ALBERT

Description / Table of Contents: The early Paleogene of northwest Europe has been the subject of intense investigation over the last 25 years, with important stimuli being provided by the search for oil and gas in the offshore basins and by lUGS-sponsored investigations of the onshore historical stage and stratotype sections. The book includes three categories of papers on the Paleocene and Eocene of NW Europe: detailed aspects of local stratigraphy in the North Sea, Denmark, Belgium, SE England and offshore NW Scotland; regional syntheses of the biostratigraphy and sequence stratigraphy in NW Europe; and papers placing the successions of NW Europe in a global context, primarily through correlation with oceanic sections of the eastern Atlantic. Topics covered include: biostratigraphy (foraminifera, calcareous nannofossils, dinoflagellate cysts, diatoms, mammals), isotope stratigraphy, tephrostratigraphy, igneous history, tectonic evolution, and sequence stratigraphy. The reader will have access to substantial amounts of new stratigraphic data and to compilations of existing data that are based on greatly improved regional and global stratigraphic frameworks.

Description / Table of Contents: The metronomic variations of the Earth-Moon system and of the Earth-Sun orbital patterns produce gravitational and temperature effects that alter the physical environment on the Earth’s surface. These give an interpenetrating effect of forcing cycles ranging from twice-daily tides, day-night alternations, various tidal patterns and the annual solar pattern. All of these have been used palaeontologically to give precision to short-term age determination in the past. It is cycles of the Milankovitch band that are showing promise of enabling new practical timescales to be established for parts of the geological record. These depend on changes in the Earth-Sun distance and changes in the tilt of the Earth’s axis with respect to the Earth’s orbit round the Sun. There is increasing evidence that small-scale sedimentary rhythmic couplets may represent the effect of such changes. The disentangling of the interpenetrating cycles to produce an orbital forcing timescale is an exciting problem and challenge for palaeobiology and sedimentology. These should enable numerical dates to be given to bio- and chronostratigraphical timescales and eventually enable many Earth processes to be analysed in real time. The papers in this volume represent major new developments in sedimentological, paIaeontological, geochemical and stratigraphical research being undertaken in this field.

Description / Table of Contents: The Weddell Sea, part of the circumpolar Southern Ocean, is probably the most remote, least known and least accessible sea in the world. Difficult ice conditions have limited the acquisition of ship data, although this has been partly offset in recent years by access to satellite radar altimetry data. The Weddell Sea was originally defined by the Admiralty Hydrographic Department in 1932 and redefined by the Antarctic Place Names Committee in 1976 (Hattersley-Smith 1991). It is bounded on the western side by the east coast of the Antarctic Peninsula, on the southern side by the Ronne and Filchner ice fronts, and on the southeastern side by the Dronning Maud Land and Coats Land coasts of East Antarctica (Fig. 1). The South Scotia Ridge separates the Weddell Sea from the Scotia Sea to the north and a line joining Southern Thule in the South Sandwich Islands and Kapp Norvegia in Dronning Maud Land, separates it from the South Atlantic Ocean to the NE. Within this volume, papers relate to the Weddell Sea as defined above, together with part of the adjoining South Atlantic Ocean up to 50°E, and to the geology of the once neighbouring continents of Gondwana. The term Weddell Sea embayment is also used informally throughout this volume to include the embayment area to the south of the Weddell Sea now covered by the Ronne and Filchner ice shelves, including Berkner Island, and the continental shelf north of the Ronne and Filchner ice fronts (Figs 1 & 2).

Description / Table of Contents: Geoscientists need to familiarize themselves with the characteristics of actual plate motions. A popular, current thesis relates the state of stress to the degree of coupling of the two convergent plates. Recent two-dimentional, finite element modelling has demonstrated how the stress in the overriding plate is critically dependent on wether the subduction zone is locked (i.e. high degree of coupling) or unlocked. Thus the compressional stress regime occurs in locked systems, and extensional strees in unlocked systems; a gradient from compression in the fore-arc to extension in the back-arc is said to characterize partially locked system. However, studies of the strain field in real cases (modern arc regions) clearly indicate the prevalence of subhorizontal extension orientated nearly perpendicular to the arc. Implicit in these real observations is the suggestion that stresses resulting from plate coupling are either not transmitted to the volcanic arc, or else locked subduction zones are uncommon and extension may be the normal mode of behaviour. The rationale and evidence for extension and coeval volcanism at consuming plate margins is presented. Using mainly Cenozoic case histories for oceanic and continental margin arcs, structural evidence is presented, which demonstrates that volcanism in most arc systems is contemporaneous with normal faulting and subsidence as a general case. Representive, modern geochemical data sets are provided and integrated in a petrological discussion for each case history. The western Pacific, now widely regard as a type region for the study of convergent plate margin processes, is particularly well represented. Also included is evidence from less commonly insvestigated regions, where subduction has ceased or is no longer obvious but an association with an arc is unequivocal. By these means, it is hoped that this volume contains a representative cross-section of current research on extension-related arc volcanism in broadest sense, and that it will stimulate further discussion and research into the complex tectonics and petrology of covergent plate margins.

Description / Table of Contents: Geological fluids are a central theme linking the petrography and chemistry of all rock types, deformation processes on the microscopic to the continental scale, and the concentration of economic resources. The fundamental importance of fluid migration and evolution to rock composition and structure is reflected in a growing interest in fluid processes, including a series of successful conferences on water-rock interaction. he papers in this volume are intended to give a review of the whole spectrum of current geofluids research. The papers include international case studies and are written by leading experts in the field. - First overview of fluids research - Examples of commercial applications of fluids research - Reviews research for the non-specialist - Up-to-date extensive bibliographies - Promotes methodological transfer between oil and minerals industries - Explains theory behind and consequences of fluid flow processes

Description / Table of Contents: This book presents a series of review articles on nine important ancient orogens on Earth. Comparison of these mountain belts provides a wealth of information for the debate on whether there has been a change in mountain-building processes through the history of the Earth. As a precursor to these papers, the rheology of the Earth’s lithosphere through time is reviewed. Theoretical analysis and insight into the behaviour of the lithosphere of other planets constrain mechanical considerations of the Earth’s lithosphere. It is clear from these overviews that geodynamic concepts and modelling, and new techniques such as deep seismic profiling and geochronology are having a profound impact on orogenic studies. It is also clear that orogenesis must not be equated with the Wilson cycle, culminating in continent-continent collision. Subduction-related orogens and intraplate orogens are also significant.

Description / Table of Contents: Petrophysics is the study of the physical properties of rocks in the broadest sense. As such it provides the fundamental understanding that enables geologists to describe the physical state of a rock, to predict its behaviour and to interpret geophysical data. Traditionally the emphasis has been on hydrocarbon reservoir evaluation, but it is equally applicable to the evolution of the Earth at all scales. This volume includes developments in pore-scale studies, electrical properties, seismic methods and measurement techniques, as well as reviewing aspects of petrophysical prediction and interpretation.

Description / Table of Contents: SE Asia is probably the finest natural geological laboratory in the world, yet is still not geologically well known. It is a spectacular region in which the manifestations and processes of plate collision can be observed at present and in which their history is recorded. It is a region that must be understood if we are to understand mountain belts, arc development marginal basin evolution and, more generally, the behaviour of the lithosphere in collision settings. Furthermore, the region is developing rapidly on the economic front, and a major part of this rapid development is built on natural resources. The geological reasons for the distribution of these resources are therefore of major importance for the inhabitants of the region and for any attempts to discover and exploit them. The volume will be of interest to all geologists working in SE Asia, particularly those involved in the petroleum industry.

Description / Table of Contents: This volume represents a review of the key topics that are important to the continuing successful exploitation of gas from one of Europe's oldest hydrocarbon provinces. In a mature hydrocarbon province such as the southern North Sea, advanced techniques are needed for stratigraphic correlation and for improving the efficiency of production. Exploration in the SNS now aims for subtle traps and satellite structures. Explorers are re-evaluating the economic value of marginal and existing fields, and they are continually searching for, and applying, new techniques and technologies for enhanced productivity. Detailed techniques in diagenesis play an important role. Re-evaluation also includes examination of old plays, using detailed knowledge of the connectivity, spatial extent and correlation of known prospective strata to make reliable predictions.

Description / Table of Contents: This book provides a synthesis of Archaean and Proterozoic crustal evolution in the North Atlantic Region. There is particular reference to Proterozoic collisional tectonics. The main topics include: Archaean crustal growth; Proterozoic crustal growth; orogenic processes during the Proterozic; geochronology of Proterozoic tectono-thermal processes; and provenance of Proterozoic sediments.

Description / Table of Contents: The Mediterranean Region represents a complex mosaic of continental, microcontinental and ophiolitic terranes, whose overall evolution has been controlled by relative movements between the African and Eurasian plates. Deciphering the sequence of tectonic events in this region can be likened to attempting to reconstruct all the pictures in a stack of jigsaw puzzles when 90% of the pieces are missing (and the remaining 10% are no longer in their original shape!). Palaeomagnetic studies have played an important part in unravelling this 3D puzzle. The palaeomagnetic technique provides quantitative constraints on our reconstruction, since it can tell us which way each of the remaining pieces should be oriented (using magnetic declinations), their relative position with respect to the top of each picture (using magnetic inclinations), and in some cases which piece belongs to which picture (using magnetic dating). Perhaps more importantly, palaeomagnetism can also tell us something about the processes that led to the present confusion in our puzzle box. The 33 papers in this volume span the full width of the Mediterranean basin and present results from Permian to Quaternary rocks. Together they provide a snap-shot of the current state of palaeomagnetic research in the Mediterranean region. In addition to tectonic and magnetostratigraphic applications of palaeomagnetism, several contributions describe archaeomagnetic studies in the Mediterranean realm.

