ALBERT

Description / Table of Contents: PREFACE The CERN Accelerator School (CAS) was founded in 1983 with the aim to preserve and disseminate the knowledge accumulated at CERN (European Organization for Nuclear Research) and elsewhere on particle accelerators and storage rings. This is being achieved by means of a biennial programme of basic and advanced courses on general accelerator physics supplemented by specialized and topical courses as well as Workshops. The chapters included in this present volume are taken from one of the specialized courses, Applied Geodesy for Particle Accelerators, held at CERN in April 1986. When construction of the first large accelerators started in the 1950's, it was necessary to use geodetic techniques to ensure precise positioning of the machines' components. Since that time the means employed have constantly evolved in line with technological progress in general, while a number of specific developments - many of them achieved at CERN - have enriched the range of available instruments. These techniques and precision instruments are used for most of the world's accelerators but can also be applied in other areas of industrial geodesy: surveying of civil engineering works and structures, aeronautics, nautical engineering, astronomical radio-interferometers, metrology of large dimensions, studies of deformation, etc. The ever increasing dimensions of new accelerators dictates the use of the best geodetic methods in the search for the greatest precision, such as distance measurements to 10 -7, riqorous evaluation of the local geoid and millimetric exploitation of the Navstar satellites. At the same time, the powerful computer methods now available for solving difficult problems are also applicable at the instrument level where data collection can be automatically checked. Above all, measuring methods and calculations and their results can be integrated into data bases where the collection of technical parameters can be efficiently managed. In order to conserve the logical presentation of the different lectures presented at the CAS school, the chapters presented here have been grouped under four main topics. The first and the fourth deal with spatial and theoretical geodesy, while the second and third are concerned with the work of applied geodesy, especially that carried out at CERN. Readers involved in these subjects will find in the following chapters, if not the complete answer to their problems, at least the beginning of solutions to them.

Description / Table of Contents: INTRODUCTION The evaporite deposits of the Werra district, especially in the Hattorf mining field, are considered a worldwide unique location for the occurence of numerous basalt dikes and magmatic fluid phases fixed in salt rocks. In spite of the great number of studies dealing with the magmatites in the Werra region, previous investigations have rarely attempted more than a predominantly 'qualitative' description of the basaltic rocks and the effects of volcanism on the evaporites (see Chapter 2). The method of interpreting the mineralogical and chemical composition of the evaporites at the basalt contact is based on previous works (KNIPPING 1984; KNIPPING & HERRMANN 1985). This study should contribute to understanding (i) the mechanism of intrusion of the basaltic rnelts and (ii) the metamorphic processes occurring in the evaporites caused by mobile phases during volcanism. Hence, the following methods were applied: The mineralogical and chemical description of the basaltic rocks with recent nomenclature including the possible differences between individual dikes and between surface- and subsurface-exposed basalts. Seven surface and 48 subsurface exposures at the Hattorf mine of Kali & Salz AG were studied. Application of the most recent knowledge on basalt genesis for interpreting observational and experimental results. Studies on the sulfur and carbon isotope distributions of the native sulfur from several subsurface exposures and the enrichments of gases (predominantly CO2) in the evaporites. Calculation of the spatial and temporal temperature distribution in the evaporite rocks following intrusion of the basaltic melts. For purposes of clarity a few of the terms which will be used frequently here will first be defined: basalt - all of the intrusive rocks studied can be assigned mineralogically and chemically to the basalt family in a broader sense. Thus, the terms basaltic rock or, in short, basalt will be used for these rocks. rock salt - instead of the term salt for halitic rocks the term rock salt is used. Besides, the evaporites are generally designated as host rocks (for the basalt dikes) as well. gases - especially in the German literature the term carbon dioxide or carbonic acid (= Kohlensäure) is frequently used for the gases enclosed in the evaporites of the Werra-Fulda district. ACKERMANN et al (1964) found, in addition to carbon dioxide, considerable amounts of nitrogen and minor amounts of methane. In the following therefore the terms gas mixture or gas will be used. The various basalt dikes found in the Hattorf mining field are described here in terms of their mineralogy and geochemistry for the first time. In doing so it is necessary to number them from east to west. To avoid confusion with older numerations (e.g. SIEMENS 1971) the various dike systems are designated by capital letters (A to P).

