Strain localization in the Morcles nappe (Helvetic Alps, Switzerland)     

Nicholas Austin  Brian Evans  Marco Herwegh  Andreas Ebert 《Swiss Journal of Geoscience》2008,101(2):341-360

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Origin of lunar fragmental matrix breccias—Highly siderophile element constraints     

Philipp Gleißner  Harry Becker 《Meteoritics & planetary science》2019,54(9):2006-2026

Ejecta at North Ray crater (Apollo 16) sampled a unique section of the lunar highlands not accessible at most other landing sites and provide important constraints on the composition of late accreted materials. New data on multiple aliquots of four fragmental matrix breccias and a fragment‐laden melt breccia from this site display a variety of highly siderophile element patterns which may represent the signatures of volatile element‐depleted carbonaceous chondrite‐like material, primitive achondrite, differentiated metal, and an impactor component that cannot be related to known meteoritic material. The latter component is prevalent in these rocks besides characterized by depletions in Re and Os compared to Ir, Ru and Pt, chondritic Re/Os, and a gradual depletion of Pd and Au. The observed characteristics are more consistent with fractionations by nebular processes, like incomplete condensation or evaporation, than with lunar crustal processes, like partial melting or volatilization. The impactor signature preserved in these breccias may stem from primitive meteorites with a refractory element composition moderately different from known chondrites. The presence of distinct impactor components within the North Ray crater breccias together with observed correlations of characteristic element ratios (e.g., Re/Os, Ru/Pt, Pd/Ir) in different impact lithologies of four Apollo landing sites constrains physical mixing processes ranging from the scale of gram‐sized samples to the area covered by the Apollo missions.  相似文献   

Generation and application of rules for quality dependent façade reconstruction     

Susanne Becker 《ISPRS Journal of Photogrammetry and Remote Sensing》2009,64(6):640-653

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Range-wide population structure and history of the northern quahog (Merceneria merceneria) inferred from mitochondrial DNA sequence data     

Baker  Patrick; Austin  James D.; Bowen  Brian W.; Baker  Shirley M. 《ICES Journal of Marine Science》2008,65(2):155-163

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Die Methodik der radioaktiven Quellen-Untersuchung     

Prof. Dr. A. Becker 《International Journal of Earth Sciences》1924,14(4):364-374

Ohne Zusammenfassung  相似文献   

Compositional variability of ice‐rafted debris in Heinrich layers 1 and 2 on the northwest European continental slope identified by environmental magnetic analyses     

John Walden  Emilie Wadsworth  William E. N. Austin  Clare Peters  James D. Scourse  Ian R. Hall 《第四纪科学杂志》2007,22(2):163-172

The composition of ice‐rafted debris (IRD) within a sediment core from the European continental slope (core OMEX‐2K; 49° 5′ N, 13° 26′ W) has been examined using environmental magnetic analyses. The data demonstrate compositional variability of the IRD within Heinrich layers 2 (H2) and 1 (H1) and these differences are most readily explained by changes in the contribution of different IRD sources to the core site. Some IRD within the main Heinrich layers show magnetic signatures that are similar to IRD derived from the Laurentide ice sheet found in cores from within the main North Atlantic IRD‐belt. In contrast, other IRD‐rich layers, both prior to and within the main Heinrich layers, demonstrate different magnetic behaviour, suggesting a contribution from a non‐Laurentide sourced IRD, most likely derived from ice streams discharging from northeast Atlantic ice sheets such as the British and Fennoscandian ice sheets. These data are consistent with published compositional data from the same core and, given the rapid, highly sensitive and non‐destructive nature of the method, suggest that environmental magnetic analysis has considerable potential for characterising IRD materials within Heinrich layers for the purposes of defining provenance. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Rockfalls triggered by the ad 1356 Basle Earthquake     

A. Becker  C. A. Davenport 《地学学报》2003,15(4):258-264

In the Basle region of Switzerland we demonstrate that rockfall blocks can be dated accurately using the radiocarbon method. Soil beneath rockfall blocks containing organic macro‐remains was sampled at four cliff sites in the Tabular Jura south‐east of Basle. A lightweight drilling rig drills a 101‐mm‐diameter hole through rockfall blocks up to 6 m in height. A downhole sampler is used to recover soil samples from below the blocks. Eighteen radiocarbon dates on charcoal, wood, needles of conifers and organic macro‐remains from 11 blocks gave dates between 970 and 440 bp . Calibrated ages range between ad 1210 and ad 1450. These results, along with field observations and historical research, suggest that a large number of blocks toppled as rockfalls within a short time interval in the epicentral area of the ad 1356 Basle earthquake.  相似文献   

Growth kinetics of enstatite reaction rims studied on nano-scale,Part I: Methodology,microscopic observations and the role of water   总被引：1，自引：0，他引：1  

