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Auteur (up) Häuselmann, P.; Granger, D.E.; Jeannin, P.Y.; Lauritzen, S.E.
Titre Abrupt glacial valley incision at 0.8 Ma dated from cave deposits in Switzerland Type Journal Article
Année 2007 Publication Geology Revue Abrégée Geology
Volume 35 Numéro Pages 143-146
Mots-Clés
Résumé Glacial erosion dramatically alters mountain landscapes, but the pace at which glaciers carve a previously fluvial landscape remains poorly defined because long-term valley incision rates are difficult to measure. Here we reconstruct the lowering history of the Aare Valley, Switzerland, over the past 4 m.y. by dating cave sediments with cosmogenic Al-26 and Be-10. Incision accelerated from similar to 120 m/m.y. to similar to 1200 m/m.y. at 0.8-1.0 Ma, at least 1 m.y. after the onset of local glaciation. Rapid incision may have been triggered by lowering of the equilibrium line altitude at the mid-Pleistocene climate transition
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Auteur (up) Lacave, C.; Koller, M.W.; Eichenberger, U.; Jeannin, P.Y.
Titre Prevention of speleothem rupture during nearby construction Type Journal Article
Année 2003 Publication Revue Abrégée Environmental Geology
Volume 43 Numéro Pages 892-900
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Résumé The cave of Milandre, located in the Swiss Jura, is characterised by a rich speleothem population. Some of the most decorated galleries lie at low depth, (40-50 m). A new highway will be built, with a tunnel, just over a decorated part of the cave. In order to prevent damage in the cave, a study was conducted in the,framework of the impact study. One of the goals was to evaluate the risk of speleothem rupture caused by explosive shots that will be used to excavate the tunnel portal. To this end, the speleothems' vulnerability to ground shaking was compared with the observed accelerations induced by experimental explosions. This procedure allowed to determine maximum acceptable explosive charges
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Numéro d'Appel refbase @ user @ collection 71
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Auteur (up) Perrin, J.; Jeannin, P.Y.; Zwahlen, F.
Titre Implications of the spatial variability of infiltration-water chemistry for the investigation of a karst aquifer: a field study at Milandre test site, Swiss Jura Type Journal Article
Année 2003 Publication Revue Abrégée Hydrogeology Journal
Volume 11 Numéro Pages 673-686
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Résumé The Milandre test site is an ideal karstic aquifer for studying the spatial heterogeneity of groundwater chemistry. Numerous observation points can be sampled: the spring, the underground river and its tributaries, and boreholes at different depths. The main causes of the spatial variability of the chemical parameters are: nature and localisation of the input, the structure of the infiltration zone, chemical reactions (transit time vs. reaction kinetics) and mixing of different waters. Physico-chemical data on springs discharging from the karstic system represent the sum of this spatial heterogeneity. Therefore, it is difficult to interpret the global-chemical response with a simple mixing model of the aquifer subsystems (runoff, matrix reservoir, epikarst). Chemical constituents related to agricultural inputs show important seasonal variations (coefficient of variation approximately 15%) and parameters linked to rainfall (delta(18)O) and to the aquifer (Ca2+, HCO3-) present variations of less than 5%. This result indicates the importance of water storage in the epikarstic aquifer for periods of a few months
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Numéro d'Appel refbase @ user @ collection 72
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Auteur (up) Perrin, J.; Pochon, A.; Jeannin, P.Y.; Zwahlen, F.
Titre Vulnerability assessment in karstic areas: validation by field experiments Type Journal Article
Année 2004 Publication Revue Abrégée Environmental Geology
Volume 46 Numéro Pages 237-245
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Résumé Several methods have been developed for vulnerability mapping in karstic areas. These methods need additional validation by field experiments. Several tests have been carried out in the Swiss Jura with natural and artificial tracers. The protective role of some intrinsic properties of the system, such as glacial deposits covering karst, epikarst storage and system dilution effect, have been clearly demonstrated. Use of three tracers in parallel showed the reactivity of the epikarst: all tracers arrived at the same time, but their relative concentration stayed clearly different. A classification of contamination scenarios into four classes is proposed. It is shown that the relevance of some intrinsic properties depends on the considered scenario class. The hydrodynamic state of the aquifer influences greatly flow velocities and can strongly modify contaminant concentrations at the output of the system. The spatial repartition (point vs diffuse) and the quantity of contaminant entering the system will also influence the output response. Hence, results from tracing experiments cannot be used straightforward for obtaining a representative value of flow velocity, dispersion or recovery rate
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Notes Approuvé no
Numéro d'Appel refbase @ user @ collection 67
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