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  • 1
    Electronic Resource
    Electronic Resource
    Lateral variations in sediment composition and bedding in Middle Triassic interplatform basins (Buchenstein Formation, southern Alps, Italy) (2003)
    Oxford, UK : Blackwell Science Ltd
    Sedimentology 50 (2003), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Hemipelagic deposits are widespread in Triassic sequences of the Alpine belt and provide important data for stratigraphy and the study of bedding rhythms. The area of the western and central Dolomites of northern Italy escaped strong alpidic deformation and preserves such deposits in their original palaeogeographic setting. The Buchenstein Formation, the object of this study, was deposited in up to 1000 m deep, Middle Triassic interplatform basins, which extend over an area of 500 km2 within the Dolomites. Excellent outcrops and volcaniclastic markers allow a detailed correlation of the formation in both laminated (anoxic) and bioturbated facies down to a bed scale, and show its relationship to coeval carbonate platforms. Correlation of lithostratigraphically well-constrained intervals in the bioturbated facies reveal that lateral thickening and thinning of the deposits depends on the amount of shallow-water debris in the succession and is a function of the distance to coeval carbonate platform sources. In the laminated background deposit, thickness variations in limestones and marls parallel the thickness variations in ash layers, and were caused by local redeposition of sediment on the basin floor. Lateral persistence of laminae indicates that bottom currents were weak in the Buchenstein basin, but were able to redeposit mud in a significant way. In the area around Seceda and Geisler (western Dolomites), a lateral transition from dark-grey laminated to grey bioturbated to red bioturbated facies is observed, which is probably linked to local relief with different oxygenation conditions on the sea floor. A comparison shows that decimetre-scale bedding is preserved in all facies types and that the bedding rhythm is partly the result of different cementation of the sediment during early diagenesis. Correlation of individual layers in the bioturbated facies reveals that beds are thicker and enriched in lime mud in the western part of the basin, and decrease in thickness and contain less micrite towards the east, further away from the main shallow-water areas. Nearslope calciturbidites change gradually from distinct layers into lateral arrays of micrite nodules and bands further out in the basin. These observations point to a platform source of lime mud in the Buchenstein basin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3091.2003.00499.x
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  • 2
    Electronic Resource
    Electronic Resource
    Morphology and curvature of delta slopes in Swiss lakes: lessons for the interpretation of clinoforms in seismic data (2001)
    Oxford UK : Blackwell Science Ltd
    Sedimentology 48 (2001), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Seismic surveys were conducted and bathymetric data obtained from four alpine lakes in Switzerland. The curvature of the delta slopes was analysed with mathematical equations. Linear or exponential profiles are observed, representing planar or concave morphologies respectively. Planar profiles are interpreted to represent sediment that rests at the angle-of-repose. The slope angle of these profiles shows a correlation with sediment calibre. Exponential profiles do not show a clear correlation between sediment calibre and slope angle; they do not rest at the angle-of-repose, and different kinds of sediment can rest at the same slope angle. At the transition from lower slope to toe- of-slope, the exponential equation fails to predict the present-day morphology. The toe-of-slope lies above the predicted trend. This is attributed to a drastic increase in turbidite deposition that provides additional sediment and raises the basin-floor profile above the predicted trend. The breaks between delta plain and slope are sharp, reflecting an abrupt change from transport by river flow and waves to gravity-driven transport. In these lakes, the base-level fluctuations relative to supply are small and insufficient to alter this sharp topographic break. The absence of sigmoidal profiles on the Swiss deltas is attributed to the high rate of progradation coupled with small fluctuations in base level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3091.2001.00389.x
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  • 3
    Electronic Resource
    Electronic Resource
    Carbonate platform-to-basin correlation by means of grain-composition logs: an example from the Vercors (Cretaceous, SE France) (1999)
    Oxford UK : Blackwell Science Ltd
