The significance of scarp retreat for cenozoic landform evolution on the Colorado Plateau,U.S.A.     

Karl-Heinz Schmidt 《地球表面变化过程与地形》1989,14(2):93-105

Since the beginning of the Cenozoic period several hundreds of metres of the sedimentary cover have been removed from the Colorado Plateau. Palaeoclimatic considerations show that the Colorado Plateau has been dominated by dry climates throughout the Cenozoic with the possible exception of the early Palaeocene. Today in the still prevailing arid climate, which strongly accentuates differences in rock resistance, the relief shows a structurally controlled cuesta scarp topography in the slightly deformed strata of alternating resistance. In examining whether the denudational efficiency of scarp retreat was sufficient to account for the wide erosional gaps in the sedimentary cover, rates of scarp retreat were determined by using the information of dated volcanic material and by applying a new method, which calculates the amount of retreat from the width of beheaded valleys of known age. Rates of retreat range from 0·5 to 6·7 km my^?1. The results show that the rates of retreat are controlled by the thickness and resistance of the caprocks. A model of Cenozoic scarp retreat demonstrates that the rates of recession calculated for the scarps in Upper Cretaceous rocks were sufficient to bring them into their present positions from the centre of the Monument Uplift on the central Colorado Plateau. The late Eocene positions of the cliffs in the Early Tertiary formations give an indication of their maximal extent. After the Upper Cretaceous sediments had been removed from the uplifts, erosion cut through successively older rocks, and activated scarps in stratigraphically lower positions. Scarp retreat can operate simultaneously and independently at different levels, which enabled this erosional mechanism to remove great proportions of the sedimentary cover of the Colorado Plateau during the Cenozoic.  相似文献   

Regional variation of mechanical and chemical denudation,upper Colorado River Basin,U.S.A.     

Karl-Heinz Schmidt 《地球表面变化过程与地形》1985,10(5):497-508

The variation of mechanical and chemical denudation is investigated using discharge and sediment yield data from the Upper Colorado River System. Annual precipitation ranges from approximately 150 mm to 1500 mm. Mean specific yield ranges from 0-2 1/s km² ( = 6 mm p a) to 151/s km² ( = 475 mm p a). The hydrological-geomorphological system adjusts itself to these varying climatic conditions; in some areas, however, the effects of lithology or land use seem to override the climatic controls. It is demonstrated that the increase in the absolute and particularly the relative amount of suspended sediment is closely related to a decrease in annual runoff and to an increase in the importance of high magnitude/low frequency events. This indicates that in areas of low annual runoff and high runoff variability, soluble rocks are more resistant than in more humid areas. During high magnitude/low frequency events, suspended sediment concentrations and loads are very high in semiarid areas due to sparse vegetation cover and dominance of direct runoff. Events of moderate magnitude and frequency, which in more humid areas transport most of the dissolved load, seldom occur. The trend towards increasing mechanical denudation is even observed in areas of very low runoff (0-221/s km² = 7 mm p a). The peak of sediment yield in dry areas seems to approximate the point of no runoff very closely. Mechanical and chemical denudation are of equal importance at a runoff of about 300 mm per year.  相似文献   

Spectral reflectance measurements of estuarine waters     

Karl-Heinz Szekielda  Christopher Gobler  Barry Gross  Fred Moshary  Samir Ahmed 《Ocean Dynamics》2003,53(2):98-102

Shapes and variations of reflectance spectra in estuarine water were investigated for the purpose of monitoring chlorophyll in situ by optical means. A survey undertaken in an estuarine environment, using reflectance measurements between 400 and 850 nm with a full-width half maximum (FWHM) of about 2 nm, revealed that the first derivative in the neighbourhood of the chlorophyll absorption band shows a defined spectral region which can be used to estimate chlorophyll concentrations. Correlation between chlorophyll and the first derivative was found to be low, but a good relationship exists between the ratio of the reflectance R680/R670 and chlorophyll concentrations. Based on dissolved organic carbon measurements, it is assumed that chromophoric dissolved organic compounds mask the absorption band of chlorophyll in the blue part of the spectrum, resulting in a low correlation coefficient in that spectral range. Therefore, the use of the red bands is an alternative for measuring photosynthetic pigments in coastal water at longer wavelengths. Results presented here demonstrate that the spectral locations of bands in the visible are not adequate and that hyperspectral data are required for positioning the very narrow bands for measuring chlorophyll at longer wavelengths.  相似文献   

S.R. Majewski (ed.): Galaxy Evolution: The Milky Way Perspective. Astronomical Society of the Pacific 1993, ASP Conference Series Vol. 49, 256 S., Preis: 55.-US-Dollar. ISBN 0-937707-68-6     

Karl-Heinz Schmidt 《Astronomische Nachrichten》1995,316(1):66-67

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Interpretation of carbon dioxide diffusion behavior in coals   总被引：3，自引：1，他引：3  

Nikolai Siemons  Karl-Heinz A.A. Wolf  Johannes Bruining 《International Journal of Coal Geology》2007,72(3-4):315-324

