ALBERT

Beschreibung / Inhaltsverzeichnis: A lake, as a body of water, is in continuous interaction with the rocks and soils in its drainage basin, the atmosphere, and surface and groundwaters. Human industrial and agricultural activities introduce new inputs and processes into lake systems. This volume is a selection of ten contributions dealing with diverse aspects of lake systems, including such subjects as the geological controls of lake basins and their histories, mixing and circulation patterns in lakes, gaseous exchange between the water and atmosphere, and human input to lakes through atmospheric precipitation and surficial runoff. This work was written with a dual goal in mind: to serve as a textbook and to provide professionals with in-depth expositions and discussions of the more important aspects of lake systems.

Beschreibung / Inhaltsverzeichnis: In diesem Buch wird einerseits die spannende Entdeckung der Stratosphäre selbst und verschiedener unerwarteter Phänomene in der Stratosphäre beschrieben: ein bemannter Ballonflug im Jahr 1901 bis in 11 km Höhe; eine Expedition zum Victoriasee im Jahr 1908; die Entdeckung der Ozonschicht um 1930, des "Berliner Phänomens" im Jahr 1952, des Einflusses von Vulkaneruptionen im Jahr 1982, des Ozonlochs im Jahr 1985 und des Einflusses der Sonnenaktivität im Jahr 1987. Andererseits wird gezeigt, wie diese Erscheinungen miteinander verknüpft sind und wie sie anthropogene und natürliche Schwankungen in unserem Klimasystem verursachen. Am Beispiel der Stratosphäre soll das Buch zum Verständnis komplizierter Zusammenhänge in der Natur beitragen.

Beschreibung / Inhaltsverzeichnis: The Arctic is considered to be one of the most sensitive environmental elements on Earth, which may respond rapidly to climate change. However, our knowledge of the present and past processes of the Arctic system is still relatively sparse. Based on a multidisciplinary approach, German and Russian scientists describe in this book the natural processes behind short- and long-term changes in the Laptev Sea and its hinterland (Arctic Siberia), using modern climate data and paleorecords which were collected over the past 6 years. These marine and terrestrial datasets provide important new insights into the causes, impacts, and feedback mechanisms of this extreme environment.

Beschreibung / Inhaltsverzeichnis: PREFACE The four-year period of activity of the Groupement de Recherche 942 (GDR) of the Centre National de la Recherche Scientifique (CNRS) came to an end in December 1993. This GDR was a scientific association grouping research teams from the academic sphere -- i.e. the Unités de Recherches Associées 723 & 724 of the CNRS as well as the Universities of Orléans and Paris-Sud -- and from the industrial world: Elf-Aquitaine Production, TOTAL and the Institut Français du Pétrole (IFP). The aim of the GDR was to understand the processes and the causes of organic carbon fossilization in sediments, especially when they can be modified by environmental conditions such as climate, eustatism, productivity etc., factors which can alko interact. This goal implies the simultaneous study of ancient geological formations (hydrocarbon source rocks from the famous Kimmeridge Clay Formation) and recent Quaternary sediments (the Lac du Bouchet or lake Bouchet maar, Massif Central, France). In the latter case, we benefit from a fine-scale stratigraphical framework as well as a reliable reconstruction of the local and regional environment. This volume is a collection of papers representing oral presentations given on December 7, 1993, at the Société Géologique de France in Paris, during the final meeting of the GDR. These articles thus report the latest developments of the studies carried out under the GDR. However, this is not the first publication of our results, which can be found in the papers referred to in each article. The Kimmeridge Clay Formation was previously studied in 1987, by the Yorkim Group from IFP, Elf-Aquitaine and the British Geological Survey, on the basis of a series of wells drilled across the Cleveland Basin of Yorkshire. In each well, the distribution with depth of the total organic content is cyclic. We have compared some of the organic cycles from two wells (Matron and Ebberston) based on mineralogy, organic and inorganic geochemistry and petrography, at a high resolution scale (centimetric). The main conclusion of this work is that the driving force for organic matter accumulation in the studied cycles was organic phytoplankton productivity. Oxygenation conditions seem to have played a secondary role as a positive feedback action enhancing organic matter storage. Lac du Bouchet is located on the Devès volcanic plateau, 15 km SW of Le Puy en Velay, at an altitude of 1205 m. The depth of the water column is 28 m. The lake has a subcircular shape (1 km in diameter) and a very restricted watershed. This site is exceptionally suitable for research on climate variations and palaeomagnetic field modifications (Euromaars EC Program). The GDR focused on sedimentary organic matter and its relationship to inorganic phases. An important result is that organic matter appears to be a good indicator of palaeoenvironmental reconstructions for over 350 000 years. In addition, the study of early diagenetic reactions in surficial sediments (porewater and solid phase) allows the specification of the processes of organic matter degradation and storage in such an oligothrophic lake.

