Cenozoic deformation within the Tien Shan of central Asia has accommod
ated part of the post-collisional indentation of the Indian plate into
Asia. Within the Urumqi - Korla region of the Chinese Tien Shan this
occurred dominantly on thrusts, with secondary strike-slip faulting. T
he gross pattern of deformation is of moderate to steeply dipping thru
sts that have overthrust foreland basins to the north and south of the
range, the Junggar and Tarim basins, respectively. Smaller foreland b
asins lie within the margins of the range itself (Turfan, Chai Wo Pu,
Korla and Qumishi basins); these lie in the footwalls of local thrust
systems. Both the Turfan and the Korla basins contain major thrusts wi
thin them; they are complex foreland basins. Deformation has progressi
vely affected regions further into the interior of the Junggar Basin,
and propagated into the interiors of the intermontane basins. No unidi
rectional deformation front has passed across the Tien Shan in the Neo
gene and Quaternary. An Oligocene unconformity may indicate the time o
f the onset of the Cenozoic deformation, but most of the Cenozoic mola
sse has been deposited after the Palaeogene. The rate of deposition in
basins next to the uplifted ranges has increased since the onset of d
eformation. There has been at least about 80 km of Cenozoic shortening
across this part of the Tien Shan. Cenozoic shortening is greater in
sections of the range further west; these are nearer to the northern m
argin of the Indian indenter. Cenozoic compression has reactivated str
uctures created by the two late Palaeozoic collisions that created the
ancestral Tien Shan. These Palaeozoic structures have exerted a stron
g control over the style and location of the Cenozoic deformation.