    Sedimentology 46 (1999), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Quantitative logs of grain composition for several sections of platform top and flank of the Vercors carbonate platform (Early Cretaceous, SE France) provide platform-to-basin correlation with a resolution of a few metres over an area of 70 km2. Grain composition was determined by point-counting thin sections. Point-count groups that characterize palaeoenvironmental realms (i.e. open sea, platform margin) were defined for the platform–basin trajectory. Grain-composition logs revealed marked peaks in the number of open-sea biota and peaks in ooid abundance. The peaks in open-sea biota correspond to back-stepping intervals and deepening upward facies successions at the platform margin. These peaks probably relate to incipient drowning of the platform and may be used to delineate marine-flooding surface-bounded sequences. Peaks in ooid occurrence show no relationship with the progradation, aggradation or retreat of the platform. Apparently, the oolitic sands were not part of a facies tract that shifted up and down the platform. Instead, they represent a depositional mode that was either on or off. Times of prolific ooid production and shedding probably occurred during wide but shallow submergence of the platform, accompanied by suitable water chemistry. Peaks in both ooids and open-sea biota are excellent markers for platform-to-basin correlation, as they are recorded in successions on the platform top as well as on the flank. Altogether, the grain-composition logs show that each of the lithologically rather similar platform tongues of the Vercors has a unique signature or compositional fingerprint. These compositional fingerprints are most helpful in evaluating the lateral extent of different stratigraphic units. In outcrops of the Vercors platform, the physical tracing of bedding surfaces delineate wedges of toe-of-slope sediments that show a conspicuous thinning towards the platform. However, our correlation shows that these sediment bodies are not truly basin-restricted wedges but have a platform top equivalent. This implies that these units were, at least partly, deposited during high stands of sea level that flooded the platform.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3091.1999.00209.x
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  • 4
    Electronic Resource
    Electronic Resource
    Identifying causes of ground-penetrating radar reflections using time-domain reflectometry and sedimentological analyses (2000)
    Oxford UK : Blackwell Science Ltd
    Sedimentology 47 (2000), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Ground-penetrating radar (GPR) is a geophysical technique widely used to study the shallow subsurface and identify various sediment features that reflect electromagnetic waves. However, little is known about the exact cause of GPR reflections because few studies have coupled wave theory to petrophysical data. In this study, a 100- and 200-MHz GPR survey was conducted on aeolian deposits in a quarry. Time-domain reflectometry (TDR) was used to obtain detailed information on the product of relative permittivity (ɛr) and relative magnetic permeability (μr), which mainly controls the GPR contrast parameter in the subsurface. Combining TDR data and lacquer peels from the quarry wall allowed the identification of various relationships between sediment characteristics and ɛrμr. Synthetic radar traces, constructed using the TDR logs and sedimentological data from the lacquer peels, were compared with the actual GPR sections. Numerous peaks in ɛrμr, which are superimposed on a baseline value of 4 for dry sand, are caused by potential GPR reflectors. These increases in ɛrμr coincide with the presence of either organic material, having a higher water content and relative permittivity than the surrounding sediment, or iron oxide bands, enhancing relative magnetic permeability and causing water to stagnate on top of them. Sedimentary structures, as reflected in textural change, only result in possible GPR reflections when the volumetric water content exceeds 0·055. The synthetic radar traces provide an improved insight into the behaviour of radar waves and show that GPR results may be ambiguous because of multiples and interference.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3091.2000.00304.x
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  • 5
    Electronic Resource
    Electronic Resource
    Computer simulation of reef growth (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 39 (1992), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Light is one of the major controls on reef growth and carbonate production. The growth of present reef builders depends largely upon the amount of light available for photosynthesis. As light decreases with water depth, so does reef growth.The computer model presented extends this principle by combining two functions, one for photosynthesis and the other for the extinction of light in water. The model is used to simulate the growth of Alacran Reef, Mexico, two reefs of the Great Barrier Reef and the reefs of the windward platform of St Croix, US Virgin Islands. The model also gives an accurate simulation of the growth of fore-reef walls in Belize, in agreement with the accretion hypothesis developed for this feature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3091.1992.tb02130.x
