Stratigraphic Records on Lithospheric Viscoelastic Deformation in Early Cretaceous, Kuqa Foreland Basin

Key words: 
• Kuqa foreland basin

Abstract: Based on the flexural process of elastic lithosphere different from that of viscoelastic lithosphere in foreland basins, this paper provides a solution to acquire the information about lithospheric dynamic property and deformation process by virtue of stratigraphic configurations at the forebulge slope belt. The Kuqa foreland basin，as an example, had gone through tectonic evolution of two thrust period and a quiescence period in the Early Cretaceous. The Kapushaliang Group and Bashenjiqike Formation had respectively developed during thrust and during quiescence. In a single thrust period, accompanied with thrust loading and lithospheric flexural deformation, lithosphere had transformed from elastic property to viscoelastic, and the basin had widen forward to carton and then had narrowed and deepened forward to thrustfault belt. Accordingly, the stratigraphic records at the forebulge slope dipping forward to the foredeep were as follows: during early thrust, the strata gradually onlapped and retrograded forward to carton so as to form a great onlap/truncation bottom unconformity; during the late thrust, the strata gradually shrank and prograded forward to thrustfault belt so as to form a great truncationtoplap top unconformity. During quiescence, the basin was wide and shallow, and the strata appeared parallel and continuous with a few slight truncation unconformities adjacent to thrustfault belt due to lithosphere rebounding.