Myung Lee  Tom Latham  Tim Collett  Gilles Guerin  George Moridis  Matthew Reagan  Dave Goldberg 《Marine and Petroleum Geology》2009,26(8):1499-1512

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An atlas of predicted exotic gravitational lenses     

Gilles Orban de Xivry  Phil Marshall 《Monthly notices of the Royal Astronomical Society》2009,399(1):2-20

We present an investigation of the relationships between the radio properties of a giant radio galaxy MRC B0319−454 and the surrounding galaxy distribution with the aim of examining the influence of intergalactic gas and gravity associated with the large-scale structure on the evolution in the radio morphology. Our new radio continuum observations of the radio source, with high surface brightness sensitivity, images the asymmetries in the megaparsec-scale radio structure in total intensity and polarization. We compare these with the three-dimensional galaxy distribution derived from galaxy redshift surveys. Galaxy density gradients are observed along and perpendicular to the radio axis: the large-scale structure is consistent with a model wherein the galaxies trace the ambient intergalactic gas and the evolution of the radio structures are ram-pressure limited by this associated gas. Additionally, we have modelled the off-axis evolution of the south-west radio lobe as deflection of a buoyant jet backflow by a transverse gravitational field: the model is plausible if entrainment is small. The case study presented here is a demonstration that giant radio galaxies may be useful probes of the warm-hot intergalactic medium believed to be associated with moderately over dense galaxy distributions.  相似文献   

Smithian and Spathian (Early Triassic) ammonoid assemblages from terranes: Paleoceanographic and paleogeographic implications     

Arnaud Brayard  Gilles Escarguel  Hugo Bucher  Thomas Brühwiler 《Journal of Asian Earth Sciences》2009,36(6):420

Early Triassic paleobiogeography is characterised by the stable supercontinental assembly of Pangea. However, at that time, several terranes such as the South Kitakami Massif (SK), South Primorye (SP) and Chulitna (respectively, and presently located in Japan, eastern Russia and Alaska) straddled the vast oceans surrounding Pangea. By means of quantitative biogeographical methods including Cluster Analysis, Non-metric Multidimensional Scaling and Bootstrapped Spanning Network applied to Smithian and Spathian (Early Triassic) ammonoid assemblages; we analyze similarity relationships between faunas and suggest paleopositions for the above-cited terranes.Taxonomic similarities between faunas indicate that primary drivers of the ammonoid distribution were Sea Surface Temperature and currents. Possible connections due to current-controlled faunal exchanges between both sides of the Panthalassa are shown and terranes such as SK, SP and Chulitna played an important role as stepping stones in the dispersal of ammonoids. SK and SP terranes show strong sub-equatorial affinities during the Smithian, thus suggesting a location close to South China. At the same time, the Chulitna terrane shows strong affinities with equatorial faunas of the eastern Panthalassa. This paleoceanographic pattern was markedly altered during the Spathian, possibly indicating significant modifications of oceanic circulation at that time, as illustrated by the development of a marked intertropical faunal belt across Tethys and Panthalassa.  相似文献   

New <Superscript>40</Superscript>Ar/<Superscript>39</Superscript>Ar age constraints on the Late Palaeozoic tectonic evolution of the western Tianshan (Xinjiang,northwestern China), with emphasis on Permian fluid ingress   总被引：1，自引：0，他引：1  

Koen de Jong  Bo Wang  Michel Faure  Liangshu Shu  Dominique Cluzel  Jacques Charvet  Gilles Ruffet  Yan Chen 《International Journal of Earth Sciences》2009,98(6):1239-1258

Laser-probe dating of mylonite whole-rock samples from the North Tianshan—Main Tianshan fault zone that cross-cuts the North Tianshan domain’s southern margin yielded ⁴⁰Ar/³⁹Ar spectra with 255–285 Ma ages. Biotite from an undeformed, Early Carboniferous granite, which cuts the steep mylonitic foliation in the Proterozoic basement of the Yili arcs’s southern margin, gave a 263.4 ± 0.6 Ma plateau age (1σ). Pre-Carboniferous metasediments overlying this basement yielded plateau ages (1σ) of 253.3 ± 0.3 (muscovite) and 252.3 ± 0.3 (biotite) Ma. The Permian ages of mylonites date movement on these ductile, dextral strike-slip shear zones, whereas the mica ages are interpreted by recrystallisation as a result of fluid flow around such transcurrent faults. We propose that the Tianshan’s Permian syn-tectonic bimodal magmatism was created in a non-plume-related Yellowstone-like extensional–transtensional tectonic regime. Gold mineralisation, tracing aqueous flow in the crust, peaked in Permian time and continued locally into the Triassic. The picture is emerging that a convective fluid system partly driven by magmatic heat, existed in a strongly fractured and weakened crust with an elevated heat flow, leading to regional-scale isotope resetting. We suggest that surprisingly young isotopic ages in the literature for early orogenic (ultra)high-pressure metamorphism are similarly due to fluid-mediated recrystallisation.  相似文献   

Influence of glass polymerisation and oxidation on micro-Raman water analysis in alumino-silicate glasses   总被引：1，自引：0，他引：1  

Maxime Mercier  Andrea Di Muro  Daniele Giordano  Priscille Lesne  Bruno Scaillet  Gilles Montagnac 《Geochimica et cosmochimica acta》2009,73(1):197-217

The development of an accurate analytical procedure for determination of dissolved water in complex alumino-silicate glasses via micro-Raman analysis requires the assessment of the spectra topology dependence on glass composition. We report here a detailed study of the respective influence of bulk composition, iron oxidation state and total water content on the absolute and relative intensities of the main Raman bands related to glass network vibrations (LF: ∼490 cm⁻¹; HF: ∼960 cm⁻¹) and total water stretching (H₂O_T: ∼3550 cm⁻¹) in natural glasses. The evolution of spectra topology was examined in (i) 33 anhydrous glasses produced by the re-melting of natural rock samples, which span a very large range of polymerisation degree (NBO/T from 0.00 to 1.16), (ii) 2 sets of synthetic anhydrous basaltic glasses with variable iron oxidation state (Fe³⁺/Fe_T from 0.05 to 0.87), and (iii) 6 sets of natural hydrous glasses (C_H2OT from 0.4 to 7.0 wt%) with NBO/T varying from 0.01 to 0.76.In the explored domain of water concentration, external calibration procedure based on the H₂O_T band height is matrix-independent but its accuracy relies on precise control of the focusing depth and beam energy on the sample. Matrix-dependence strongly affects the internal calibrations based on H₂O_T height scaled to that of LF or HF bands but its effect decreases from acid (low NBO/T, SM) to basic (high NBO/T, SM) glasses. Structural parameters such as NBO/T (non-bridging oxygen per tetrahedron) and SM (sum of structural modifiers) describe the matrix-dependence better than simple compositional parameters (e.g. SiO₂, Na₂O + K₂O). Iron oxidation state has only a minor influence on band topology in basalts and is thus not expected to significantly affect the Raman determinations of water in mafic (e.g. low SiO₂, iron-rich) glasses. Modelling the evolution of the relative band height with polymerisation degree allows us to propose a general equation to predict the dissolved water content in natural glasses: