Multimodal water age distributions and the challenge of complex hydrological landscapes     

Nicolas B. Rodriguez  Paolo Benettin  Julian Klaus 《水文研究》2020,34(12):2707-2724

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Experimental impact cratering: A summary of the major results of the MEMIN research unit          下载免费PDF全文

Thomas Kenkmann  Alex Deutsch  Klaus Thoma  Matthias Ebert  Michael H. Poelchau  Elmar Buhl  Eva-Regine Carl  Andreas N. Danilewsky  Georg Dresen  Anja Dufresne  Nathanaël Durr  Lars Ehm  Christian Grosse  Max Gulde  Nicole Güldemeister  Christopher Hamann  Lutz Hecht  Stefan Hiermaier  Tobias Hoerth  Astrid Kowitz  Falko Langenhorst  Bernd Lexow  Hanns-Peter Liermann  Robert Luther  Ulrich Mansfeld  Dorothee Moser  Manuel Raith  Wolf Uwe Reimold  Martin Sauer  Frank Schäfer  Ralf Thomas Schmitt  Frank Sommer  Jakob Wilk  Rebecca Winkler  Kai Wünnemann 《Meteoritics & planetary science》2018,53(8):1543-1568

This paper reviews major findings of the Multidisciplinary Experimental and Modeling Impact Crater Research Network (MEMIN). MEMIN is a consortium, funded from 2009 till 2017 by the German Research Foundation, and is aimed at investigating impact cratering processes by experimental and modeling approaches. The vision of this network has been to comprehensively quantify impact processes by conducting a strictly controlled experimental campaign at the laboratory scale, together with a multidisciplinary analytical approach. Central to MEMIN has been the use of powerful two-stage light-gas accelerators capable of producing impact craters in the decimeter size range in solid rocks that allowed detailed spatial analyses of petrophysical, structural, and geochemical changes in target rocks and ejecta. In addition, explosive setups, membrane-driven diamond anvil cells, as well as laser irradiation and split Hopkinson pressure bar technologies have been used to study the response of minerals and rocks to shock and dynamic loading as well as high-temperature conditions. We used Seeberger sandstone, Taunus quartzite, Carrara marble, and Weibern tuff as major target rock types. In concert with the experiments we conducted mesoscale numerical simulations of shock wave propagation in heterogeneous rocks resolving the complex response of grains and pores to compressive, shear, and tensile loading and macroscale modeling of crater formation and fracturing. Major results comprise (1) projectile–target interaction, (2) various aspects of shock metamorphism with special focus on low shock pressures and effects of target porosity and water saturation, (3) crater morphologies and cratering efficiencies in various nonporous and porous lithologies, (4) in situ target damage, (5) ejecta dynamics, and (6) geophysical survey of experimental craters.  相似文献   

Estimation of the 3D correlation structure of an alluvial aquifer from surface-based multi-frequency ground-penetrating radar reflection data     

Zhiwei Xu  James Irving  Kyle Lindsay  John Bradford  Peimin Zhu  Klaus Holliger 《Geophysical Prospecting》2020,68(2):678-689

Knowledge about the stochastic nature of heterogeneity in subsurface hydraulic properties is critical for aquifer characterization and the corresponding prediction of groundwater flow and contaminant transport. Whereas the vertical correlation structure of the heterogeneity is often well constrained by borehole information, the lateral correlation structure is generally unknown because the spacing between boreholes is too large to allow for its meaningful inference. There is, however, evidence to suggest that information on the lateral correlation structure may be extracted from the correlation statistics of the subsurface reflectivity structure imaged by surface-based ground-penetrating radar measurements. To date, case studies involving this approach have been limited to 2D profiles acquired at a single antenna centre frequency in areas with limited complementary information. As a result, the practical reliability of this methodology has been difficult to assess. Here, we extend previous work to 3D and consider reflection ground-penetrating radar data acquired using two antenna centre frequencies at the extensively explored and well-constrained Boise Hydrogeophysical Research Site. We find that the results obtained using the two ground-penetrating radar frequencies are consistent with each other, as well as with information from a number of other studies at the Boise Hydrogeophysical Research Site. In addition, contrary to previous 2D work, our results indicate that the surface-based reflection ground-penetrating radar data are not only sensitive to the aspect ratio of the underlying heterogeneity, but also, albeit to a lesser extent, to the so-called Hurst number, which is a key parameter characterizing the local variability of the fine-scale structure.  相似文献   

