Mnin restraining stepover – evidence of significant Cretaceous–Cenozoic dextral strike-slip faulting along the Teisseyre-Tornquist Zone?

Abstract

ABSTRACT:Konon, A., Ostrowski, S., Rybak-Ostrowska, B., Ludwiniak, M., Śmigielski, M., Wyglądała, M., Uroda, J., Kowalczyk, S., Mieszkowski, R. and Kłopotowska, A. 2016. Mnin restraining stepover -evidence of significant Cretaceous-Cenozoic dextral strike-slip faulting along the Teisseyre-Tornquist Zone? Acta Geologica Polonica, 66 (3), 429-449. Warszawa.A newly recognized Mnin restraining stepover is identified in the Permo-Mesozoic cover of the western part of the Late Palaeozoic Holy Cross Mountains Fold Belt (Poland), within a fault pattern consisting of dextral strikeslip faults. The formation of a large contractional structure at the Late Cretaceous -Cenozoic transition displays the significant role of strike-slip faulting along the western border of the Teisseyre-Tornquist Zone, in the foreland of the Polish part of the Carpathian Orogen. Theoretical relationships between the maximum fault offsets/mean step length, as well as between the maximum fault offsets/mean step width allowed the estimation of the values of possible offsets along the Snochowice and Mieczyn faults forming the Mnin stepover. The estimated values suggest displacements of as much as several tens of kilometres. The observed offset along the Tokarnia Fault and theoretical calculations suggest that the strike-slip faults west of the Late Palaeozoic Holy Cross Mountains Fold Belt belong to a large strike-slip fault system.We postulate that the observed significant refraction of the faults forming the anastomosing fault pattern is related also to the interaction of the NW-SE-striking faults formed along the western border of the TeisseyreTornquist Zone and the reactivated WNW-ESE-striking faults belonging to the fault systems of the northern margin of the Tethys Ocean.

Swelling and flow of expanding clays as a cause for non‐tectonic deformations in a glacial–interglacial environment: Holy Cross Mountains, Poland

“…According to earlier models, the upturning of the Callovian strata is due to the presence of a right‐lateral Gnieździska–Brzeziny fault (Konon, 2007; Mastella & Konon, 2002), which stretches for about 27 km along the Bathonian–Callovian boundary. This fault would have been accompanied by flower structures responsible for the steepening of the Callovian strata.…”

“…From the examples cited, it is clear that shearing of unaltered clays could be initiated by an overburden thickness of slightly more than 30 m, while an overburden thickness of 2-3 m is sufficient to shear weathered clays. According to earlier models, the upturning of the Callovian strata is due to the presence of a right-lateral Gnieździska-Brzeziny fault (Konon, 2007;Mastella & Konon, 2002), which stretches for about 27 km along the Bathonian-Callovian boundary. This fault would have been accompanied by flower structures responsible for the steepening of the Callovian strata.…”

“…The contact between the Callovian gaizes and underlying Bathonian black clays is thus an important rheological boundary (Figure 2b). At the contact of these two extremely rheologically different complexes, steep, vertical and overturned layers are observed (Figure 2d,e) (Konon, 2007; Konon et al, 2016; Mastella & Konon, 2002). In previous papers, this arrangement has been explained by tearing along the Gnieździska‐Brzeziny strike‐slip fault associated with flower structures (Konon et al, 2016; Rybak‐Ostrowska et al, 2020).…”

“…At the contact of these two extremely rheologically different complexes, steep, vertical and overturned layers are observed (Figure 2d,e) (Konon, 2007; Konon et al, 2016; Mastella & Konon, 2002). In previous papers, this arrangement has been explained by tearing along the Gnieździska‐Brzeziny strike‐slip fault associated with flower structures (Konon et al, 2016; Rybak‐Ostrowska et al, 2020). According to Mastella & Konon (2002), this fault developed in several phases under transpression during which en echelon Riedel shears originated.…”

“…One such example where clay swelling and flow appear to have been responsible for the deformation of overlying rigid layers is the Triassic/Jurassic boundary in the southern part of the Mesozoic cover of the Holy Cross Mountains, which has previously been attributed to purely tectonic deformation connected with strike‐slip faults (Konon, 2007; Konon et al, 2016; Mastella & Konon, 2002). This paper explores such a possibility by analysing the geological setting, climatic conditions, mechanical properties, lithology and mineralogy of the deformed rocks and concludes that non‐tectonic phenomena rather than endogenous processes are the main cause.…”