Description / Table of Contents: Paleomagnetism is a relatively young geoscience which incorporates aspects of geomagnetism, rock magnetism and geology. This volume investigates the use of paloenmagnetism in oil exploration and production. It presents various techniques including a newly emerging technique which will be of general interest to the oil industry. The main areas in which paleomagnetic data may be useful to the petroleum geologist are : paleomagnetic dating and magnetostratigraphy; susceptibility logging of cores; magnetic fabric studies for paleocurrent analysis; using remagnetization to date diagenetic events including those associated with hydrocarbon migration; and identification of magnetic anomalies associated with hydrocarbon plumes and oil seeps. Most papers deal with case studies performed on wells from active exploration or production locations worldwide. The book is the first of its kind and presents much previously unpublished data. It will be of particular interest to both academics and professionals in the oil industry.

Description / Table of Contents: Field geology is, by definition, the geology of exhumed rocks. This book provides a broad range of examples of deep exhumation and emphasizes the competition between the various exhumation processes: normal faulting, ductile thinning and erosion. The papers include examples from all parts of the world and from a variety of tectonic settings, including oceanic subduction zones, continental collision zones and continental rifts. The volume explores the relationship between climate, erosion and tectonics. It provides innovative applications of thermochronology to understanding the rates and geometry of normal faulting, and the interaction between erosion and tectonics. The book will be of broad interest to any student of mountain belts and orogenesis, including those in tectonics, structural geology, geodynamics, metamorphic petrology, sedimentology and geomorphology.

Description / Table of Contents: An interdisciplinary collection of papers related to long-term landscape development, integrating landscape and tectonic processes. The presentations demonstrate that studies of present-day processes can be successfully placed within an evolutionary framework and geological setting, the necessity for which increases as appreciation of the antiquity of many landscapes grows. Coverage includes: British Isles, NW Europe, Mediterranean Basin, Middle East, Himalaya, Andes and Antarctica. The papers highlight the significance of recent advances in analytical technology for improving interpretation of both geologically ‘ancient’ and ‘young’ landscapes. It is hoped that, by demonstrating the benefits of interdisciplinary discourse, a widening of interest in landscape studies will be encouraged.

Description / Table of Contents: This volume represents a multi-disciplinary research effort into the development of basins of carboniferous to Tertiary age on the North West Seaboard of the British Isles and includes 30 contributions from oil company personnel, university research groups, consultants and geological surveys. The series of basins which stretches from west of Shetland to the west coast of Ireland constitutes one of the largest basin systems in Europe. Regions covered in this volume include the Hebrides, off-shore N Ireland/SW Scotland, onshore N Ireland, the Porcupine Basin and the Celtic Seas. All of these regions are attracting the attention of hydrocarbon exploration programmes and have already seen drilling activity. This interest is reflected in papers on basin burial and thermal histories, source rock potential, depositional models for reservoir rocks and diagenetic studies. Beyond the British Isles, papers are included on the NE Atlantic Seaway and the Canadian Margin, and several authors make comparisons between the Canadian and European Margins. The models and data reported in the volume will be of value to all concerned with an area which has an important future both in hydrocarbon exploration and in fundamental research into basin evolution.

Description / Table of Contents: Although it has long been recognized that what ultimately drives metamorphism and metamorphic reactions is heat, what was less certain is the distribution of heat within the crust, the type and location of major heat sources and the rates of heat flux through crustal rocks. This book explores the factors that control metamorphism and rates of metamorphic processes.

Description / Table of Contents: From a geological perspective, gas hydrates are an important feature of the shallow geosphere. If current estimates are correct, gas hydrates contain more potential fossil fuel energy than is present in conventional oil, gas and coal deposits, although it is uncertain how much of this can be exploited. They are also geological agents that affect the physical, geophysical and geochemical properties of sediments. Oceanic gas hydrates are increasingly recognized as a major potential ha~rd for the stability of offshore structures in various deep-water hydrocarbon provinces. The possibility also exists that a large release of methane from gas hydrates may have a significant impact on the radiative properties of the atmosphere and thus influence global Climatei past~ present and future, Following an introduction and overviews, this book covers; analysis .and modelling of hydrate formation; exploration strategy and reservoir evaluation; regional case studies; relevance to margin~stability and climate change. Hydrate research informatiloln is presented from the USA, Russia, South Asia and the European Union. The individual papers, drawing on hydrate research: by leading :European and American scentists, are well written, with extensive references and high quality graphs and figures. Thorough index. Recommended as a valuable state,of-the-art reference in natural gas hydrates, marine geology, and the environment for students in all the earth science disciplines.

Description / Table of Contents: During the 1980s the increasing availability of seismic reflection data prompted an upsurge of interest in extensional tectonics, early work concentrating on ‘listric’ thrust-belt type models and the concepts of section balancing. However, earthquake seismology and detailed fault studies have shown recently that faults involved in crustal extension may be essentially planar. This volume concerns the geological setting and interpretation of both listric and planar normal faults. Normal faults are of particular importance in UK hydrocarbon exploration as they are directly or indirectly responsible for the majority of the pre-Tertiary oil and gas accumulations in the North Sea. As the economic size of fields reduces, the modern geologist will require an improved understanding of the origins, geometry and sealing capabilities of these faults. The volume is divided into four sections, dealing with: the geometry and kinematics of large-scale, crustal-stretching faults which typically delimit major hydrocarbon accumulations; case studies ranging from the small-scale fractures associated with the movement of salt to the large-scale intra-plate kinematics of whole fault arrays; studies of detailed displacement patterns shown by individual faults and small fault arrays; and modelling studies of normal fault geometry. The editors believe that this volume will clarify the circumstances in which the diverse models of normal fault geometry might be applicable and thus provide a useful source of reference for both industry- and academia-based research workers. Another volume on extensional tectonics? Yes, but not only is this one very nicely put together, it is also very timely … The editors have wisely placed the emphasis on observations and data … Roberts et al. deserve a great deal of credit for the very high standard of presentation. Most of the contributions contain sensible stuff that is clearly written. Illustrations are excellent … and there are hardly any typos … Ican thoroughly recommend this book to both libraries and individuals.

Description / Table of Contents: Conventional studies of oceanic structure and evolution are inevitably hampered by the difficulties with sampling the crust in the third dimension. Subsurface studies with deep seismic techniques provide some measure of understanding below the seafloor. Ophiolite studies, however, can provide a vast body of knowledge with regard to the deeper structure and crustal compositions, which is unattainable in the deep sea. In turn, many of the recent regional and detailed structures identified at mid-ocean spreading systems such as ridge segmentation patterns and ridge axis discontinuities, now form a significant contribution to recent studies of ophiolite complexes. The book will be of interest to academics from undergraduates upwards and also to industrial researchers concerned with metal sulphide and platinum group element deposits. Cover illustration: Deep-tow sidescan sonograph of the axial floor of the Mid-Atlantic Ridge around 24°N. Data were recorded using the IOSDL Towed Ocean Bottom Instrument. View is 6×8 km in a water depth of around 3500 m. Cratered seamounts, freshly mounded pillow constructs and linear fault scarps are clearly imaged. These currently active ridge processes compare directly with their ancient analogues discussed in this publication.

Description / Table of Contents: The Cadomian orogeny was first defined over 60 years ago to describe the earth movements which resulted in an unconformity between an Upper Proterozoic supracrustal sequence, namely the Brioverian, and Cambrian molasse in the north Armorican region. Since that time the terminology has been extended to encompass an extensive orogenic cycle lasting from approximately 700 - 450 Ma recorded in a belt running from the northern Appalachians to Armorica and the Southern British Isles. This volume is the first to collect together the views of workers from a variety of geological disciplines working on a range of aspects of Cadomian geological evolution. The 27 contributions contained provide both reviews and detailed studies of such topics as basement/cover relationships, nature of supracrustal sequences, deformation, metamorphism and magmatism. Lithological, geochemical, geochronological and palaeomagnetic data presented allow petrogenetic and evolutionary models to be erected and assessed and correlations to be considered within the Cadomian belt so that global geodynamic evolutionary models may be postulated. The Volume thus provides an essential reference to current thinking on the Cadomian orogeny and the date to guide future research. Part 1 is concerned with the Cadomian orogeny in the Armorican Massif Starting with a review of the Cadomian orogeny, the contributors discuss Cadomian magmatism and tectonics of northern France and the Channel Islands. Part 2 examines the Cadomian orogeny in other parts of the world, including the UK, Ireland, Iberia and Canada.

Description / Table of Contents: The 47 papers that make up this volume are gathered into eight groups that reflect current research themes: Role of fluid in rock deformation; Fracture and faulting; Instabilities and localization; Flow mechanisms and flow laws; Rock fabrics; Deformation of weak sediments; Experimental modelling using analogue materials; Deformation mechanisms and tectonics. Some of these sections contain review papers, presenting an introductory framework for those new to the subject but the volume is dominated by original research papers.

Description / Table of Contents: 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...

