Correction to: Estimation of satellite position,clock and phase bias corrections     

Patrick Henkel  Dimitrios Psychas  Christoph Günther  Urs Hugentobler 《Journal of Geodesy》2018,92(10):1219-1221

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Apatite Reference Materials for SIMS Microanalysis of Isotopes and Trace Elements     

Allen K. Kennedy  Jörn-Frederik Wotzlaw  James L. Crowley  Mark Schmitz  Urs Schaltegger  Benjamin Wade  Laure Martin  Cristina Talavera  Bryant Ware  Thi Hao Bui 《Geostandards and Geoanalytical Research》2023,47(2):373-402

Twelve apatite samples have been tested as secondary ion mass spectrometry (SIMS) reference materials. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis shows that the SLAP, NUAN and GR40 apatite gems are internally homogeneous, with most trace element mass fractions having 2 standard deviations (2s) ≤ 2.0%. BR2, BR5, OL2, AFG2 and AFB1, which have U > 63 μg g^-1, ²⁰⁶Pb/²⁰⁴Pb > 283, and homogeneous SIMS U-Pb data, have respective isotope dilution thermal ionisation mass spectrometry (ID-TIMS) ages of 2053.83 ± 0.21 Ma, 2040.34 ± 0.09 Ma, 868.87 ± 0.25 Ma, 478.71 ± 0.22 Ma and 473.25 ± 0.09 Ma. Minor U-Pb heterogeneity exists and accurate SIMS results require correction with the 3D Concordia-constrained common Pb composition. Among the studied samples, AFG2 and BR5 are the most homogeneous U-Pb reference materials. The SIMS sulfur isotopic compositions of eight of the apatites shows they are homogeneous, with 2s for both 10³δ³⁴S and 10³δ³³S < 0.55‰. One apatite, BR96, has Δ³³S = -0.36 ± 0.2‰. The apatite samples have ID-TIMS ⁸⁷Sr/⁸⁶Sr between 0.704214 ± 0.000030 and 0.723134 ± 0.000035.  相似文献   

Quality assessment of FORMOSAT-3/COSMIC and GRACE GPS observables: analysis of multipath, ionospheric delay and phase residual in orbit determination   总被引：2，自引：2，他引：0  

Cheinway Hwang  Tzu-Pang Tseng  Ting-Jung Lin  Dražen Švehla  Urs Hugentobler  Benjamin Fong Chao 《GPS Solutions》2010,14(1):121-131

The precise orbit determination antennas of F3/C and GRACE-A satellites are from the same manufacturer, but are installed in different configurations. The current orbit accuracy of F3/C is 3 cm at arcs with good GPS data, compared to 1 cm of GRACE, which has a larger ratio of usable GPS data. This paper compares the qualities of GPS observables from F3/C and GRACE. Using selected satellites and time spans, the following average values for the satellite F3/C and satellite A of GRACE are obtained: multipath effect on the pseudorange P1, 0.78 and 0.38 m; multipath effect on the pseudorange P2, 1.03 and 0.69 m; occurrence frequency of cycle slip, 1/29 and 1/84; standard error of unit weight, 4 and 1 cm; dynamic–kinematic orbit difference, 10 and 2 cm. For gravity determination using F3/C GPS data, a careful selection of GPS data is critical. With six satellites in orbit, F3/C’s large amount of GPS data will make up the deficiency in data quality.  相似文献   

Diurnal fluctuations in glacier ice deformation: Haut Glacier d'Arolla,Switzerland     

Douglas Mair  Bryn Hubbard  Peter Nienow  Ian Willis  Urs H. Fischer 《地球表面变化过程与地形》2008,33(8):1272-1284

Measurements of surface velocity, ice deformation (at 42 and 89% ice depth) and proglacial stream discharge were made at Haut Glacier d'Arolla, Switzerland, to determine diurnal patterns of variation in each. Data are analysed in order to understand better the relationship between hydraulically induced basal motion and glacier ice deformation over short timescales. The data suggest that hydraulically induced localized basal ‘slippery’ spots are created over diurnal cycles, causing enhanced basal motion and spatially variable glacier speed‐up. Our data indicate that daily glacier speed‐up is associated with reduced internal deformation over areas previously identified as slippery spots and increased deformation in areas located adjacent to or down‐glacier from slippery spots. We interpret this pattern in terms of a transfer of mechanical support for basal shear stress away from slippery spots to adjacent sticky areas, where the resulting stronger ice–bed coupling causes increased ice deformation near the bed. These patterns indicate that basal ice is subjected to stress regimes that are variable at a high spatial and temporal resolution. Such variations may be central to the creation of anomalous vertical velocity profiles measured above and down‐glacier of basal slippery zones, which have shown evidence for ‘plug flow’ and extrusion flow over annual timescales. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Post-granulite facies monazite growth and rejuvenation during Permian to Lower Jurassic thermal and fluid events in the Ivrea Zone (Southern Alps)   总被引：11，自引：2，他引：9  

