| To better constrain central Asian Mesozoic tectonic history, basin analysis of entirely nonmarine, Mesozoic strata of the north Tarim, south Junggar, and west Turpan basins, Xinjiang, NW China was conducted. Paleocurrent measurements trend consistently away from the modern Tian Shan, suggesting a Mesozoic "paleo-Tian Shan". Mesozoic sedimentary facies of each basin are remarkably similar. Contemporaneous alluvial conglomerates occur in the Upper Triassic (Junggar, Tarim, Turpan), the uppermost Jurassic (Junggar, Tarim, Turpan), and the Upper Cretaceous (Junggar, Tarim). A marked, possibly angular, Cretaceous-Tertiary unconformity is present in the Turpan basin. Subsidence profiles for each basin possess similar shape and contain several concave-down segments temporally-associated with alluvial depositional episodes. Secular changes in Mesozoic sandstone composition are unusual and difficult to explain by climate, transport-induced selective attrition, or unroofing of a static section.; Data described above are interpreted as reflecting episodic structural reactivation of the Mesozoic Tian Shan by deformation associated with accretion of the Qiantang Block (Late Triassic), Lhasa Block (latest Jurassic), and Kohistan-Dras arc complex (Upper Cretaceous). Episodic Tian Shan reactivation rejuvenated the range's physiography, resulted in progradation of coarse clastic pulses, accelerated basin subsidence rates, and produced secular changes in sandstone compositions not easily explained otherwise.; Lower-Middle Jurassic coals and organic-rich shales of central Xinjiang basins are dominated by terrestrial organic matter and are mainly gas-prone. Macroscopic higher plant detritus is common; macerals are dominated by vitrinite and intertinite; atomic O/C and H/C ratios characterize Type III kerogens, and pyrolyzates are dominated by alkane-alkene doublets and low molecular weight aromatic compounds. C29 homologues dominate sterane distributions, and diterpenoids and hopanes are abundant, consistent with a higher plant interpretation. Except for anomalously high maturity coals from lower thrust plate positions in northwest Tarim, all samples are slightly immature to moderately mature with respect to hydrocarbon generation.; Fission-track analysis of 11 Mesozoic detrital apatite samples from south Junggar and north Tarim depocenters suggest Lower-Middle Tertiary cooling from partial annealing zone temperatures. This uplift timing requires that Himalayan-associated deformation propagated over 1200 km during an absolute maximum of 25 Ma, suggesting that Cenozoic Asian crustal elements behaved as discrete, rigid entities. |