Beschreibung / Inhaltsverzeichnis: PREFACE In recent years, there has been increasing interest from geoscientists in potassic igneous rocks. Academic geoscientists have been interested in their petrogenesis and their potential value in defining the tectonic setting of the terranes into which they were intruded, and exploration geoscientists have become increasingly interested in the association of these rocks with major epithermal gold and porphyry gold-copper deposits. Despite this current interest, there is no comprehensive textbook that deals with these aspects of potassic igneous rocks. This book redresses this situation by elucidating the characteristic features of potassic (high-K) igneous rocks, erecting a hierarchical scheme that allows interpretation of their tectonic setting using whole-rock geochemistry, and investigating their associations with a variety of gold and copper-gold deposits, worldwide. About twothirds of the book is based on a PhD thesis by Dr Daniel MOiler which was produced at the Key Centre for Strategic Mineral Deposits within the Department of Geology and Geophysics at The University of Western Australia under the supervision of Professor David Groves, the late Dr Nick Rock, Professor Eugen Stumpfl, Dr Wayne Taylor, and Dr Brendon Griffin. The remainder of the book was compiled from the literature using the collective experience of the two authors. The book is dedicated to the memory of Dr Rock who initiated the research project but died before its completion...

Beschreibung / Inhaltsverzeichnis: PREFACE The sedimentology of Chalk describes processes that caused the rhythmic vertical variation in grain size, structures and authigenic mineral concentrations in Late Cretaceous and Early Tertiary, subtropical, shallow marine, fine-grained, detrital bioclastic carbonates of northwest Europe. In particular, attention is paid to the sedimentology of the Tuffaceous Chalk of Maaslricht (The Netherlands), a coarsegrained variety of Chalk that resembles the Chalk (coccolithic mudstones) as well as modern shallow marine carbonate sands. Numerical models are presented that enable the simulation of the genesis of flint nodule layers, hardgrounds and complex wavy bedded sequences, such as the K/T boundary sequence of Stevns Klint (Denmark). The aim of this book is to show how depositional and early diagenetic features, which are observed in small-scale Chalk outcrops, can be used to reconstruct the large-scale dynamics of the northwest European continent during the Late Cretaceous and Early Tertiary...

