Abstract:

A series of  thrust-fold belts were  formed  in  the southern Junggar  foreland basin during  the Cenozoic. This paper
provides  regional structural analyses of  the  thrust  fold belts based on  the growth strata,  interpretation of seismic profiles, and
balanced cross-sections,  together with available magnetostratigraphic  results. Our analyses show  that  three paralleled  rows of
anticlinal belts have been developed sequentially from the south to the north since ~7 Ma for the southern, ~2 Ma for the middle,
and ~1 Ma for the northern  anticlinal belt, respectively. The systemic studies of the sedimentary sequences show that the source
rocks, reservoirs, seal rocks, and traps between the northern and southem margins of the Tian Shan are similar and there are three
petroleum systems (or plays) in the southern Junggar Basin. The reason why there has been no discovery large oil-gas field of so far
in the southern Junggar may be mainly due to the very late deformation and the existence of two detachment layers, i. e., the upper
detachment  layer of  the Ahjihaihe Formation  (E2-3a) and  the  lower detachment  layer of  the middle Jurassic coal beds  (J2x). This
paper proposes  that  the  lower play,  i.e.,  the Upper Jurassic  reservoirs sealed by  the Lower Cretaceous,  is  favorable  for  forming
large-scale oil-gas field and should be potential targets for future exploration.

Key words: southern Junggar Basin, foreland thrusts, hydrocarbon accumulation, large oil-gas field, tectonic control