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  • 6
    Electronic Resource
    Electronic Resource
    Clastic sediments associated with radiolarites (Tauglboden—Schichten, Upper Jurassic, Eastern Alps) (1973)
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 20 (1973), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: During the early Upper Jurassic, widespread deep-sea radiolarites were deposited in most parts of the Northern Limestone Alps. In the formation described (Tauglboden-Schichten), these pelagic sediments interfinger with local-source clastic material. Depending on the topography and the kind of material, either slides and slumps, mudflows, grain flows or turbidity currents operated and formed slump-folded beds, mud-flow breccias, fluxoturbidites or turbidites.A breccia had been traced over an area of 20 km2. Its variation is described in terms of lithological columns, bed thicknesses, maximum grain sizes and grain orientations. It forms a tongue-shaped body, which was probably a part of a submarine fan. The fluxoturbidites of the proximal area grade distally on three sides into turbidites within 3–5 km.The clastic material consists of marls and limestones of Rhaetian and Jurassic age. It was probably derived from a tectonically uplifted palaeo-high by an interplay of tectonics and gravity. The clastics were deposited on submarine fans bordering this high.In its lithology the formation closely resembles certain marginal facies of flysch troughs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3091.1973.tb01607.x
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  • 7
    Electronic Resource
    Electronic Resource
    Compositional variations in calciturbidites due to sea-level fluctuations, late Quaternary, Bahamas (1989)
    Springer
    International journal of earth sciences 78 (1989), S. 477-486 
    Details
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract Piston cores in Tongue of the Ocean, Bahamas, revealed an alternating sequence of periplatform ooze and bankderived turbidites of the past 5 glacial and interglacial periods. By using the point-count method we have analyzed the composition of the turbidite sediment. Variations in the bank-derived fraction are clearly linked to the glacial-interglacial cycles. Nonskeletal components (pellets; ooids; grapestones) are most abundant in interglacial turbidites, while skeletal components (calcareous algae; peneroplids and reef builders) dominate in glacial turbidites. We attribute this pattern to the exposure and flooding of the surrounding carbonate platforms during Late Quaternary sea-level cycles. Because nonskeletal sediment is produced in the interior of the platforms, its growth and subsequent export to the flanks are at a maximum when the banks are flooded, i.e. during interglacial periods. During glacials, skeletal grains dominate because the banks are exposed and carbonate production is limited to a narrow belt of skeletal sands and fringing reefs. The resulting compositional signal appeared to have a good correlation with aragonite variations in the periplatform ooze between the turbidites. Further, compositional variation parallels the change in turbidite frequency described earlier (»highstand bundling«). Frequency and composition of turbidites are both unaffected by diagenesis and therefore provide an excellent monitor of sealevel fluctuations.
    Abstract: Résumé Dans le »Tongue of the Ocean« (Bahamas), des sondages à piston effectués dans les sédiments des cinq dernières périodes glaciaires et interglaciaires montrent une alternance de turbidites et de boues déposées en périphérie de plate-forme. La composition de la fraction néritique des turbidites, dé terminée par la méthode du compteur de points, montre une relation claire avec les cycles glaciaires. Les composants abiogènes (pellets, ooïdes, grapestones) dominent dans les turbidites interglaciaires, tandis que les composants biogènes (algues calcaires, foraminifères de type pénéroplide et organismes constructeurs) sont prépondérants dans les turbidites glaciaires. Nous attribuons cette répartition aux émersions et submersions successives du banc des Bahamas, consécutives aux variations du niveau de la mer au Quaternaire récent. Comme les composants abiogènes ont été formés sur la partie interne de la plate-forme, leur développement et leur transport vers les flancs étaient maximaux lorsque le banc était submergé, au cours des périodes interglaci aires. Par contre, les composants biogènes dominaient pendant les épisodes glaciaires, où la plate-forme était exondée et où la production de carbonate était restreinte à une zone étroite de récifs frangeants et de sables biogènes. Ces variations dans la composition des turbidites présentent une bonne corrélation avec la teneur en anhydrite des boues de périphérie de plate-forme intercalées entre les turbidites. Il existe également une bonne corrélation avec la fréquence des turbidites, plus élevée pendant les interglaciaires. La fréquence et la composition des turbidites ne sont pas affectées par la diagenèse et constituent donc un excellent témoin des fluctuations du niveau de la mer.
