STRATIGRAPHY AND TECTONICS OF THE ROER VALLEY GRABEN

The Roer Valley Graben is the most prominent Cenozoic tectonic feature in the Netherlands onshore, filled with up to 2000 m of predominantly Upper Oligocene to Quaternary sediments. It forms the northwestern br anch of the Rhine Graben rift system. To the northeast the graben is b ordered by a major faultzone, the Peel Boundary Fault, and to the sout hwest by a number of downstepping faults. The Roer Valley Graben devel oped upon pre-existing sedimentary basins of Carboniferous, Triassic t o Early Jurassic and Late Jurassic age. The Cenozoic graben is structu rally closely related to the Late Jurassic basin and to the area affec ted by inversion tectonics at the end of the Cretaceous. Differential subsidence of the Roer Valley Graben started during the Late Oligocene . Displacements along the Peel Boundary Fault were recorded from the L ate Oligocene onwards. Initially the average displacement was 0.01 mm a(-1), but it increased during the Quaternary to 0.8 mm a(-1). Fault d isplacements at the southwestern boundary faults of the Roer Valley Gr aben are smaller than at the Peel Boundary Fault.