Description / Table of Contents: PREFACE There are problems, when applying statistical inference to the analysis of data, which are not readily solved by the inferential methods of the standard statistical techniques. One example is the computation of confidence intervals for variance components or for functions of variance components. Another example is the statistical inference on the random parameters of the mixed model of the standard statistical techniques or the inference on parameters of nonlinear models. Bayesian analysis gives answers to these problems. The advantage of the Bayesian approach is its conceptual simplicity. It is based on Bayes' theorem only. In general, the posterior distribution for the unknown parameters following from Bayes' theorem can be readily written down. The statistical inference is then solved by this distribution. Often the posterior distribution cannot be integrated analytically. However, this is not a serious drawback, since efficient methods exist for the numerical integration. The results of the standard statistical techniques concerning the linear models can also be derived by the Bayesian inference. These techniques may therefore be considered as special cases of the Bayesian analysis. Thus, the Bayesian inference is more general. Linear models and models closely related to linear models will be assumed for the analysis of the observations which contain the information on the unknown parameters of the models. The models, which are presented, are well suited for a variety of tasks connected with the evaluation of data. When applications are considered, data will be analyzed which have been taken to solve problems of surveying engineering. This does not mean, of course, that the applications are restricted to geodesy. Bayesian statistics may be applied wherever data need to be evaluated, for instance in geophysics. After an introduction the basic concepts of Bayesian inference are presented in Chapter 2. Bayes' theorem is derived and the introduction of prior information for the unknown parameters is discussed. Estimates of the unknown parameters, of confidence regions and the testing of hypotheses are derived and the predictive analysis is treated. Finally techniques for the numerical integration of the integrals are presented which have to be solved for the statistical inference. Chapter 3 introduces models to analyze data for the statistical inference on the unknown parameters and deals with special applications. First the linear model is presented with noninformative and informative priors for the unknown parameters. The agreement with the results of the standard statistical techniques is pointed out. Furthermore, the prediction of data and the linear model not of full rank are discussed. A method for identifying a model is presented and a less sensitive hypothesis test for the standard statistical techniques is derived. The Kalman-Bucy filter for estimating unknown parameters of linear dynamic systems is also given. Nonlinear models are introduced and as an example the fit of a straight line is treated. The resulting posterior distribution for the unknown parameters is analytically not tractable, so that numerical methods have to be applied for the statistical inference. In contrast to the standard statistical techniques, the Bayesian analysis for mixed models does not discriminate between fixed and random parameters, it distinguishes the parameters according to their prior information. The Bayesian inference on the parameters, which correspond to the random parameters of the mixed model of the standard statistical techniques, is therefore readily accomplished. Noninformafive priors of the variance and covariance components are derived for the linear model with unknown variance and covariance components. In addition, informative priors are given. Again, the resulting posterior distributions are analytically not tractable, so that numerical methods have to be applied for the Bayesian inference. The problem of classification is solved by applying the Bayes rule, i.e. the posterior expected loss computed by the predictive density function of the observations is minimized. Robust estimates of the standard statistical techniques, which are maximum likelihood type estimates, the so-called M-estimates, may also be derived by Bayesian inference. But this approach not only leads to the M-estimates, but also any inferential problem for the parameters may be solved. Finally, the reconstruction of digital images is discussed. Numerous methods exist for the analysis of digital images. The Bayesian approach unites some of them and gives them a common theoretical foundation. This is due to the flexibility by which prior information for the unknown parameters can be introduced. It is assumed that the reader has a basic knowledge of the standard statistical techniques. Whenever these results are needed, for easy reference the appropriate page of the book "Parameter Estimation and Hypothesis Testing in Linear Models" by the author (Koch 1988a) is cited. Of course, any other textbook on statistical techniques can serve this purpose. To easily recognize the end of an example or a proof, it is marked by a A or a t~, respectively. I want to thank all colleagues and students who contributed to this book. In particular, I thank Mr. Andreas Busch, Dipl.-Ing., for his suggestions. I also convey my thanks to Mrs. Karin Bauer, who prepared the copy of the book. The assistance of the Springer- Verlag in checking the English text is gratefully acknowledged. The responsibility of errors, of course, remains with the author.

Description / Table of Contents: This volume contains the proceedings of a symposium held at Freiburg im Breisgau, October 7-11, 1990. The symposium was sponsored mainly by the Deutsche Forschungsgemeinschaft (DFG), by the Geological Institute of the University of Freiburg, and by the International Association of Mathematical Geology. We thank these and all other sponsors of the meeting. The symposium whose participants came from more then twenty countries was the first international meeting dedicated entirely to geological applications of threedimensional computer graphics, a rapidly growing field of scientific visualization in geology. The selection of papers in this volume covers a wide range of methods developed in the last decade.

Description / Table of Contents: The present interest in sediments which are rich in organic matter results not only from their economic significance as potential oil and gas source rocks, but also from the fact that their deposition is the result of special environments. Subtle changes in the environmental conditions may result in great variations in the geochemical and petrographical characteristics of the organic matter. Therefore, the study of organic matter-rich sediments can provide a key to past sedimentary conditions. In addition, the elucidation of the depositional controls is of importance for oil and gas exploration strategies, for which the knowledge of source rock distribution and quality is critical. Furthermore, organic matter reacts extremely sensitive to changes in temperature during burial. The result of this sensitivity is the generation of volatile products such as carbon dioxide, water, nitrogen, oil and gas and a reorganization of the solid organic residue. Some of these changes are quantified as maturity parameters which can be used as calibration tools in basin modelling, i.e., in the modelling of temperature histories of sedimentary basins. The use of maturity parameters and other organic matter characteristics as indicators for diagenetic conditions and depositional processes is, however, restricted, if analyses are performed on outcrop samples, because weathering also affects organic matter.

Description / Table of Contents: PREFACE This monograph is a compendium of revised papers which were originally presented at the "Ron Mather Symposium on Four-Dimensional Geodesy", 28-31 March, 1989, held at the University of New South Wales, Sydney, Australia. The symposium had the enthusiastic support of the International Association of Geodesy and the Australian Academy of Sciences. The symposium served two purposes: to honour the achievements of the late Professor Ron S. Mather, the distinguished Australian geodesist who died in 1978, and to review and report on the latest developments in four-dimensional geodesy. Four-dimensional geodesy is a convenient term for those geodetic principles and techniques which yield position, gravity and their time variations. In the past geodesists have tended to think of the earth as a static body, save from occasional savage earthquakes or volcanic eruptions. So, why the need to coin the term "four-dimensional geodesy") Because it explicitly recognises that time is an integral part of understanding geodetic measurements. But let's first identify the scope of modern geodesy. Geodesy has traditionally been concerned with two separate, though closely related, topics: accurate positioning of objects on the earth's surface, and mapping the earth's external gravity field. These are still the fundamental tasks of geodesy, although the spheres of application have now extended into space. However, present and emerging geodetic measurement technologies for gravity field mapping and positioning are sensitive to defolTnations of the earth's surface and gravity field. Within the geodetic community, this new emphasis on accounting for the time-varying characteristics of position and gravity has fundamental principles; in particular the establishment and maintenance of appropriate global reference systems for geodesy. At the same time, there has been a growing recognition by the earth sciences in general of the important role of geodesy in studying earth deformations, as well as atmosphere and ocean dynamic phenomena. The geodetic measurements, for example, are taken over time scales of hours to decades, and occasionally to a century or longer. Though this is only a small part of the whole deformation spectrum, it is a very important one. Geodesy bridges the low frequency part of the spectrum available from geological observations, with the high frequency end observed from, for example, seismic instrumentation. It's role in atmospheric and oceanographic studies is as a unique, high precision remote sensing tool. The revolution in geodesy is not, however, restricted to the measurement technology only. It is true that without the advances of space geodesy and terrestrial metrology, the notion of four-dimensional geodesy is a rather academic one. These advances, which now reveal time-variable signals above the measurement noise level, have important implications for all geodetic activities. The geodetic activities we refer to can be identified as: experiment design and measurement processes; definition and maintenance of highly stabie geodetic reference systems; data analysis; and interpretation of position and gravity results. Ultra high precision measurements are of little use without sophisticated analysis tools to extract the small signals in the data. The interpretation of geodetic results will be in error if insufficient attention is paid to ensuring that the reference systems to which the results relate are themselves stable. Clearly four-dimensional geodesy is as much about concepts and principles, as about computers and geodetic equipment. This diversity is reflected in the papers selected for this book. They range over topics related to the modem measurement tools, the reduction and analysis techniques, to the interpretation of geodetic results within the context of problems currently being investigated in the earth sciences. We would like to thank the International Association of Geodesy and the Australian Academy of Sciences for sponsorship of the Symposium. Unisearch Ltd., the commercial arm of the University of New South Wales, was the managing agent, and staff members of the School of Surveying and of Unisearch Ltd. were involved in the organisation of the Symposium. We would like to gratefully acknowledge these excellent contributions. Let us express also our gratitude for the useful guidance which we received from Prof. K. Lambeck, A. Prof. A. Stolz and Dr. R. Coleman of the Scientific Advisory Committee and the continuous support given by Prof. E.W. Grafarend. Sincere thanks are due to the authors of the selected papers for agreeing to contribute to this Monograph, and for their positive cooperation during the production of this volume.