Description / Table of Contents: PREFACE The Lower Triassic Buntsandstein in Middle Europe which originated in mainly continental fluvla] environment in the Mid-European Triassic Basin is a famous terrestrial red bed sequence that is discussed in the geological literature since more than 200 years. Much of the earlier work had been devoted to stratigraphical, palaeogeographical and petrographical problemsof the Buntsandstein. The sedimentological analysis and deposltional modelling in the German-type facies, however, is the youngest branch of Buntsandstein investigation and started only a few decades ago. During the last ten years when I began to concentrate on the interpretation of the genesis of the Buntsandstein, much work has been carried out and has already been documented in numerous papers that focussed on various aspects of sedimentology, particularly on reconstruction of fluvial and aeolian depositional mechanisms, significance of palaeosols, importance of fluvial conglomerates, palaeoecology of the fossils, interdisciplinary sedimentology, diagenesis of heavy minerals and origin of the red colour. A summary of the present knowledge in the western part of the German Basin is given in a compilation of regional articles together with general discussions and comparative contributions and especially with an extensive colour photographic documentation in an earlier book (reference on p. 12). In the last few years when more and more material became available not only from the Buntsandstein s. str. (Lower Triassic Scythian) in the Mid-European Triassic Basin, but also from correlative sequences in adjoining areas and even older or younger series of similar facies and origin, it became more and more evident that a synthesis of the state of the art would be necessary, if not inevitably for outlining the general frame and illustrating the diversification of facies associations in numerous temporal and spatial scales. That is why I decided to edit an international proceedings volume on the Buntsandstein which is to compile contributions from many regions and different stratigraphic units with emphasis on various aspects of fluvia] sedi~ntation, but stressing also the importance of the distribution of associated environments such as aeolian dunes and calcrete palaeosols. In spite of my own enthusiasm for the Buntsandstein continental red bed formation (the Lower Triassic red rocks seem to have a very special flavour for being so attractive for me) and regardless of the expansion of my investigations from my original Eife] area (where I learnt how to assess the facies assoCiations in terms of depositional modelling and where I collected an enormous amount of data that served as a valuable base for the production of various case studies which were published during the last years) to several other regions, it was without any doubt that it would not be possible for me alone to finish such an overregional proceedings book within a reasonable time, but that I had to beg various colleagues for their collaboration by writing papers on the Buntsandstein in their investigated areas for this volume. Although the response to my first and second circulars soon showed that it would not be possible to publish a compilation of articles from almost all the studied regions, formations and aspects within a reasonable time with avoiding too much delay of appearance for early contributors, I am very happy that finally many colleagues provided me with papers from almost all the countries in Europe where Buntsandstein is cropping out at the surface. In spite of the tremendous editorial work which was necessary to polish the English, to improve the contents of text and drawings and to put the sequence of papers into a general stream line, I would like to thank all my colleagues who contributed to this volume for their support of the project and particularly for their understanding of my editorial task, especially in case of my frequently serious intervention into their early manuscripts and illustrations. Looking for a publisher in the early stages of planning the volume, I found immediately support by Dr. W. Engel (Department of Geological Sciences of the Springer- Verlag) who generously offered me to take the book into the newly