Ergebnisse neuer Untersuchungen über Fazies und Bildung von Trias und Jura in Südwest-Deutschland

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Plate tectonics and intracratonic mountain ranges in Morocco - The mesozoic-cenozoic development of the Central High Atlas and the Middle Atlas

Plate tectonic processes in the Atlantic and western Tethyan realm directed the post-Variscan sedimentary and structural evolution of the High Atlas and Middle Atlas intracontinental mountain ranges of Morocco. Plate movements caused a reactivation of an inherited pan-African or Hercynian fault pattern by the variation of stress regimes through time. This resulted in strike-slip as well as vertical tectonics. During times of relative tectonic quiescence eustatic sea-level changes governed the sedimentary development. The most important, often interacting, global tectonic determinants are: taphrogenesis of the NW-African continental margin lasting until the Early Cretaceous (Triassic rifting and subsequent mid-Atlantic spreading), strike-slip-faulting at the Newfoundland-Gibraltar fault zone (Liassic — earliest Eocene), and continental convergence between Europe (Iberia) and Africa which started in the Late Cretaceous and reached its acme in the Neogene. In the realm of the Central High Atlas and the Middle Atlas the interaction of these processes triggered continental rifting (Triassic) and subsequent marine flooding of the intergrown riftgrabens prograding from the Tethys realm (Early Jurassic — earliest Middle Jurassic). After its abortion, the former Atlas rift was filled up with marine sediments (Bajocian — Bathonian), followed by continental redbeds and final uplift (late Mid Jurassic — late Early Cretaceous). Eustatic sea-level changes mostly governed the sedimentary evolution from Aptian to latest Mid Eocene. After a first weak uplift of the central High Atlas during the Senonian major uplift of the intracontinental chains commenced at the Mid/ Late Eocene transition. Diastrophism of the Atlas ranges during the Miocene and Pliocene coincided with the main orogenic movements of the Betico-Rifean arc.

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Zusammenfassung Die post-variskische sedimentäre und strukturelle Entwicklung der intrakontinentalen Gebirgsketten des Hohen und des Mittleren Atlas wurde durch plattentektonische Prozesse im atlantischen und westmediterranen Raum gesteuert, die auf ein ererbtes panafrikanisches bzw. variskisches Störungsmuster einwirkten. Zu Zeiten relativer tektonischer Ruhe bestimmten eustatische Meeresspiegelschwankungen die sedimentäre Entwicklung. Die von horizontaler und vertikaler Bruchtektonik beherrschte Atlas-Tektonik wurde durch in der Zeit wechselnde Streßfelder bestimmt. Wichtigste großtektonische, oft zusammenwirkende Steuerungsfaktoren waren: die bis in die Unterkreide wirkende Taphrogenese im Bereich des NW-afrikanischen Kontinentalrandes (triadisches Rifting und anschließendes Spreading im Atlantik), Transform-Bewegungen an der Neufundland-Gibraltar-Störungszone zwischen Lias und ältestem Eozän sowie die Konvergenz zwischen Europa (Iberia) und Afrika, welche nach ihrem Beginn in der späten Kreide ihren Höhepunkt im Neogen erreichte. Das Zusammenspiel dieser Faktoren bewirkte im zentralen Hohen Atlas und im Mittleren Atlas die Entstehung kontinentaler Riftgräben während der Trias, die von der Tethys ausgehende Flutung der zusammengewachsenen Riftgräben im Lias und untersten Dogger (Sinemurium — Aalenium) sowie die zuerst marine (Bajocium — Bathonium), dann kontinentale Füllung und Heraushebung der stillgelegten Riftzone zwischen spätem Mitteljura und später Unterkreide. Zwischen Apt und Ende des Mitteleozän kontrollierten vor allem eustatische Meeresspiegelschwankungen die sedimentäre Entwicklung. Nach ersten Hebungen im zentralen Hohen Atlas während des Senon begann die eigentliche Heraushebung der intrakontinentalen Ketten an der Wende Mittel-/Obereozän. Die mio-/pliozäne Hauptphase der Atlas-Tektogenese war zeitgleich mit der Orogenese im Betico-Rif-Bogen.

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Résumé L'évolution sédimentaire et structurale postvarisque des chaînes intracontinentales du Haut et du Moyen Atlas a été régie par les processus de la tectonique des plaques qui se déroulaient dans l'Atlantique et dans la Méditerrannée occidentale. Ces mouvements de plaques ont réactivé un ensemble de failles héritées des phases pan-africaine et hercynienne, en y produisant des déplacements verticaux et horizontaux en réponse aux fluctuations temporelles des champs de contraintes. Au cours des périodes de calme tectonique relatif, les changements eustatiques du niveau de la mer ont déterminé le régime de la sédimentation. Les facteurs de la tectonique les plus importants, à action d'ailleurs souvent combinée, ont été: la traphrogenèse, active jusqu'au Crétacé inférieur, de la marge nord-ouest du continent africain (rifting triasique et ouverture subséquente de l'Atlantique), les mouvements de décrochement le long de la zone transformante de Terre Neuve-Gibraltar depuis le Lias jusqu'au début de l'Eocène, ainis que la convergence entre l'Europe (Ibérie) et l'Afrique qui débuta au Crétacé supérieur pour culminer au Néogène. Dans le Haut Atlas central et dans le Moyen Atlas, le jeu combiné de ces facteurs a provoqué la formation de grabens continentaux (Trias) puis leur envahissement par la mer à partir de la Téthys (Lias-Dogger inférieur). Après la fin de son activité, le rift atlasique a été comblé par des sédiments, d'abord marins (Bajocien-Bathonien), puis continentaux jusqu'au soulèvement final (fin du Jurassique moyen — fin du Crétacé inférieur). De l'Aptien à la fin de l'Eocène moyen, l'évolution sédimentaire a été régie par les changements eustatiques du niveau de la mer. Après un premier soulèvement modéré du Haut Atlas central au cours du Sénonien, le soulèvement majeur des chaînes intracontinentales débuta à la limite Eocène moyen-Eocène supérieur. Le diastrophisme de l'Atlas au cours du Mio-Pliocène a coïncidé avec les mouvements orogéniques de l'arc bético-rifain.

