Mesozoic-Cenozic Basin and Orogeny Evolution of Northern Tianshan and Its Implications for Hydrocarbon Exploration in Southern Junggar Basin

Fang, Shihu; Guo, Zhaojie; Zhao, Mengjun; Zhang, Zhicheng; Liu, Shaobo

The analyses of depositional facies, sandstone composition, heavy minerals and geologic information of several sections in Tianshan Mountains and southern Junggar basin suggested that several separate small basins existed within Tian Shan during Jurassic. The Triassic basin boundary was much small relative to that of Jurassic basin (which migrated southward to near turpan-Hami basin), and the Cretaceous basin boundary shrank near to southern Junggar basin boundary of nowadays. The Upper Jurassic Kalazha conglomerate and the Cretaceous bottom conglomerate in southern Junggar basin recorded obvious uplift and denudation during Late Jurassic to the Earliest Cretaceous, led to the Bogeda Mountain uplifted and became another source provenance of southern Junggar basin.

Fission-track data from intra-Tianshan show a complex thermal history with multiple paleothermal events during Late Jurassic-Early Cretaceous, Late Oligocene-Miocene. The rate of uplift and denudation increased rapidly in recent ~10Ma, especially in recent 5Ma. These Mesozoic-Cenozoic cooling events and rapid crust shortening of Late Cenozoic suggest rapid uplift of Tianshan during Late Jurassic-the Earliest Cretaceous and Late Cenozoic. Moreover, increase of unstable heavy minerals is consistent with Late Jurassic-the Earliest Cretaceous, Late Cretaceous and Late Cenozoic, implying a temporal link between sedimentation and deformation. Stratigraphic analysis of northern Tianshan indicates that the Changjihe group (N1-2ch) (~10Ma~2.58Ma)is a set of growth strata, proved the intensive uplift and deformation were initiated at about 10Ma B.P. This conclusion is also proved by apatite fission-track analysis and relative data modelling.

So, the Mesozoic stratigraphic record in Junggar basin supports the hypothesis that rejuvenation of the Tianshan markedly influenced the depositional succession during the Early Cretaceous period. Intracontinental deformation of central Asia during Late Cenozoic has been attributed to the India-Asia collision, the intensively deformation in Tianshan region led to the formation of Rejuvenated foreland basin. Besides, Petrology, apatite fissin-track data and tectonic analysis also proved active settings during Late Jurassic-the Earliest Cretaceous and Late Cenozoic, led to the formation of composite petroleum system in southern Junggar basin.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013