    Notes: Zusammenfassung In Kolbenlotkernen aus der Tongue of the Ocean, Bahamas, bestehen die jüngsten fünf Glaziale und Interglaziale aus einer Wechselfolge von Periplattform-Schlamm und Turbiditen mit Flachwasser-Material. Die Zusammensetzung der neritischen Kornfraktion in den Turbiditen wurde durch Punktzählung ermittelt. Sie schwankt deutlich im Verlauf eines glazialen Zyklus. Abiogene Komponenten (Pellets, Ooide, Traubenklumpen) dominieren in den interglazialen Turbiditen, während Biogene (Kalkalgen, peneroplide Foraminiferen und Riffbildner) in glazialen Turbiditen vorherrschen. Wir erklären diese Schwankungen mit dem Auftauchen und Überfluten der Bahama Bänke während der jungquartären Schwankungen des Meeresspiegels. Die abiogenen Komponenten werden auf der Innenseite der Plattformen gebildet. Ihre Produktion und Export zu den Plattformflanken erreichen daher ein Maximum während der interglazialen Hochstände des Meeres. In den Glazialen dominieren biogene Komponenten, weil die Plattformen trocken liegen und die Karbonat-Produktion auf einen schmalen Streifen von Saumriffen und Biogensanden beschränkt ist. Die Zusammensetzung der Turbidite variiert im gleichen Rhythmus wie der Aragonitgehalt der zwischengeschalteten Periplattform-Schlamme. Überdies korreliert die Zusammensetzung gut mit der Häufigkeitsverteilung der Turbidite. Während der Interglaziale sind Turbidite häufiger als während der Glaziale (»Hochstand-Bündel«). Häufigkeitsverteilung und Zusammensetzung der Turbidite zusammen ergeben ein gutes, durch Diagenese nicht verwischbares Abbild der Schwankungen des Meeresspiegels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01776186
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  • 8
    Electronic Resource
    Electronic Resource
    Das Zusammenwirken von Sedimentation und Bruchtektonik in den triadischen Hallstätterkalken der Ostalpen (1969)
    Springer
    International journal of earth sciences 59 (1969), S. 289-308 
    Details
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract As they bear classical stratigraphic localities of the Upper Triassic, the East Alpine Hallstätterkalke are of general interest. Their area of deposition was a starved basin between shallow water carbonate platforms with reduced sedimentation and subsolution on one side and influence of syngenetic tectonics on the other. The vertical successions and their lateral changes within the Hallstätterkalk are remarkably constant. A schematical standard succesion can be given. Besides the facies of Hallstätterkalk with generally red sediments there exists another with more argillaceous gray deposits, differing in details of lithology but not in the general rhythm of lime and clay sedimentation. Syngenetic tectonic activity causes fracturing in the highly consolidated sediments. Among the joints most frequently tension cracks occur, some meters wide and filled with younger sediment. Tilted blocks and displacements are common, but shearing and tectonic compression are rare. The tectonic activity consisted of many small jerks, but was continuous during a long period, i. e. the Carnian an the Norian. This is shown by the interference with sedimentation. From the stratigraphic point of view the cracks are important as they act as traps for fossils and as these fossil-rich fillings are deposited in older rocks, breaking the law of stratigraphic succession. But in most cases deposits in cracks can easily be distinguished from those in normal sediment.
    Abstract: Résumé Les calcaires de Hallstatt des Alpes Orientales contiennent les profils classiques du Triassique supérieur et sont donc d'un grand interêt. Leur lithologie est déterminée par une sédimentation réduite dans un «starved basin» d'une part et par l'effet d'une tectonique syngénétique d'autre part. Leur succession verticale et leur variation latérale particulièrement constantes dans la région classique du Salzkammergut permettent de dresser un profil typique schématique. A part le faciès des calcaires rouges il existe un autre à sédiments gris plus colloidal dont les détails se distinguent du premier mais leur rhythme principal calcaire-colloide est analogue. La tectonique synsédimentaire est caractérisée par une déformation rupturelle des sédiments largement consolidés. Il se forme un système de diaclases ouvertes qui sont remplies peu à peu. Des phénomènes de cisaillement et de resserrement sont assez rares, des diaclases d'extension et des basculements de blocs sont observés plus souvent à l'échelle de quelques mètres. Pour des périodes limitées les mouvements tectoniques ont eu lieu par secousses, mais vu l'ensemble des périodes du Carnien et du Norien on se rend compte de la continuité de leur activité. Du point de vue stratigraphique les diaclases ont la fonction de pièges à fossiles. Des sédiments fossilifères se trouvent souvent dans des roches plus anciennes. Mais ce dépôts à fossiles peuvent être distingués nettement des couches stratifiées dans les calcaires de Hallstatt.
