THE FLYSCH FACIES OF MIDDLE CARBONIFEROUS IN THE NORTHERN TIANSHAN, XINJIANG

The zonal trench of the Northern Tianshan was formed in the middle Devonian and devcioped into the one of the late Carboniferous. The middle Carboniferous filled in thcarcnch outcrops compictcly and ivpical's along the Duku highway, south of Dushanzi, Wusu. The lower pan is ophiolitc suite and the upper part is the Pvsch series of more than 2000 meters. The present paper laid the stress on the dcmonstratior of the cha-acterstics of the flysch suit in the section. The Flysch facics is composed of the rhythimitcs or dark grey green- grey black volcaniclastic rock of turbidity current origin, as well as contourites. The vertical sequence can be seperated into two part. The lower part is composed of the turbidite A, E sequence. A section, the middle to fine particles mainly, is 10-30cm thick, but E section is only several centimeters. The thickness and size of lower part have no obvious variation vernation; and its sedimentary environment can be attributed to the smooth portion of suprafan lobe in turbidite fan . The upper pan, except two successions of sequence which is thin-and fine upward, show the trend that thickcning- and coarsening - upward. This sequence represented the progradation forward of the mid-fan. As for the chemical composition of volcaniclastic turbidites SiO₂amounts to 60-65%, K₂O to 1.91-2.50%, Na₂O to 2.65-3.84%, δ 3.3. So it can be assigned to the basalt-andesites. Eight ichnogenus were found in flysch facies: Chondrites furcatus; Cosmorhaphe sp.; phycosiphon incertum Fischer-Ooster; Hclminthopsis sp.; Zoophycos sp.; Nereites sp.; Neonereites uniserialis Seilachcr; Lophoctenium sp.; They are all attributed to Nereites ichnofacies relevent to the deep-sea turbidites.