Depositional style and subsidence history of the Turpan Basin (NW China)

The Turpan Basin has a complex polycyclic sedimentary and tectonic history from Late Permian to late Tertiary time. Main stratigraphic boundaries are unconformities that bound tectonically induced sedimentary cycles. The depo sitional style reflects a continental environment exhibiting changes from a lluvial fan/fluvial to lacustrine conditions within each cycle. More than 7 000 m of elastic sediments accumulated during the evolution of the basin. P aleocurrent analysis reveals a complex pattern of sediment dispersal pathwa ys into the basin. On the southern margin of the basin, the transport direc tion is always directed from south to north indicating sediment sources in the Jueluotage Shan, while in the northern part the Late Jurassic uplift of the Bogda Shan provided an important source area from the Early Cretaceous onwards with transport directions from north to south. After basin formati on during the Late Permian, the Turpan Basin underwent first thermal subsid ence and then flexural subsidence. The thermal subsidence took place during the Late Permian and Early Triassic following the period of magmatic activ ities in this region. The flexural subsidence was throughout the Middle Tri assic to early Tertiary induced by collisions and accretions onto the south Asian continental margin of the Qiangtang Block in the Late Triassic/Early Jurassic, the Gangdise Block in latest Jurassic/earliest Cretaceous, and t he Indian Subcontinent in the latest Cretaceous/early Cenozoic. (C) 1999 El sevier Science B.V. All rights reserved.