J. Alvarez-marron et al., Accretionary complex structure and kinematics during Paleozoic arc-continent collision in the southern Urals, TECTONOPHYS, 325(1-2), 2000, pp. 175-191
The southern Urals contain a well-preserved accretionary complex that has o
verthrust the continental margin during are-continent collision between the
East European Craton (EEC) and the Magnitogorsk island are in the Late Dev
onian. Within the accretionary complex, we study three tectonic units that
differ in deformation style, and each provides a unique geodynamic implicat
ion. The Zilair Nappe, the largest and best exposed unit, consists of 5-6 k
m of syncollisional, are-derived Upper Devonian to Lower Carboniferous poly
mictic and graywacke turbidites that were deposited across the continental
margin and incorporated by frontal accretion into the accretionary complex.
The Zilair Nappe is a bivergent thrust imbricate where the west-vergent th
rusts dominate and have associated kilometer-scale ramp anticlines with wel
l developed east-dipping axial planar cleavage. Along its eastern contact,
however, the cleavage fans until it dips moderately westward and the folds
are east-vergent. Following its emplacement, west-vergent, basement-involve
d thrusting that breached the whole accretionary complex imbricated the Zil
air Nappe. The Timirovo Duplex is structurally beneath the Zilair Nappe, an
d outcrops for several tens of kilometers along its northwestern margin. Th
e duplex forms a west-vergent thrust stack composed of a highly deformed an
d sheared Lower and Middle Devonian reef carbonates of the former EEC margi
n platform. These rocks were shallowly underplated at the base of the accre
tionary complex during emplacement over the margin. The Suvanyak Complex ou
tcrops along the eastern contact of the Zilair Nappe, and consists of polyd
eformed greenschist facies metasediments of the former EEC slope that were
offscraped, underplated and incorporated at the rear of the accretionary co
mplex. (C) 2000 Elsevier Science B.V. All rights reserved.