Abstract. The exposed Variscan basement in central Europe is
well-known for its complex structural and lithological architecture
resulting from multiple deformation phases. We studied the southwestern
margin of the Bohemian Massif, which is characterized by major and
long-lived shear zones, such as the Pfahl and Danube shear zones, extending
over > 100 km and initiated during Variscan tectonics. We
integrated Bouguer gravity anomaly and lidar topographic data analyses and
combined our results with available data and observations from
low-temperature thermochronology, metamorphic grades, and the exposed
granite inventory to detect patterns of basement block segmentation and
differential exhumation. Three NW–SE-striking basement blocks are bordered
by the Runding, Pfahl, and Danube shear zones from the northeast to the
southwest. Basement block boundaries are indicated by abrupt changes in
measured gravity patterns and metamorphic grades. By applying high-pass
filters to gravity data in combination with lineament analysis, we
identified a new NNW–SSE-striking tectonic structure (Cham Fault), which
further segments known basement blocks. Basement blocks that are segmented
by the Cham Fault differ in the abundance and spatial distribution of
exposed late Variscan granites and are further characterized by variations in apparent thermochronological age data. Based on our observations and
analyses, a differential exhumation and tectonic tilt model is proposed to
explain the juxtaposition of different crustal levels. Block segmentation
along the NW–SE-striking Pfahl and Runding shear zones most likely occurred
prior, during, and after late orogenic granite emplacement at ca. 320 ± 10 Ma, as some of the granites are cross-cut by the shear zones, while others utilized these structures during magma ascent and emplacement. In contrast,
activity and block segmentation along the Cham Fault occurred after granite
emplacement as the fault sharply truncates the granite inventory. Our study
provides evidence of intense and continuous fault activities during late
and post-orogenic times and highlights the importance of tectonic structures
in the exhumation and juxtaposition of different crustal levels and the
creation of complex lithological patterns in orogenic terrains.
Late to post-Variscan basement segmentation and differential exhumation along the SW Bohemian Massif, central Europe
