Onlap stratal architectures in the Grès d'Annot: geometric models and controlling factors
Ru Smith, Philippe Joseph, 2004. "Onlap stratal architectures in the Grès d'Annot: geometric models and controlling factors", Deep-Water Sedimentation in the Alpine Basin of SE France: New perspectives on the Grès d'Annot and related systems, P. Joseph, S. A. Lomas
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Onlap terminations of deep-marine sandstones in the Grès d'Annot, SE France, exhibit a range of styles, from abrupt onlap to feathering ‘aggradational onlap’ geometries. These are well exhibited in the large exposure of southward onlap terminations at Montagne de Chalufy, on the southern end of the Trois Evêchés Massif (Alpes de Haute Provence). These stratal architectures are here simulated by geometrical models that are governed simply by bounding slope gradients and the ratio of coeval slope to basinal aggradation rates. In cases of no coeval deposition on bounding slopes, pure onlap results. In cases of high slope aggradation rates relative to basinal aggradation rates, a feathered geometry results with successive sandstone beds onlapping against successively younger slope drapes. The cyclicity of alternating sand-rich and sand-poor packets seen at Chalufy results in a stepped climbing trajectory of successive slope base positions, with climb angle equal to bounding slope angle when mud-poor sandy flows deposited sandstone bodies with abrupt onlap, and climbing more steeply when slope drapes are deposited. An implication of this result is that any zones of facies change and palaeocurrent swing that are related to distance from bounding slope will exhibit a comparable vertical trajectory through time. The two end member termination types can be compared with the convergent-baselapping and convergent-thinning seismic facies used in the Gulf of Mexico subsurface and elsewhere. The convergent-baselapping seismic facies may include both abrupt onlap and intervals of feathering aggradational onlap if the presence of slope drapes is not resolvable by the frequency content of the available seismic data.
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Deep-Water Sedimentation in the Alpine Basin of SE France: New perspectives on the Grès d'Annot and related systems
The Grès d′Annot Formation of SE France constitutes a classic and outstanding example of a sand-rich turbidite system controlled by synsedimentary tectonics, and has often been used as an outcrop analogue for deep-water hydrocarbon reservoirs. Over the last 10 years, research efforts by different academic and industrial teams have led to important reappraisals of prevailing ideas on the Gres d′Annot, particularly on the nature and controlling factors of the depositional processes, the small-scale architecture and sequence organization of the deposits, the tectonic regime of the basin and its impact on palaeogeography, and the interaction between sediment gravity flows and basin-floor topography.
This volume offers a multidisciplinary overview and draws up the ′state-of-the-art′ of scientific knowledge on this influential turbidite system. Complementary aspects are covered, from structural geology, sedimentology and sequence stratigraphy, to modelling of sedimentary processes and architectures, geochemistry, reservoir characterization, seismic modelling and uses as analogues for deep-marine hydrocarbon fields.
This book will be of use to both academic researchers (geologists and geophysicists) and industry professionals dealing with the characterization and modelling of deep-water sediments.