Gerhard Vavra  Urs Schaltegger 《Contributions to Mineralogy and Petrology》1999,134(4):405-414

U-Pb analyses of single monazite grains from two granulite facies metapelites in the Ivrea Zone (Southern Alps) reveal the presence, in both samples, of at least three different ages and prove that earlier interpretations of supposedly concordant monazite data as cooling ages are unwarranted. One group of monazite data defines a subconcordant discordia line with an upper intercept age of 293.4 ± 5.8 Ma and a lower intercept age of 210 ± 14 Ma. The upper intercept is interpreted as the real cooling age of the monazites. The lower intercept is interpreted as an episode of fluid-driven Pb-loss, indicated by the presence of internal and external corrosion structures not only of the monazites but also of the zircons in the same samples that are also rejuvenated at 210 ± 12 Ma. Another group of monazite data lies above the concordia. The presence of excess ²⁰⁶Pb indicates that these crystals have grown below the monazite blocking temperature, thus after the granulite facies metamorphism. The age of growth of the new monazite crystals is approached by their ²⁰⁷Pb/²³⁵U ages that range between 273 and 244 Ma. The two groups of post-cooling age (post-293.4 ± 5.8 Ma) monazite data correspond to two distinct late- and post-Variscan geotectonic regimes that affected the Southern Alps, (1) Permian transtension with decompression and anatectic melting; (2) Upper Triassic to Lower Jurassic rifting with geographically dispersed hydrothermal activity and alkaline magmatism. Received: 7 July 1998 / Accepted: 4 November 1998  相似文献   

U–Pb geochronology of detrital zircons from a contact metamorphic Brixen Quartzphyllite (South-Tyrol, Italy): evidence for a complex pre-Variscan evolution of the Southalpine basement     

Stefan Wyhlidal  Werner F. Thöny  Peter Tropper  Urs Klötzli  Volkmar Mair 《Swiss Journal of Geoscience》2010,103(2):273-281

Laser ablation ICP-MS U–Pb zircon geochronology of detrital zircons from a contact metamorphic sample of the Brixen Quartzphyllite from the innermost part of the contact aureole adjacent to the Brixen granodiorite yielded three different Precambrian concordia ages: zircon cores and an older generation of zircons give a maximum age of 2,023 ± 31 Ma, zircon rims and a younger generation of single grains yield a concordia age of 882 ± 19 Ma. A third generation of single zircon grains yields an age of 638 ± 20 Ma. In contrast to Austroalpine quartzphyllite complexes from the Eastern Alps neither Cambrian/Ordovician (570–450 Ma) nor Carboniferous (360–340 Ma) ages on single zircons have been observed so far in these samples. These ages provide evidence of a complex pre-Variscan evolution of the Southalpine basement since these data suggest a possible affinity of the Southalpine basement to Gondwana-related tectonic elements as well as to a possible Cadomian hinterland. This study shows that dating detrital zircons of the Brixen Quartzphyllites has great potential for providing age constraints on the complex geological evolution of the Southalpine basement.  相似文献   

Indigenous knowledge related to climate variability and change: insights from droughts in semi-arid areas of former Makueni District,Kenya   总被引：1，自引：1，他引：0  

Chinwe Ifejika Speranza  Boniface Kiteme  Peter Ambenje  Urs Wiesmann  Samuel Makali 《Climatic change》2010,100(2):295-315

