163-G 3.4

Testing long-term controls of sedimentary basin architecture in the broken foreland

The spatial architecture of sedimentary facies in a basin exert a fundamental control over the patterns of fluid flow and determines the regional distribution of possible reservoirs and seal units. The distribution of sedimentary facies can be predicted to some extent by sequence stratigraphic theories. These models offer a conceptual framework to extrapolate facies distribution at a regional scale in 2D, ranging from continental to basinal. However, as soon the scale of observation increases, these models are not able to represent the geological complexity and facies variability in a realistic way. Furthermore, these concepts are rarely applied in 3D. Field studies reveal much more complex facies mosaics and patterns than predicted by 2D-models. Here, we will characterize the 3D facies distribution and sedimentary architecture evolution of a post-rift basin at different temporal and spatial scales prior to its evolution as a foreland basin. More specifically, the goal is to model the above mentioned parameters by coupling integrative seismic data, petrographic investigations of well logs, and outcropping sedimentary successions. Specific attention will be given to sedimentary discontinuities that often point to noteworthy events or record significant modifications of the environmental conditions, but also have the potential to affect fluid flow behavior and to compartmentalize reservoirs. Petrographic and geochemical analyses will be used to identify environmental parameters and assess diagenetic overprint in various limestone intervals. The outstanding quality of the sedimentary successions of several subbasins of the Salta Group (Yacoraite Formation) in NE Argentina offers a fantastic natural laboratory to study spatial facies variability in a postrift basin. The integration of facies analysis and stratigraphic units together with petrographic and geochemical studies on their bounding unconformities will provide data to test the role of extrinsic and autocyclic controls (tectonic, climate and sediment supply, inherited topography) on the stratigraphic successions. Constrained by stratigraphic and sedimentological information from field, well-log, and seismic data, numerical forward modeling will provide a valuable tool for testing stratigraphic correlations and the geological hypotheses controlling their occurrence. We will employ numerical modeling (DIONISOS, Petrel) to explore hypotheses concerning their occurrence and spatial distribution. This project will thus contribute to characterizing and quantifying sedimentary 3D facies distribution in outcrops (analogs for subsurface exploration) at basin and reservoir scales and to evaluate controls over their vertical and lateral stratigraphic architecture.