EXTRUSION OF THE ALTYN-TAGH WEDGE - A KINEMATIC MODEL FOR THE ALTYN TAGH-FAULT AND PALINSPASTIC RECONSTRUCTION OF NORTHERN CHINA

We propose that the Altyn Tagh uplift of northwest China is a southwes t-tapered structural wedge that has been extruded northeastward along the wedge-bounding, left-slip Ruoqiang-Xingxingxia fault and the net-r ight-slip Altyn Tagh fault, currently active as a left-slip fault. Thi s model posits that the leading edge of the Altyn Tagh wedge lies alon g the northern margin of a reactivated middle Paleozoic orogenic belt, the Beishan, which is the right-laterally offset equivalent of the Qi lian Shan orogen. This internally consistent and testable model explai ns the partitioning of shortening in the Tarim and Qaidam blocks and a djacent areas, the amount and sense of strike slip on the Ruoqiang-Xin gxingxia 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 basem ent from the Tarim block, through the Altyn Tagh wedge, to the North C hina block actually reflects structural juxtaposition during wedge ext rusion of two originally separate blocks.