Description / Table of Contents: PREFACE This volume contains a selection of papers presented and discussed at the COMTAGWorkshop on "Dynamics and Geomorphology of Mountain Rivers". COMTAG (Commission on Theory, Measurement and Application in Geomorphology) is a commission of the International Geographical Union (IGU). The meeting was held in the monastery of Benediktbeuern in the Bavarian Alps in June 1992. The main objective of the meeting was to review the most recent developments in research on river bed dynamics and bedload transport in mountain rivers. Questions of mountain torrent control and environmental protection were also addressed. The general theme of the meeting finds its appropriate scientific and spatial location in the long tradition of bedload transport studies carried out in the fluvially active German Alps, which are often affected by flood and mass movement hazards. The conference provided an impulse for discussions between researchers in the fields of mountain torrent hydrology, water resources management and bedload transport modelling. In the five years preceding the meeting the editors of this volume had headed a DFG (Deutsche Forschungsgemeinschaft) project on "Bedload transport and river bed adjustment in the Lainbach catchment" within the priority programme "Fluvial Geomorphodynamics in the late Quaternary". Results of the investigations and newly developed measurement techniques were introduced to the participants during the meeting and an excursion to the nearby Lainbach River. The meeting was attended by sixty four scientists from fifteen countries. Thirty four papers were presented in sessions on bedload transport in mountain torrents, measurement techniques of solid material transport, mass movements and sediment supply, river bed adjustment and roughness characteristics of steep mountain torrents, models of bedload transport, and catastrophic flooding. From a regional perspective the majority of the contributions dealt with the Alps with a special focus on investigations carried out at the northern fringe of the Alps. Most of the papers presented were submitted for publication, and selected papers have been included in this volume. The workshop was financially supported by the Deutsche Forschungsgemeinschaft, the Commission of the European Communities (Directorate General for Science, Research and Development), the Freistaat Bayern (Ministerium fOr Unterricht, Kultur, Wissenschaft und Kunst) and the US-Army Research and Development Standardization Group. The participants and the organizers are grateful for these grants. We thank the president of COMTAG, Asher Schick, for his friendly support during the preparation and organization of the workshop. We are also very much indebted to the Kathoiische Stiftungsfachhochschule M~nchen and the Salesianer Don Bo~cos, Benediktbeuern, who opened the rooms of the monastery of Benedikbeuern for scientific sessions and social events during the conference. The organization of the meeting would not have been possible without the help of the local and regional administration, water and forest authorities. We highly appreciate this assistance. In addition, the editors thank the Springer-Verlag for the inclusion of the conference proceedings in this series and the colleagues F. Ahnert, J. Bathurst, W. Bechteler, I. Campbell, P. Carling, N.J. Clifford, S. Custer, T. Davies, A. Dittrich, R. Ferguson, K. Garleff, M. Hassan, R. Hey, H. Ibbeken, J. Karte, H. Keller, D. Knighton, J. Laronne, M. Meunier, M.D. Newson, D. Oostwoud-Wijdenes, I. Reed, K.S.Richards, A. Scheidegger and W. Symader for their valuable contributions as reviewers of the manuscripts that were submitted for this volume.

Description / Table of Contents: INTRODUCTION Ecometry concerns measurements and interpretation of ecological data and relationships between data. It deals with most matters involved in the scientific aspects of the representativity and information value of samples and does not, in fact, concern statistical methods. In particular, ecometry can be regarded as an approach to obtain so-called load models and load diagrammes (effect-dose-sensitivity diagrammes), which are one of the aims/final products in aquatic environmental consequence analysis (H~- kanson, 1990; all these terms will be explained later on). This publication is meant to demonstrate what can and cannot be done using ecometric approaches. It must be emphasized at the outset that the main intention here is not to provide new radioecological knowledge on how Cs-137 is dispersed in aquatic ecosystems after the Chernobyl accident and is taken up in fish, but to use Cs-137 as a type substance and pike as a biological indicator to go through methods which should also apply to other types of environmentally hazardous substances (it could just as well have been substance X in ecosystem Y). As a secondary effect, we may also learn something about Cs-137. Several terms and methods, which have not been used earlier in the aquatic environmental sciences, e.g., ecometric analysis and dynamic modelling using moderators, will be discussed and defined...

Description / Table of Contents: PREFACE Following the economical and social development of the local communities, mountain regions of temperate climates are increasingly becoming the site of valuable infrastructures and important urban and industrial settlements. As the catastrophic events of last years in the European Alps have clearly shown, the vulnerability of these territories has correspondingly increased, in terms of both property damage and losses of human life. Until recently, the hydraulic scientific community has paid little attention to mountain watersheds, except perhaps during the period if the hydropower development. Nevertheless attention was then focused on problems and methodologies somewhat different from the issues of actual environmental concern. More recently, however, hydraulic engineers have joined their colleagues from forest and rural engineering, who have traditionally dealt with erosion control in mountain areas, to bring in their own methodology, already experienced in lowland rivers. At the same time, academic people focused an interest in some phenomena, like massive transport, which is typical of mountain environment. To bring together all these contributions and to make the state of the art of the mountain river science (oropotamology) and technology, an International Workshop was called at the University of Trent (Italy), on October 1989, under the sponsorship of Fluvial Hydraulic Section of the IAHR. Three main topics have been recognized as particularly relevant from the point of view of both research and professivnal people: a) Hydrodynamics of steep channels and local scale process; b) Sediment movement and sediment training, with special emphasis on massive transport; c) Particular features of sediment transport related to non-uniform grain-size. However, as it is the case in these circumstances, the contest of several contributions often spread over more than one topic. In the following Introduction to papers, the three topics were split into 11 Sections, each one devoted to a more particular aspect recurrently addressed during the discussion. The same paper, thus, may be mentioned in different Sections of the Introduction.

Description / Table of Contents: PREFACE This volume presents results from members of the Project 216 "Global Biological Events in Earth History" of the International Geological Correlation Programme (IGCP). The project, initiated by the elder editor (O.H.W.) within the framework of the International Palaeontological Association (IPA) in the late 70s, was officially established in 1984. Subsequently, it led to the first three conferences on Global Bio-Events, and their respective symposia volumes: 1) In G6ttingen, West Germany in 1986 (WaUiser, O. H., Ed., 1986, Global Bio-Events, Springer-Verlag); in Bilbao, Spain in 1987 (Lamolda, M. A., Kauffrnan, E. G., and Walliser, O. H., Eds., 1988, Paleontology and Evolution: Extinction Events; Rev. Espafiola de Paleont., n. extraord.); and in Boulder, Colorado, U.S.A. in 1988 (this volume). The next meeting, on Innovations and Revolutions in the Biosphere, is planned in Oxford, England in 1990, to be hosted by Martin Brasier. During the history of this project, the focus of our research has shifted significantly. Initial focus was on specific global mass extinctions (e.g. the Precambrian/Cambrian, Frasnian/Fammenian, Cretaceous/Tertiary, and Eocene/Oligocene events) to a broader treatment of Phanerozoic mass extinctions, their differences or unifying factors, and their causal mechanisms. Subsequent meetings have attempted to focus attention on a fuller spectrum of global bio-events in Earth history. The Boulder Conference, and this volume, although still strongly influenced by the excitement of mass extinction research, expresses these new trends in bioevent studies. The Boulder conference, held on May 16-23, 1988, focused on a broad spectrum of Abrupt Changes in the Global Biota. Over 100 participants from 13 nations attended this meeting, representing diverse disciplines of palaeobiology, palaeoclimatology, palaeoceanography, sedimentology, geochemistry, and a broad spectrum of the stratigraphic and geological sciences. Four days of talks were supplemented by field trips to the continental Cretaceous/Tertiary boundary in the Raton Basin, New Mexico, and to the Cenomanian/Turonian mass extinction interval exposed near Pueblo, Colorado. The Conference itself was characterized by a great diversity of approaches to bio-event research, and the phenomenon of mass extinction. In particular, interactive causes involving both extraterrestrial and earthbound (tectonic, oceanographic, climatic) forces were discussed, and each major Phanerozoic mass extinction was treated by specialists in the field. In addition, many presentations focused on the causal mechanism and patterns of bio-event development that were not restricted to mass extinction intervals, but which could cause regional to global biotic response at any time in Earth history. Thus, both the conference, and this volume, focus attention on climatic and oceanic perturbations from anoxia, advection, rapid thermal change, toxic chemical enrichment, and energy shock from impacts and giant tsunamis as forcing mechanism for regional to global bio-events. The delicate balance of perched ocean/ctimate~fe systems under typical warm equable non-glacial Phanerozoic conditions, and their susceptibility to shock from even small perturbations, was a philosophical theme that ran throughout the meeting. The case for extraterrestrial forcing of tectonic, volcanic, and biological events was greatly strengthened by new data presented at this conference, with special concern for the effects of small comet/meteorite impacts in the oceans, and their chemical/physical/biological signature which might be used, in the absence of shocked minerals, microspheres or trace metals, to identify extraterrestrial events associated with global and regional bio-events. The conference benefitted from the introduction of much new data at high levels of resolution, especially from poorly studied mass extinction intervals. Interactive discussions, and many new ideas characterized the meeting. The new scientific results of this meeting are exciting; they are reviewed in the Conference Report published in Episodes (1988, v. 11, n. 4, p. 289-292). Most of the key papers presented at the Boulder meeting appear in this volume. What lies ahead in bio-event research? Clearly, a great deal of excitement and an age of discovery. We have only touched the surface of this new and dynamic field. We are starting to comprehend the dynamics of global mass extinctions, integrating detailed geochemical, physical and biological data into scenarios of cause and effect. But in the years ahead lies the job of understanding the whole spectrum of regional bioevents preserved in the ancient record, and especially the application of this research to solutions of the critical problems inherent in global change and the modern biotic crisis. Future directions for research at this conference include the investigation and modeling of abrupt chemical and thermal shifts in the ocean, the effects of impacts at deep ocean sites, the documentation of successful survival strategies and repopulation patterns following biotic crises, the deep ocean record of bio-events, and focus on alternative forces other than impacting to account for mass extinction events. This volume introduces some of these new pathways in bio-event research.

