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  • 1985-1989  (517,009)
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  • 1
    facet.materialart.
    Berlin ; Heidelberg : Springer
    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.
    Pages: Online-Ressource (183 Seiten)
    ISBN: 9783540179375
    Language: English
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  • 2
    Description / Table of Contents: PREFACE It is increasingly necessary to develop industrial and hydraulic engineering constructions under unfavourable geological or geotechnical conditions. Furthermore, it becomes more and more important to build effectively and economically and to find optimal solutions for a long-term steady function of the constructions. This emphatically demands exhaustive information on the structural situations and engineering parameters of local site assessments by areal investigations of the sites and the petrophysical parameters in situ. This requires, however, the use of geophysical techniques. During the last two or three decades international applied geophysics has systematically developed new possibilities for site investigations for the determination of petrophysical parameters in situ as well as for observation of the system building and site. As in "New techniques in engineering", geophysical methods make it possible to develop areal models of subsurface conditions of building sites, to quantify relevant engineering parameters in situ, as well as to analyze the longterm behaviour of the buildings, which are influenced by internal or external factors. With regard to the broad spectrum of applied geophysics, there are few methods, that especially favour application in engineering and groundwater studies. These methods are distinguished by a relatively simple measuring technique and good measuring progress, e.g. the geoelectrical self-potential method, the geoelectrical resistivity method as well as a newly developed devices for geothermic measurements. There exist numerous publications, broadly scattered in the technical literature, concerning the theoretical bases and applications of these methods, but until now, there have been only a few meetings to exchange experience and results on an international level. This was the aim of the symposium "Detection of Subsurface Flow Phenomena by Self-Potential/Geoelectrical and Thermometric Methods", held in Karlsruhe from 14-18 March 1988. An outstanding part of the symposioum was represented by the results of a research project, coordinated by the University of Karlsruhe (Department of Geology and Institute of Soil and Rock Mechanics) and the Federal Waterway Engineering and Research Institute (BAW), Karlsruhe. Regarding the subject "Experiments to ascertain the relations between hydraulic potentials in the underground and the geoelectrical and thermic potentials set off by these", the research work took four years. The project was sponsered by the Volkswagen Foundation/Hannover. The goal was to develop and test objective techniques for detecting leakages in dams, locating, demarcating and designating quantitatively inhomogeneous spheres in dams with the aim of detecting damage and subsurface flow phenomena as soon as possible. The symposium consisted of a three-day lecture meeting with about 40 papers and a summarizing respectively closing roundtable discussion, a visit to the laboratories and to the in situ constructions within the area of BAW developed in the frame of the research project. This included a technical excursion to the Rhine-Staustufe Iffezheim with its very impressive waterway constructions and an excursion to the Geophysical Observatory near Schiltach (Black Forest). The Observatory belongs to the Universities of Karlsruhe and Stuttgart. Approximately 80 scientists from 15 countries participated the symposium. They were welcomed by the Rector of the University, Professor Dr. A. Kunle and the representative of the Federal Ministry of Traffic, Dr. G. Schröder. Professor Dr. H. Hötzl elucidated the scientific problems and the economical importance of the project as a speaker of the research group. The following papers dealt with the fundamental aspects of geoelectrical and thermometric measurements, with the theory of these methods, the state and developing ter~dencies concerning devices, data acquisition, processing and interpretation as well as noise effects. It became clear that the solution of the complex scientific-technical problems of waterway constructions and environmental protection requires broad, interdisciplinary cooperation and international collaboration. Thus it would be possible to minimize the personnel, temporal and economic efforts. The intended cooperation of geoscientists, engineering geologists, building engineers and representatives of other disciplines make it possible, not only to exchange experiences and results relating to international problems unsolved until now, but also to determine new guidelines with regard to the scientific organization of further investigations. Thus in order to inform all interested parties of the main topics of the symposium and to advance international cooperation in the future, the present review includes a part of the papers and reports of the excursions recommended by the participants of the meeting, which have been divided into the following topics: - Introduction to engineering-geophysical problems and attempts at their solution; - Geoelectrical self-potential measurements; - Geoelectrical resistivity measurements; - Geothermic measurements; - Case histories; - Some topics of the roundtable discussion; - Reports concerning the excursions. The editors wish to thank very much all those, who contributed to the success of the symposium and to the publication of the present report. Finally they venture the note, that the authors theirselves are responsible for the content of their papers.
