Mesozoic to Cenozoic exhumation history of the Odenwald and Heidelberg, Germany

In Germany, the first apatite fission-track study was performed in the Odenwald (Wagner 1968) with the results of Mesozoic apatite fission-track ages. The presentation will re-examine the Mesozoic-Cenozoic exhumation history of the Odenwald and Heidelberg area with new thermochronological data. The Odenwald as part of the Mid-German Crystalline Zone is characterized by outcrops of the Variscan basement and overlain Mesozoic and Cenozoic strata. Towards the West, the Variscan Basement is bound by the Upper Rhine Graben basin and towards the East by the Mesozoic and Cenozoic cover. Variscan basement rocks, Mesozoic, and Oligocene sandstones have been studied by apatite fission-track and apatite (U-Th-Sm)/He thermochronology. Apatite fission-track ages range between 70.4±3.8 Ma and 116.7±5.2 Ma and apatite (U-Th-Sm)/He ages between 66.4 ± 4.0 Ma and 121.3 ± 16.7 Ma. Apatite of the Oligocene sandstone deposit near Heppenheim revealed a central fission-track age of 49.4±3.6 Ma. The thermochronological data show a differentiated age distribution with cooling ages getting younger from north to south. Consequently, we assume that exhumation of the rocks in the northern part set in earlier a took place slower than in the southern part of the Odenwald. Numerical modelling using the software code HeFtyimplies either a high Cretaceous heat flow or a maximum of up to 2830 meters of Mesozoic sedimentary rocks that could have covered the Odenwald crystalline basement during the Cretaceous. The modelled t-T-evolution hints at two major phases of exhumation, one in the Cretaceous and one in the Neogene.