founded series "Lecture Notes in Earth Sciences". From the beginning of organization, writing and editing, I appreciated very much the close cooperation with Dr. Engel who always had an ear for my problems and gave me the necessary freedom to finish the volume along the lines of my intention. Although the preparation of the camera-ready manuscript leaves nearly all the work and responsibility with the author, I am especially grateful to Dr. Engel for his guarantee of almost immediate publication after receipt of the final manuscript which allowed me to polish and incorporate latest ideas up to the very terminal moment. Writing on a subject like the Buntsandstein which has proven to be considerably diversified in terms of sedimentary processes and depositional mechanisms, it became soon apparent that a full discussion along my original intention would easily end up with several thousands of pages in size and would consume much more than a few years. Having already rePeatedly experienced in the past that during course of incorporation of nearly all the relevant literature, the reference l i s t of the final paper is often longer than the whole first draft of the article after one or two years collection of data and ideas, there was no other way than to decide to keep the bibliography short. In order to restrict the book to an economical frame and not to frighten the readership to death, but especially to avoid drowning of the red line through the volume, many contributions had to be written as summary presentations without detailed discussion of the literature. Speaking particularly for the articles that have been written by myself either alone or together with friends, I can assure that this is by no means the result of proud neglectance of other works, but only the necessity of streamlining of the book, and that much of the detailed discussion of comparative examples from the literature has to be done in subsequent special papers. It is impossible to acRnowledge all the people that helped me to arrive at the present goal. Special merits, however, deserve those who stimulated my interest for the Buntsandstein. I am especially indebted to Prof. Dr. G. Fuchs (Landessammlungen fur Naturkunde, Karlsruhe) who proposed me ten years ago to work on the Eifel Buntsandstein for my M.Sc. Thesis, and who later supervised together with Prof. Dr. W. Dachroth (Department of Geology and Palaeontology, University of Heidelberg) the preparation of my Ph.D. Thesis. The good luck of the former to choose the Eifel for me as a starting region (which later proved to have a key position for approaching the evolution of fluvial sedimentation in many other Buntsandstein areas), and the earlier investigations of the latter (although largely unpublished and even only briefly touched in his contribution to this volume) triggered my love of the Buntsandstein which has reached a preliminary climax with the present book. It is my pleasure to dedicate this volume to my two former supervisors with very many thanks for their support and in honour of their merit to have lighted the fire. It is my sincere wish to acknowledge again all the people who contributed with articles to this volume for their help to prepare this summary of the state of the art of Buntsandstein fluvial sedimento]og~y. I also want to sincerely thank all friends and colleagues who supplied ideas and facts in oral or written form and who guided me in the field during course of my comparative investigations that helped me considerably in proceeding with the interpretation of the Buntsandstein. Thanks are also due to Helmut Mader (my father) and Martha Herrmann (my aunt) for their support. I am further indebted to those who have been involved in the various technical aspects of the preparation of the manuscript from the beginning of word processor typesetting of the text and reprography of the illustrations to the final printing. I do hope that the compilation of articles on fluvial aspects of the Buntsandstein in this book will stimulate the interest of many people in the topic of sedimentological modelling of terrestrial red bed sequences and will internationally highlight the position of the Buntsandstein as an extraordinarily attractive case history of fluvial deposition.

