Erosion rates and mechanisms of knickzone retreat inferred from 10Be measured across strong climate gradients on the northern and central Andes Western Escarpment     

Luca M. Abbühl  Kevin P. Norton  John D. Jansen  Fritz Schlunegger  Ala Aldahan  Göran Possnert 《地球表面变化过程与地形》2011,36(11):1464-1473

A steep escarpment edge, deep gorges and distinct knickzones in river profiles characterize the landscape on the Western Escarpment of the Andes between ~5°S and ~18°S (northern Peru to northern Chile). Strong north–south and east–west precipitation gradients are exploited in order to determine how climate affects denudation rates in three river basins spanning an otherwise relatively uniform geologic and geomorphologic setting. Late Miocene tectonics uplifted the Meseta/Altiplano plateau (~3000 m a.s.l.), which is underlain by a series of Tertiary volcanic‐volcanoclastic rocks. Streams on this plateau remain graded to the Late Miocene base level. Below the rim of the Meseta, streams have responded to this ramp uplift by incising deeply into fractured Mesozoic rocks via a series of steep, headward retreating knickzones that grade to the present‐day base level defined by the Pacific Ocean. It is found that the Tertiary units on the plateau function as cap‐rocks, which aid in the parallel retreat of the sharp escarpment edge and upper knickzone tips. ¹⁰Be‐derived catchment denudation rates of the Rio Piura (5°S), Rio Pisco (13°S) and Rio Lluta (18°S) average ~10 mm ky^?1 on the Meseta/Altiplano, irrespective of precipitation rates; whereas, downstream of the escarpment edge, denudation rates range from 10 mm ky^?1 to 250 mm ky^?1 and correlate positively with precipitation rates, but show no strong correlation with hillslope angles or channel steepness. These relationships are explained by the presence of a cap‐rock and climate‐driven fluvial incision that steepens hillslopes to near‐threshold conditions. Since escarpment retreat and the precipitation pattern were established at least in the Miocene, it is speculated that the present‐day distribution of morphology and denudation rates has probably remained largely unchanged during the past several millions of years as the knickzones have propagated headward into the plateau. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Identifying rift zones on volcanoes: an example from La Réunion island,Indian Ocean   总被引：1，自引：1，他引：0  

Fabio Luca Bonali  Claudia Corazzato  Alessandro Tibaldi 《Bulletin of Volcanology》2011,73(3):347-366

We describe a methodology for identifying complex rift zones on recent or active volcanoes, where structures hidden by recent deposits and logistical conditions might prevent carrying out detailed fieldwork. La Réunion island was chosen as a test-site. We used georeferenced topographic maps, aerial photos and digital terrain models to perform a statistical analysis of several morphometric parameters of pyroclastic cones. This provides a great deal of geometric information that can help in distinguishing the localisation and orientation of buried magma-feeding fractures, which constitute the surface expression of rift zones. It also allowed the construction of a complete GIS database of the pyroclastic cones. La Réunion is a perfect example where past and active volcanic rift zones are mostly expressed by clusters of monogenic centres. The data has been validated in the field and compared and integrated with the distribution and geometry of dyke swarms. Results show the presence of several main and secondary rift segments of different ages, locations and orientations, whose origin is discussed considering regional tectonics, local geomorphology, and volcano deformation.  相似文献   

Variability of the GSI Index Estimated From Different Quantitative Methods   总被引：1，自引：0，他引：1  

Gian Luca Morelli 《Geotechnical and Geological Engineering》2015,33(4):983-995

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Experiments on Surface Waves Interacting with Flexible Aquatic Vegetation     

Luca Cavallaro  Antonino Viviano  Giovanni Paratore  Enrico Foti 《Ocean Science Journal》2018,53(3):461-474

Surface wave interaction with aquatic vegetation appears to play a key role in coastal hydro-morpho-dynamics. As an example, the presence of a dense meadow at intermediate water depth is usually associated with a stable and resilient shore. Wave-meadow interactions are investigated here by means of physical modelling, with a focus on wave height distribution and hydrodynamics. The central part of a wave flume is covered by flexible artificial seagrass, composed of polyethylene leaves. This vegetation is tested in both near emergent and submerged conditions. The wave height reduction is evaluated by means of a drag coefficient defined from linear wave theory, which contains all the unknowns of the adopted methodology. The behaviour of such a coefficient is investigated as a function of a wave related Reynolds number. The influence of the flexibility of the leaves is also considered, together with a wave frequency parameter. The results show a complex behaviour with three different trends for near rigid, intermediate or highly flexible leaves. Amplitudes of the orbital velocities are investigated and show a fairly good match with the linear wave theory. On the contrary, the mean velocity along the water column appears to be modified by the seagrass for submerged leaves.  相似文献   

In situ X-ray tomographic microscopy observations of vesiculation of bubble-free and bubble-bearing magmas     

Mattia Pistone  Luca Caricchi  Julie L. Fife  Kevin Mader  Peter Ulmer 《Bulletin of Volcanology》2015,77(12):1-16

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ESEEM of industrial silica-bearing powders: reactivity of defects during wet processing in the ceramics production     

Maurizio Romanelli  Francesco Di Benedetto  Gabriele Fornaciai  Massimo Innocenti  Giordano Montegrossi  Luca A. Pardi  Alfonso Zoleo  Fabio Capacci 《Physics and Chemistry of Minerals》2015,42(5):363-372

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Using large-scale diagnostic quantities to investigate change in East Coast Lows     

Fei Ji  Jason P. Evans  Daniel Argueso  Lluis Fita  Alejandro Di Luca 《Climate Dynamics》2015,45(9-10):2443-2453

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Exhumation patterns along shallow low‐angle normal faults: an example from the Altotiberina active fault system (Northern Apennines,Italy)          下载免费PDF全文

Chiara Caricchi  Luca Aldega  Massimiliano R. Barchi  Sveva Corrado  Domenico Grigo  Francesco Mirabella  Massimiliano Zattin 《地学学报》2015,27(4):312-321

A multi‐method approach (palaeothermal and thermochronological analyses; thermal modelling) is applied to reconstruct the exhumation history of the Altotiberina Fault (ATF), a representative example of crustal‐scale active low‐angle normal faulting in the Northern Apennines (Italy). Thermal maturity and thermochronological data yield similar burial histories but different exhumation patterns for the sedimentary successions in the hangingwall and the footwall of the ATF. Since 3.8 Ma, the ATF footwall has exhumed at rates of 0.90 mm a^?1. Exhumation led to bending and deactivation of the ATF uppermost portion as a result of tectonic unloading and isostatic adjustment, followed by migration of extension and the development of a set of domino‐like, east‐dipping normal faults, rooting on the buried portion of the ATF. ATF activity and isostatic rebound exhumed Triassic rock units from depths of about 4 km. We suggest that isostatic instability is accommodated at shallow crustal levels, in a similar way to what is observed on larger structures at mid‐low crustal levels.  相似文献   

Refinements to the Silvestri’s theory for the evaluation of the seismic actions in flat-bottom silos containing grain-like material     

Luca Pieraccini  Stefano Silvestri  Tomaso Trombetti 《Bulletin of Earthquake Engineering》2015,13(11):3493-3525

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Process-based design flood estimation in ungauged basins by conditioning model parameters on regional hydrological signatures     

Daniela Biondi  Davide Luciano De Luca 《Natural Hazards》2015,79(2):1015-1038

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