Middle-Late Jurassic tectonostratigraphic evolution of Central Asia, implications for the collision of the Karakoram-Lhasa Block with Asia

Abstract

Mesozoic basins in different regions of Central Asia provide important records for investigating relationships between intraplate deformation in Central Asia and tectonic processes at Asian boundaries. The present study gives a review of the stratigraphic and structural evolution of basins in different regions of Central Asia during the Middle-Late Jurassic. It is shown that basins and mountain belts in northwest China experienced compressional deformation and were wholly or partially uplifted during the late Middle-Late Jurassic. Compared to extensively-distributed Middle Jurassic coal-bearing strata in northwest China, Upper Jurassic strata characterized by red mudstones and conglomerates have a much smaller distribution. In the mean time, the Tibet-Pamir plateau also underwent a folding and uplift event, and Upper Jurassic sedimentary rocks are generally missing in the Pamir and western Tibet. The intense compressional deformation and uplift event of the late Middle-Late Jurassic from the Tibet-Pamir plateau to northwest China requires a new tectonic model, as proposed here. We suggest that the Karakoram and Lhasa blocks were a single giant block, which was accreted to Asia in the late Middle Jurassic-earliest Cretaceous and cross-cut by the Karakoram Fault in the Cenozoic. During the Callovian, the western part of the Karakoram-Lhasa Block initially collided with the southern Asian margin. Collision and continued convergence during the late Middle-Late Jurassic caused sinistral strike-slip faulting along the Central Badakhshan Fault and South Tian Shan Suture, accommodating crustal shortening in areas to the southeast of the faults: the Pamir, western Tibet, Tarim Block, Qilian-Qaidam Block, and Bei Shan. Meanwhile, the northeastward transpressional motion of the Tarim Block produced strong compressional stresses to areas north of the Tarim Block: the Kyrgyz Tian Shan, Central Tian Shan, Junggar Basin, and Turfan Basin. With the northward movement of the Karakoram-Lhasa Block, the eastern part of the Karakoram-Lhasa Block began to collide with the southern Asian margin during the latest Jurassic-earliest Cretaceous, resulting in strong crustal deformation and thickening in East Asia and Central Asia.