Miocene Depocenters and Sediment Supply in the Roer Valley Rift System: Impacts of Tectonics, Eustacy and Climate

The Miocene sequence in the Roer Valley Rift System consists of alternating shallow marine, coastal and fluvio-deltaic deposits. In this study seismostratigraphy and biostratigraphy are used to determine major unconformities and sediment dispersal patterns. This research is important for future studies related to the geothermal energy potential, and for the improvement of cross-border correlations with the German and Belgian stratigraphic framework. Results show that a depocenter developed in the south-eastern part of the Roer Valley Graben above the Early Miocene Unconformity (EMU) during the Early- and Middle Miocene. Clinoforms are present in a limited area here, but show sediment dispersal from the south-east towards the north-west during periods of progradation. From the late Middle Miocene onwards, larger displacement rates occurred along the major bounding fault zones, i.e. the Peel Boundary Fault Zone, the Feldbiss Fault Zone and the Veldhoven Fault. As a result, the depocenter narrowed and shifted to the central part of the Roer Valley Graben, where accumulation rates increased and larger-scale clinoforms start prograding both towards the west-north-west. This phase coincides with the development of a regional hiatus on the structural highs and forced regression in the south-eastern Roer Valley Graben, caused by a major sea-level fall related to the Middle Miocene Climatic Transition. The effects of tectonics, eustacy and climate resulted in the formation of the Mid-Miocene Unconformity (MMU), which represents a series of events related both to tectonics and sea-level fluctuations, and is therefore expressed differently throughout the Roer Valley Rift System. Sedimentation continued through this period in the deeper parts of the Roer Valley Graben and on the Venlo Block, while an erosional hiatus is evident on the Campine Block and Peel Block. During the latest Miocene, the depocenter migrated to the south-western rim of the Roer Valley Graben, where the youngest Miocene sediments are deposited during a latest Tortonian-Messinian sea level fall that led to the formation of the Late Miocene Unconformity (LMU).