Late Cenozoic tectonic deformation across the northern foreland of the Chinese Tian Shan

摘要

To understand the reactivation and intensified uplift of the Tian Shan range in the Cenozoic, the age of development of the associated series of anticlinal belts formed in the southern and northern foreland basins must be constrained. To estimate the shortening magnitude and rates in the northern foreland basin, we provide here regional structural analysis based on identified growth strata dated with existing magnetostratigraphy, together with balanced cross sections from interpreted seismic data. These results indicate that three paralleled rows of anticlinal belts have developed sequentially from south to north accommodating a total shortening of ~15 km at the location of the structurally restored seismic section provided here. These three belts present different structural deformational styles with the southern (Qingshuihe) anticline as a basement-involved fold, the middle (Huoerguosi) anticline as a fault-bend fold and the northern (Anjihai) anticline as a fault-propagation fold. Growth strata inferred from seismic profiles start stratigraphically far below growth strata observed on the outcrop. The latter coincide with accelerated folding of the anticlinal belts at ~6 Ma for the southern, ~2 Ma for the middle ~1 Ma for the northern. Our results imply that the northern Tian Shan foreland rates of deformation were lower until late Miocene and increased in more recent times to values in line with GPS-derived rates.