Structural Patterns in a Rifted Thrust Belt: Jianghan Basin, China

R. W. Wiener, J. A. Helwig, Jiang Rongpei, and Myra Keep

The Jianghan Basin is a Cretaceous-Tertiary nonmarine rift basin; it is superimposed on two Jurassic-age detached fold and thrust belts developed within late Precambrian to Jurassic passive margin and foreland basin strata. Hence a complex fold and thrust belt is overprinted by extensional deformation.

In the northwestern Jianghan Basin, southwest vergent fold and thrust belt structures formed during Triassic-Jurassic collision of the North China and Yangtze blocks. Deformation progressed from the Dabie Shan/Tan Lu collision zone in the north to the Jianghan Basin during the Jurassic. Major detachments in the thrust belt occur in late Precambrian and Triassic strata. The south flank of the Jianghan Basin contains north-vergent thrusts associated with the Sichuan thrust belt, suggesting that the central depression of the Tertiary basin is underlain by a zone of sinistral strike slip and a buried Jurassic foredeep.

Seismic analysis and structural restoration are complicated by extensional reactivation of thrust systems. Cretaceous north-northwest trending rifts prevail in the northern Dangyang area, whereas a Tertiary east-west trending basin with complex fault patterns forms the Jiangling depression in the south. These rift patterns reflect reactivation of northwest trending thrust ramps in the north during Cretaceous east-west extension, and of east-west trending thrust ramps in the south during early Tertiary north-south extension. Thus, the extensional faulting interacted with pre-existing structural grains to yield complex 3-D fault patterns.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California