Genesis of a mottled horizon by Fe-depletion within a laterite cover in the Amazon BasinGenèse d'un horizon tacheté par déferruginisation dans une couverture à latérite du Bassin amazonien     

Vania Rosolen  Mathieu Lamotte  René Boulet  Jean Trichet  Olivier Rouer  Adolpho José Melfi 《Comptes Rendus Geoscience》2002,334(3):187-195

A mottled horizon in a laterite cover (without any duricrust) was studied by microscopy and quantitative chemical microanalysis. Apart from the voids, light red spots consisting of Fe-rich particles (≈2 μm) are set in clayey plasma. Dark red spots consisted of concentrations of Fe-rich particles. These patterns are inherited. On the border of structural or biological voids, where Fe-depletion features are systematic, gray or yellow spots result from dissolution of the Fe-rich particles and impregnation of the plasma by iron, respectively. The present Fe-depletion is the dominant process that explains the mottled differentiation and the absence of lateritic duricrust. To cite this article: V. Rosolen et al., C. R. Geoscience 334 (2002) 187–195.  相似文献   

Lacustrine wave-dominated clastic shorelines: modern to ancient littoral landforms and deposits from the Lake Turkana Basin (East African Rift System,Kenya)     

Mathieu Schuster  Alexis Nutz 《Journal of Paleolimnology》2018,59(2):221-243

This paper presents an overview of some of the most significant, recent to ancient, littoral morpho-sedimentary structures and deposits from the Lake Turkana Basin. We highlight the importance of wave-related sedimentary processes in lakes, and more specifically in rift lakes. In the published literature, references to wave-dominated shorelines are mainly in regards to coastal marine environments. However, numerous modern lakes exhibit typical wave-dominated littoral landforms, and related sedimentary deposits are known from several paleolake successions in the geological record. Wave-related processes are often of relatively minor importance in depositional models for lacustrine environments. Classical models emphasize clastics transported by rivers, which are then distributed by fan-deltas and/or deltas into a water body of fluctuating depth, where reworking of clastics is limited in the littoral domain, and episodic in deep waters. Modern processes in Lake Turkana and the exposed paleolake deposits of the Turkana Basin demonstrate that this view is incomplete. Wave-dominated shorelines are evident (1) for modern Lake Turkana based on prominent and active littoral landforms (e.g., beach ridges, sand spits, washover fans, and arcuate-cuspate deltas); (2) for the Holocene (African Humid Period) climate-driven highstand of Megalake Turkana and its subsequent forced regression based on conspicuous raised beach ridges and spits; and (3) for the Pliocene–Pleistocene (Omo Group, Nachukui Formation) from typical nearshore sedimentary facies and stratigraphic architectures associated with paleolake Turkana. These examples from the Turkana Basin coupled with examples from other lacustrine settings, suggest that wave-dominated clastic shorelines represent significant portions of existing and ancient lake-shores. As this view contrasts with classic depositional models for lakes, notably for those found in rift setting, we also present examples of wave-influenced littoral landforms from other lakes of the East African Rift System. Identifying lacustrine paleoshorelines from typical clastic landforms and deposits is the key to the spatial reconstruction of lakes over time, and to determine transgressive–regressive cycles. Waves action is an important agent in lakes for the erosion, transport, and deposition of clastics at the basin-scale, an aspect that needs to be integrated in sedimentary models.  相似文献   

Integrated 3D forward stratigraphic and petroleum system modeling of the Levant Basin,Eastern Mediterranean     

Jessica Barabasch  Mathieu Ducros  Nicolas Hawie  Samer Bou Daher  Fadi Henri Nader  Ralf Littke 《Basin Research》2019,31(2):228-252

The Eastern Mediterranean Levant Basin is a proven hydrocarbon province with recent major gas discoveries. To date, no exploration wells targeted its northern part, in particular the Lebanese offshore. The present study assesses the tectono‐stratigraphic evolution and related petroleum systems of the northern Levant Basin via an integrated approach that combines stratigraphic forward modeling and petroleum systems/basin modeling based on the previous published work. Stratigraphic modeling results provide a best‐fit realisation of the basin‐scale sedimentary filling, from the post‐rift Upper Jurassic until the Pliocene. Simulation results suggest dominant eastern marginal and Arabian Plate sources for Cenozoic siliciclastic sediments and a significant contribution from the southern Nilotic source mostly from Lower Oligocene to Lower Miocene. Basin modeling results suggest the presence of a working thermogenic petroleum system with mature source rocks localised in the deeper offshore. The generated hydrocarbons migrated through the deep basin within Jurassic and Cretaceous permeable layers towards the Latakia Ridge in the north and the Levant margin and offshore topographic highs. Furthermore, the basin model indicates a possibly significant influence of salt deposition during Messinian salinity crisis on formation fluids. Ultimately, the proposed integrated workflow provides a powerful tool for the assessment of petroleum systems in underexplored areas.  相似文献   

Linking a linear pockmark train with a buried Palaeozoic structure: a case study from the St. Lawrence Estuary     

Nicolas Pinet  Mathieu Duchesne  Denis Lavoie 《Geo-Marine Letters》2010,30(5):517-522

The 15-km-long Matane pockmark train belongs to a series of NNE-striking alignments of pockmarks mapped on the seafloor of the St. Lawrence Estuary. It includes 109 pockmarks that show a complete transition from well-defined, relatively deep (up to 8.6 m), crater-like depressions to subtle, partly buried morphological features, suggesting that pockmarks have formed at different periods along the whole alignment and that the location of fluid release has changed through time. On seismic profiles, pockmarks are characterized by vertical seismic chimneys that root in the (fractured?) hinge zone of an open anticline within the autochthonous Palaeozoic rocks of the St. Lawrence Platform. In absence of a geochemical characterization of expelled gas, the relationship between the Matane pockmark train and the anticline in a domain characterized by mature source rocks is the strongest evidence for the genetic link between pockmarks and the release of gas from an active hydrocarbon system or a reservoir located in the Palaeozoic succession.