Analysis of the Significance of Erosional Denudation on the Geometrical and Stratigraphic Evolution of Foreland Basins and on Strain Partitioning in their Orogens

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9614286 Jordan Foreland basins have been studied extensively I the last years to explore the relationships between crustal thickening in the orogen and the stratigraphic and geometrical response of the adjacent foreland basin. Since 60% of the total deflection of foreland basins may be due to the sediment load, temporal and spatial variations in sediment flux due to changing erosional denudation rates and patterns in the hinterland have a great potential to significantly affect the geometrical and stratigraphic evolution of foreland basins. Furthermore, as revealed by critical taper wedge models, variable erosional denudation rates in the orogen are likely to control strain partitioning, which in turn affects the geometrical evolution of foreland basins. We propose to explore the influence of temporal and spatial variations of erosional denudation rates on the geometrical and stratigraphic evolution of the Molasse and Bermejo Basins and on strain partitioning in the Alps (Switzerland) and the Precordillera (Argentina). These systems are ideally suited to our objectives because of the extensive data available and because they represent denudation/dispersion end members. The erosional denudation rates will be compiled from the dense data set of cooling and metamorphic ages in the Alps, and by restoring the volumes of sediment preserved in the internally drained Bermejo Basin to their specific source terrains. These data will be compared with the subsidence histories of the foreland basins determined by backstripping, which will allow us to recognize the importance of sediment flux on the evolution of the Molasse and the Bermejo Basins. Similarly, a careful three dimensional subsidence analysis will allow us to compare the subsidence patterns of the internally drained Bermejo Basin and the open Molasse Basin. Comparing and contrasting the subsidence histories, the sediment flux, and progradation/retreat rates of facies will allow us to critically evaluate whether unconformities are mo re likely to form in open than in closed basins. In addition, we propose to explore whether the sensitivity of the basin stratigraphy to tectonic episodes depends on the location of the principle sediment source area. The evolution of facies and geometries of the basins will be visualized by stratigraphic simulation with Strata2.11. Using this software, we will be able to test whether sediment flux rather than tectonic subsidence and/or eustatic sea level changes caused the regressions and transgressions in the Molasse Basin. Furthurmore, applying Strata2.11 to the Molasse and Bermejo Basins, we can explore the significance of varying sediment flux on the generation of unconformities in fluvial systems. Comparing the temporal and spatial variations of erosional denudation rates with strain partitioning in the orogens will enable us to critically evaluate whether erosion significantly controlled the sequence of thrust motions as predicted by critical taper wedge models. We propose to analyze how climate and erodibility of rocks affect the chronology of thrusting in orogens by contrasting the two denudation end members.