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Geochemical characterisation of organic matter in Keg River Formation (Elk point group, Middle Devonian), La Crete Basin, Western Canada

Carbonates from the Keg River Formation, La Crete Basin, Alberta, western Canada were examined in order to define: (a) oil source rock potential; (b) bulk maceral composition; (c) extract yield; and finally (d) facies variations using PY-GC-MS. Thirty samples from 6 different wells were examined from the lower Keg River member and 4 from the upper Keg River member using conventional geochemical methods. As maturity differences are absent within the sample set, variations in TOC, T_max, hydrogen index, organic petrography and extract yields are caused by variability in organic matter input, which is revealed by molecular characterisation using PY-GC-MS. Lower Keg River member bituminous wackestones are excellent potential source rocks containing Types I–II and Type II organic matter. Types I–II organic matter contains large well preserved (up to 200μm in diameter) thick-walled Tasmanites (10–15% of sample) and akinete algal cells indicative of algal blooms within an amorphous bituminite. Type II organic matter contains a higher proportion of degraded alginites/bituminite relative to well-preserved alginites. Extract yields (mg/g TOC) were seen to increase from Types I–II to Type II organic matter. PY-GC-MS revealed that 1,2,3,4-tetramethylbenzene was a major peak in most samples. This is a pyrolysis product arising from β-cleavage of C₄₀ diaromatic carotenoids incorporated within the kerogen during diagenesis. The source of this compound is thought to be from an unknown diaromatic compound with a 2,3,6-/3,4,5-trimethyl substitution pattern and isorenieratene, which is specific to photosynthetic green sulphur bacteria (Chlorobiaceae) suggesting that the photic zone was at least partially anoxic during deposition of these samples. The relative abundance of this compound/n-C11-alkene and organic sulphur (calculated from the thiophene ratio) both increase from Types I–II to Type II organic matter. This trend was grossly similar to the trend seen in the variability of extract yield with hydrogen index. A similar trend for HI and T_max indicates samples containing a higher proportion of degraded alginites/bituminite relative to well-preserved alginite are more labile than Type I–II organic matter. Upper Keg River member marls contain Type II organic matter, which is characterised by heavily degraded algal material within a bituminous groundmass. Pyrolysates of two of the marl samples contain only low amounts of 1,2,3,4-tetramethylbenzene, in contrast to the bituminous wackestones, indicating that the depositional environment/source input was different during deposition of the marl samples. Although both marls contain similar organic matter, their pyrolysates were significantly different. One marl (1141.9 m) was highly paraffinic containing dominantly short-chain alkene/alkane doublets, while the other marl (1137.6 m) contained a bimodal n-alkane/alkene distribution and high amounts of alkylphenols, which may be derived from preservation of resistant algal polyphenolic molecules or suggest a terrestrial input.     

Distribution of uranium in German bottled and tap water

The results presented in this paper on uranium in bottled and tap water were determined within the scope of the project “European Groundwater Geochemistry: Bottled Water” of the Geochemistry Expert Group of EuroGeoSurveys. The analyses of bottled water provide an inexpensive approach to obtain information about European groundwater geochemistry. For this study, the uranium concentrations in 1785 European mineral water samples were analyzed by ICP–QMS in the BGR laboratories. The dataset is used to obtain a first impression about natural concentration levels and variation of uranium in groundwater (and bottled water) at the German and European scale.     

Neural Networks: A General Framework for Non-Linear Function Approximation

The focus of this paper is on the neural network modelling approach that has gained increasing recognition in GIScience in recent years. The novelty about neural networks lies in their ability to model non‐linear processes with few, if any, a priori assumptions about the nature of the data‐generating process. The paper discusses some important issues that are central for successful application development. The scope is limited to feedforward neural networks, the leading example of neural networks. It is argued that failures in applications can usually be attributed to inadequate learning and/or inadequate complexity of the network model. Parameter estimation and a suitably chosen number of hidden units are, thus, of crucial importance for the success of real world neural network applications. The paper views network learning as an optimization problem, reviews two alternative approaches to network learning, and provides insights into current best practice to optimize complexity so to perform well on generalization tasks.     

FFT-enhanced IHS transform method for fusing high-resolution satellite images

Existing image fusion techniques such as the intensity–hue–saturation (IHS) transform and principal components analysis (PCA) methods may not be optimal for fusing the new generation commercial high-resolution satellite images such as Ikonos and QuickBird. One problem is color distortion in the fused image, which causes visual changes as well as spectral differences between the original and fused images. In this paper, a fast Fourier transform (FFT)-enhanced IHS method is developed for fusing new generation high-resolution satellite images. This method combines a standard IHS transform with FFT filtering of both the panchromatic image and the intensity component of the original multispectral image. Ikonos and QuickBird data are used to assess the FFT-enhanced IHS transform method. Experimental results indicate that the FFT-enhanced IHS transform method may improve upon the standard IHS transform and the PCA methods in preserving spectral and spatial information.