The Architecture of Lower Triassic Aeolian Reservoirs Shaped by Synsedimentary Tectonics and Unconformity Development— Ems Basin, Northwestern Germany

Radies, Dirk, Harald Stollhofen, Peter Kukla, RWTH Aachen University, Aachen, Germany

The Early Triassic succession of the Central European Basin represents an important storage of natural gas resources. This continental succession was repeatedly affected by tectonic pulses associated with the earliest phases of Tethyan and Arctic-North Atlantic rift­ing. Effects of differential tectonic subsidence by the formation of intrabasinal highs during the Lower Triassic are particularly well recorded by unconformities, which bear a significant impact on the architecture of potential reservoir sandstones. This study uses a 3D-seismic cube located between the western margin of the Ems Basin (EB) and the East Netherlands High (ENH) in northwestern Germany. Accompanied by core- and log-based facies analysis of 18 cores from this area the effects of differential subsidence and growth faulting on the generation of sedimentary sequences of the Middle Buntsandstein Group are analysed. The fining-upward sequences of the unconformity-bound Volpriehausen-, Detfurth- and Solling Formations each bear basal reservoir sandstone units that represent mostly aeolian dune and sandsheet deposits indicating low relief in the depositional environment. The thickness distribution of these units is directed by the tectonically provided accomodation potential, which is least developed on the ENH where an amalgamation of unconformities occurs. The architecture of these units is further modified by locally developed synsedimentary growth­faults that create a stepwise decrease of stratigraphic completeness from the EB to the ENH. These faults originate from deep rooting, north–south extending basement faults in Upper Carboniferous strata that were decoupled by intercalated Permian evaporites.