Description / Table of Contents: The subject of the book is an indepth description of the theory and mathematical models behind the application of the Global Positioning System in geodesy and geodynamics. The text has been prepared by leading experts in the field, contributing their particular points of view. Unlike a collection of disjoint papers, the text provides a continous flow of ideas and developments. The mathematical models for GPS measurements are developed in the first half of the book, followed by the description of GPS solutions for geodetic applications on local, regional and global scales.

Description / Table of Contents: PREFACE The emergence of new information from drilling in deep-sea and coastal areas and the surfacing of the plate tectonics theory probably had the greatest impacts in recent decades on the highly accelerated growth of knowledge regarding the evolution of sediments and sedimentary rocks. Studies in recent years have also provided new insights on global sedimentary processes, and isotopic tools in many ways have enhanced our knowledge and have provided even an unexpected added dimension to the mechanisms of some specific processes. Many different uses of isotopic tools in studies of sedimentary processes can be found in the literature, but the information is highly scattered in the vast field of sedimentology. The disseminated state of existing isotopic knowledge on sedimentary systems has undoubtedly deprived many practitioners in the field to fully appreciate the benefits and limitations, and even the apparent confusion, concerning the use of isotopic tools. We have endeavored here to bring together discussions on some major sedimentary systems in the sedimentary cycle and to analyze them according to isotopic evidence. To accomplish such a task required contributions from many individuals. We were fortunate to have friends who accepted to share our goals. We most sincerely thank all the contributors to this book and deeply appreciate their patience and fortitude despite our undue demands on them to reach our objectives...

Description / Table of Contents: PREFACE Through the last few decades inversion concepts have become an integral past of experimental data interpretation in several branches of science. In numerous cases similar inversion-like techniques were developed independently in separate disciplines, sometimes based on different lines of reasoning, and sometimes not to the same level of sophistication. This fact was realized early in inversion history. In the seventies and eighties "generalized inversion" and "total inversion" became buzz words in Earth Science, and some even saw inversion as the panacea that would eventually raise all experimental science into a common optimal frame. It is true that a broad awareness of the generality of inversion methods is established by now. On the other hand, the volume of experimental data varies greatly among disciplines, as does the degree of nonlinearity and numerical load of forward calculations, the amount and accuracy of a priori information, and the criticality of correct error propagation analysis. Thus, some clear differences in terminology, philosophy and numerical implementation remain, some of them for good reasons, but some of them simply due to tradition and lack of interdisciplinary communication. In a sense the development of inversion methods could be viewed as an evolution process where it is important that "species" can arise and adapt through isolation, but where it is equally important that they compete and mate afterwards through interdisciplinary exchange of ideas. This book was actually initiated as a proceedings volume of the "Interdisciplinary Inversion Conference 1995", held at the University of Aarhus, Denmark. The aim of this conference was to further the competition and mating part of above-mentioned evolution process, and we decided to extend the effect through this publication of 35 selected contributions. The point of departure is a story about geophysics and astronomy, in which the classical methods of Backus and Gilbert from around 1970 have been picked up by helioseismology. Professor Douglas Gough, who is a pioneer in this field, is the right person to tell this success story of interdisciplinary exchange of research experience and techniques [1-31] (numbers refer to pages in this book). Practitioners of helioseismology like to stress the fact that the seismological coverage on the Sun in a sense is much more complete and accurate than it is on Earth. Indeed we witness vigorous developments in the Backus & Gilbert methods (termed MOLA/SOLA in the helioseismology literature) [32-59] driven by this fortunate data situation. Time may have come for geophysicists to look into helioseismology for new ideas. Seismic methods play a key role in the study of the Earth's lithosphere. The contributions in [79 - 130,139 - 150] relate to reflection seismic oil exploration, while methods for exploration of the whole crust and the underlying mantle axe presented in [131 - 138, 151 - 166]. Two contributions [167 - 185] present the application of inversion for the understanding of the origin of petroleum and the prediction of its migration in sedimentary basins. Inversion is applied to hydrogeophysical and environmental problems [186 - 222], where again developments are driven by the advent of new, mainly electromagnetic, experimental techniques. The role of inversion in electromagnetic investigations of the lithosphere/astenosphere system as well as the ionosphere axe exemplified in [223 - 238]. Geodesy has a fine tradition of sophisticated linear inversion of large, accurate sets of potential field data. This leads naturally to the fundamental study of continuous versus discrete inverse formulations found in [262-275]. Applications of inversion to geodetic satellite data are found in [239 - 261]. General mathematical and computational aspects are mainly found in [262 - 336]. Nonlinearity in weakly nonlinear problems may be coped with by careful modification of lineaxized methods [295 - 302]. Strongly nonlinear problems call for Monte Carlo methods, where the cooling scedule in simulated annealing [303 - 311,139 - 150] is critical for convergence to a useful (local) minimum, and the set of consistent models is explored through importance sampling [89 - 90]. The use of prior information, directly or indirectly, is a key issue in most contributions, ranging from Bayesian formulations based a priori covariances e.g. [98 - 112,122 - 130, 254 - 261], over more general but also less tractable prior probability densities [79 - 97], to inclusion of specific prior knowledge of shape [284 - 294, 312 - 319]. Given the differences and similarities in approach, can we benefit from exchange of ideas and experience? In practice ideas and experience seldom jump across discipline boundaries by themselves. Normally one must go and get them the hard way, for instance by reading and understanding papers from disciplines far from the home ground. Look at the journey into the interdisciplinary cross-field of inversion techniques as a demanding safari into an enormous hunting ground. This book is meant to provide a convenient starting point.

Description / Table of Contents: PREFACE The search for tin dates back to the earliest days of civilization. For about 40 years, world tin mining has oscillated at a level of 150,000-250,000 t Sn/year, with a mine output in 1989 of 210,000 t Sn (MCS 1990). This figure corresponds to a current annual value of about US$1.5 billion and places tin ninth on the metal market behind iron, gold, uranium, copper, zinc, silver, platinum and nickel. Tin deposits belong to the granite-related ore deposit spectrum which includes many metals vital to current and future technologies such as Cu, W, Mo, U, Nb, Ta, Ag, Au, Sb, Bi, As, Pb, Zn, REE, Be, Ga and Li. The granitic rocks associated with tin and tin-tungsten deposits have long been identified as a special group of granites, the so-called tin granites. These rocks provide a unique opportunity to study the magmatic and hydrothermal history of tin ore formation. Tin granites are more easily identifiable as parent rocks for tin (and tungsten) mineralization than is the case for other mineralized granitic rocks such as molybdenum and copper porphyries. The magmatic molybdenum and copper distribution patterns are more complex (control by sulfide solubilities), and commonly obliterated by fluid interaction. The relatively simple situation of tin granites provides therefore an invaluable opportunity to study some metallogenic aspects of magmatic-hydrothermal ore deposits in general. The present study attempts to develop a general metallogenic model for tin in identifying the essential or relevant processes in tin ore formation. The methodological principle is based, on an interplay between a background of some basic petrogenetic concepts and a number of specific local and regional data on tin deposits and tin provinces, with particular reference to those areas with which the author is most familiar with (Bolivia, SE Asia, Europe). This inductive approach condenses the many apparently specific complexities encountered in individual ore deposits to a few major processes of general importance. The inherent reductionism may have a personal bias which is probably inevitable in any simple and broad-scale picture ("Apr6s tout, la raison est bien I'esclave des passions"; Feyerabend 1979:210). The critical problem of the relevance of those factors chosen for our model can be judged by its degree of consistency and predictive capability for new and analogous cases...