This article describes the indigenous knowledge (IK) that agro-pastoralists in larger Makueni District, Kenya hold and how they use it to monitor, mitigate and adapt to drought. It examines ways of integrating IK into formal monitoring, how to enhance its value and acceptability. Data was collected through target interviews, group discussions and questionnaires covering 127 households in eight villages. Daily rainfall data from 1961–2003 were analysed. Results show that agro-pastoralists hold IK on indicators of rainfall variability; they believe in IK efficacy and they rely on them. Because agro-pastoralists consult additional sources, the authors interpret that IK forms a basic knowledge frame within which agro-pastoralists position and interpret meteorological forecasts. Only a few agro-pastoralists adapt their practices in anticipation of IK-based forecasts partly due to the conditioning of the actors to the high rainfall variability characteristic of the area and partly due to lack of resources. Non-drought factors such as poverty, inadequate resources and lack of preparedness expose agro-pastoralists to drought impacts and limit their adaptive capacity. These factors need to be understood and effectively addressed to increase agro-pastoralists’ decision options and the influence of IK-based forecasts on their decision-making patterns. The limited intergenerational transfer of IK currently threatens its existence in the longer term. One way to ensure its continued existence and use is to integrate IK into the education curriculum and to link IK with formal climate change research through the participation of the local people. However, further studies are necessary to address the reliability and validity of the identified IK indicators of climate variability and change.  相似文献   

Elemental characterization and source identification of PM_2.5 using Positive Matrix Factorization: The Malraux road tunnel, Nice, France   总被引：1，自引：0，他引：1  

Jean-Franois Fabretti  Nathalie Sauret  Jean-Franois Gal  Pierre-Charles Maria  Urs Schrer 《Atmospheric Research》2009,94(2):320-329

This work was dedicated to the characterization of the elemental composition of atmospheric particles associated with urban traffic. PM_2.5 sampling campaigns were conducted in an urban road tunnel within the area of Nice: the Malraux tunnel. Samples were analyzed by ICP-MS-DRC for the determination of 16 metallic trace elements: Na, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, As, Sr, Rb, Cd, Sn, Sb and Pb. An in depth study was carried out on the PM_2.5 dataset collected with specific characterisation tools (enrichment factors, elemental ratio) and a receptor model: the Positive Matrix Factorization (PMF). The model showed that different profiles of emission could influence the ambient air of the tunnel and their contribution to the metal concentration in the air. Elemental fingerprints were used to attribute to each profile a specific emission source linked to road traffic. Finally, results showed that road traffic emissions could be divided into 3 main “subcategory” sources of emission: “soil resuspension” by automobile movement, “vehicular wear” and “fuel combustion”.  相似文献   

Pollution and eutrophication history AD 1800–2005 as recorded in sediments from five lakes in Central Chile     

Lucien von Gunten  Martin Grosjean  Urs Eggenberger  Philipp Grob  Roberto Urrutia  Arturo Morales 《Global and Planetary Change》2009,68(3):198-208

One of the fundamental problems to quantifying past impact of anthropogenic activities is that long series of observational data for pollutant deposition and changes in the nutrient cycling of ecosystems (eutrophication) are often not available. Lake sediments may provide suitable archives to decipher the history of local and regional pollution and eutrophication.Here we provide quantitative high-resolution data for the history of airborne pollutants and eutrophication from sediments of five lakes in Central Chile between ca. AD 1800–2005. We use spheroidal carbonaceous particles (SCPs) from fossil fuel combustion and excess atmospheric Cu deposition from mining activities as a proxy for atmospheric deposition. Organic carbon and nitrogen flux rates to the sediments and C/N ratios are used as a proxy for aquatic primary production and eutrophication.We show that the lake sediment SCP and Cu records are highly consistent and depict in great detail the local and regional history of urban, industrial and transportation history as reported in independent documentary sources and statistics. The pre-industrial and pre-1950 background concentrations (and flux rates) of the substances can be quantified. We can also show that technical measures taken in the early 1980s to trim down Cu emissions from the copper mines reduced the excess atmospheric Cu fallout to the lakes by about 50%.Eutrophication of the lakes did not start before ca. 1980. Prior to that time, warm season temperatures explain most of the variance in TOC and N flux to the sediments. The three dimictic lakes show only moderate eutrophication responses to enhanced N supply (as atmospheric fallout; enrichment factors for TOC and N 1.1–2.6), suggesting that mainly phosphorus controls aquatic primary production. The meromictic lake, where phosphorus recycling is likely, shows the largest response (enrichment factors for TOC and N between 9–20).While all five lakes show overall consistent and similar trends for the pollution history during the 19th and 20th century, there are significant differences in the details of the individual profiles. This suggests that local sources are highly important and the common regional (background) signal is relatively marginal. This is very different from Europe.  相似文献   

Stability and isotopic dating of monazite and allanite in partially molten rocks: examples from the Central Alps     

Alfons Berger  Claudio Rosenberg  Urs Schaltegger 《Swiss Journal of Geoscience》2009,102(1):15-29

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