Subaerial terminoglacial fans I: a semi-quantitative sedimentological analysis of the proximal environment

Fans formed under subaerial terminoglacial (previously called ice-contact) conditions have several characteristics that differ from those formed under other conditions. Twenty-five such fans in NE Poland were investigated to model the dominant genetic processes involved. These fans show, as do other types, a proximal, a middle and a distal environment. The present study deals with the proximal environment. The fans date from the last, i.e. Weichselian or Vistulian, glacial. The proximal terminoglacial fan comprises abundant gravelly sediments, resembling the glacial deposits from which they were derived. Three facies, each subdivided into two subfacies, can be distinguished; these are dominated by mass flows, unchannelised flows, and stream (= channelised) flows, respectively. The characteristics of the facies are described and illustrated. It is concluded that the irregular supply of water by the nearby ice masses dominates the sedimentary processes.     

Multi-sensor data fusion for the detection of underground coal fires

The spontaneous combustion of coal causes widespread underground coal fires in several countries, amongst which is China. These coal fires cause serious environmental, economic and safety problems. In northern China, the coal fires occur within a wide region stretching 5000 km east-west and 750 km north-south. Remote sensing therefore provides an ideal tool for monitoring this environmental hazard over such a large and remote area. As part of a research project to detect, measure, monitor and extinguish these coal fires, this paper describes a remote-sensing-based multi-sensor data-fusion methodology for detecting the underground fires. The methodology is based on fusing a variety of satellite-based image types (optical, thermal, microwave) together with airborne data (optical and thermal infrared) and ancillary data sources such as geological and topographic maps. The results of the remote-sensing data fusion are presented, using pixel-based, feature-based and decision-based fusion approaches.     

Discussion: Oil seepage or fossil podzol? An Early Oligocene oil seepage at the southern rim of the North Sea Basin,near Leuven (Belgium) by E.D. van Riessen & N. Vandenberghe,Geologie en Mijnbouw 74: 301-312 (1996)

Geologie en Mijnbouw -     

Imaging spectrometry for geological remote sensing

Without use of imaging spectrometry, imaging of the Earth's surface from aircraft and from spacecraft is hampered by the low spectral resolution and limited number of spectral bands, typically less than 10 bands of 100 to 200 nm width. Imaging spectrometry in remote sensing concerns the acquisition of image data in many narrow (< 40 nm wide) contiguous spectral bands with the ultimate goal of producing detailed spectral reflectance curves for each pixel in the image. Many minerals and rocks have unique spectral signatures with characteristic absorption features that are 20 to 40 nm wide. Imaging spectrometers allow to depict these narrow features and thus map surface mineralogy based on spectral image characterization. This paper gives a review of imaging spectrometry and addresses the following topics: airborne and spaceborne systems available, spectral and geometric data pre-processing, atmospheric correction, techniques for thematic data analysis, and applications in the field of geological remote sensing. In the final section a case study is described where imaging spectrometer data is used for mapping surface mineralogy in a hydrothermal alteration system, thus guiding gold exploration.     

Analysis of oil lens removal by extraction through a seepage face

Removal of LNAPL (oil) from an aquifer is described using a multiphase flow model. At the well boundary seepage face conditions are imposed. These conditions are implemented in a numerical model and withdrawal in a twodimensional domain is simulated for two different geometries of the oil lens and for varied values of the physical parameters. Assuming vertical equilibrium, the oil flow equation is reduced by vertical integration. The well boundary condition is approximated by imposing zero oil lens thickness. Similarity solutions of the reduced equations for the two geometries show good agreement with the numerical results in most cases.     

The role of modelling in geochemical engineering—a (re)view

Modelling is an indispensable tool in geochemical engineering in predicting the outcome of our intended interferences in geochemical systems. Because such systems are highly complex, investigation by means of designed experiment can only apply to subsystems and processes. Models too can only capture a partial, simplified image of the true system. Conceptual models play a vital role. Advantages of the use of models are, a.o., better testing of our understanding of geochemical processes, better formulation of this understanding, and better prediction of the outcome of our conjectures. Examples from hydrogeochemistry are discussed to demonstrate this.     

Transformation of phosphorus in the Elbe estuary

The distribution of dissolved and particle-bound phosphorus (P) was investigated in the Elbe estuary during March 1995. The forms of particulate P were studied with a sequential extraction technique. Organic P dominated particle-bound P in the outer reaches of the estuary (52%), decreased to a minimum of 21% in the turbidity zone, and increased to 33% further upstream. Fe-bound P was the second most important P species in the outer reaches (27%) and dominated in the turbidity zone (up to 57%) and upstream of the turbidity zone (up to 48%). The P:Fe ratio increased with decreasing salinity, from 0.11 in the outer reaches to about 0.22 at zero salinity. Dissolved inorganic P release from reverine suspended matter was about two to three times larger than release, from marine suspended matter and was dominated by release of Fe-bound P. Dissolved inorganic P release from marine and from riverine organic matter were of equal importance. Because marine suspended matter dominates in the estuary, this suggests riverine organic matter is remineralized much faster than marine organic matter. This is in line with the refractory nature of marine organic matter (no phytoplankton bloom) and the easily degradable character of the riverine suspended matter (phytoplankton bloom) in the Elbe estuary during March 1995.     

Stellar evolution models for Z = 0.0001 to 0.03

We have calculated a grid of empirically well tested evolutionary tracks with masses M between 0.5 and 50 M⊙, spaced by approximately 0.1 in log M , and with metallicities Z  = 0.0001, 0.0003, 0.001, 0.004, 0.01, 0.02 and 0.03. We use a robust and fast evolution code with a self-adaptive non-Lagrangian mesh, which employs the mixing-length theory but treats convective mixing as a diffusion process, solving simultaneously for the structure and the chemical composition. The hydrogen and helium abundances are chosen as functions of the metallicity: X  = 0.76 − 3.0 Z Y  = 0.24 + 2.0 Z .   Two sets of models were computed, one without and one with a certain amount of enhanced mixing or 'overshooting'. This amount has been empirically chosen by means of various sensitive tests for overshooting: (1) the luminosity of core helium burning (blue loop) giants of well-known mass, (2) the width of the main sequence as defined by double-lined eclipsing binaries with well-measured masses and radii, and (3) the shape and implied stellar distribution of isochrones of various open clusters. The first two tests have been the subject of previous papers, the third test is discussed in this paper. On the basis of these tests, we recommend the use of the overshooting models for masses above about 1.5M ⊙.   We describe here the characteristics of the models, the procedure for constructing isochrones for arbitrary age and metallicity from the models, and the performance of these isochrones for several intermediate-age and old open clusters. All original models are available in electronic form and we describe the means by which they may be obtained.     

Role of Helicity in the Formation of Intermediate Filaments

In the last few years new observations have shown that solar filaments and filament channels have a surprising hemispheric pattern. To explain this pattern, a new theory for filament channel and filament formation is put forward. The theory describes the formation of a specific type of filament, namely the intermediate filament which forms either between active regions or at the boundary of an active region. It describes the formation in terms of the emergence of a sheared activity complex. The complex then interacts with remnant flux and, after convergence and flux cancellation, the filament forms in the channel. A key feature of the model is the net magnetic helicity of the complex. With the correct sign a filament channel can form, but with the opposite sign no filament channel forms after convergence. It is shown how the hemispheric pattern of helicity in emerging flux regions produces the observed hemispheric pattern for filaments.