Description / Table of Contents: Pages 1-13 / Maars of the Westeifel, Germany / G. Büchel --- Pages 15-60 / Syn- and post-eruptive mechanism of the Alaskan Ukinrek Maars in 1977 / G. Büchel, V. Lorenz --- Pages 61-80 / Maars and maar lakes of the Westeifel Volcanic Field / Jörg F. W. Negendank, Bernd Zolitschka --- Pages 81-94 / Maars of northern Auvergne (Massif Central, France): State of knowledge / E. Juvigné, G. Camus, A. de Goër de Herve --- Pages 95-107 / Palaeoenvironmental investigations on long sediment cores from volcanic lakes of Lazio (central Italy)—An overview / Maria Follieri, Donatella Magri, Biancamaria Narcisi --- Pages 109-116 / Geophysical mapping of organic sediments / Stefan Wende, Reinhard Kirsch --- Pages 117-118 / Preliminary uniboom survey of the Monticchio Lakes (southern Italy) / A. Stefanon --- Pages 119-128 / Sonar investigations in the Laghi di Monticchio (Mt. Vúlture, Italy) / Ralph B. Hansen --- Pages 129-148 / Climatic and tectonic effects on sedimentation in central Italian volcano lakes (Latium)—Implications from high resolution seismic profiles / F. Niessen, A. Lami, P. Guilizzoni --- Pages 149-161 / Sediments and basin analysis of Lake Schalkenmehrener Maar / T. Heinz, B. Rein, J. F. W. Negendank --- Pages 163-171 / Organic carbon contents of sediments from Lake Schalkenmehrener Maar: A paleoclimate indicator / B. Rein, J. F. W. Negendank --- Pages 173-194 / Basin analysis for selected time-frames using sedimentation rates in Lake Meerfelder Maar (Westeifel FRG) / F. Wegner, J. F. W. Negendank --- Pages 195-208 / Turbidites in the sediments of Lake Meerfelder Maar (Germany) and the explanation of suspension sediments / D. Drohmann, J. F. W. Negendank --- Pages 209-222 / Paleoclimate reconstruction at the Pleistocene/Holocene transition—A varve dated microstratigraphic record from Lake Meerfelder Maar (Westeifel, Germany) / D. Poth, J. F. W. Negendank --- Pages 223-235 / Paleoenvironmental reconstruction of the Late- and Postglacial sedimentary record of Lake Weinfelder Maar / A. Brauer, J. F. W. Negendank --- Pages 237-275 / Sedimentology and paleoenvironment from the Maar Lac du Bouchet for the last climatic cycle, 0-120,000 years (Massif Central, France) / Elisabeth Truze, Kerry Kelts --- Pages 277-288 / Lago Grande di Monticchio (southern Italy) a high resolution sedimentary record of the last 70,000 years / Bernd Zolitschka, Jörg F. W. Negendank --- Pages 289-304 / A multidisciplinary study of the Vico Maar sequence (Latium, Italy): Part of the last cycle in the Mediterranean area. Preliminary results / P. Francus, S. Leroy, I. Mergeai, G. Seret, G. Wansard --- Pages 305-316 / Environmental geology and geochemistry of lake sediments (Holzmaar, Eifwl, Germany) / B. G. Lottermoser, R. Oberhänsli, B. Zolitschka, J. F. W. Negendank, U. Schütz… --- Pages 317-332 / Geochemistry of Lago Grande di Monticchio, S. Italy / C. Robinson, G. B. Shimmield, K. M. Creer --- Pages 333-348 / Tephrochronology of core C from Lago Grande di Monticchio / Anthony J. Newton, Andrew J. Dugmore --- Pages 349-365 / A palaeomagnetic study of maar-lake sediments from the Westeifel / B. Haverkamp, Th. Beuker --- Pages 367-376 / Preliminary 50m palaeomagnetic records from Lac du Bouchet, Haute Loire, France / T. Williams, K. M. Creer, N. Thouveny --- Pages 377-392 / Palaeomagnetic investigations of Lago Grande di Monticchio, southern Italy / Ian Turton --- Pages 393-420 / Late-Glacial/Holocene changes of the climatic and trophic conditions in three Eifel maar lakes, as indicated by faunal remains. I. Cladocera / Wolfgang Hofmann --- Pages 421-433 / Late-glacial/Holocene changes of the climatic and trophic conditions in three Eifel maar lakes, as indicated by faunal remains. II. Chironomidae (Diptera) / Wolfgang Hofmann --- Pages 435-439 / Ostracoda (Crustacea) and trichoptera (Insecta) from Late-and Postglacial sediments of some European maar lakes / Burkhard W. Scharf --- Pages 441-446 / Oligocence dinoflagellate-cysts in Quaternary freshwater sediments of Eifel maars / H. Weiler --- Pages 447-465 / Tertiary maars of the Hocheifel Volcanic Field, Germany / G. Büchel, M. Pirrung --- Pages 467-476 / Some aspects of Cenozoic maar sediments in Europe: the source-rock potential and their exceptionally good fossil preservation / W. Zimmerle --- Pages 477-484 / Palaeoecological implications from the sedimentary record of a subtropical maar lake (Eocene Eckfelder Maar; Germany) / Bernd Zolitschka --- Pages 485-489 / Arthropods from the Eocene Eckfelder Maar (Eifel, Germany) as a source for paleoecological information / H. Lutz --- Pages 491-497 / Flowers from the Middle Eocene of Eckfeld (Eifel, Germany)— First results / H. Frankenhäuser, V. Wilde --- Pages 499-503 / Initial results on the importance of a flora from the Middle Eocene of Eckfeld (Eifel, W.-Germany) / V. Wilde, H. Frankenhäuser --- Pages 505-509 / International Maar Deep Drilling Project (MDDP) a challenge for earth sciences? / Jörg F. W. Negendank, Bernd Zolitschka

Description / Table of Contents: 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...

Description / Table of Contents: The present study will provide an introduction into the biomechanics of trees and will give a critical survey of the phylogeny and the constructional principles of the tree habit. Since the trunk is considered the basic and crucial element of a tree, the analysis is largely restricted to a functional comparison of the stem anatomy of the various tree forms. It is based on the concept of constructional morphology, thus considering simultaneously the functional aspect and the ontogenetical and phylogenetical development of the various trunk types. The main questions to be answered in this study are; Why do trees exist? - Which are the constructional principles of tree trunks and when and in which group of plants do they appear? - How important are internal (phylogenetic) and external (functional, constructional) constraints? - What are the specific properties of the different constructional principles and does a correlation between trunk design and growth habit exist? - Is there a tendency in phylogeny to a better performance? The study does not (and cannot) intend to provide a detailed biophysical analysis of individual cases because experimental data on the mechanical properties of the structural elements of the different kinds of trees are still lacking. Instead, it will he the task to evaluate in a comprehensive and qualitative or semi-quantitative manner the available data of the morphology, anatomy and phylogeny of fossil and recent trees by using concepts of biomechanics and constructional morphology. Thus a somewhat holistic approach is used, which is becoming increasingly more acceptable today.

Description / Table of Contents: PREFACE The application of thermal analysis to earth science has a long history. This is evidenced by the extensive coverages by Mackenzie (1957, 1970), Langier-Kuzniarowa (1967), Schultze (1971), Liptay (t973), Smykatz- Kloss (1974), Todor (1976) and Heide (1982). The chief thermal method has been differential thermal analysis (DTA). Additionally, thermogravimetry (TG; Duval, 1963; Keattch, 1969; Earnest, 1988) and thermodilatometry (Schomburg & Strörr, 1984) have gained some importance. All these methods are still widely ltsed. But recently several new techniques have gained attention, such as thermomagnetometry, thermomechanical analysis and thermosonimetry. Improved equipment made possible the application of thermal methods to problems in thermodynamics and kinetics (e.g. by means of differential scanning calorimetry, DSC). This progress in the construction of new instruments as well as the combination of existing methods to enable simultaneous determinations (e.g. TG/DTA; TG/IR spectroscopy; DTA/mass spectrometry; DTA/microscopy; high-pressure DTA) have led to a resurgence in the use and application of thermal analysis in the earth sciences. Here the applications cover such diverse areas as the examination of individual minerals, mineral mixtures, rocks, soils, ceramics, cements, raw materials as well as their industrial evaluation, performance assessment and quality control. In the field of solid fossil fuels thermal determinations range from proximate analysis of inorganic constituents and the measurement of calorific values to the assessment of the environmental aspects of fly ashes and mineral residues. To support this tendency, the International Confederation for Thermal Analysis (ICTA) has recently founded a "Committee for Thermal Analysis in Geosciences". The aim of this committee shall be to discuss, improve and distribute the knowledge about the possibilities of solving geoscientific questions by means of thermal analytic methods...

Description / Table of Contents: PREFACE Turbidity currents have been comprehensively studied in the past although much remains unknown about both their flow characteristics and resultant sedimentary deposits. Much of this uncertainty arises from the catastrophic nature of their formation which makes them difficult to study in the environment, and has resulted in the majority of studies being experimental or theoretical. Experiments have shown that reversals in the flow of density currents can be associated with the generation of internal solitary waves. This is in contrast to the belief held by many workers that the reversal of a turbidity current simply generates an identical flow travelling in the opposite direction. This book arose from the need for a detailed experimental study to examine the effects and to consider the consequences of density current reversals from a variety of obstructions to their flow. The first part of this book comprises a detailed review of literature covering the fluid dynamics and sedimentology relevant to the experimental study (chapter one). Chapter two presents the results from the comprehensive experimental programme which are discussed and compared with appropiate theoretical hypotheses. This permits the synthesis of a model for the general features of flows that result from the incidence of density currents upon obstructions to the flow. The application of this model to both modern and ancient turbidite systems is then discussed in chapter three. This book is suitable for earth scientists with an interest in the dynamics of turbidity currents. In addition, workers from other fields such as applied maths, meteorology and engineering who have an interest in density currents and bores in practical situations may find it useful...