    Notes: Zusammenfassung Die Hallstätterkalke der Ostalpen verdienen als Träger der Obertriasstratigraphie der Tethys allgemeines Interesse. Ihre Lithologie wird bestimmt durch Ablagerung in einem von Flachwasserkarbonaten umgebenen Hungerbecken mit fast stagnierender Sedimentation einerseits und durch die Wirkung synsedimentärer Tektonik andererseits. Die vertikale Abfolge und ihr horizontaler Wechsel innerhalb der Hallstätterkalke sind in der klassischen Region des Salzkammergutes auffallend konstant, so daß ein schematisches Normalprofil aufgestellt werden konnte. Neben der Hallstätterkalk-Fazies gibt es eine solche mit tonreicheren Grausedimenten, die im einzelnen deutlich davon differiert, aber im Großrhythmus der Kalk-TonSedimentation ähnlich ist. Die synsedimentäre Tektonik wird beherrscht von brechender Verformung der weitgehend festen Sedimente. Es bildet sich ein Netz von Zugklüften mit stellenweise meterbreiten, offenen Spalten, die allmählich verfüllt werden. Tektonische Einengung wurde nur selten beobachtet, häufiger Versetzung und Kippung von Schollen im Meterbereich. Die Interferenz der Sedimentation mit den tektonischen Bewegungen beweist, daß letztere im kleinen ruckartig verliefen, im großen aber während des Karn und Nor ziemlich gleichmäßig andauerten. Sie stehen möglicherweise in Zusammenhang mit der relativen Hebung des gesamten Hallstätter Beckens gegenüber den rasch absinkenden Dachsteinkalk-Plattformen. In stratigraphischer Hinsicht wirken die Spalten als Fossilfallen und lagern oft sehr fossilreiche Sedimente unter Durchbrechung des Lagerungsgesetzes in stratigraphisch älteres Gestein ein. Die Unterscheidung von Spalten- und Schichtlagern im Hallstätterkalk ist jedoch im allgemeinen gut durchführbar.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01824958
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  • 9
    Electronic Resource
    Electronic Resource
    Die Geologische Vereinigung verlieh im Jahre 1990 die Gustav-Steinmann-Medaille an Professor Dr. Hans Füchtbauer (1991)
    Springer
    International journal of earth sciences 80 (1991), S. III 
    Details
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01829360
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  • 10
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    Radar reflections from sedimentary structures in the vadose zone (2003)
    In:  Geological Society Special Publication 211: 257-273.
    Details
    Publication Date: 2003-01-01
    Description: Ground penetrating radar (GPR) is a suitable technique for imaging sedimentary structures in the vadose zone because small texture-related capillary-pressure variations lead to changes in water content and electromagnetic properties. To study exactly how GPR reflections are generated by sedimentary structures, GPR profiles of an aeolian sedimentary succession are combined with measurements of textural, electromagnetic and water-retention characteristics from a trench. Time domain reflectometry indicates that small variations in texture in the high-angle dune sediment are associated with changes in water content. Synthetic modelling shows that these changes cause clear GPR reflections. In an experimental approach to estimate the radar response of structures below the wave resolution, i.e. features smaller than {lambda}/4, variations in grain-size distribution and porosity in a thin section were used to reconstruct water-retention curves and impedance models of the thinly layered sediment. Synthetic radar records calculated from the impedance models show that reflections from the studied subcentimetre-scale structures are composites of interfering signals. Although these low-amplitude interfering signals will commonly be overprinted by more prominent reflections, they may cause reflection patterns that change with frequency and do not represent primary bedding.
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