Beschreibung / Inhaltsverzeichnis: PREFACE Seismic imaging is the process through which seismograms recorded on the Earth's surface are mapped into representations of its interior properties. Imaging methods are nowadays applied to a broad range of seismic observations: from nearsurface environmental studies, to oil and gas exploration, even to long-period earthquake seismology. The characteristic length scales of the features imaged by these techniques range over many orders of magnitude. Yet there is a common body of physical theory and mathematical techniques which underlies all these methods. The focus of this book is the imaging of reflection seismic data from controlled sources. At the frequencies typical of such experiments, the Earth is, to a first approximation, a vertically stratified medium. These stratifications have resulted from the slow, constant deposition of sediments, sands, ash, and so on. Due to compaction, erosion, change of sea level, and many other factors, the geologic, and hence elastic, character of these layers varies with depth and age. One has only to look at an exposed sedimentary cross section to be impressed by the fact that these changes can occur over such short distances that the properties themselves are effectively discontinuous relative to the seismic wavelength. These layers can vary in thickness from less than a meter to many hundreds of meters. As a result, when the Earth's surface is excited with some source of seismic energy and the response recorded on seismometers, we will see a complicated zoo of elastic wave types: reflections from the discontinuities in material properties, multiple reflections within the layers, guided waves, interface waves which propagate along the boundary between two different layers, surface waves which are exponentially attenuated with depth, waves which are refracted by continuous changes in material properties, and others. The character of these seismic waves allows seismologists to make inferences about the nature of the subsurface geology. Because of tectonic and other dynamic forces at work in the Earth, this first-order view of the subsurface geology as a layer cake must often be modified to take into account bent and fractured strata. Extreme deformations can occur in processes such as mountain building. Under the influence of great heat and stress, some rocks exhibit a taffy-like consistency and can be bent into exotic shapes without breaking, while others become severely fractured. In marine environments, less dense salt can be overlain by more dense sediments; as the salt rises under its own buoyancy, it pushes the overburden out of the way, severely deforming originally flat layers. Further, even on the relatively localized scale of exploration seismology, there may be significant lateral variations in material properties. For example, if we look at the sediments carried downstream by a river, it isclear that lighter particles will be carried further, while bigger ones will be deposited first; flows near the center of the channel will be faster than the flow on the verge. This gives rise to significant variation is the density and porosity of a given sedimentary formation as a function of just how the sediments were deposited. Taking all these effects into account, seismic waves propagating in the Earth will be refracted, reflected and diffracted. In order to be able to image the Earth, to see through the complicated distorting lens that its heterogeneous subsurface presents to us, in other words, to be able to solve the inverse scattering problem, we need to be able to undo all of these wave propagation effects. In a nutshell, that is the goal of imaging: to transform a suite of seismograms recorded at the surface of the Earth into a depth section, i.e., a spatial image of some property of the Earth (usually wave speed or impedance). There are two main types of spatial variations of the Earth's properties. There are the smooth changes (smooth meaning possessing spatial wavelengths which are long compared to seismic wavelengths) associated with processes such as compaction. These gradual variations cause ray paths to be gently turned or refracted. On the other hand, there are the sharp changes (short spatial wavelength), mostly in the vertical direction, which we associate with changes in lithology and, to a lesser extent, fracturing. These short wavelength features give rise to the reflections and diffractions we see on seismic sections. If the Earth were only smoothly varying, with no discontinuities, then we would not see any events at all in exploration seismology because the distances between the sources and receivers are not often large enough for rays to turn upward and be recorded. This means that to first order, reflection seismology is sensitive primarily to the short spatial wavelength features in the velocity model. We usually assume that we know the smoothly varying part of the velocity model (somehow) and use an imaging algorithm to find the discontinuities. The earliest forms of imaging involved moving, literally migrating, events around seismic time sections by manual or mechanical means. Later, these manual migration methods were replaced by computer-oriented methods which took into account, to varying degrees, the physics of wave propagation and scattering. It is now apparent that all accurate imaging methods can be viewed essentially as linearized inversions of the wave equation, whether in terms of Fourier integral operators or direct gradient-based optimization of a waveform misfit function. The implicit caveat hanging on the word "essentially" in the last sentence is this: people in the exploration community who practice migration are usually not able to obtain or preserve the true amplitudes of the data. As a result, attempts to interpret subtle changes in reflector strength, as opposed to reflector position, usually run afoul of one or more approximations made in the sequence of processing steps that makes up a migration (trace equalization, gaining, deconvolution, etc.) On the other hand, if we had true amplitude data, that is, if the samples recorded on the seismogram really were proportional to the velocity of the piece of Earth to which the geophone were attached, then we could make quantitative statements about how spatial variations in reflector strength are related to changes in geological properties. The distinction here is the distinction between imaging reflectors, on the one hand, and doing a true inverse problem for the subsurface properties on the other. Until quite recently the exploration community was exclusively concerned with the former, and today the word "migration" almost always refers to the imaging problem. The more sophisticated view of imaging as an inverse problem is gradually making its way into the production software of oil and gas exploration companies, since careful treatment of amplitudes is often crucial in making decisions on subtle lithologic plays (amplitude versus offset or AVO) and in resolving the chaotic wave propagation effects of complex structures. When studying migration methods, the student is faced with a bewildering assortment of algorithms, based upon diverse physical approximations. What sort of velocity model can be used: constant wave speed v? v(x), v(x, z), v(x, y, z)? Gentle dips? Steep dips? Shall we attempt to use turning or refracted rays? Take into account mode converted arrivals? 2D (two dimensions)? 3D? Prestack? Poststack? If poststack, how does one effect one-way wave propagation, given that stacking attenuates multiple reflections? What domain shall we use? Time-space? Time-wave number? Frequency-space? Frequency-wave number? Do we want to image the entire dataset or just some part of it? Are we just trying to refine a crude velocity model or are we attempting to resolve an important feature with high resolution? It is possible to imagine imaging algorithms that would work under the most demanding of these assumptions, but they would be highly inefficient when one of the simpler physical models pertains. And since all of these situations arise at one time or another, it is necessary to look at a variety of migration algorithms in daily use. Given the hundreds of papers that have been published in the past 15 years, to do a reasonably comprehensive job of presenting all the different imaging algorithms would require a book many times the length of this one. This was not my goal in any case. I have tried to emphasize the fundamental physical and mathematical ideas of imaging rather than the details of particular applications. I hope that rather than appearing as a disparate bag of tricks, seismic imaging will be seen as a coherent body of knowledge, much as optics is...

Beschreibung / Inhaltsverzeichnis: This book presents the proceedings of the Sixth International Conference on Computer Analysis of Images and Patterns, CAIP '95, held in Prague, Czech Republic in September 1995. The volume presents 61 full papers and 75 posters selected from a total of 262 submissions and thus gives a comprehensive view on the state-of-the-art in computer analysis of images and patterns, research, design, and advanced applications. The papers are organized in sections on invariants, segmentation and grouping, optical flow, model recovery and parameter estimation, low level vision, motion detection, structure and matching, active vision and shading, human face recognition, calibration, contour, and sessions on applications in diverse areas.

Beschreibung / Inhaltsverzeichnis: PREFACE In the geologic record, vertical crustal uplift has often resulted in erosional removal of huge thicknesses of sedimentary strata. If the uplift is of a broad regional nature or the uplifted strata remain relatively undeformed and sediments deposited after the uplift are not preserved, the magnitude of uplift and subsequent erosion may be difficult to quantify. This may lead to misinterpretation or omission of chapters of geologic history of a region. Fortunately, a number of indirect methods can be used to infer the thicknesses of missing strata and reconstruct the geologic history. Our book titled "Thick Post-Devonian Sediment Cover Over New York State: Evidence from Fluid-Inclusion, Organic Maturation, Clay Diagenesis and Stable Isotope Studies" uses four techniques of paleotemperature measurements in sedimentary rocks in order to determine burial depths of the existing Paleozoic strata in New York State. Since every technique has its own analytical and interpretative uncertainties, the use of four techniques allowed us to place a better constraint on our results. We show how regionally extensive paleotemperature data can be used to estimate the thicknesses of strata lost from an uplifted sedimentary basin. We also provide a tentative tectonic-, paleogeographic- and depositional history of New York State after the Devonian when the missing strata were deposited...