Description / Table of Contents: OPENING ADDRESS On behalf of the Local Organizing Committee, I welcome you all to the first International Workshop on GPS-techniques in surveying and geodesy held at this university. This workshop is designed to bring together experts from various countries and also scientists who carry out, analyze and interpret such measurements with those who work on instrumental and theoretical problems. The workshop focuses hereby on high-precision applications with emphasis on monitoring time-dependent phenomena such as those relevant to geodynamics as well as men-made constructions as those in civil engineering and similar fields. It is astonishing to see how, in spite of all earlier satellite work over the last two decades, GPS-methods became so fast a relevant new technology, in its proper sense, in modern geodesy and surveying besides VLBI and Satellite Laser Ranging (SLR). With the recent development of new dual-frequency receivers the role of GPS-procedures in monitoring large-scale phenomena over big distances will still expand; and the application of kinematical GPS-approaches is of utmost interest in solving high-precision problems. It is indeed fascinating to realize how GPS-methods have become in such a short time a surprisingly efficient and effective, this means : fast, precise and easy to apply, tool which is able to replace already now, after a few years of existence and with an incomplete set of a few out of the 18 satellites (of the final stage), at least partially some expensive, slow and cumbersome classical surveying methods. On the other hand, it cannot be overemphasized that GPS-procedures are still at their beginning and the full spectrum of their capabilities still has to be explored. In Europe, for example, where excellent classical surveying systems do exist the situation is quite different from the situation in other countries such as Canada or the USA. Even within Europe the application types of GPS-methods will vary; for example, in Norway the situation is quite different from central European countries. It is often forgotten, that together with GPS we will have to introduce new concepts and a new thinking in combination with other modern satellite procedures. GPS itself can resolve only a small part of the problems to be solved by modern geodesy but it will open the way to a great variety of new applications and capabilities. Modern global tectonics is just one of the new disciplines of high interest and great practical impact. I could continue in citing other similarly important new fields. GPS is, however, of special importance because it replaces old technologies and fills gaps where modern and efficient tools are most needed. Consequently, also the optimal combination of GPS-methods with new auxiliary and also classical high-precision techniques is of great importance, mainly under the european conditions outlined above. Moreover, the real-time or almost-real-time use of GPS in combination with photogrammetry, inertial geodesy, gravity gradiometry or even classical surveying is of substantial interest. It is indeed important to realize the new concepts in modern satellite and space methods and I, therefore, spoke above of a new "technology" which should be optimally developed as there is a worldwide need of such capabilities and tools. In view of the few active NAVSTAR-satellites in sky in 1988 this is perhaps not the best year for GPS-applications but the right time for a review of the experience gained until now and using it as a base for the planning of the future...

Description / Table of Contents: INTRODUCTION In the context of evolutionary studies, it is the privilege of paleontologists to trace the actual course of evolutionary change over time spans that are adequate for such a slow process. At the same time it is their crux that they can not always hope to do this with the resolution necessary to reveal the causal relationships involved. The Tübingen Sonderforschungsbereich 53, "Palökologie", was primarily geared to study the interrelationships between organisms and environments in the fossil record. As is pointed out in this volume, such an approach will necessarily emphasize the static aspect of this relationship, all the more since this is what we need for the practical purposes of facies recognition. This was clone during a time interval of thirteen years at the level of individual species and taxonomic groups ("Konstruktions-Morphologie"), of characteristic facies complexes ("Fossil-Lagerstätten") and of assemblages ("Fossil- VergeseIlschaftungen") with the aim to recognize general patterns that persist in spite of the historical and evolutionary changes in the biosphere. But as our project came closer to its end, the possible causal relationships between physical and evolutionary changes became more tangible. This trend is expressed by symposia devoted to the biological effects of long term tectonic changes (KULLMANN & SCHÖNENBERG, eds., 1983) and of short term physical events (EINSELE & SEILACHER, eds., 1982). But in retrospect it appears that the time scales of the environmental changes chosen were either too large or too small to reveal the mechanisms of evolutionary response. The present volume is the outcome of a symposium of the projects B 20 ("Bankungsrhythmen in sedimentologischer, ökologischer und diagenetischer Sicht", directed by U. BAYER), D 40 ("Analoge Gehäuse-Aberrationen bei Ammonoideen", directed by J. WIEDMANN) and D 60 ("Substratwechsel im marinen Benthos", directed by A. SEILACHER) in September, 1983. tt addresses environmental changes at time scales large enough to produce more than a local ecological response and short enough to observe evolutionary and/or migratory changes at the species and genus levels. It also focusses on basins which by various degrees of isolation provided suitable sites for "evolutionary experiments", such as lakes and marginal epicontinental basins. In a way, this book is a successor of the previous one on "Cyclic and event stratification" (EINSELE & SEILACHER, eds., 1982). Small scale cycles and events are the 'primitives' of a sedimentary sequence, the lowermost scale from which it can be deciphered. However, medium and long term physical cycles commonly impress sedimentological and lithological trends on the stratigraphic column which are accompanied by faunal replacements and cycles. But since sedimentation is controlled both by physical and biological processes, which are intercorrelated in complicated ways, we also need to decode the stratigraphic text. In this effort, paleontological and sedimentological interpretation must go hand in hand. On the 'megascale' of global sea-level changes faunal and species evolution is triggered by opening and closing of migration pathways, sometimes providing us with malor biostratigraphic boundaries. As it turns out, however, integrated research and the choice of suitable scales do not free us from problems of resolution. Thus our inability to distinguish local speciation from ecophenotypic modification and from immigration in the fossil record excludes definite evolutionary answers even in well studied cases. Nevertheless we hope that this approach opens a fruitful discussion, in which stratigraphy, systematic paleontology and paleoecology will be reconciled in a concerted effort to eventually understand the evolutionary mechanisms of our biosphere.

