Subsurface deformation in hypervelocity cratering experiments into high‐porosity tuffs          下载免费PDF全文

Rebecca Winkler  Michael H. Poelchau  Stefan Moser  Thomas Kenkmann 《Meteoritics & planetary science》2016,51(10):1849-1870

Hypervelocity impact experiments on porous tuff targets were carried out to determine the effect of porosity on deformation mechanisms in the crater's subsurface. Blocks of Weibern Tuff with about 43% porosity were impacted by 2.5 mm and 12.0 mm diameter steel spheres with velocities between 4.8 km s^?1 and 5.6 km s^?1. The postimpact subsurface damage was quantified with computer tomography as well as with meso‐ and microscale analyses of the bisected crater subsurface. The intensity and style of deformation in mineral clasts and the tuff matrix were mapped and their decay with subsurface depth was determined. Subsurface deformation styles include pore space compaction, clast rotation, as well as microfracture formation. Evaluation of the deformation indicates near‐surface energy coupling at a calculated depth of burial of ~2 projectile diameters (d_p), which is in conflict with the crater shape, which displays a deep, central penetration tube. Subsurface damage extends to ~2 d_p beneath the crater floor in the experiments with 2.5 mm projectiles and increases to ~3 d_p for 12 mm projectiles. Based on overprinting relationships and the geometrical orientation of deformation features, a sequence of subsurface deformation events was derived (1) matrix compaction, (2) intragranular crack formation in clasts, (3) deformation band formation in the compacted matrix, (4) tensile fracturing.  相似文献   

Control factors on turbidite sedimentation in a deep-sea trench setting. – The example of the Schlieren Flysch (Upper Maastrichtian-Lower Eocene,Central Switzerland)     

Wilfried Winkler 《Geodinamica Acta》2013,26(2):81-102

Abstract

Deep-sea turbidite sedimentation in convergent margin settings generally is controlled by tectonic uplift, climate and eustatic sea-level variations. The rate of tectonic uplift governs the relief of the source area and the position of the base level (coinciding with sea-level), climate influences the rate and style of weathering and continental runoff and eustatic seal-level additionally shifts the base level, functioning with the concurrently working tectonic movements. Thus, these factors primarly determine the availability of sediment (yield and nature of material and the site of intermittent storage) at the basin margin which is unlocked periodically to flow downslope to the basin.

This paper attempts to decipher quantitatively the importance of the individual factors in the Late Maastrichtian to Early Eocene Schieren Flysch Croup. The flysch was deposited in a moderately converging remnant oceanic trench basin. Mean parameters are calculated on the basis of formations and the duration of nannofossil zones comprised in. For transposing these zone into absolute age intervals the problem of inconsistent durations in current time scales had to be solved by a best-fit approach. Frequencies and periodicities of turbidite events, decompacted and compacted sedimentation rates (the latter are considered as apparent denudation rates) are calculated to reveal the dynamics of sedimentation. Climatic evidence is deduced from clay mineralogy. Changing uplift rates in the drainage area are indirectly interpreted from back-stripped tectonic subsisdence rates in the basin.

The obtained data point to an immediate control of sub-duction-Iinked tectonic uplift in the bordering drainage and shelf area on turbidite sedimentation, as frequency and thickness of the turbidite events are closely correlated with the increasing tectonic subsisdence in the basin (assumed to match the rate of subduction and underplating). This general trend is modified by the temporary migration of the oceanic hinge zone towards the trench causing periodically the starvation of outer portions of the basin at the transition from Early to Late Paleocene and Late Paleocene to Eocene. Regional climatic trends additionnaly rule the turbidite facies development and apparent denudation rates. In the upper part of Early Eocene series high rate mud dominated sediments correlate with warm/humid conditions and in Late Paleocene deposits low rate sandy sediments coincide with cool ones. During the Late Paleocene period the global 2nd-order sea-level lowering probably may be responsible for the by-passing of the shelf by the coarse grained sediments.  相似文献   

Roles of forest disturbance and climate variability on streamflow components in snow-dominated paired watersheds at multiple temporal scales     

Qiang Li  Mingfang Zhang  Xiaohua Wei  Rita Winkler  Sheena Spencer  Yiping Hou  David F. Scott 《水文研究》2021,35(12):e14414

