Pre-Late Carboniferous geology along the contact of the Saxothuringian and Teplá-Barrandian zones in the area covered by younger sediments and volcanics (western Bohemian Massif, Czech Republic)

Abstract

The boundary between the Saxothuringian and the Teplá-Barrandian zones at the western margin of the Bohemian Massif represents an important tectonic suture of the Central European Variscides. However, most of this boundary is covered by Late Carboniferous and younger sedimentary and volcanic rocks, which prevent direct observation of particular geological units. We present a compilation of geological and depth measurement data from 12,134 exploration boreholes that reached the basement of the volcanic and sedimentary infill in the area of the Eger Graben in the north-western Bohemia, and correlate covered geological units with those exposed on the present-day surface. The resulting compilation reveals the relief of the sedimentary basins basement and interprets the real extent of the basement geological units in the western part of the Bohemian Massif. It also shows the position of the contact between units with the Saxothuringian and the Teplá-Barrandian affinities and suggests the boundary between rocks with Devonian metamorphic record and those metamorphosed during the Early Carboniferous period of the Variscan tectonometamorphic cycle.

Crustal structures beneath the Saxonian Granulite Massif, the České středohoří and the Doupovské hory Mts. based on the depth-recursive tomography

“…8), the contact zone between the Saxothuringian and the Teplá-Barrandian units is located under the Bílina Block at depths of 5-10 km. The collision zone generally dips to the northwest, which is in accord with the geological interpretation of this part of the SXT-TBU boundary by Mlčoch and Konopásek (2010). …”

“…The Altenberg-Teplice Caldera region is located near the contact zone where the Saxothuringian rock assemblages were thrust over the Teplá-Barrandian Unit (Mlčoch and Konopásek 2010). The contact is represented by the gravity-defined Litoměřice Deep Fault (e.g.…”

“…Based on the presented P-wave velocity and gravity models and extensive borehole data in the region (e.g. Mlčoch and Konopásek 2010), a subsurface geological model along the S04 line is composed. The model involves partially the root zone of the Saxonian Granulite Massif, further the southwestern margin of ATC structures and the collision zone of the Saxothuringian and the Teplá-Barrandian units.…”

Slope Dependent Morphometric Analysis as a Tool Contributing to Reconstruction of Volcano Evolution

“…The Eger Graben runs across the north-western part of the Bohemian Massif in the ENE-WSW direction (Fig. 2), roughly following the Variscan suture between the Saxothuringian and Teplá-Barrandian domains of the Bohemian Massif (Babuška et al, 2010;Mlčoch & Konopásek, 2010). It is interpreted as an incipient rift structure formed during two distinct extensional phases (Rajchl et al, 2009 NNE-SSW to N-S oriented horizontal extension, oblique to the rift axis.…”

“…Later, lithospheric folding in the Alpine-Carpathian foreland and stretching along the crest of a growing regional-scale anticlinal feature resulted in an orthogonal extensional phase (Dèzes et al 2004; Bourgeois et al 2007;Rajchl et al 2009). Several geological units meet in the basement of the DHVC in the form of a heterogeneous crustal mosaic (Mlčoch & Konopásek, 2010;Valenta et al, 2011). Paragneisses, felsic granulites, orthogneisses, mica schists, and phyllites of the Saxothuringian Unit extend from the north in the basement of the DHVC.…”