Description / Table of Contents: INTRODUCTION Theoretical modelling and the use of mathematical methods are presently gaining in importance since progress in both geology and mathematics offers new possibilities to combine both fields. Most geological problems are inherently geometrical and morphological, and, therefore, amenable to a classification of forms from a "Gestalt point of view". Geometrical objects have to possess an inherent stability in order to preserve their essential quality under slight deformations. Otherwise, we could hardly conceive of them or describe them, and today's observation would not reproduce yesterday's result (DANGELMAYR & GÜTTINGER, 1982). This principle has become known as "structural stability" (THOM, 1975), i.e. the persistence of a phenomenon under all allowed perturbations. Stability is also, of course, an assumption of classical Newtonian physics, which is essentially the theory of various kinds of smooth behavior (POSTON &STEWART, 1978). However, things sometimes "jump". A new species with a different morphology appears suddenly in the paleontological record (EI.DREDGE & GOULD, 1972), a fault develops, a landslide moves, a computer program becomes unstable with a certain data configuration, etc. It is, surprisingly, the topological approach which permits the study of a broad range of such phenomena in a coherent manner (POSTON & STEWART, 1978; LU, 1976; STEWART, 1982). The universal singularities and bifurcation processes derived from the concept of structural stabiIity determine the spontaneous formation of qualitatively similar spatio-temporal structures in systems of various geneses exhibiting critical behavior (DANGELMAYR & GÜTTINGER, 1982; THOM, 1975; POSTON & STEWART, 1978; GÜTTINGER & EIKEMEIER, t979; STEWART, 1981). In addition, this return to a "geometrization of phenomena"-- after decades of algorithmization-- comes much closer to the geologist's intuitive geometric reasoning. It is the aim of this study to elucidate, by examples, how the qualitative geometrical approach allows one to classify forms and to control the behavior of complex computer algorithms...

