51,218 research outputs found
Snow Accumulation in the Talos Dome Area: Preliminary Results
No full textIce divide-dome migration is a key parameter in mass balance studies and in the interpretation of ice cores. The stability of the dome and position of the ice divide must be known to accurately interpret ice core records and to complete mass balance studies. Models of depth-age relationships for deep ice cores are sensitive to migration of the dome position (Anandakrishnan et al., 1994). The evolution of an ice divide is driven by the accumulation-rate history, its spatial pattern and conditions at ice-sheet boundaries (e.g. Frezzotti et al., 2004; Hindmarsh, 1996; Nereson et al., 1998). Ice divide migration is also important in determining the input parameter of large Antarctic drainage basins. Due to the very low slope (less than a decimetre per km) of East Antarctic domes and to surface morphology (e.g. sastrugi), it is very difficult to determine the summit point of a dome and its migration in time. In 2004 a new ice coring project, TALDICE (Talos Dome Ice
Core Project), started at TD to recover 1550 m of ice spanning the last 120 000 years (Frezzotti et al., 2004). This paper discusses preliminary findings on the present and past morphology of Talos Dome based on detailed snow accumulation data, radar-derived isochrons and ice velocity measurements in the last 10 years.Published51-543.8. Geofisica per l'ambienteN/A or not JCRope
TALOS DOME MIGRATION : PRELIMINARY RESULT
No full textIce divide-dome migration is a key parameter in mass balance studies and in the interpretation of ice cores. The stability of the dome and position of the ice divide must be known to accurately interpret ice core records and to complete mass balance studies. Models of depth-age relations for deep ice cores are sensitive to migration of the dome position (Anandakrishnan et al., 1994). The evolution of an ice divide is driven by the accumulation-rate history, its spatial pattern and conditions at ice-sheet boundaries (e.g. Frezzotti et al., 2004; Hindmarsh, 1996; Nereson et al. 1998). Ice divide migration is also important in determining the input parameter of large Antarctic drainage basins. Due to the very low slope (less than a decimetre per km) of the East Antarctic domes and to the surface morphology (e.g. sastrugi), it is very difficult to determine the summit point of the dome and its migration in time. In 2004 a new ice coring project, TALDICE (Talos Dome Ice Core Project), started at TD to recover 1550 m of ice spanning the last 120,000 years (Frezzotti et al., 2004).
The objective of the paper is to discuss the preliminary result of the present and past morphology of the Talos Dome from detailed snow accumulation, radar derived isochrons and ice velocity measurements in the last 10 years
P. Fogagnolo, P. Frezzotti, P. Mittica, M. Digiuni, R. Paderni, E. Vallenzasca, L. Rossetti
No full text
Manganese bearing fluids in composite vein systems in the braunite deposit from Molinello Mine (Val Graveglia, Notrthern Apennine, Italy)
No full textAlteration of braunite ores from Eastern Liguria (Italy) during syntectonic veining processes: mineralogy and fluid inclusions.
No full textGeophysical Survey at Talos Dome (East Antarctica)
No full textTalos Dome is an ice dome on the edge of the East Antarctic plateau (Fig. l), about 290 km
from the Southern Ocean and 250 km from the Ross Sea. It is adjacent to the Victoria Land
mountains and overlies the eastern margin of the Wilkes Subglacial Basin. To the West, an ice saddle (2260 m) divides the Dome from an ice ridge coming from Dome C. Ice flows southeastward from this ridge into outlet glaciers (Priestley, Reeves and David Glaciers) which drain into the Ross Sea, and north-westward into the Rennick and Matusevich Glaciers which drain into the Southern Ocean. Another ice ridge trends northward from the Dome, passing behind the
USARP Mountain. As part of the ITASE project, two traverse surveys were carried out in the Talos Dome area in November 1996 (Frezzotti et al., 1998) and January 2002 (Frezzotti et al., this volume). Airborne radar surveys were conducted in 1997, 1999 and 2001. Research aimed to better understand the latitudinal (North-South) and longitudinal (East-West) gradient along two East-West (Talos Dome - D66) and North-South (GV7 - Talos Dome - Taylor Dome) transepts,
documenting climatic, atmospheric and surface conditions in the Talos Dome area and northern Victoria Land throughout the last 200-1000 years. The study of the Talos Dome area aimed to find the best location to extract an ice core down to the bedrock.
Six shallow snow-firn cores (two during 1996 and four during 2001-02), up to 90 m deep,
were drilled in the Talos Dome area. An eight century-long record of volcanic signal and
climatic change was obtained at Talos Dome through geochemical analysis of the deepest core (TD, 90 m deep), drilled in 1996 (Becagli et al., 2003; Narcisi et al., 2001; Stenni et al., 2002). The core was dated through seasonal variations in nss SO4 raised to the power of 2- concentrations coupled with the recognition of tritium marker level (1965-66) and the nss SO4 raised to the power of 2- spikes attributed to the most important historical volcanic events (Pinatubo 1991, Agung 1963, Krakatoa 1883, Tambora 1815, Kuwae 1452, Unknown 1259).PublishedMilan, 25-26 June 2002 / Dipartimento di Scienze Ambiente e Territorio (DISAT), Università di Milano Bicocca, P.zza della Scienza 1, 20126 Milano3.8. Geofisica per l'ambienteope
Comparison between glacier ice velocities inferred from GPS and sequential satellite images
No full textMeasurements derived from remote-sensing research and field surveys have provided new ice-velocity data for David Glacier-Drygalski Ice Tongue and Priestly and Reeves Glaciers, Antarctica. Average surface velocities were determined by tracking crevasses and other patterns moving with the ice in two sequential satellite images. Velocity measurements were made for different time intervals (1973-90, 1990-92, etc.) using images from various satellite sensors (Landsat 1 MSS, Landsat TM, SPOT XS). In a study of the dynamics of David Glacier-Drygalski Ice Tongue and Priestley and Reeves Glaciers, global positioning system (GPS) measurements were made between 1989 and 1994. A number of points were measured on each glacier: five points on David Glacier, three on Drygalski Ice Tongue, two on Reeves Glacier-Nansen Ice Sheet and two on Priestley Glacier. Comparison of the results from GPS data and feature-tracking in areas close to image tie-points shows that errors in measured average velocity from the feature-tracking may be as little as ±15-20 m a-1. In areas far from tie-points, such as the outer part of Drygalski Ice Tongue, comparison of the two types of measurements shows differences of about ±70 m a-1
Transmission electron microscopy applied to fluid inclusion investigation
No full textThe transmission electron microscope (TEM) allows a detailed characterization of textural and chemical features of fluid inclusions (shape inner compositions and inner textures), a: a resolution higher than that attainable with an optical microscope (OM). TEM investigation indicates that most fluid inclusions appear as perfectly euhedral negative crystals, with variable shape (from prismatic to equant) and size (typically from <0.02 to 0.15 μ). Inner texture (fluid phase/melt distribution) and composition are variable as well. Different kinds of negative crystals may coexist in the same trail of inclusions, possibly indicating locally variable trapping conditions. A critical feature, revealed by TEM, is that inclusions are often connected to structural defects (in particular, to dislocation arrays), which are undetected by optical microscopy. The identification of these hidden nanostructures should be taken into account for the correct petrological interpretation of microthermometric results, particularly when controversial data have been obtained. In fact, these nanostructures may represent a possible path for fluid phase leakage, thus modifying the original composition and/or density of the inclusions. © 2001 Elsevier Science B.V. All rights reserved
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