Turbidity currents transport land-derived sediment to deep sea where theirdeposits form large geological structures termed submarine fans. Giventheir large areal extent and high sand content, submarine-fan deposits formsignificant hydrocarbon reservoirs. Their internal architecture is often poorlyresolved. With much of the three-dimensional architecture of the turbiditelobes below seismic resolution, there is commonly a significant level of un-certainty associated with respect to the reservoir geometry and quality.At the end of submarine channels, turbidity currents lose confinementand encounter a slope break, in response, the current decelerates and forms a deposit, a turbidite. Repeated passage of turbidity currents forms a stackof deposits that are generically termed lobes.Subsequent flow events modify the bathymetry by erosion and deposi-tion, thereby affecting the trajectory of subsequent flow events. Due to self-formed relief, beds start stacking laterally, in 'compensation'. A complex but ordered stratigraphy is created by repeated cycles of shifts in deposition, which results in variability in deposits that governs reservoir connectivity. In this study, multiple consecutive turbidity currents flowing over self-formed relief are modeled using a process-based numerical model (Delft3D-FLOW). The response of successive turbidity currents and their deposits to variations in channel slope was tested. Models with steeper channel slope were observed to result in more vigorous flows with deposits that cover a larger surface area. Following passages of turbidity currents were observed to erode bed sediment in the channel and thereby diminish the amount ofreadily erodible bed sediment for following turbidity currents. With the current model set-up, the deposit relief was insufficient to observe lateral stacking of deposits. These simulations provide insight into the depositional processes and the controls on the geometry and sedimentary trends of the deposits emplaced by successive turbidity currents flowing over a slope break and losing confinement.
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A three-dimensional geological model has been constructed of a 49 square km area in the sub-Alpine chains in the French Drôme department. The area was situated in the Vocontian Basin, which was an epicontinental sea situated at the western margin of the Alpine Tethys Ocean, between former continents of Gondwana and Laurasia. Formations of limestones and marls have been deposited over a time span of approximately 80 Ma from the Late Jurassic to the Early Cretaceous, which can be classified into eight distinct formations. This was followed by two phases of deformation. First, the counter-clockwise rotation of Iberia into Europe inducing S-N compression in this area. Second, the collision of Adria with the European continent inducing E-W compression. Both events uplifted the area by an estimated 2500 to 3000 m.
This thesis uses data collected during the second year fieldwork (course AESB2430) of the Applied Earth Sciences bachelor at Delft University of Technology. The cross sections and geological map from this fieldwork were revised where necessary. Three new cross-sections were constructed along the north, east, and west boundaries of the area for more coverage. All cross-sections were digitized using the Move software package. To check whether these were geologically feasible, they were restored to their pre-deformation state by removing the effect of faulting and folding. These cross-sections form the basis for a 1:25 000 scale three-dimensional model. Horizon surfaces were created between cross-section horizons using spline interpolation and fault surfaces using linear interpolation
Fauld displacements are removed and an unfolding is performed on the 3D model, in an attempt to reconstruct a balanced pre-deformational setting. The result is a viable model, with some inaccuracies such as gaps and overlaps between formation surfaces and slight variation s in layer thickness. The aim of this 3D model is to aid the understanding of the configuration of rocks and of the structural evolution of the area. The average shortening due to deformation for cross-sections was found to be 14.71 %. The surface reduction value of the area is found to be 8.2 푘푚 or 14.3 %.
The direction of shortening is primarily in the S-N, due to the Iberian collision, and to lesser extent in the E-W direction, due to the Adriatic collision. ... Read more