Description / Table of Contents: INTRODUCTION Over the past 18 years the author and several colleagues have developed a mathematical model designed to predict the propagation characteristics of acoustic waves in marine sediments. The model is based on the classical work of Maurice Biot who developed a comprehensive theory for the mechanics of porous, deformable media in a series of papers spanning the time period from 1941 to 1973. Since our objective was to develop a practical working model that could be used as a guide in planning and interpreting experimental work, we began with the simplest possible form of the model and added various complexities only as they were needed to explain new variations in the data that were obtained. Thus the number of material parameters that had to be measured or assumed at any stage in the development of the model was kept to a minimum. Since the first version of the model was introduced in 1970, we have published over twenty technical papers covering various stages of its development and many papers have been published by colleagues who have utilized our work in various ways. This monograph is an attempt to summarize the development and use of the model to date. Acoustic waves in ocean sediments may be considered as a limiting case in the more general category of mechanical waves that can propagate in fluid-saturated porous media. The general problem of wave motion in this kind of material has been studied extensively over the past thirty years by engineers, geophysicists and acousticians for a variety of reasons. In some cases, interest is focused on low-frequency waves of rather large amplitude, such as those that arise near the source of an earthquake or near a building housing heavy, vibrating machinery. At other times, the main interest is in waves of low frequency and amplitude that have traversed long distances through the sediment. In still another category, high-frequency waves that are able to resolve thin layering and other fine structural details are of interest in studying near-bottom sediments. Thus the full spread of frequency and amplitude has been studied for geological materials ranging from soft, unconsolidated sediments to rock. Because of the almost limitless combinations of different types of sediment, stratification and structure, accurate mathematical description of the wave field produced by a particular source can be constructed only if accurate descriptions of the acoustic properties of individual components can be specified. These properties depend on the geological history of the sediment deposit, on the frequency content of the wave field and on a number of other factors that depend on the environment in situ. A survey of the literature suggests that there are a number of parameters that play principal roles in controlling the dynamic response of saturated sediments...

Description / Table of Contents: This volume contains the contributions which have been presented at the 5. ALFRED WEGENER-Conference , held in Göttingen, Federal Republic of Germany, 21 - 24 May 1986. This conference was the first international meeting of the IGCP Project 216 :"global biological events in earth history". The aim of the conference was, to discuss (a) the state-of-the-art in respect to the recognition of bio-events and to the analysis of their causes (b) the presentation of new data (c) the strategies which are needed for further research, carried out in the international cooperation programme of Project 216. It was intended to achieve with these discussions a more critical approach to the problems of global bio-events.

Description / Table of Contents: Biolaminated deposits, produced by microbial communities, were studied in modern peritidal environments and in the rock record. The term microbial, mat refers to modern, the term stromatolite to ancient analogs. The term biolaminated deposits was used to encompass both microbial mats and stromatolites. Microbial mat environments studied are the Gavish Sabkha, the Solar Lake, both hypersaline back-barrier systems at the Gulf of Aqaba, Sinai Peninsula, and the "Farbstreifen-Sandwatt" (versicolored sandy tidal flats) on Mellum, an island in the estuary embayment of the southern North Sea coast. Three facies-relevant categories were distinguished: (i) the mat-forming microbiota, (2) environmental conditions controlling mat types and lithology, (3) bioturbation and grazing. Cyanobacteria account for biogenic sediment accretion in all cases studied. Three major groups occur: filamentous cyanobacteria, coccoid unicells with binary fission and those with multiple fission. In the presence of these groups the following mat types evolve: (i) continuously flat (stratiform) L~-laminae (occur in all environments studied); (2) translucent, vertically extended Lv-laminae (only Gavish Sabkha and Solar Lake); (3) nodular granules (only Gavish Sabkha). Basically, the development of mats is controlled by moisture. Thus high-lying parts where the groundwater table runs more than 40 cm below surface are bare of mats. These are: The circular slope and elevated center of the Gavish Sabkha, the shorelines of the Solar Lake and the episodically flooded upper supratidal zone of Mellum Island. The following situations of water supply were found to stimulate mat growth: (i) Capillary movement of groundwater to exposed surfaces, (2) shallowest calm water, both realized in the Gavish Sabkha and the Solar Lake. On