Features of the Thrust Wedge of Deformation Belt in Kuqa Rejuvenation Foreland Basin

Abstract

Kuqa rejuvenation foreland basin and its thrust wedge of foreland deformation belts are structurally responsed to the India Eurasia collision in the interior of Asia continent. Based on the detailed surface geology reconnaissance and interpretations of many seismic profiles, we conclude that thrust wedge of deformation belt in Kuqa rejuvenation foreland basin is divided into five structural units, including the marginal thrust and hidden structural zone, the Shidike anticline zone, the North linear anticline zone, the Baicheng piggy back depression and the Qiulitage thrust frontal zone. The fault related folds are the basic deformation styles of the rejuvenation foreland thrust wedge, which are classified into nine kinds of fault related folds, including fault bend fold, fault propagation fold, detachment kink fold, duplex, pop up, hybrid fault bend/detachment fold, stacked anticline, composed wedge structure and superimposed fault bend/fault propagation fold. In the northern part of the flat/ramp thrust wedge, the fault related folds are mainly of fault bend folds, fault propagation folds, and duplexes. For the very front of the wedge there exist well developed blind thrusts and detachment kink folds, forming a typically cryptic thrust wedge front edge. Growth strata recorded accurately initial emplacement ages of every structure belt and detailed forming processes. Thrusts and thrust related folds propagate from the north to the south within the thrust wedge, i. e. Misibulake anticline initiated in the Miocene (23.3Ma), velocity of blind thrust 0.16mm/a ; Kalabahe anticline and Kelasu anticline in 16.9Ma, velocity of hidden thrust 0.16mm/a and 0.16mm/a; Dawanqi anticline in 3.6Ma, velocity of hidden thrust 0.82mm/a; Dongqiulitage anticline in 3Ma, velocity of blind thrust 1.3mm/a; and Yaken anticline in 1.87Ma, velocity of hidden thrust 3mm/a. The crustal shortening velocity which caused the thrusting is slow at about 0.355mm/a in average in the Miocene, then approaches 0.82mm/a in middle Pliocene. During the late Pliocene and the Quaternary the velocity gets faster in about one magnitude order, up to 1.29-3mm/a, implicating that an accelerating crustal shorting process occurred in the late Cenozoic in the Kuqa thrust belt and approached a climax in the Pliocene and the Pleistocene.