Analysis of the Cretaceous Sequence-stratigraphic Pattern and Controlling Factors in Kuna Foreland Basin

The cretaceous Kuqa depression is a foreland basin generated by flexural subsidence resulting from the southward thrusting of the southern Tianshan Mountains. This paper has divided Cretaceous sequence stratigraphy of Kuqa foreland basin into two tectonic sequences and eight 3rd order sequences based on outcrops, well loggings and seismographic profiles. The sequences and system tracts in the Kuqa foreland basin spread from east to west as a whole and vary obviously from south to north. Two different models of sequence stratigraphic framework were established through studying the internal composition of sequence strata and boundary of individual sequences. In the kapushaliangqun group, this basin appeared as a strong compressive piedmont alluvial-hungry basin, a typical foreland basin. The development of sequence is attributed to the foreland tectonic process from flexural subsidence caused by thrust loading to rebounded uplift due to the erosion and stress release. In contrast, the basin shows smooth and expansive features in the bashijiqike age,and it has a unique model of sequence stratigraphy framework and special internal stratigraphic composition. The sequence framework and depositional pattern of the Cretaceous foreland basin were predominantly determined by the foreland tectonism and the changes of climate mainly impacted on sedimentary facies within sequence frameworks.