Late Palaeozoic strike-slip tectonics versus oroclinal bending at the SW outskirts of Baltica: case of the Variscan belt’s eastern end in Poland

Abstract

Geophysical and geological data from the eastern sector of the Central European Variscan belt are presented and reviewed in the regional tectonic context. Matched filtering of isostatic gravity, guided by results of spectral analysis, along with other derivatives of gravity and magnetic fields reveal a dominant WNW-ESE-trending pre-Permian structural grain in the external zones of the Variscan belt in Poland. This trend is confirmed by regional distribution of dips in Carboniferous and Devonian strata that were penetrated by boreholes beneath Permian-Mesozoic sediments. Based on these data, two alternative concepts explaining the connection of the Variscan belt and its NE foreland, those of strike-slip tectonics versus oroclinal bending, are discussed. The WNW-ESE structural trend in the Variscan foreland is parallel to a set of major strike-slip fault zones in the area, including those of Upper Elbe, Intra-Sudetic, Odra, Dolsk and Kraków-Lubliniec. These faults are considered to convey a significant dextral displacement between Laurussia and Gondwana. The revised position of the Variscan deformation front shows a similar, uninterrupted, generally WNW-ESE trend, up to the SE border of Poland, which indicates an initial continuation of the Variscan belt into the area of the present-day Western Carpathians. The geometry of the Variscan deformation front along with the pattern of the Variscan structural grain are inconsistent with the idea of an oroclinal loop affecting the external, non-metamorphic Variscan belt. However, the data presented do not entirely rule out an oroclinal loop within the Variscan internides. The still possible options are (1) a semi-oroclinal model postulating ~ 90° bending of the Variscan tectonostratigraphic zones into parallelism with the WNW-ESE strike-slip faults or (2) an orocline limited only to the belt linking the Wolsztyn High and Moravo-Silesian non-to weakly-metamorphic fold-and-thrust belt. Regardless of the kinematic model preferred, our data indicate that structural evolution of the Polish Variscides was concluded with the end-Carboniferous NNE-SSW shortening that resulted in the present-day extent of the Variscan deformation front.

Long‐distance fluid migration defines the diagenetic history of unique Ediacaran sediments in the East European Craton

“…The general distribution of illite diagenetic ages of >400 Ma in the north and east, and <360 Ma in the south of the study area, with mixed data in the western and central part, seems to follow the order and timing of the successive Caledonian and Variscan orogenic events at the SW periphery of the EEC (Mazur et al., 2018, 2020). The lack of ages older than 390 Ma in the basins onlapping the SW slope of the EEC along the TTZ (Figure 1; Kowalska et al., 2019; Środoń, Clauer, et al, 2009) indicates that the oldest brine migration must have come from the Scandinavian Caledonides front in the NW.…”

“…This sedimentary succession was mostly eroded off before the Permian. The exception makes the area of SE Poland, where the EEC was overridden by a Variscan orogenic wedge (Mazur et al., 2020). This section of the craton margin is characterized by the latest Carboniferous K–Ar ages (Kowalska et al., 2019), corresponding to the time of Variscan shortening.…”

European tectosphere and slabs beneath the greater Alpine area – Interpretation of mantle structure in the Alps-Apennines-Pannonian region from teleseismic V&lt;sub&gt;p&lt;/sub&gt; studies

“…This differs somewhat from current seismological definitions, which treat plates as entities comprising only seismically fast mantle lithosphere (e.g., Piromallo & Morelli, 2003;Wortel & Spakman, 2000). Schmid et al (2004) and; Thin black lines -tectonic lineaments separating Variscan tectonometamorphic domains after Franke (2017Franke ( , 2000, Mazur et al (2020), and Schulmann et al (2014). Blue lines are traces of vertical tomographic profiles in Figs.…”

“…The reader is referred to Kind et al (2021) for a reassessment of Moho depth. The crustal structure in the profiles is taken from Alpine cross sections of Schmid et al (2004Schmid et al ( , 2013Schmid et al ( , 2017 and Cassano et al (1986), whereas schematic Variscan crustal cross sections are from Franke et al (2017), Franke (2020, Mazur et al (2020) and Schulmann et al (2014). A striking feature in horizontal slices at 100 to 220 km depth is the continuation of negative velocity anomalies of up to 3-4% from the northern Alpine foreland across the Alpine orogenic front to beneath the Western and Central Alps, as well as the westernmost part of the Eastern Alps (Fig.…”

Structural Evolution at the Northeast North German Basin Margin: From Initial Triassic Salt Movement to Late Cretaceous‐Cenozoic Remobilization

“…Within the central part of the NGB, the prominent Mesozoic-Cenozoic Glückstadt Graben marks the western border of the study area (Figure 1). Vejbaek & Britze, 1994;Schlüter et al, 1997;Baldschuhn et al, 2001;Pharaoh et al, 2010;Al Hseinat & Hübscher, 2017;Seidel et al, 2018;Mazur et al, 2020). Inset shows approximate outline of the northern and southern Permian Basin.…”