The Cenozoic structural evolution of the southwestern Tarim Basin, China

The vast Tarim basin is surrounded by Tian Shan Mountains in the north, West Kunlun Mountains in the southwest, and the Altyn Mountains in the southeast. The southwestern Tarim Basin developed within the foreland of the West Kunlun Mountains and cumulated up to 10 km of Cenozoic strata. Despite several decades of geological studies its structural styles and details of its geological evolution are still being debated. In this study, we used seven regional seismic transects from the Yecheng - Hotan area calibrated by deep wells to assess lateral variations of a structural style and syn-tectonic sedimentation in this part of the basin.

The basement of the SW Tarim Basin is covered by Paleozoic and Cenozoic strata, as revealed by several deep calibration wells. The regional north-directed basement thrust together with two evaporitic detachments including the Middle Cambrian evaporites (Awatage Formation) and Paleogene evaporites (Aertashi Formation) controlled the overall tectonic framework and structural evolution of this part of the basin. The visible growth strata on seismic data indicate progressive development of the structural wedge within the frontal W Kunlun Mountains from the Late Miocene to the Present day.

Four main Cenozoic evolutionary stages of the W Kunlun Mountains and adjacent SW Tarim Basin have been determined. At the end of Paleogene, evaporites of the Aertashi Formation have been deposited in SW Tarim Basin; their thickness, as indicated by seismic data, increases towards the Kunlun orogenic wedge which suggests their deposition within the flexural foreland basin. Then, during the Early to Middle Miocene, about 4000m of sediments have been deposited in rapidly subsiding foreland basin. Towards the end of Late Miocene-Pliocene, tectonic wedging along thrust front led to significant uplift of the Kunlun Mountains that presently form S margin of the Tarim Basin. Quaternary migration of compressional deformations towards the North, towards the basin interior led to formation of the intra-basinal Jade anticline that was re-interpreted as a thin-skinned syn-depositional “fish tail” structure detached within the Paleogene evaporites. Present-day activity along some deeply buried thrusts of the Kunlun Mts. tectonic wedge might be related to current earthquakes.