The structure of the south Urals foreland fold and thrust belt at the transition to the Precaspian Basin

Abstract

The structural architecture of the south Urals foreland fold and thrust belt at the transition into the Precaspian Basin is that of a wedge-shaped, west-vergent thrust stack with a significant amount of basement involvement. The surface geology of this part of the thrust belt is dominated by the south Urals accretionary complex, whose internal structure was primarily developed during Late Devonian to Early Carboniferous arc–continent collision and which was subsequently incorporated into the thrust belt. A number of thrusts, identified in the field and in seismic profiles, breach the accretionary complex, suggesting that they post-date its emplacement and may be related to the development of the foreland fold and thrust belt. A basal detachment can be confidently defined only beneath the frontal part of the thrust belt, making it difficult to construct balanced and restored cross-sections and therefore to calculate the amount of shortening. Nevertheless, the amount of shortening appears to be of the order of only a few tens of kilometres. There is a major change in the structural style along the frontal part of the thrust belt that may be related to basement topography and/or basement response to the deformation across a basement fault oriented at a high angle to the structural grain of the thrust belt.

Geodynamics of the Ural Foredeep and Geomechanical Modeling of the Origin of Hydrocarbon Accumulations

“…However, the formations of the Upper Paleozoic stratified complexes in the Frontal Fold Zone are of the same age as those in the southern part of the Ural Foredeep. Data from regional surveying, seismic operations, and specialized studies in this area [27,28,40] indicate that the Ural Frontal Fold Zone is made up of Ordovician (perhaps, Ordovician-Silurian), Devonian, Carboniferous, and Lower Permian stratified sedimentary units.…”

Structural architecture of the southern and middle Urals foreland from reflection seismic profiles

“…Throughout the southern and middle Urals, the foreland thrust and fold belt deforms syntectonic Late Carboniferous to Early Triassic sediments of the foreland basin, Paleozoic continental margin rocks, the Archean and Proterozoic basement and, in the southern Urals, the Middle to Late Devonian arc‐continent collision accretionary complex (Figure 1) [ Ablizin et al , 1982; Zhivkovich and Chekhovich , 1985; Kamaletdinov , 1974; Giese et al , 1999; Brown et al , 2004]. In the middle Urals, between approximately 56°N and 59°N, the thrust belt is a narrow, overall N‐S trending, west‐verging basement‐involved thrust stack measuring ∼50–90 km in width from the Main Uralian fault (the arc‐continent suture) to the frontal folds [ Ablizin et al , 1982; Zhivkovich and Chekhovich , 1985].…”

“…To date, balanced and restored cross sections and, consequently, the amount of shortening have not been determined for the middle Urals part of the foreland thrust and fold belt. By far the best studied area of the foreland thrust and fold belt structure is in the southern Urals, from approximately 56°N to 51°N [ Kamaletdinov , 1974; Bastida et al , 1997; Brown et al , 1997, 1998, 1999, 2004; Perez‐Estaun et al , 1997; Giese et al , 1999; Alvarez‐Marron et al , 2000], where it forms a ∼150 km wide, west vergent thrust stack. On the basis of balanced and restored cross sections constructed from surface geology, the minimum amount of Paleozoic shortening recorded in the thrust belt in the southern Urals has been estimated to be about 20 km [ Perez‐Estaun et al , 1997; Brown et al , 1997].…”

“…This calculation assumes only minor pre‐Uralide deformation between the Tashly thrust and the Zuratkul fault, an assumption that fits well with a section across the southern termination of the Bashkirian anticlinorium [ Brown et al , 1997], where control is provided by Paleozoic sediments (Figure 1). East of the Zuratkul fault we have no control on the amount of Uralide shortening, although in sections farther south it appears to be minor [ Brown et al , 2004].…”

The Appalachian area as a tectonostratigraphic analogue for the Barents Sea shelf

“…Hence, the overarching goal of this paper is to investigate possible analogue relationships between the U.S. Appalachian and BSS systems of basins and platforms. Elements of the Appalachian system (Figure 1a) have been previously used as possible analogues for the nearby Timan–Pechora Basin (e.g., Artyushkov & Baer, 1986), and earlier generic comparisons of the Appalachian orogen with the Caledonian and Uralian orogens have been attempted (Allen & Allen, 2013; Arthaud & Matte, 1977; Artyushkov & Baer, 1983, 1985; Brown et al., 2004, 2006; Hatcher, 2010; Knapp et al., 1998; Kruse & McNutt, 1988; Matte, 2002; Puchkov, 2009). For example, Puchkov (2009) briefly suggested that evolution of the Uralian Orogeny was like that of the Taconian and Alleghanian orogenies in the Appalachian area but went no further in defining the analogue.…”