1,354,206 research outputs found
Geological setting of the Concordia Trench-Lake system in East Antarctica
No full textThis study presents the interpretation of radio echo-sounding (RES) data collected during the
2003 geophysical campaign of PNRA (Italian National Research Project in Antarctica), which
focused on the exploration of the Concordia Trench-Lake system in East Antarctica. The data
allow us to identify a new lake (ITL-28) at the southern edge of the Concordia Trench and
a series of N–S trending subglacial troughs cutting through the Belgica Highlands. We have
mapped the bedrock morphology at 3 km resolution, which led to an improved geographical
and geomorphological characterization of the Concordia Trench, Concordia Ridge, Concordia
Lake and South Hills. Improved knowledge of the Concordia Trench allowed us to model
the 3-D geometry of the Concordia fault, suggesting that it played a role in governing the
morpho-tectonic evolution of the bedrock in the Dome C region, and to propose a Cenozoic
age for its activity. We recognize the importance of catchment basin morphology in hosting
subglacial lakes, and discuss the role played by tectonics, glacial scouring and volcanism in
the origin of the trench lakes, basin lakes and relief lakes, respectively
Physiography and tectonic setting of the subglacial lake district between Vostok and Belgica subglacial highlands (Antarctica)
No full textWe present the interpretation of 11 radio echo-sounding (RES) missions carried out over the
Vostok–Dome Concordia region during the Italian Antarctic expeditions in the period 1995–
2001. The extension and the density of the radar data in the surveyed area allowed to reconstruct
a reliable subglacial morphology and to identify four relevant morphological structures namely:
the Aurora trench, the Concordia trench, the Concordia ridge and the South Hills. These
structures show evidence compatible with the presence of tectonic features. Morphological
considerations indicate their development in Cenozoic time. Hybrid cellular automata (HCA)-
based numerical modelling allowed to justify a possible role played by the tectonics of the
Aurora and Concordia trench evolution. This was accomplished by matching the bed profiles
along opportunely projected sections with the modelled surfaces as derived by the activity of
normal faults with variable surfaces within the continental crust. The Vostok–Dome C region
is characterized by a large number of subglacial lakes. From the analysis of basal reflected
power echo, we identified 14 new lakes and obtained information about their physiography as
well as their possible relations with tectonics.We propose a grouping of subglacial lakes on the
base of their physiography and geological setting, namely relief lakes, basin lakes and trench
lakes. Relief lakes located in the Belgica subglacial highlands and are characterized by sharp
and steep symmetric edges, suggesting a maximum water depth of the order of 100 m. Their
origin may well relate to localized, positive geothermal flux anomalies. Basin lakes located
in the Vincennes subglacial basin and are characterized by wider dimension that allow the
development of well-defined, flat ice surface anomalies. Trench lakes characterize the Aurora
and Concordia trenches as the possible effect of normal fault activity
Physiography and tectonic setting of the subglacial lake district between Vostok and Belgical subglacial highlands (Antarctica)
No full textWe present the interpretation of 11 radio echo-sounding (RES) missions carried out over the Vostok-Dome Concordia region during the Italian Antarctic expeditions in the period 1995-2001. The extension and the density of the radar data in the surveyed area allowed to reconstruct a reliable subglacial morphology and to identify four relevant morphological structures namely: the Aurora trench, the Concordia trench, the Concordia ridge and the South Hills. These structures show evidence compatible with the presence of tectonic features. Morphological considerations indicate their development in Cenozoic time. Hybrid cellular automata (HCA)-based numerical modelling allowed to justify a possible role played by the tectonics of the Aurora and Concordia trench evolution. This was accomplished by matching the bed profiles along opportunely projected sections with the modelled surfaces as derived by the activity of normal faults with variable surfaces within the continental crust. The Vostok-Dome C region is characterized by a large number of subglacial lakes. From the analysis of basal reflected power echo, we identified 14 new lakes and obtained information about their physiography as well as their possible relations with tectonics. We propose a grouping of subglacial lakes on the base of their physiography and geological setting, namely relief lakes, basin lakes and trench lakes. Relief lakes located in the Belgica subglacial highlands and are characterized by sharp and steep symmetric edges, suggesting a maximum water depth of the order of 100 m. Their origin may well relate to localized, positive geothermal flux anomalies. Basin lakes located in the Vincennes subglacial basin and are characterized by wider dimension that allow the development of well-defined, flat ice surface anomalies. Trench lakes characterize the Aurora and Concordia trenches as the possible effect of normal fault activity
Salinity stress effects on direct and indirect defence metabolites in maize
