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121.
Erich Wasmund 《International Journal of Earth Sciences》1936,27(6):492-498
Zusammenfassung Es werden vom winterlichen pommerschen Flachstrand menschliche Relieffährten beschrieben, deren Erhöhung über Strandflächenniveau mit Tieffrieren der Eindruckstellen durch Druck, Regelation usw., und nachträgliches Herauspräparieren der ursprünglichen Hohlform durch Abtragungsvorgänge erklärt wird. Ihre Bedeutung für die Paläontologie (Chirotherienspuren) wird erörtert. 相似文献
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Erich Wasmund 《International Journal of Earth Sciences》1933,24(3-4):241-246
Ohne Zusammenfassung 相似文献
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Lake sediment cores, dated by 210Pb, were collected from Spectacle Pond (SP), Massachusetts, and Side Pistol Lake (SPL) and Sargent Mountain Pond (SMP), Maine, USA. SP is a kettle seepage lake in granitic sand and gravel. SMP is a drainage pond on granite with little soil in the small watershed. SPL is a drainage lake in granitic till. The three cores were analyzed for total Cd. For SP and SMP, maximum concentrations of 1.7 and 3.9 mg/kg, four and eight times background concentrations, respectively, occur in the late 1960s. Accumulation rates reach maximum values concurrently with concentration and are 0.054 and 0.016 μg/cm2/a, more than 10 times background. Concentration and accumulation rate age relationships in SMP and SP are similar for background values, timing and magnitude of increase to peak values, and the decrease nearly to background values since about 1975. The chemical response to decreased atmospheric deposition lags in SPL sediment. Kettle-like lakes more clearly indicate changes in atmospheric deposition than drainage lakes. 相似文献
126.
Lennart Bengtsson Kevin I. Hodges Erich Roeckner Renate Brokopf 《Climate Dynamics》2006,27(7-8):743-760
We suggest that climate variability in Europe for the “pre-industrial” period 1500–1900 is fundamentally a consequence of internal fluctuations of the climate system. This is because a model simulation, using fixed pre-industrial forcing, in several important aspects is consistent with recent observational reconstructions at high temporal resolution. This includes extreme warm and cold seasonal events as well as different measures of the decadal to multi-decadal variance. Significant trends of 50-year duration can be seen in the model simulation. While the global temperature is highly correlated with ENSO (El Nino- Southern Oscillation), European seasonal temperature is only weakly correlated with the global temperature broadly consistent with data from ERA-40 reanalyses. Seasonal temperature anomalies of the European land area are largely controlled by the position of the North Atlantic storm tracks. We believe the result is highly relevant for the interpretation of past observational records suggesting that the effect of external forcing appears to be of secondary importance. That variations in the solar irradiation could have been a credible cause of climate variations during the last centuries, as suggested in some previous studies, is presumably due to the fact that the models used in these studies may have underestimated the internal variability of the climate. The general interpretation from this study is that the past climate is just one of many possible realizations and thus in many respects not reproducible in its time evolution with a general circulation model but only reproducible in a statistical sense. 相似文献
127.
Lithology‐controlled evolution of stream bed sediment and basin‐scale sediment yields in adjacent mountain watersheds,Idaho, USA
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The composition, grain‐size, and flux of stream sediment evolve downstream in response to variations in basin‐scale sediment delivery, channel network structure, and diminution during transport. Here, we document downstream changes in lithology and grain size within two adjacent ~300 km2 catchments in the northern Rocky Mountains, USA, which drain differing mixtures of soft and resistant rock types, and where measured sediment yields differ two‐fold. We use a simple erosion–abrasion mass balance model to predict the downstream evolution of sediment flux and composition using a Monte Carlo approach constrained by measured sediment flux. Results show that the downstream evolution of the bed sediment composition is predictably related to changes in underlying geology, influencing the proportion of sediment carried as bedload or suspended load. In the Big Wood basin, particle abrasion reduces the proportion of fine‐grained sedimentary and volcanic rocks, depressing bedload in favor of suspended load. Reduced bedload transport leads to stronger bed armoring, and coarse granitic rocks are concentrated in the stream bed. By contrast, in the North Fork Big Lost basin, bedload yields are three times higher, the stream bed is less armored, and bed sediment becomes dominated by durable quartzitic sandstones. For both basins, the geology‐based mass balance model can reproduce within ~5% root‐mean‐square error the composition of the bed substrate using realistic erosion and abrasion parameters. As bed sediment evolves downstream, bedload fluxes increase and decrease as a function of the abrasion parameter and the frequency and size of tributary junctions, while suspended load increases steadily. Variable erosion and abrasion rates produce conditions of variable bed‐material transport rates that are sensitive to the distribution of lithologies and channel network structure, and, provided sufficient diversity in bedrock geology, measurements of bed sediment composition allow for an assessment of sediment source areas and yield using a simple modeling approach. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
128.
Polished ore samples from the world-class Bleiberg lead-zinc deposit in Austria were studied by Field Emission Scanning Electron Microscopy (FESEM) at magnifications in the range of 105–106. The zinc ore shows nano-sized sphalerite filaments and spherules which are morphologically similar to recent biofilms of sulphate-reducing bacteria. The activity of sulphate-reducing bacteria is suggested by a large 34S difference of ~40 between coeval seawater sulphate (+16 ) and sulphide sulphur (< –25 ) in the Bleiberg ores, and by variable sulphur valences. Peloids of sphalerite, Zn-bearing calcite and pyrite have features typical of bacterial colonies. Combined with geological and mineralogical evidence, a significant role of bacteria during ore deposition at Bleiberg is likely.Eugen F. Stumpfl deceasedEditorial handling: B. Lehmann 相似文献
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Erich Neuwirth 《Mineralogy and Petrology》1956,5(4):347-361
Inhalt Einleitung — Beschreibung der Untersuchungsmethoden — Ihre Anwendung bei der Bestimmung der wichtigsten Tonminerale.Mit 15 Textabbildungen 相似文献