The paired watershed experimental (PWE) approach has long been used as an effective means to assess the impacts of forest change on hydrology in small watersheds (<100 km²). Yet, the effects of climate variability on streamflow are not often assessed in PWE design. In this study, two sets of paired watersheds, (1) Camp and Greata Creeks and (2) 240 and 241 Creeks located in the Southern Interior of British Columbia, Canada, were selected to explore relative roles of forest disturbance and climate variability on streamflow components (i.e., baseflow and surface runoff) at different time scales. Our analyses showed that forest disturbance is positively related to annual streamflow components. However, this relationship is statistically insignificant since forest disturbance can either increase or decrease seasonal streamflow components, which eventually limited the positive effect on streamflow at the annual scale. Interestingly, we found that forest disturbance consistently decreased summer streamflow components in the two PWEs as forest disturbance can augment earlier and quicker snow-melt processes and hence reduce soil moisture to maintain summer streamflow components. More importantly, this study revealed that climate variability played a more significant role than forest disturbance in both annual and seasonal streamflow components, for instance, climate variability can account for as much as 90% of summer streamflow components variation in Camp, suggesting the role of climate variability on streamflow should be highlighted in the traditional PWE approach to truly advance our understanding of the interactions of forest change, climate variability and water for sustainable water resource management.  相似文献   

Laser ablation U/Pb age patterns of detrital zircons in the Schlieren Flysch (Central Switzerland): new evidence on the detrital sources     

Endrio Bütler  Wilfried Winkler  Marcel Guillong 《Swiss Journal of Geoscience》2011,104(2):225-236

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The 29th ESLAB Symposium: Towards The Source of Gamma-Ray Bursts     

Kevin Bennett  Christoph Winkler 《Astrophysics and Space Science》1995,231(1-2):xi-xii

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The early interaction between the Caribbean Plateau and the NW South American Plate     

Cristian Vallejo  Richard A. Spikings  Leonard Luzieux  Wilfried Winkler  David Chew  Laurence Page 《地学学报》2006,18(4):264-269

The determination of accurate and precise ages for the timing of collision between oceanic plateaus and continental crust requires an understanding of how the indenting and buttressing plates respond to the collision. We present geochronological, thermochronological, geochemical and isotopic analyses of magmatic rocks from the Ecuadorian Andes, which relate to the collision of the Late Cretaceous Caribbean Plateau and Great Arc sequence with NW South America. The cessation of subduction magmatism during 65–64 Ma beneath the eastern edge of Caribbean Plateau was synchronous with accelerated surface uplift and exhumation within the buttressing continental margin during 75–65 Ma. We interpret this as the collision of the leading edge of the Caribbean Plateau and arc sequence with the South American Plate at 75–65 Ma. A U/Pb (zircon) SHRIMP age of 87.10 ± 1.66 (2σ) Ma, yielded by an accreted fragment of the plateau, precludes previous estimates of collision at 85–80 Ma if the plateau erupted above the Galápagos hotspot. Terra Nova, 18, 264–269, 2006  相似文献   

Möglichkeiten der Korrelation unterschiedlicher Wasseranalysenverfahren     

F. Winkler  B. Düwert  H. Patecki 《洁净——土壤、空气、水》1984,12(3):239-246

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Der Prozeß der Anatexis: Seine Bedeutung für die Genese der Migmatite     