Description / Table of Contents: INTRODUCTION The study is essentially empirical, since it portrays and appraises two different water management systems, and relates them to one another. Yet the analysis has also been made with definite research aims in mind. Its focus has been narrowed down to the environmental assessment of urban water management systems in arid and semi-arid regions, especially with an eye to deal with information problems in the Developing World. The study addresses a set of very critical issues of global concern, and, thus, delineates a crucial topic for international research. The fact that a wide range of critical issues usually complicates and aggravates the given problem setting provides the comparative analysis with a special practical incentive to explore the opportunities for joint strategies and comprehensive solutions. However, the complexities involved between water management and the environment and the relative lack of a joint theory in that field pose certain difficulties to such an undertaking. In order to fully appreciate the underlying purpose of the study and the scope of its implications, the various facets of the problem setting and the essential ingredients of the general line of approach have first to be unravelled and expounded at some length. Above all, it needs to be shown how these facets combine to produce the complex, burning issues which in turn seem to, both in theory and practice, require correspondingly intricate, strategic approaches for their solutions...

Description / Table of Contents: 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...

Description / Table of Contents: Introduction / Pages 1-32 --- Interpretation using nomograms / Pages 33-47 --- Linear parameters / Pages 49-114 --- Non-linear parameters / Pages 115-173 --- Maximum likelihood and maximum entropy / Pages 175-193 --- Analytic inversion / Pages 195-211 --- Advanced inversion methods / Pages 213-227 --- Error analysis / Pages 229-243 --- Parallel computation in modelling and inversion / Pages 245-255

Description / Table of Contents: PREFACE This book represents the first attempt in three decades to marshall out available information on the regional geology of Africa for advanced undergraduates and beginning graduate students. Geologic education in African universities is severely hampered by the lack of a textbook on African regional geology. This situation is greatly exacerbated by the inability of most African universities to purchase reference books and maintain journal subscriptions. Besides, geologic information about Africa is so widely dispersed that a balanced and comprehensive course content on Africa is beyond the routine preparation of lecture notes by university teachers. Since geology is a universal subject and Africa is one of the largest landmasses on Earth with one of the longest continuous records of Earth history, there is no doubt that geologic education in other parts of the world will benefit from a comprehensive presentation of African geologic case histories. The scope of this text also addresses the need of the professional geologist, who may require some general or background information about an unfamiliar African geologic region or age interval. Africa occupies a central position in the world's mineral raw materials trade. Because of its enormous extent and great geologic age, the diversity and size of Africa's mineral endowment is unparalleled. Africa is the leading source of gold, diamond, uranium, and dominates the world's supply of strategic minerals such as chromium, manganese, cobalt, and platinum. Consequently, African nations from Algeria to Zimbabwe depend solely on mineral exports for economic survival. The geologic factors which govern economic mineral deposits are stressed in this text. The geological history of Africa spans 3.8 billion years, a record that is unique both in duration and continuity. Few other parts of our planet match the plethora of geologic phenomena and processes that are displayed in the African continent. From the various stages of crustal evolution decipherable from the Archean of southern Africa, through the plate tectonics scenarios in the ubiquitous Late Proterozoic-Early Paleozoic Pan-African mobile belts and in the Hercynian and Alpine orogenies of northwest Africa, to the East African Rift Valley, Africa is replete with excellent examples and problems for a course on regional tectonics. Teachers of igneous and metamorphic petrology can hardly ignore Africa's anorogenic magmatism (e.g.. layered ultramafic intrusives such as the Great Dyke and the Bushveld Complex; the Tete gabbro-anorthosite pluton; alkaline complexes; basaltic volcanism), or tantalizing highgrade metamorphic terranes such as the Limpopo belt, the Namaqua mobile belt, and the Mozambique belt. From the extensive Precambrian supracrustal sequences throughout the continent with enormous thicknesses of sedimentary rocks that have hardly been deformed or metamorphosed, to the stratigraphic evolution of Africa's present-day passive continental margin, there is a complete spectrum of facies models upon which to base a course on basin analysis and stratigraphy. To maintain its integrity a course on historical geology anywhere in the world must address the theory of Continental Drift beyond invoking past continuities between West Africa and South America. Past connections between West Africa and eastern North America must equally be explored, so also connections between northeast Africa and Arabia, and the paleogeography of southern Gondwana where Africa occupied centre stage. The Precambrian fossil record, the transitions from reptiles to the earliest mammals and dinosaurs, and the evolution of Man are among Africa's unique contributions to the history of life and the story of organic evolution. Although it lies today in the tropics Africa was the theatre of the Earth's most-spectacular glaciations. Even after the scene of continental glaciation had shifted to the northern continents only lately during the Pleistocene, Africa still witnessed spectacular climatic fluctuations during the Quaternary. Certainly students of archeology and paleoanthropology cannot overlook the Quaternary paleoenvironmental record of the Olduvai Gorge in Tanzania, the Lake Turkana basin in Kenya, the Nile valley, the Sahara, and southern Africa. But since African examples have already been cited in standard geologic textbook, I have often been asked why it has become necessary to revive the idea of a full-length textbook on African geology, 30 years after this idea was abandoned by the geologic community. My simple answer, as already stated, is that the wealth of available geologic information about Africa is so enormous and fascinating, but so diffuse, that an attempt must be made to assemble and pass on this knowledge.

Description / Table of Contents: INTRODUCTION The International Summer School of Theoretical Geodesy on Satellite Altimetry in Geodesy and Oceanography was held in Trieste (Italy) from May 25 to June 6, igg2. It was organized by Prof. R. Rummel of the Delft University of Technology and by Prof. F. Sansò of the Politecnico di Milano and was attended by 63 participants and 7 lecturers from 17 countries. The School was hosted by the International Centre of Theoretical Physics of Trieste. Satellite altimetry provides a lot of data that require more and more sophisticated models in order to be interpreted and exploited. One of the main problems related to the practical treatment of the data can be summarized as follows: oceanographers would like to ask geodesists to compute precise orbits and a precise geoid in order to put into evidence the Sea Surface Topography that can be interpreted as an oceanographic signal related to currents and to several physical parameters; on the other hand, geodesists would like to ask oceanographers to a-priori determine the Sea Surface Topography, in order to be able to extract from the altimeter data the geoid and the orbit errors to be used in the gravity field modelling. The solution to this dilemma can only be found in a cooperative frame. An integrated model to be used for a single-step treatment of altimetry is probably far to be defined, so at present geodesists and oceanographers must cooperate to obtain step-wise and iterative modelling of the gravity field and of the oceanographic phenomena. This is precisely the reason why the school on Satellite Altimetry was organized on an interdisciplinary basis...

Description / Table of Contents: PREFACE Sedimentation as a Three-Component System describes the most common styles of deposition in marine environments as they relate to sediment composition. Three components, organic matter, carbonate, and siliciclastic sediment, may settle concurrently, but at different rates, intermixing on the sea floor to form a particular sediment composition. A change in the flux of one component is capable of relatively diluting or concentrating the other two components, which can be expressed in the characteristic ratio of organic carbon to carbonate in the resulting sediment. The basic concept of this book is to address organic carbon-carbonate associations in terms of depositional inputs and time spans. In addition, the three-component system describes organic carbon changes related to major facies transitions. Examples include models of the genesis of carbonaceous sediments, with their various laminated to bioturbated lithotypes, and numerical organic carbon prediction. I hope that this book will encourage stimulating discussions and promote a new approach to quantitative stratigraphy...

Description / Table of Contents: INTRODUCTION "The geological history, as expressed by the stratigraphic column, is basically composed of cycles of sedimentation, stratification and magmatism which correlate with relative changes in sea level determined in turn by different types of crustal movements. The classical sequence of stages "transgression - inundation - differentiation - regression - emergence" is believed to reflect the deformation phases of a geotectonic cycle" (Wezel,1988: p.37). The concept of geotectonic cycle is fundamental in geology because it links tectonics with sedimentary processes. According to Wezel (1988) the geotectonic cycle is an expression of cyclic variations in the behavior of the crust; more precisely,it is a geodynamic response to the Earth's variations in the rate of rotation (Mörner,19869 Whyte,1977~ Carey,1976).Based on a global analysis of geotectonic data, synchronous episodes of intense global swelling, governed by cyclically ordered diastrophic processes, were identified (Wezel,1985;1988). The process leading to these swells was termed krikogenesis (Wezel, 1988).It basically consists of not steady, localized, migratory vertical movements linked to mantle diapirism and concentrated in single zones.The overlying crust adjusts itself to mantle motions induced by krikogenesis, with the formation of transient troughs and swells ('touche-de-piano' tectonics).This mechanism was individuated in several areas (Wezel,1988). The history of the Earth is described by six episodes that repeat in the same way in the course of geological time.Their duration progressively decreases:the first cycle has a duration of about 200 million years, the following,younger cycles lasted 150, 115, 65, A5 and 20 m.y. ...