    Pages: Online-Ressource (514 Seiten)
    ISBN: 9783540518754
    Language: English
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  • 3
    Description / Table of Contents: PREFACE During the so-called Mid-Cretaceous interval, approximately 100 million years ago, the earth experienced a dynamic phase in its geologic history. Enhanced global tectonic activity resulted in a major rearrangment of the continental plates; accelerated spreading rates induced a first-order sea level highstand; intense off-ridge volcanism contributed to a modeled high atmospheric CO 2 rate; climatic conditions fluctuated; and major changes occurred in biologic evolutionary patterns. With the initiation of a gradual change from an equatorial, east-west directed current-circulation pattern to a regime, dominated by south-north and north-south directed current systems, the earth's internal clock was set for Cenozoic, "modern" times. The Mid-Cretaceous dynamic phase is recorded in a suite of sediments of remarkable similarity around the globe. Shallow-water carbonate platforms drowned on a global scale; widespread sediment-starved, glauconite and phosphate- rich sequences developed; and consequently, pelagic sedimentary regimes "invaded" shelf and epicontinental sea areas. This typical "deepening-upward" pattern is well-documented in Mid-Cretaceous sequences along the northern Tethys margin. Shallow-water carbonates are overlain by condensed glauconitic and phosphatic sediments, which, in turn, are blanketed by pelagic carbonates. In this volume, the example of the western Austrian helvetic Alps, built up of inner and outer shelf sediments deposited along the northern Tethys margin, is used to elucidate the paleoceanographic conditions, under which the Mid-Cretaceous triad of platform carbonates, condensed phosphatic and glauconitic sediments, and pelagic carbonates was formed. In the first part, the evolution of this sequence is traced from the demise of the platform (Aptian) to the return of detritus-dominated deposition (Upper Santonian). The second part includes a discussion of the reconstructed paleoceanographic and tectonic variables, their possible interaction, as well as their influence on sediment properties during this period. Special attention is paid to (1) subsidence behavior of the inner, platform-based shelf and the outer shelf beyond the platform, (2) ammonoid paleobiogeography, (3) the northern tethyan current system and its impact on sediment patterns, (4) the influence of an oxygen minimum zone, (5) sediment bypassing mechanisms on the inner shelf, (6) condensation processes, (7) phosphogenesis, (8) relative sea level changes, (9) genesis and the development of unconformities, (10) tectonic phases and their impact on sediment configuration, (11) drowning of the shallow-water carbonate platform, and (12) "asymmetric" sedimentary cycles. The detailed reconstruction of the development of sedimentary patterns both in time and space in this particular area, and its environmental interpretation, given in this volume, may serve as a contribution to a better understanding of the Mid-Cretaceous dynamic phase in earth's history...
    Pages: Online-Ressource (153 Seiten)
    ISBN: 9783540513599
    Language: English
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  • 4
    facet.materialart.
    Berlin ; Heidelberg : Springer
    Description / Table of Contents: INTRODUCTION The awareness that mankind is able to influence and modify not only the local but also the global climate has led to a strongly growing interest in climate research. Strengthened research activities, which also made use of improved and novel experimental techniques, have yielded a wealth of information on climatic patterns in the past. At the same time, climate modelling has made much progress. While some questions have been answered, new problems have been recognized. One question related to anthropogenio climatic change is about the nature and causes of natural variations, against the background of which man-made changes must be viewed. The contributions to this volume all deal with the variabilitY of climate. Some papers are reviews of the knowledge to a current topic, others have more the character of an original contribution. The obseryational studies cover the range from year-to-year variations up to glacial-interglacial contrast, thereby going from instrumental data to results from proxy records...
    Pages: Online-Ressource (175 Seiten)
    ISBN: 9783540188438
    Language: English
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  • 5
    facet.materialart.
    Berlin ; Heidelberg : Springer
    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...
    Pages: Online-Ressource (229 Seiten)
    ISBN: 9783540139836
    Language: English
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  • 6
    Description / Table of Contents: PREFACE In a densily populated industrialized country, waste disposal must be compatible with the requirements of the environment. This is one of the indispensable requirements to guarantee an effective protection of the environment. In the past years the waste disposal industry has been given increasing attention by the general public as well as the authorities. This confirms the necessity of adapting the quality of waste disposal to the technological standard of the production. While in the past, waste disposal performance was more or less evaluated in terms of short-term costs, there is at present a reorientation in the direction of a science-based waste disposal industry. These new tendencies are taking into account ecological factors as well as the long-term consequences - i.e., for decades and centuries to come - of waste disposal methods. In this light, particular attention is given to the depositing of residues whose utilization does not appear meaningful from an ecological point of view, or would require disproportionate ressources. It is an important concern of the Federal Authorities to encourage the rapid materialization of disposal solutions which can function as ultimate deposits, and which will therefore cause neither water pollution nor gaseous emissions. In view of this goal it is necessary to establish criteria and regulations for the wastes to be deposited as well as for the characteristics of the deposits. This field confronts science with an urgent but rewarding challenge and calls for close collaboration between many different specialized disciplines...
    Pages: Online-Ressource (438 Seiten)
    ISBN: 9783540506942
    Language: English
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  • 7
    facet.materialart.
    Berlin ; Heidelberg : Springer
    Description / Table of Contents: PREFACE During the last few years, evaporites have increasingly been regarded as sediments and not only as chemical precipitates. Especially the intensive study of the Zechstein facies has resulted in a vast amount of observations and interpretations which are of general significance, offering important information to all sedimentologists interested in carbonates and evaporites. It seems therefore useful to introduce the sedimentological approach in a basin where various chemical concepts have been developed. This is the aim of the present volume, and this approach will be recognized by the reader in most of the chapters. The idea of publishing a collection of papers on the Zechstein facies and related rocks found an enthusiastic response, although later some contributors were, for various reasons, unable to meet the deadline. However, the papers submitted cover all major fields and will certainly stimulate further research...
    Pages: Online-Ressource (272 Seiten)
    ISBN: 9783540177104
    Language: English
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  • 8
    facet.materialart.
    Berlin ; Heidelberg : Springer
    Description / Table of Contents: This book is the collection of the Lecture Notes of an International Summer School of Theoretical Geodesy held in Assisi (Italy) from May 23 to June 3 -1988.
    Pages: Online-Ressource (491 Seiten)
    ISBN: 9783540515289
    Language: English
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  • 9
    facet.materialart.
    Basel, Boston, Berlin : Birkhäuser
    Keywords: quiet daily geomagnetic field variations ; lunar variations ; ionospheric dynamo currents ; thermotidal currents
    Pages: Online-Ressource (235 Seiten)
    ISBN: 9783764323387
    Language: English
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  • 10
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