Prof. Dr. Helmut G. F. Winkler 《Mineralogy and Petrology》1966,11(3-4):266-287

Zusammenfassung Gegenüber den metasomatisch-transformistischen Vorstellungen über die Genese der in situ-Migmatite wird dargelegt, daß allein Anatexis von Gneisen. ohne großräumige Metasomatose, die Entstehung der Migmatite erklärt. Der Prozeß der Anatexis wird erläutert, und es wird mittels des Q-Ab-An-Or-H₂O-Systems gezeigt, daß die Zusammensetzung der entstehenden eutektischen Erst-schmelze bei verschiedenen Gneisen verschieden und zwar um so reicher an Or-und auch Q-Komponente ist, je größer das normative An/Ab-Komponentenverhältnis des Gneises ist. Selbst wenn kein Alkalifeldspat in einem Paragneis vorkommt, enthält die jeweilige eutekiische Schmelze einen großen Anteil an Or-Komponente. Durch Reaktionen von Glimmer mit Quarz unter Beteiligung von Plagioklas entsieht nämlich bei nicht zu hohen Drucken Alkalifeldspat noch vor Beginn der Anatexis, bei höheren Drucken entstehtmit Beginn der Anatexis Or-Komponente, die in der Schmelze gelöst ist. Die Glimmer eines Paragneises sind eine potentielle Quelle für Or-Komponente bei der Anatexis. Mit steigender Temperatur ändert sich die Zusammensetzung der eutektischen granitischen Schmelze, und zwar wird sie bei den plagioklas- und biotitreichen Paragneisen granodioritisch oder sogar trondhjemitisch. Wenn dagegen in einem Gneis der K₂O-Gehalt nicht wesentlich geringer als der Na₂O-Gehalt ist, dann behält die Schmelze eine granitische Zusammensetzung.

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Summary Contrary to the metasomatic transformists' concepts, it is pointed out that the petrogenesis of in situ-migmatites can be fully understood solely by anatexis of gneisses without large scale metasomatism. The process of anatexis is outlined. It is shown with the help of the Q-Ab-An-Or-H₂O system that the chemical composition of the eutectic melt formed at the beginning of anatexis is different, depending on the normative An/Ab-ratio of any gneiss; the eutectic melt contains relatively more Or- and also Q-component the larger that ratio. Even if no alkalifeldspar is present in a paragneiss, the eutectic melt formed by anatexis does contain a large proportion of Or-component. This is due to reactions of micas with quartz, in presence of plagioclase. At pressures not too high, alkalifeldspar is formed by these reactions somewhat below the temperature of the beginning of anatexis, while at higher H₂O-pressure mica reacts together with plagioclase and quartz at the very beginning of anatexis, furnishing Or-component for the eutectic melt. Therefore, the micas are a potential source for Or-component in the process of anatexis. Depending on the composition of a gneiss system the anatectic melts existing at temperatures above the beginning of anatexis remain granitic in chemical character, or they become granodioritic or trondhjemitic.

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Herrn Prof. Dr.H. Leitmeier zum 80. Geburtstag gewidmet.  相似文献   

Groundwater flow dynamics in the complex aquifer system of Gidabo River Basin (Ethiopian Rift): a multi-proxy approach   总被引：2，自引：0，他引：2  

Abraham Mechal  Steffen Birk  Martin Dietzel  Albrecht Leis  Gerfried Winkler  Aberra Mogessie  Seifu Kebede 《Hydrogeology Journal》2017,25(2):519-538

Hydrochemical and isotope data in conjunction with hydraulic head and spring discharge observations were used to characterize the regional groundwater flow dynamics and the role of the tectonic setting in the Gidabo River Basin, Ethiopian Rift. Both groundwater levels and hydrochemical and isotopic data indicate groundwater flow from the major recharge area in the highland and escarpment into deep rift floor aquifers, suggesting a deep regional flow system can be distinguished from the shallow local aquifers. The δ¹⁸O and δ²H values of deep thermal (≥30 °C) groundwater are depleted relative to the shallow (<60 m below ground level) groundwater in the rift floor. Based on the δ¹⁸O values, the thermal groundwater is found to be recharged in the highland around 2,600 m a.s.l. and on average mixed with a proportion of 30 % shallow groundwater. While most groundwater samples display diluted solutions, δ¹³C data of dissolved inorganic carbon reveal that locally the thermal groundwater near fault zones is loaded with mantle CO₂, which enhances silicate weathering and leads to anomalously high total dissolved solids (2,000–2,320 mg/l) and fluoride concentrations (6–15 mg/l) exceeding the recommended guideline value. The faults are generally found to act as complex conduit leaky barrier systems favoring vertical mixing processes. Normal faults dipping to the west appear to facilitate movement of groundwater into deeper aquifers and towards the rift floor, whereas those dipping to the east tend to act as leaky barriers perpendicular to the fault but enable preferential flow parallel to the fault plane.  相似文献   

Book Review     

Anne Marie de Grosbois  Massimo Gasparon  Jörg Matschullat  Andreas Winkler 《Environmental Geology》2005,49(2):344-346

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