Description / Table of Contents: PREFACE The ocean has always been reluctant to reveal its secrets. Its size and the inaccessibility of its deeper regions have made their safeguard a reasonably simple matter with the result that significant misconceptions persisted for many years. Two of the most widespread of these concerned the featureless nature of the sea floor and the silence of the deep ocean. Underwater acoustics has played a key role in discrediting both and in so doing introduced new and exciting developments in oceanography and geophysics. In the years following World War II, echosounders and subbottom profilers based on new active sonar technology, revealed the true nature of the seafloor topography and led to the major advances represented by plate tectonics. Research driven by the requirements of passive sonar, on the other hand, was to demonstrate that the sea was not silent but was characterised by a complex noise spectrum. Many individual mechanisms and sources ranging from man-made, biological and geophysical activity to the intrinsic noise of the sea itself were found to contribute to this spectrum. A major component, which is the subject of this book, was to remain unrecognised to underwater acoustics until noise measurements could be made effectively at very low frequencies, although its presence had been indicated by seismology long before these measurements were possible. By virtue of its geographical isolation in the Southern Ocean, New Zealand has provided an ideal environment for long-range propagation and ambient noise investigations and numerous studies have been reported. Our interest in the subject of this book was aroused initially in the course of one such experiment in 1966. For the first time it had been possible to extend the recording bandwidth to 1 Hz and the improved performance of this new system was anticipated eagerly. However the main purpose of the experiment was nearly aborted by the appearance of a new and unsuspected noise component at frequencies below 10 Hz. Due primarily to technical limitations in the equipment then available, a subsequent programme, designed to identify the properties and origin of the source more clearly, was not productive and was soon abandoned. An opportunity to revisit the problem arose some 10 years later, when the University of Auckland became involved in a major environmental study in support of the development of an offshore gas field in Cook Strait. The technology then available provided an opportunity to examine afresh the relationship between sea state and the seismo-acoustic response generated. An initial trim demonstrated the potential of the site. Accordingly a long-term programme, involving the parallel measurement of the oceanwave field and acoustic response, was undertaken in a series of student research theses. The data so gathered were of sufficiently high quality to ultimately establish wave-wave interactions as the source of the acoustic effects observed and to identify many of its characteristics. This result was soon to be confirmed by other studies. As the noise data accumulated, however, it became apparent that certain refinements to the theories describing the mechanism were required. Our attempts to provide these refinements have been reported in a number of contributions in recent years. The accounts of these and similar contributions by others have unfortunately appeared in the literature in a somewhat disjointed manner, with the result that the evolution of the subject has not been easy to follow. This book attempts to present a more coherent account of the subject and its development. Most of the early experimental and theoretical results from our group have arisen from two key Ph.D. theses, due to Dr. K.C. Ewans and Dr. C.Y. Wu. The painstaking and careful instrumentation development and data analysis provided by Dr. Ewans were critical to the definitive correlation which we were able to establish between wind field, seastate and the acoustic response so generated. Dr. Wu's thesis presented the first phase of our attempt at the resolution of certain key theoretical issues, which were identified in the course of the experimental programme. Both studies owe much to the support of Shell BP Todd Oil Services Ltd., acting for Maui Development Ltd., and to the University of Auckland. The support of the Electricity Corporation of New Zealand Ltd. during a later experimental investigation of the Southern Ocean wave field is also acknowledged...

Description / Table of Contents: 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...

Description / Table of Contents: PREFACE The aim of this volume is two-fold. At the more pragmatic level, it is to help answer the many questions about the structure of the Pacific continental margin of North America, which have arisen over the years as a result of continuing field mapping and geophysical surveys. The second objective is methodological - to illustrate the irreplaceable role of geological information among the various data sets used in earth-science studies. The need to address these issues became apparent to the author during the several years he spent taking part in geological and geophysical studies on the west coast of Canada. All too often, results of geologic field mapping disagreed with tectonic predictions from too-straightforward local applications of global plate reconstructions, which due to their generality do not always take a full account of specific character of particular regions. To be sure, the global approach has during the last q~/artercentury greatly expanded the vision of geoscientists, previously restricted to continental regions. However, a negative by-product of this expansion has been a decline of attention paid to local information, as tectonic studies have increasingly relied on simply fitting the development of a particular region into this or that prefabricated tectonic template. Direct geological observations have limitations of their own. The observer in most cases deals with products of geologic processes, rather than with the processes themselves. Field mapping provides local information, and many years of effort are needed before a regional overview becomes possible. Geologic mapping is restricted to the ground surface, and even the deepest drillholes cannot sample more than the outermost shell of the Earth. The factual side of geologic mapping is usually limited to determination of rock types and their relationships in areas of exposure. Conclusions about the three-dimensional structure of a region and its evolution are still mostly inferential. Broad incorporation into geological studies of geophysical data, assisted by ever-more-sophisticated modern computers, provides a huge volume of information unobtainable in other ways. Geophysical methods quickly afford regional coverage or images of the Earth's deep interior. Geophysical methods have prompted the application in geological sciences of methodologies borrowed from exact sciences, such as mathematics and physics. Particularly important has been quantitative modeling, which allows a scientist to use the known parameters of a system to predict others. But in taking this approach too far, one encounters a dangerous pitfall. A model is a simplified representation of a natural phenomenon. The quality of this or that representation is relative, and a representation is never perfect. To incorporate all characteristics of a geologic phenomenon, in a parametrized form, into a numerical or physical imitation is impossible. This requires one to rely on simplifying assumptions, and a model is no better than the assumptions at its base. Unrealistic assumptions lead to unrealistic models. When a disagreement arises between model predictions and observations - such as those from geologic field mapping - a modeler may be tempted to downplay the differences or the significance of the offending observations. It becomes tempting to underestimate the role of an experienced geologist as a principal arbiter of the realism of a model. But it is geological data and geological control that provide the ultimate means of testing abstract models. From this methodological position, the present study of the western North American continental margin is organized as follows: 1. Geological information, available from field mapping and drilling, is gathered and summarized. 2. Current geophysical models for this region are considered, with particular attention to their underlying assumptions. 3. The available data, geological and geophysical, are synthesized into an internally consistent geologic-evolution concept. 4. This concept is tested by comparison with direct geological observations from field mapping and drilling. Because most current data sets and models cover northwestern Washington and western British Columbia, particular attention was paid to these areas. Fortunately, these areas contain many keys that help understand the structure of the entire western North American continental margin, which has baffled scientists for decades. The author does not claim to have resolved all these problems, but he does believe he has made a useful contribution to understanding continental-oceanic plate interrelations at this continental margin. Rigidity of lithospheric plates is a critical assumption in current models of plate evolution. The lithophere of a plate is created at spreading centers manifested in the global system of mid-ocean ridges. It moves away from the place of its birth towards boundaries with other plates, with which it can interact in a variety of ways. Some interactions are of strike-slip type, with two plates simply sliding past each other. However, to compensate for the creation of new lithosphere at spreading centers, older lithosphere at some plate boundaries descends into the mantle as it is overriden by other plates. At such plate boundaries lie subduction zones. If both regimes occur along a single plate boundary, the transition between them must be abrupt. Unless it can be tied to a change in orientation of the boundary, it must be associated with a junction of not two, but three different plates. Such a template was used to interpret the structure and tectonic evolution of the western North American continental margin in the late 1960s and thereafter (Atwater, 1970; McManus et al., 1972; Barr and Chase, 1974; Riddihough and Hyndman, 1976). To satisfy the principles of rigid-plate tectonics, both regimes have to exist along this continental margin. Also needed in rigid-plate reconstructions is a plate triple junction somewhere between the areas of proven ongoing subduction (in Oregon and southern Washington) and transform plate motion (along the southeastern Alaska margin; Atwater, 1970; McManus et al., 1972). Such a triple junction has been placed off Queen Charlotte Sound offshore British Columbia (Keen and Hyndman, 1979; Riddihough et al., 1983), where a spreading center has been postulated between the Pacific and Explorer oceanic plates (Hyndman et al. 1979; Riddihough, 1984). Off northern Vancouver Island, a transform boundary between the Explorer and Juan de Fuca oceanic plates has been postulated, but both these plates are assumed to be subducting beneath Vancouver Island (Hyndman et al., 1979; Riddihough and Hyndman, 1989)o With the assumed universality of the rigid-plate model, "broad similarity" has been suggested between the geology of western Oregon and that of western British Columbia, and the Cascadia zone of active subduction has been extended as far north as the mouth of Queen Charlotte Sound (Riddihough, 1979, 1984). An accretionary sedimentary prism (Yorath, 1980) - or even an accretionary complex containing several exotic "terranes" (Davis and Hyndman, 1989) - has been postulated off Vancouver Island. Geological observations onshore and offshore (Shouldice, 1971; Tiffin et al., 1972) have come to be considered too "surficial" to be of major consequence for large-scale tectonic modeling (Yorath et al., 1985a,b; Yorath, 1987). Variants of the principal geophysical model for this area during the last decade (Clowes et al., 1987; Hyndman et alo, 1990; Spence et al. 1991; Yuan et al., 1992; Dehler and Clowes, 1992) have become increasingly distant from geological observations. As new model variants emerged, they were checked for internal consistency, compatibility with neighboring local models and fidelity to the overall assumed tectonic picture. However, detailed geological work continued, and many of its results proved incompatible with the conventional wisdom (Gehrels, 1990; Babcock et al., 1992, 1994; Allan et al., 1993; Lyatsky, 1993a). Importantly, questions arose about the applicability in this region of the conventional, simple rigid-plate assumption, as it was shown to be unable to account for all the geological and geophysical peculiarities in some areas (Carbotte et al., 1989; Allan et al., 1993; Davis and Currie, 1993). New solutions were made necessary by new findings and by rediscovery of forgotten old data (see Lyatsky et al., 1991; Lyatsky, 1993b). Without aiming to resolve all the outstanding debates, tectonic implications of the geologic mapping and drilling results in this region are considered in the following chapters. These results are integrated with geochemical and geophysical data. Interpretations of these data, made by this author and by other workers, are verified by geological observations and by geologically plausible extrapolations from these observations. In searching for solutions consistent with all the information, the author has restricted himself to analyzing continental-crust structures along this continental margin. He believes, however, that future models for the offshore regions of the northeastern Pacific should consider the results obtained herein.