Tajik Basin and Southwestern Tian Shan, Northwestern India-Asia Collision Zone: 1. Structure, Kinematics, and Salt Tectonics in the Tajik Fold-and-Thrust Belt of the Western Foreland of the Pamir

Łukasz Gągała , Lothar Ratschbacher , Jean-Claude Ringenbach (1, 2) , Sofia-Katarina Kufner , Bernd Schurr , Ralf Dedow , Sanaa Abdulhameed , Edouard Le Garzic (3) , Mustafo Gadoev , Ilhomjon Oimahmadov

1 TOTAL S.A.
2 LFCR - Laboratoire des Fluides Complexes et leurs Réservoirs
3 IPGS - Institut de physique du globe de Strasbourg

Surface, seismic, and borehole data characterize the Neogene-Recent Tajik fold-and-thrust belt of the Tajik basin. The basin experienced little sub-detachment basement deformation, acting as a rigid foreland plate during the Pamir orogeny. The Tajik fold-and-thrust belt contains variable thinskinned structural styles, changing along and across strike as a function of the thickness and facies of Upper Jurassic evaporites, which constitute the basal detachment, and the influence of the surrounding thickskinned belts. The southern Tajik fold-and-thrust belt shows regularly spaced, salt-cored, thrusted detachment anticlines that transition northward into imbricated thrust sheets grouped in oppositely verging stacks facing each other across a common footwall syncline. The width of the fold-and-thrust belt decreases northeastward accommodated by the Ilyak fault, a lateral ramp developed over a seismically active dextral basement fault. The southeastern Tajik fold-and-thrust belt contains massive subaerial salt sheets, formed by squeezing of preexisting salt diapirs. The salt-tectonic domain originates from a local depocenter within the Late Jurassic Amu Darya-Tajik evaporitic basin. Serial cross sections, integrating the structural geometries, yielded minimum thinskinned shortening oriented at~90°to the India-Asia convergence direction, increasing from~93 km in the south to~148 km in the center, and dropping tõ 22 km in the northeast; total shortening-including the foreland buttress-is ≥170 km. Most of the shortening in the central-southern Tajik fold-and-thrust belt occurred by hinterland-vergent, high-displacement back thrusts. The Pamir played a dominant role in the transfer of shortening to the sedimentary infill of the Tajik basin with the Tian Shan acting as a semi-passive buttress.

Domaines: Sciences de la Terre

Łukasz Gągała, Lothar Ratschbacher, Jean-Claude Ringenbach, Sofia-Katarina Kufner, Bernd Schurr, et al.. Tajik Basin and Southwestern Tian Shan, Northwestern India-Asia Collision Zone: 1. Structure, Kinematics, and Salt Tectonics in the Tajik Fold-and-Thrust Belt of the Western Foreland of the Pamir. Tectonics, 2020, ⟨10.1029/2019TC005871⟩. ⟨insu-02873593⟩