Triassic sequence stratigraphy in Kuqa foreland basin

A systematic study on Triassic sequence stratigraphy in Kuqa foreland basin has been carried out by integration of seismic, logging and drilling data and outcrop survey. 13 sequences' boundaries have been identified, and they were divided into 12 sequences and 33 system tracts. Two different models of sequence stratigraphic framework were established through studying the internal composition of sequence strata and boundary of individual sequences. From early Triassic to the end of Huangshanjie stage of late Triassic, this basin appeared as a strong compressive piedmont alluvial-hungry basin, a typical foreland basin. The model of the sequence stratigraphic framework and its internal composition are similar to that of Vail's passive continental marginal basin, respectively. In contrast, from Taliqike stage of late Triassic to the end of Cretaceous, the basin shows smooth and expansive features, and has a unique model of sequence stratigraphy framework and its special internal stratigraphic composition. The evolution of sequences was mainly controlled by regional tectonic activities, paleoclimate and sediment supplies. The main factors controlling the changes of lake or base-level are orogenic episodes of the tectonic activities. The period for the lake to be deepened as a result of strong orogeny is the major period of lake transgression whilst the stage of the relatively weak orogeny is the major period of lake degression. The changes of climate mainly impacted on sedimentary facies within sequence frameworks.