Glacier outburst floods reconstructed from lake sediments and their implications for Holocene variations of the plateau glacier Folgefonna in western Norway     

Torgeir O. Rthe  Jostein Bakke  Eivind Wilhelm Nagel Stren 《Boreas: An International Journal of Quaternary Research》2019,48(3):616-634

A sudden release of large volumes of water during a glacier outburst flood (GLOF) is a major hazard worldwide. Here, we identify the sedimentary signature of glacial and non‐glacial processes, including GLOFs, based on lacustrine sediments from the distal glacier‐fed Lake Buarvatnet in western Norway. Historically documented GLOFs in 2002 CE and during the 1980s CE are identified in the ²¹⁰Pb‐ and ¹⁴C‐dated sediments. These events have the same sedimentary signature as 12 earlier events throughout the Holocene interpreted to represent previous GLOFs in the catchment. The GLOFs are interpreted to have occurred during periods when the glacier extent was similar to the modern positions, and the events are thus used to pinpoint past positions of the glacier terminus and, hence, the equilibrium line altitudes (ELAs). The results indicate that the glacier Svartenutbreen, located at the eastern part of Folgefonna, had a similar size in 2002 CE as c. 8200–8300 cal. a BP, corresponding to the 8.2 ka event in the North Atlantic region. The regrowth of Sørfonna after the Holocene Thermal Optimum occurred at c. 6900 cal. a BP and Svartenutbreen was at modern size and extent in the periods c. 6400, c. 5450, c. 4850, c. 3850, c. 3550 and c. 1650 cal. a BP. Since 1650 cal. a BP, we infer that the glacier was larger than the 2002 CE glacier extent until 1910 CE when a GLOF occurred. Svartenutbreen has been retreating since 1910 CE, which led to the ice damming of the two historical GLOFs in the 1980s and 2002 CE separated by a glacier advance in the 1990s CE. The findings are discussed and compared to other regional glacier reconstructions in Norway, and emphasize the value of identifying and utilizing GLOFs as an indicator of past ELA variability.  相似文献   

Empirical assessment of rockfall and debris flow risk along the Karakoram Highway,Pakistan     

Ali  Sajid  Haider  Rashid  Abbas  Wahid  Basharat  Muhammad  Reicherter  Klaus 《Natural Hazards》2021,106(3):2437-2460

Natural Hazards - The Karakoram Highway links north Pakistan with southwest China. It passes through unique geomorphological, geological and tectonic setting. This study focused 200-km-long section...  相似文献   

Blind Source Separation for Compositional Time Series     

Nordhausen  Klaus  Fischer  Gregor  Filzmoser  Peter 《Mathematical Geosciences》2021,53(5):905-924

Many geological phenomena are regularly measured over time to follow developments and changes. For many of these phenomena, the absolute values are not of interest, but rather the relative information, which means that the data are compositional time series. Thus, the serial nature and the compositional geometry should be considered when analyzing the data. Multivariate time series are already challenging, especially if they are higher dimensional, and latent variable models are a popular way to deal with this kind of data. Blind source separation techniques are well-established latent factor models for time series, with many variants covering quite different time series models. Here, several such methods and their assumptions are reviewed, and it is shown how they can be applied to high-dimensional compositional time series. Also, a novel blind source separation method is suggested which is quite flexible regarding the assumptions of the latent time series. The methodology is illustrated using simulations and in an application to light absorbance data from water samples taken from a small stream in Lower Austria.