Mellum Island, mats form in the lower supratidal zone, which is flooded in the spring tide cycle and wetted during low tide by capillary groundwater. Salinity is almost that of normal seawater, whereas in the Solar Lake, it ranges from 45 °/oo to 180 °/oo and in the Gavish Sabkha, it reaches more than 300 °/oo. Salinity increase is correlated with rising concentrations of magnesium and sulfate ions. In the Gavish Sabkha, episodic sheetfloods cause high-rate sedimentation which is accidental to the living mats. Episodic low-rate sedimentation stimulates the mats to grow through the freshly deposited sediment layer. This occurs predominantly on Mellum Island due to eolian transport. Within the Gavish Sabkha, mineralogy of sediments, community structures, standing crops, redox potentials and pH are highly correlative to the increasing evenness in moisture supply which is realized by the inclination of the system below mean sea level. These conditions bring about a lateral sequence of facies types which include (I) siliciclastic biolaminites at the coastal bar base, (2) nodular to biolaminoid carbonates at saline mud flats, (3) regularly stratified stromatolitic carbonates with ooids and oncoids within the hypersaline lagoon, (4) biolaminated sulfate towardthe elevated center. High-magnesium calcite in facies type 3 precipitates around decaying organic matter and forms also the ooids and oncoids. These occur predominantly within hydroplastic Lv-laminae which provide numerous nucleation centers. Within the Solar Lake, facies type 3 (stromatolitic carbonates with ooids and oncoids) is most important, and grows to extraordinary thickness at the lake's shelf. The regular alternation of dark and light laminae results from seasonally oscillating water depths. These conditions couple back over changing light and salinity intensities to changing dominance structures of mat-building communities. Increasing salinity correlates with decreasing water depth and accounts for the relative abundance of coccoid unicells and diatoms, both active producers of extracellular slimes (Lv-laminae). Water depths locally or temporarily increased favor surface colonization by Mic~ocoleu8 chthonoplastes (Lh-laminae). The biolaminated deposits of the versicolored tidal flats on Mellum Island are similar to facies type 1 of the Gavish Sabkha (siliciclastic biolaminites). Differences exist in the lithology: Sediments upon or through which the mats on Mellum Island grow are made up of clean sand. The grains originate predominantly from re-worked glacial sediments and are rounded to well rounded. By contrast, the strong angularity of siliciclastic grains in the Gavish Sabkha clearly shows their status as primary weathering products. In all environments studied, insects play a significant role. Mainly salt beetles contribute to the lebensspuren spectrum. There is no indication that burrowing and grazing beetles and dipterans are detrimental to the growing mat systems. According to the marine fauna, two distributional barriers exist: (i) physical and (2) biogeochemical factors. Physical barriers are (a) hypersalinity and barrier-closing, which restrict the marine fauna in the Gavish Sabkha and the Solar Lake to a few species, mainly meiofaunal elements such as ostracods and copepods. Only in the Gavish Sabkha, one marine gastropod species occurs which colonizes mud flats of lower salinity. A salinity barrier of about 70 °/oo separates the gastropod habitats from the zones of growing mats. Under reduced salinity, the snails are able to destroy the microbial mats completely. (b) Decreasing regularity of flooding in the microbial mat environment of Mellum Island excludes intertidal deformative burrowers such as cockles and lugworms. However, locally the mats are pierced by numerous dwelling traces. These stem from small polychaetes and amphipod crustaceans which are able to spread over the intertidal-supratidal boundary and settle up to the MHWS-Ievel. Biogeochemical barriers are oxygen depletion within the sediments, high ammonia and sulfide contents, which generate through bacterial break-down of organic matter. Within the highly productive mats of Mic~ocoleu8 chthonoplastes on Mellum Island, dwelling traces of marine polychaetes and amphipod crustaceans disappear due to these conditions. The name of the mat-forming species, Microcoleus chthonoplastes, indicates its capacity to form "soils" (Greek chthonos). While lithology is not altered, the presence of Mic~ocoleu8 mats leads to a habitat change which excludes trace-making "arenophile" invertebrate species and favors "chthonophile" species which do not leave traces. Stromatolitic microstructures studied in rock specimens were interpreted using modern analogs: Microcolumnar buildups in Precambrian stromatolites, ooids and oncoids were compared with those of modern microbial mats. The nodular to biolaminoid facies type found in the Gavish Sabkha was suggested to be an analog to the Plattendolomite facies of Permian Zechstein, North Poland. Studies of the Lower Jurassic ironstone of Lorraine clearly indicate that fungi have been involved in the formation of stromatolites, ooids and oncoids. In conclusion, the comparative study of microstructures in microbial mats and stromatolites reveals a better understanding in both fields. In many cases, it was geology which first revealed the similarity of recent forms to those ancient ones and consequently encouraged research into them.