Storage of carbon dioxide in geological formations is for many countries one of the options to reduce greenhouse gas emissions and thus to satisfy the Kyoto agreements. The CO₂ storage in unminable coal seams has the advantage that it stores CO₂ emissions from industrial processes and can be used to enhance coalbed methane recovery (CO₂-ECBM). For this purpose, the storage capacity of coal is an important reservoir parameter. While the amount of CO₂ sorption data on various natural coals has increased in recent years, only few measurements have been performed to estimate the rate of CO₂ sorption under reservoir conditions. An understanding of gas transport is crucial for processes associated with CO₂ injection, storage and enhanced coalbed methane (ECBM) production.A volumetric experimental set-up has been used to determine the rate of sorption of carbon dioxide in coal particles at various pressures and various grain size fractions. The pressure history during each pressure step was measured. The measurements are interpreted in terms of temperature relaxation and transport/sorption processes within the coal particles. The characteristic times of sorption increase with increasing pressure. No clear dependence of the characteristic time with respect to the particle size was found. At low pressures (below 1 MPa) fast gas diffusion is the prevailing mechanism for sorption, whereas at higher pressures, the slow diffusion process controls the gas uptake by the coal.  相似文献   

Observations of suspended material from spacecraft altitudes     

Prof. Dr. Karl-Heinz Szekielda 《Ocean Dynamics》1974,27(4):159-170

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Alluvial Styles and Arehitecture as Guides to Cenozoic Tectonic and Environmental Events at the Northern Margins of the Qin ghai-Xizang Plateau     

Karl-Heinz Wyrwoll  et al 《地学前缘》2000,(Z1)

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The observational study of Herbig-Haro shock waves     

Karl-Heinz Böhm 《Astrophysics and Space Science》1995,233(1-2):11-25

We review the basic shock properties and the origin and the geometry of Herbig-Haro (H-H) shock waves. We first discuss different aspects of “normal” H-H objects which are connected with working surfaces (including internal working surfaces) of jets from young stellar objects. The emphasis is on unsolved problems of the H-H shock waves and not on the problems of the jet. We study the line flux ratios of high excitation H-H objects (high velocity shocks) and low excitation HH objects (low velocity shocks) and carry out a comparison with theoretical predictions in both cases. We emphasize an unexplained deficit of higher ions (especially OIII and SIII, but also various other ions) in high excitation objects. This lets the line flux ratios of HH objects appear as if their shock velocities are almost never above 100 km s^?1, while other shock diagnostics (position-velocity diagrams, integrated line profiles, distributions of fluxes along the axis of the bow shock, etc.) definitely indicate higher shock velocities. Some aspects of the spectrum interpretation of the very low velocity shocks (like HH7) are explained quite well by the theory. A basic unsolved problem is, however, the explanation of the CI lines whose flux is up to a factor 10 times stronger than predicted for any model. Obviously we are very far from correctly predicting the ionization of C in shock models. In the last chapter we discuss, as one example of a very unusual HH-object, HH255 (Burnham's nebula). Detailed line fluxes in the immediate environment of T Tauri (the source of HH255) have shown that HH255 has a shock wave spectrum and is definitely an HH object. In the very narrow region between 3″ and 4″ S of T Tauri we find a sharp peak of the velocity dispersion, the centroid velocity, and N_e. In the same region there is an almost discontinous increase in ionization. Between 4″ and 10″ S (corresponding to 600-1600 a.u.) of T Tauri (the source of HH255) the ionization remains high but the centroid velocity is zero (with respect to T Tauri) and the velocity dispersion is very small. This result is completely surprising for a shock wave which according to the flux ratios must have ～90 km s^?1-1 shock velocity. Why should a cooling region of a shock have a centroid velocity of ～0 km s^?1 over a large range of distance from the stellar source? At present the geometry of the HH255 is enigmatic.  相似文献   

The transient response mechanism and Pi2 pulsations at substorm onset—Review and outlook     

Wolfgang Baumjohann  Karl-Heinz Glaßmeier 《Planetary and Space Science》1984,32(11):1361-1370

Pi2 pulsations are nowadays thought to be transient hydromagnetic signals associated with the build-up of a new stationary magnetosphere-ionosphere coupling system after the sudden formation of the substorm current wedge. To illustrate this transient response mechanism, we will first briefly describe the substorm current circuit. Subsequently, we will demonstrate that the gross characteristics of high-latitude Pi2 can be explained by the sudden switch-on of this current wedge during substorm onset if its westward expansion is taken into account. We will conclude by discussing some additional phenomena and processes (like conductivity and electron density gradients, kinetic Alfvén waves, ionospheric polarization electric fields, and mode coupling) which have to be included into a realistic model for Pi2 pulsations and thus timedependent magnetosphere-ionosphere coupling.  相似文献   

Estimation of spatially distributed soil information: dealing with data shortages in the Western Bug Basin,Ukraine     

Filipa Tavares Wahren  Maria Tarasiuk  Andriy Mykhnovych  Myron Kit  Karl-Heinz Feger  Kai Schwärzel 《Environmental Earth Sciences》2012,65(5):1501-1510

Integrated watershed models require spatially differentiated soil information. However, in many regions of the world the limited availability of soil data hinders an appropriate simulation of hydro-ecological processes. Such circumstances lead to unsupported statements, poor statistics, misrepresentations, and, ultimately, to bad resource management. The Western Bug catchment in west Ukraine is an example of such a region. In the former Soviet Union, soil classification primarily focused on soils of agricultural importance, whereas, forested, urban, industrial, and shallow soil territories were left underrepresented in the classification and soil maps. Spatially differentiated soil texture data are required to predict soil hydraulic properties using pedotransfer functions (PTFs), along with soil maps. Furthermore, the Ukrainian soil texture scheme does not match the particle size classes commonly used with PTFs. To overcome these shortcomings, a fuzzy logic methodology was applied, based on terrain and vegetation/land use analysis and soil sampling, to close the information gaps. For the application of PTFs, a procedure was tested to estimate missing values of soil texture distribution. Applied methods were evaluated using recent soil surveys, measured soil texture, and water retention properties, while having in consideration the limitations brought by scarce soil data for integrated watershed modelling purposes.  相似文献