Abstract

We propose that the Altyn Tagh uplift of northwest China is a southwest-tapered structural wedge that has been extruded northeastward along the wedge-bounding, left-slip Ruoqiang-Xingxingxia fault and the net-right-slip Altyn Tagh fault, currently active as a left-slip fault. This model posits that the leading edge of the Altyn Tagh wedge lies along the northern margin of a reactivated middle Paleozoic orogenic belt, the Beishan, which is the right-laterally offset equivalent of the Qilian Shan orogen. This internally consistent and testable model explains the partitioning of shortening in the Tarim and Qaidam blocks and adjacent areas, the amount and sense of strike slip on the Ruoqiang-Xingxingxia fault and Altyn Tagh fault, and the location of the westward continuation of the truncated Qilian Shan orogen. The wedge model also implies that the apparent present-day continuity of Precambrian basement from the Tarim block, through the Altyn Tagh wedge, to the North China block actually reflects structural juxtaposition during wedge extrusion of two originally separate blocks.

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