Description / Table of Contents: INTRODUCTION Sediments are increasingly recognized as both a carrier and a possible source of contaminants in aquatic systems, and these materials may also affect groundwater quality and agricultural products when disposed on land. Contaminants are not necessarily fixed permanently by the sediment, but may be recycled via biological and chemical agents both within the sedimentary compartment and the water column. Bioaccumulation and food chain transfer may be strongly affected by sediment-associated proportions of pollutants. Benthic organisms, in particular, have direct contact with sediment, and the contaminant level in the sediment may have greater impact on their survival than do aqueous concentrations. Following the findings of positive correlations between liver lesions in English Sole and concentrations of certain aromatic hydrocarbons in Puget Sound (Washington) sediment, it can be suspected that such substrates may also be responsible for a host of other serious and presently unrecognized changes at both the organismal and ecosystem levels (Malins et al., 1984). Modern research on particle-bound contaminants probably originated with the idea that sediments reflect the biological, chemical and physical conditions in a water body (Züllig, 1956). Based on this concept the historical evolution of limnological parameters could be traced back from the study of vertical sediment profiles. In fact, already early in this century Nipkow (1920) suggested that the alternative sequence of layers in a sediment core from Lake Zürich might be related to variations in the trophic status of the lake system. During the following decades of limnological research on eutrophication problems sediment aspects were playing only a marginal role, until it was recognized that recycling from bottom deposits can be a significant factor in the nutrient budget of an aquatic system. Similarly, in the next global environmental issue, the acidification of inland waters sediment-related research only became gradually involved. Here too, it is now accepted that particle-interactions can affect aquatic ecosystems, e.g. by enhancing the mobility of toxic metals. In contrast to the eutrophication and acidification problems, research on toxic chemicals has included sediments aspects from its beginning: Artificial radionuclides in the Columbia and Clinch Rivers in the early sixties (Sayre et al., 1963); in the late sixties heavy metals in the Rhine River system (De Groot, 1966) and methyl mercury (Jensen & Jerne- 16v, 1967) at Minamata Bay in Japan, in Swedish lakes, in Alpine Lakes, Laurentian Great Lakes and in the Wabigoon River system in Canada; organochlorine insecticides and PCBs in Lakes St. Clair and Erie during the seventies (Frank et al., 1977); chlorobenzenes and TCDDs in the Niagara River system and Lake Ontario in the early eighties (Oliver & Nicol, 1982; Smith et al., 1983). In the present lecture notes, following the description of priority pollutants related to sedimentary phases (Chapter 2), four aspects will be covered, which in an overlapping succession also reflect the development of knowledge in particle-associated pollutants during the past twenty-five years: - the identification, surveillance, monitoring and control of sources and distribution of pollutants (Chapter 3); - the evaluation of solid/solution relations of contaminants in surface waters (Chapter 4); - the study of in-situ processes and mechanisms in pollutant transfer in various compartments of the aquatic ecosystems (Chapter 5);- The assessment of the envlroD-mental impact of particle-bound contaminants, i.e. the development of sediment quality criteria (Chapter 6). A final chapter will focus on practical aspects with contaminated sediments. Available technologies will be described as well as future perspectives for the management of dredged materials. Here too, validity of remedial measures can only be assessed by integrated, multidisciplinary research. In the view of the growing information on the present subject and owing to the limitations in the framework of this monography, the reader is referred to additional selected bibliography, which is attached at the end of this Chapter i. Additional information on the more recent publications on contaminated sediments is given in the annual review volume of the Journal of the Water Pollution Control Federation, June edition.