Abstract:

The transitional belt between Junggar basin and northern Tianshan Mountain is a NWW-trending or near EW-trending complex tectonic deformation zone.According to the differences of tectonic deformation styles,the configuration within the transitional belt could be divided into several parallel zones from south to north,se-veral sectors from west to east,and 2-3 levels from basement to shallow cover.The northern Tianshan is a "thrust-upheaval basement zone" consisting of parallel alignment of basement that involves thrust faults and folds.There are 2-3 major thrust faults of high-angle dipping to the south within the "thrust-upheaval basement zone.The transitional zone is a "basement-cover" that involves thrust flexure zone consisting of basement-involved thrust faults and sedimentary cover of monocline dipping toward basin.There are several branch thrust faults of middle-and low-angle dipping to the south of the basin within the "basement-cover" and some of them have associated anticlines in the hanging-wall.The inner part of Junggar basin is a "delaminated contraction and vertical stack zone" consisting of 2 lines of detachment anticline and basement-involved high-angle faults.Structural styles are similar in the same zones,sectors,or levels,but vary in different zones,sectors and levels.The transitional belt was influenced by superpositional tectonic deformation from regional extension during the Early Permian,trans-contraction during the Late Jurassic,and contraction during the Pliocene.However,it was mainly the result of the upheaval of northern Tianshan Mountain since the Pliocene.The main factors influencing the tectonic style of the transitional belt include the pre-existing faults,weak beds within sedimentary basin cover,and upheaval and compression of northern Tianshan.

Key words: fracture zone, structural style, tectonic level, tectonic evolution, northern Tianshan, Junggar Basin