Abstract
The Molasse Basin in Southern Germany is part of the North Alpine Foreland Basin and hosts the largest accumulation of deep geothermal production fields in Central Europe. Despite the vast development of geothermal energy utilization projects especially in the Munich metropolitan region, the evolution of and control factors on the natural geothermal field are still debated. Especially seismic and deep well data from extensive oil and gas exploration in the Molasse Basin led to conceptual hydrogeological and thermal-hydraulic models. Corrected borehole-temperature data helped to constrain subsurface temperatures by geostatistical interpolation and facilitated the set-up of 3D temperature models. However, within the geothermally used Upper Jurassic (Malm) carbonate aquifer, temperature anomalies such as the Wasserburg Trough anomaly to the east of Munich and their underlying physical processes are yet poorly understood. From other foreland basins like the Alberta Basin in Western Canada, it is known that climate during the last ice age has a considerable effect even on subsurface temperatures up to two kilometres depth. Therefore, we study the impact of paleoclimatic changes on the Molasse Basin during the last 130 ka including the Würm glaciation. We consider the hydraulic and thermal effects of periglacial conditions like permafrost formation and the impact of the numerous glacial advances onto the Molasse Basin. The major difference between the thermal-hydraulic regime in the western and eastern parts of the Southern German Molasse Basin are delineated by calculating two contrasting permeability scenarios of the heterogeneously karstified Malm carbonate aquifer. Thermal-hydraulic modelling reveals the effect of recurrent glacial periods on the geothermally drillable subsurface, which is minor compared to the effect of permeability-related, continuous gravity-driven groundwater flow as a major heat transport mechanism. Practically, the results might help to reduce the exploration risk for geothermal energy projects in the Molasse Basin. More importantly, this study serves as a reference for the comparison and understanding of the interplay of high permeability aquifers, gravity-driven groundwater flow and paleoclimate in other orogenic foreland basins worldwide.
Volcanism and Volcanogenic Submarine Sedimentation in the Paleogene Foreland Basins of the Alps: Reassessing the Source-to-Sink Systems with an Actualist View