Search results for "Acier"
showing 10 items of 79 documents
A quantitative high-resolution summer temperature reconstruction based on sedimentary pigments from Laguna Aculeo, central Chile, back to AD 850
2009
We present a pigment-based quantitative high-resolution (five years) austral summer DJF (December to February) temperature reconstruction for Central Chile back to AD 850. We used non-destructive in situ multichannel reflection spectrometry data from a short sediment core of Laguna Aculeo (33°50′S/70°54′W, 355 m a.s.l., central Chile). Calibration-in-time (period AD 1901—2000, cross-validated with split periods) revealed robust correlations between local DJF temperatures and total sedimentary chlorin (relative absorption band depth (RABD) centred in 660—670 nm RABD660;670: r=0.79, P<0.01; five-years triangular filtered) and the degree of pigment diagenesis ( R660nm/670 nm: r=0.82, P<…
The Jura glaciers: palaeogeography in the Würmian circum-Alpine zone
2008
Since the first studies on the glacial formations of the Jura mountains there have been two concepts concerning type of glaciation and ice origin during the Wurmian glaciation. Some authors believed that the Jura was totally inundated by ice of Alpine origin, while others believed that the Jura had its own glaciers, originating from a single ice-cap. Several recent studies on both the NW and SE slopes of the range define the problem more accurately. This paper presents a synthesis of the new results from mapping the moraine systems and studying the stratigraphic relationships between Alpine and Jura tills. It is concluded that even the highest level of Alpine glaciers could not lead to a pe…
Subglacial bed deformation and dynamics of the Apriķi glacial tongue, W Latvia
2011
Saks, T., Kalvans, A. & Zelcs, V. 2012 (January): Subglacial bed deformation and dynamics of the Apriķi glacial tongue, W Latvia. Boreas, Vol. 41, pp. 124–140. 10.1111/j.1502-3885.2011.00222.x. ISSN 0300-9483. We evaluate the glacial dynamics and subglacial processes of the Apriķi glacial tongue in western Latvia during the Northern Lithuanian (Linkuva) oscillation of the last Scandinavian glaciation. The spatial arrangement of glacial bedforms and deformation structures are used to reconstruct the ice dynamics in the study area. The relationship between geological structures at the glacier bed and the spatial distribution of drumlins and glacigenic diapirs, on the one hand, and the permeab…
Optical properties of deep glacial ice at the South Pole
2006
We have remotely mapped optical scattering and absorption in glacial ice at the South Pole for wavelengths between 313 and 560 nm and depths between 1100 and 2350 m. We used pulsed and continuous light sources embedded with the AMANDA neutrino telescope, an array of more than six hundred photomultiplier tubes buried deep in the ice. At depths greater than 1300 m, both the scattering coefficient and absorptivity follow vertical variations in concentration of dust impurities, which are seen in ice cores from other Antarctic sites and which track climatological changes. The scattering coefficient varies by a factor of seven, and absorptivity (for wavelengths less than ∼450 nm) varies by a fact…
A Brief Review of Ground Penetrating Radar Investigation Results of Ice Caps on Galindez, Winter and Skua Islands (Wilhelm Archipelago, Antarctica) f…
2019
This paper represents results of GPR surveying of the ice caps on Galindez (–64.24716W; –65.24992S), Winter (–64.25954W; –65.24944S) and Skua (–64.26530W; –65.25309S) islands (Wilhelm Archipelago, Antarctica) for the period April 2017 — January 2019. The main objectives were identification of the ice layering, monitoring of interglacial heterogeneities (crevasses, interglacial channels and voids) and measurements of the ice thickness. Methods: Surveying on the glaciers has been done with ground coupled shielded bowtie antenna VIY3-300 (300 MHz) GPR and with air coupled dipole Zond 12-e (75 MHz) antenna system. Monitoring investigation of glacier’s interior has been done with VIY3-300. Zond …
CHIRONOMID (DIPTERA) BIOCOENOSES IN SCANDINAVIAN GLACIER BROOKS
1971
AbstractGlacier brooks in Northern Scandinavia have been investigated for the occurrence of chironomid larvae and pupae. In the uppermost zone of glacier brooks with a very narrow temperature amplitude, Diamesa lindrothi is the most abundant species. In a lower zone with a wide diurnal temperature amplitude during summer months, the simuliid Prosimulium macropyga is more abundant, along with other species of Diamesa. Lacking any primary organic production, the diptera larvae living here feed on particles drifted up on the glacier surface, conserved there and released into the glacier brook by the melting of the ice. The larvae of Diamesa lindrothi have developed adjustments to obviate the s…
Rapid transformation of inorganic to organic and plant-available phosphorous in soils of a glacier forefield
2012
Abstract Chemical weathering of rocks or sediments is extremely important for the generation of soils, for the evolution of landscape, and as a main source of inorganic nutrients for plant growth and therefore for life. Temporal trends in weathering mechanisms, plant succession and nutrients availability in cold environments can be successfully studied in soil chronosequences along a glacier forefield. In the present paper, this was carried out in the pro-glacial area of Morteratsch. Different forms of phosphorous in the soil, stream and spring water chemistry were investigated. Apatite constitutes the main source of P, but it occurs only as a minor accessory mineral phase in the granitic/g…
Evidence for cryptic glacial refugia from North American mountain sheep mitochondrial DNA
2006
The separation of populations by ice sheets into large refugia can account for much of the genetic diversity found in present day populations. The evolutionary implications of small glacial refugia have not been as thoroughly explored. To examine refugial origins of North American mountain sheep Ovis spp., we analyzed a 604 bp portion of the mitochondrial DNA (mtDNA) control region from 223 O. dalli and O. canadensis. Major refugia were identified in eastern Beringia and southern North America, and we found evidence for two smaller refugia situated between the Laurentide and Cordilleran glaciers. Our results are the first to demonstrate support for survival of any organism in the latter two…
Contribution to the study of physico-chemical properties of surfaces modified by last treatment : application to the enhancement of localized corrosi…
2011
Metallic materials are more and more used in severe conditions with particularly strong request for improving their behavior in aggressive environment and especially over long periods. The objective of this PhD work is to estimate the potentiality of a laser surface melting treatment on the improvement of the stainless steel 304L corrosion resistance, surface treatments by laser can be revisited on the basis of a recent change in the laser technology. In the frame of this work, a nano-pulsed laser fiber was chosen : it allows the treated surface to be melted for few microns in depth, followed by an ultra-fast solidification occuring with cooling rates up to 1011 K/s. The combination of thes…
Gradual caldera collapse at Bardarbunga volcano, Iceland, regulated by lateral magma outflow
2016
Large volcanic eruptions on Earth commonly occur with a collapse of the roof of a crustal magma reservoir, forming a caldera. Only a few such collapses occur per century, and the lack of detailed observations has obscured insight into the mechanical interplay between collapse and eruption.We usemultiparameter geophysical and geochemical data to show that the 110-square kilometer and 65-meter-deep collapse of Bárdarbunga caldera in 2014–2015 was initiated through withdrawal of magma, and lateral migration through a 48-kilometers-long dike, from a 12-kilometers deep reservoir. Interaction between the pressure exerted by the subsiding reservoir roof and the physical properties of the subsurfac…