Post-Variscan sedimentary record of the SW margin of the Bohemian massif: a review

Abstract

The late-Palaeozoic to Cenozoic stratigraphic and structural record of the southwestern margin of the Bohemian massif and its extension beneath the southward adjacent Molasse basin shows that it is controlled by a system of basement-involving faults which came into evidence during StephanianAutunian times and which were subsequently repeatedly reactivated. Thick Permo-Carboniferous clastics accumulated in fault-bounded transtensional basins aligned with the southwestern Bohemian border zone (SWBBZ). Following late-Autunian deformation of these basins, the SWBBZ was overstepped by latePermian to Late Jurassic platform sediments, reflecting tectonic stability. During the Early Cretaceous the SWBBZ was strongly reactivated, causing disruption and erosion of its Mesozoic sedimentary cover. Sedimentation resumed in the area of the SWBBZ during late Early and Late Cretaceous with clastic influx from the Bohemian massif reflecting gradually increasing tectonic activity along the SWBBZ. During the Late Senonian and Paleocene transpressional deformations resulted in upthrusting of major basement blocks. In the Molasse basin such structures are sealed by transgressive Late Eocene marine strata. Mio-Pliocene uplift of the Bohemian massif, involving mild reactivation of the SWBBZ, is related to the development of the volcano-tectonic Eger zone. The structural configuration of the SWBBZ is largely the result of Late Senonian-Paleocene compressional intraplate tectonics which play a major role in the structural framework of the northern Alpine and Carpathian foreland.

The KTB apatite fission-track profiles: Building on a firm foundation?

“…Up to 2.5 km predominantly red beds (Rotliegend) accumulated in the deeper parts. Most of them derived from the BM, which underwent 4-5 km Carboniferous-Permian uplift and erosion (Helmkampf et al, 1982) with a lesser contribution from the Naab Mountains (Schrö der, 1988;Schrö der et al, 1997). A considerable thickness of the trough infill was removed by erosion before the deposition of Late Permian.…”

“…Detailed geomorphological investigations that started with the KTB project (e.g., Schrö der, 1987;Bischoff, 1993;Bischoff et al, 1993;Peterek et al, 1997, and references therein;Schrö der et al, 1997) and continued thereafter (Peterek and Schrö der, 2010;Peterek et al, 2011;Peterek, 2012, and references therein) identified a number of marker horizons that allow to estimate the extent and timing of vertical displacements and erosion of the different blocks in the southwest ER and its surroundings. The first is a Palaeogene peneplain: after the Late Cretaceous to Palaeocene uplift and denudation, a thick saprolite developed into the levelled Variscan basement under humid tropical conditions and tectonic quiescence.…”

Repeated hydrothermal quartz crystallization and cataclasis in the Bavarian Pfahl shear zone (Germany)

“…These fluorite-barite veins formed from fluids showing strong geochemical similarities with those responsible for precipitation of the Pfahl quartz (Horn et al, 1986;Gerler, 1990;Reutel, 1992). Later deformation along the Pfahl shear zone took place in the late Cretaceous to Paleocene during reactivation of the south-western Bohemian border zone (Schr€ oder et al, 1997), evidenced by Upper Cretaceous SW-directed thrusting along the northern extension of the Pfahl zone in Mesozoic rocks of the South German Basin near Amberg (Gudden, 1956) (Fig. 1), along Danube (Siebel et al, 2010) and the Rodl shear zones (Brandmayr et al, 1995).…”

The late-and post-Variscan tectonic evolution of the Western Border fault zone of the Bohemian massif (WBZ)

“…During intra-and post-Permian block faulting this Naab trough (Schro¨der 1988) was separated into individual basins (Peterek et al 1996a). Synsedimentary faulting is particularly indicated by the variation of lateral thickness and changing facies of the trough sediments (Schro¨der 1988;Schro¨der et al 1997). Fault activity during the Permo-Carboniferous is well constrained for individual faults of the WBZ (Mu¨ller 1994).…”