Ralf Milke  Ralf Dohmen  Hans-Werner Becker  Richard Wirth 《Contributions to Mineralogy and Petrology》2007,154(5):519-533

The kinetics of (Mg, Fe)SiO₃ pyroxene layer growth within silicate thin films with total thickness <1 μm was studied experimentally at 0.1 MPa total pressure, controlled fO₂ and temperatures from 1,000 to 1,300°C. The starting samples were produced by pulsed laser deposition. Layer thickness before and after the experiments and layer composition as well as microstructures, grain size and shape of the interfaces were determined by Rutherford back scattering and transmission electron microscopy assisted by focused ion beam milling. Due to the miniaturization of the starting samples and the use of high resolution analytical methods the experimentally accessible temperature range for rim growth experiments was extended by about 300°C towards lower temperatures. The thickness of the layers at a given temperature increases proprotional to the square root of time, indicating a diffusion-controlled growth mechanism. The temperature dependence of rim growth yields an apparent activation energy of 426 ± 34 kJ/mol. The small grain size in the orthopyroxene rims implies a significant contribution of grain boundary diffusion to the bulk diffusion properties of the polycrystalline rims. Based on microstructural observations diffusion scenarios are discussed for which the SiO₂ component behaves immobile relative to the MgO component. Volume diffusion data for Mg in orthopyroxene from the literature indicate that the measured diffusivity is probably controlled by the mobility of oxygen. The observed reaction rates are consistent with earlier results from dry high-temperature experiments on orthopyroxene rim growth. Compared to high pressure experiments at 1,000°C and low water fugacities, reaction rates are 3–4 orders of magnitude smaller. This observation is taken as direct evidence for a strong effect of small amounts of water on diffusion in silicate polycrystals. In particular SiO₂ changes from an immobile component at dry conditions to an extremely mobile component even at very low water fugacities.  相似文献   

Experimental determination of the Raman CH₄ symmetric stretching (ν₁) band position from 1-650 bar and 0.3-22 °C: Application to fluid inclusion studies     

F. Lin  S.P. Becker 《Geochimica et cosmochimica acta》2007,71(15):3746-3756

The position of the Raman methane (CH₄) symmetric stretching band (ν₁) over the range 1-650 bar and 0.3-22 °C has been determined using a high-pressure optical cell mounted on a Raman microprobe. Two neon emission lines that closely bracket the CH₄ band were collected simultaneously with each CH₄ spectrum. The peak position was determined after least squares fitting using a summed Gaussian-Lorentzian method, resulting in a precision of ≈±0.02 cm⁻¹ in peak position determination. The CH₄ν₁ band position shifts to lower wave number with increasing pressure. At a given pressure, the band shifts to lower wave number with decreasing temperature, and the magnitude of the temperature shift increases with increasing pressure. The relationship between the Raman CH₄ν₁ band position and temperature and pressure determined here may be used to estimate the internal pressure in natural or synthetic CH₄-bearing fluid inclusions. This information, in turn, may be used to determine the density of pure CH₄ fluid inclusions and the salinity of CH₄-bearing aqueous inclusions.  相似文献   

Fine-scale acoustic tomographic imaging of shallow water sediments     

Dezhang Chu Dajun Tang Austin  T.C. Hinton  A.A. Arthur  R.I.  Jr. 《Oceanic Engineering, IEEE Journal of》2001,26(1):70-83

In acoustic tomographic system capable of performing in situ two-dimensional (2D) acoustic imaging of shallow water sediments is described. This system is capable of resolving inhomogeneities greater than 10 cm and differentiating sound-speed variations greater than 2%, A tomographic inversion is performed in a 2D vertical slice of about 1 m ² (1 m×1 m) using three identical probes, with each consisting of 70 evenly distributed transducers. In normal deployments, two of the probes are oriented vertically and are separated by about 1 meter, and the third is positioned horizontally right above the two vertical probes. The additional horizontal probe greatly improves the horizontal resolution of the system compared to conventional crosshole tomographic setups. Numerical simulations are performed to evaluate the influences of arrival time detection error and transducer position error on the performance of the tomography system. For an arrival time of 500 ns (standard deviation) and a position error of 4 mm (standard deviation), sound-speed anomalies of greater than 0.8% can be correctly predicted near the upper portion (close to the horizontal probe) and are resolvable near the lower portion. A controlled laboratory experiment was conducted to evaluate the performance of the system. The location of a polyurethane block (Conap EN22) used as a known target is correctly predicted while the inverted sound speed is about 9% lower than that from its actual value. Field data taken from a saturated muddy site are presented and analyzed. The inverted mean sound speed and attenuation are about 1480 ms^-1 and 20 dBm^-1, respectively  相似文献