No full text© 2015 Elsevier B.V. In nature, plants are often exposed to multiple stress factors at the same time. The effects of single biotic or abiotic stresses on plant metabolism are well documented but how plants respond to a combination of these is little researched. Here we studied the effects of high salinity and herbivory on levels of secondary compounds and gene expression associated with defences against insects. Hydroponically grown maize plants were subjected to sodium chloride (1, 50, 100 mM NaCl) and/or damage by caterpillars of Spodoptera exigua. Salt-stressed plants showed stunted growth, reduced chlorophyll fluorescence and enhanced levels of reactive oxygen species and 1,4-benzoxazin-3-one aglycones (aBX). Herbivory induced higher transcript levels of the Zm-Bx1 gene involved in aBX biosynthesis and of the Zm-SerPIN gene coding for a serine proteinase inhibitor which might affect plant feeding insects. Herbivory also triggered the emission of volatile organic compounds (VOCs) that are attractive signals for parasitoids and predators and thus regarded as an indirect defence. Herbivore-induced metabolites were differentially affected in salt-stressed plants. High salinity resulted in transient priming of jasmonic acid while aBX levels were reduced in double-stressed plants. Salt stress led to lower herbivore-induced VOC emission per plant but not per unit biomass. However, quantitative shifts in individual compounds were found in both cases. Our study confirms the notion that combined stresses produce a unique phenotype that cannot be derived from single-stress effects. The ecological implications of these changes for organisms from different trophic levels and for plant fitness remain to be tested
Five subglacial lakes and one of the Antarctica's thickest ice covers newly determined by radio echo sounding over the Vostok DomeC region
No full textRadio echo sounding (RES) measurements were collected from 1995 to 2003 during Italian Antarctic expeditions over the Vostok-Dome C region. The data collected allow for the reconstruction of a bedrock elevation map between the Belgica Highlands and the Aurora Subglacial Basin (112.0° - 124.0° E; 74.0° - 78.0° S). Moreover, analysis of the RES data has revealed one of the thickest ice covers in Antarctica (4755 ± 16 m; 118.321° E, 76.059° S) as well as five new subglacial lakes
Electromagnetic reflecting properties of sub ice surfaces
No full textThe power strength of the radio-echo signal coming from reflecting sub-ice surfaces is used to determine the nature of the reflecting surface, i.e. rock, water or sea water. Electromagnetic analysis shows that the amplitude variations detected by radio-echo sounding are mainly due to the nature of the interface as well as the concave or convex shape of the reflectors. In this paper, some relevant profiles showing the power variations due to the different nature of the interface and the shape of the reflectors are presented. These results are important both for surface shape determination and for subglacial lake detection
Physiography and tectonic setting of the subglacial lake district between Vostok and Belgica Subglacial Highlands (Antartica)
No full textWe present the interpretation of 11 radio echo-sounding (RES) missions carried out over the
Vostok–Dome Concordia region during the Italian Antarctic expeditions in the period 1995–
2001. The extension and the density of the radar data in the surveyed area allowed to reconstruct
a reliable subglacial morphology and to identify four relevant morphological structures namely:
the Aurora trench, the Concordia trench, the Concordia ridge and the South Hills. These
structures show evidence compatible with the presence of tectonic features. Morphological
considerations indicate their development in Cenozoic time. Hybrid cellular automata (HCA)-
based numerical modelling allowed to justify a possible role played by the tectonics of the
Aurora and Concordia trench evolution. This was accomplished by matching the bed profiles
along opportunely projected sections with the modelled surfaces as derived by the activity of
normal faults with variable surfaces within the continental crust. The Vostok–Dome C region
is characterized by a large number of subglacial lakes. From the analysis of basal reflected
power echo, we identified 14 new lakes and obtained information about their physiography as
well as their possible relations with tectonics.We propose a grouping of subglacial lakes on the
base of their physiography and geological setting, namely relief lakes, basin lakes and trench
lakes. Relief lakes located in the Belgica subglacial highlands and are characterized by sharp
and steep symmetric edges, suggesting a maximum water depth of the order of 100 m. Their
origin may well relate to localized, positive geothermal flux anomalies. Basin lakes located
in the Vincennes subglacial basin and are characterized by wider dimension that allow the
development of well-defined, flat ice surface anomalies. Trench lakes characterize the Aurora
and Concordia trenches as the possible effect of normal fault activity.
Key words: Antarctica, HCA modelling, radio echo sounding, subglacialPublished(1029-1040)JCR Journalreserve
Radio Echo Sounding investigations at Talos Dome (East Antarctica): bedrock topography and ice thickness
No full textRadio echo sounding measurements were collected during two Antarctic expeditions to determine the ice thickness and the sub-glacial morphology of Talos Dome in the region around 72°48′S; 159°06′E (about 6400 km2) on the edge of the East Antarctic plateau adjacent to Victoria Land in the western Ross Sea sector. The increasing interest in this region is due to the fact that in this area the ice accumulation is higher than in other sites in East Antarctica. Because of this, Talos Dome could be a new site for a project of a deep ice core drilling to obtain information on climate changes near the coast of Antarctica. In this frame, the knowledge of the bedrock topography is of great importance to choose the best location for the drilling site. In this paper, airborne radio echo sounding results from two Antarctic expeditions (1997 and 1999) are presented. Bedrock topography in bi- and three-dimensions for the Talos Dome region are discussed
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