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Interannual variability patterns of the world’s total column water content: Amazon River basin     

Isabella Bordi  Roberto De Bonis  Klaus Fraedrich  Alfonso Sutera 《Theoretical and Applied Climatology》2015,122(3-4):441-455

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Sedimentology of early Pliocene sandstones in the south-western Taiwan foreland: Implications for basin physiography in the early stages of collision     

Sébastien Castelltort  Stefan Nagel  Frédéric Mouthereau  Andrew Tien-Shun Lin  Andreas Wetzel  Boris Kaus  Sean Willett  Shao-Ping Chiang  Wei-Yi Chiu 《Journal of Asian Earth Sciences》2011,40(1):52-71

This work presents sedimentological observations and interpretations on three detailed sections of the Pliocene Yutengping/Ailiaochiao formations, deposited in the early stages of collision in Taiwan. Seven facies associations record paleoenvironments of deposition ranging from nearshore to lower offshore with a strong influence of tidal reworking, even in shelfal sub-tidal environments, and a pro-delta setting characterized by mass-flows. The association of shallow facies of the upper offshore to lower shoreface with pro-delta turbidite facies sourced in the orogen to the east suggests a peculiar setting in which turbidite deposition occurred below wave base but on the shelf, in water depths of probably less than 100 m. This adds to the examples of “shallow turbidites” increasingly commonly found in foreland basins and challenges the classical view of a “deep” early underfilled foreland basin. Time series analysis on tidal rhythmites allow us to identify a yearly signal in the form of periodic changes of sand-supply, energy and bioturbation that suggests a marked seasonality possibly affecting precipitation and sediment delivery as well as temperature. The Taiwan foreland basin may also present a potentially high-resolution record in shallow sediments of the early installation of monsoonal circulation patterns in east Asia. We confirm partly the paleogeography during the early stages of collision in Taiwan: the Chinese margin displayed a pronounced non-cylindrical geometry with a large basement promontory to the west in place of the modern Taiwan mountain range. Collision in Taiwan may have happened at once along the whole length of the modern mountain range, instead of progressively from north to south as classically considered.  相似文献   

Lattice-preferred orientations of late-Variscan granitoids derived from neutron diffraction data: implications for magma emplacement mechanisms     

Axel Müller  Bernd Leiss  Klaus Ullemeyer  Karel Breiter 《International Journal of Earth Sciences》2011,100(7):1515-1532

The lattice-preferred orientation (LPOs) of two late-Variscan granitoids, the Meissen monzonite and the Podlesí dyke granite, were determined from high-resolution time-of-flight neutron diffraction patterns gained at the diffractometer SKAT in Dubna, Russia. The results demonstrate that the method is suitable for the LPO analysis of polyphase, relatively coarse-grained (0.1–6 mm) rocks. The Meissen monzonite has a prominent shape-preferred orientation (SPO) of the non-equidimensional minerals feldspar, mica and amphibole, whereas SPO of the Podlesí granite is unapparent at the hand-specimen scale. The neutron diffraction data revealed distinct LPOs in both granitoids. The LPO of the non-equidimensional minerals feldspar, mica and amphibole developed mainly during magmatic flow. In the case of the Meissen monzonite, the magmatic flow was superimposed by regional shear tectonics, which, however, had no significant effect on the LPOs. In both samples, quartz shows a weak but distinct LPO, which is atypical for plastic deformation and different in the syn-kinematic Meissen monzonite and the post-kinematic Podlesí granite. We suggest that, first of all, the quartz LPO of the Meissen monzonite is the result of oriented growth in an anisotropic stress field. The quartz LPO of the Podlesí granite, which more or less resembles a deformational LPO in the flattening field of the local strain field, developed during magmatic flow, whereby the rhombohedral faces of the quartz crystals adhered to the (010) faces of aligned albite and to the (001) faces of zinnwaldite. Due to shape anisotropy of their attachments, the quartz crystals were passively aligned by magmatic flow. Thus, magmatic flow and oriented crystal growth are the major LPO-forming processes in both granitoids. For the Meissen monzonite, the solid-state flow was too weak to cause significant crystallographic re-orientation of the minerals aligned by magmatic flow. Finally, the significance of our results for the evaluation of the regional tectonic environment during magma emplacement is discussed. The discussion on the regional implications of the more methodologically oriented results provides the basis for future, more regionally aimed studies in view of the fabric characteristics of such plutons and their developing mechanisms.  相似文献   

Geostandards and Geoanalytical Research Bibliographic Review 2014          下载免费PDF全文

Ulrike Weis  Beate Schwager  Uwe Nohl  Laura M. Otter  Brigitte Stoll  Patricia Karlowski  Klaus Peter Jochum 《Geostandards and Geoanalytical Research》2015,39(4):497-500

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