Search

International audience; We present a study to estimate the large-scale landscape history of a continental margin, by establishing a source-to-sink volume balance between the eroding onshore areas and the offshore basins. Assuming erosion as the primary process for sediment production, we strive to constrain a numerical model of landscape evolution that balances the volumes of eroded materials from the continent and that deposited in the corresponding basins, with a ratio imposed for loss of erosion products. We use this approach to investigate the landscape history of Madagascar since the Late Cretaceous. The uplift history prescribed in the model is inferred from elevations of planation surfaces formed at various ages. By fitting the volumes of terrigenous sediments in the Morondava Basin along the west coast and the current elevation of the island, the landscape evolution model is optimized by constraining the erosion law parameters and ratios of sediment loss. The results include a best-fit landscape evolution model, which features two major periods of uplift and erosion during the Late Cretaceous and the middle to late Cenozoic. The model supports suggestions from previous studies that most of the high topography of the island was constructed since the middle to late Miocene, and on the central plateau the erosion has not reached an equilibrium with the high uplift rates in the late Cenozoic. Our models also indicate that over the geological time scale, a significant portion of materials eroded from Madagascar was not archived in the offshore basin, possibly consumed by chemical weathering, the intensity of which might have varied with climate.

A transparent polymer film with embedded micro mirrors is developed, and it can be attached to a window glass pane for daylighting, improving visual comfort and reducing cooling load in buildings by redirecting sunlight. Despite existing cutting-edge techniques, the fabrication of large-area, linear micro structured surfaces combining high aspect ratio, curve sidewalls and a controlled shape remains challenging. In order to solve the problem, a novel mechanical scanning engraving method using blades with micro-teeth of desired patterns on soft substrates is developed. The usage of a blade enables the combination of high aspect ratio with almost any closed profile. Such blades can be obtained in a large variety of shapes using UV-LIGA technology which combines photolithography and electroforming. Master molds were prepared and the following steps of micro UV-imprinting from the master molds are also introduced. The present work confirms the feasibility of the fabrication for parabolic sidewall microstructures of aspect ratio of 3.8 and 6.7 with good controlled shapes. With a scanning speed of 0.15 m/min, the method is proven to be efficient and appropriate for large-area microstructured fabrication.