Abstract：The early-middle Jurassic Mugagangri Group widespread in the middle-western section of the Bangongco-Nujinag junction zone, the rock association seems like accordance from a macroscopic perspective. However, the chronostratigraphy is inconsistent in different areas since the establishment of Mugagangri Group; it is a tectonic melange with disorder sequence and complex composition. Taking the sedimentary basins as a whole, and according to features of sedimentary assemblage, sedimentary sequence, rock geochemistry, lithofacies, provenance, detrital model, basin classification, and tectonic evolution about the Mugagangri Group, the geodynamic background had been studied. We proposed that the early-middle Jurassic sedimentary environment of Kangtuo area corresponded to abyssal-bathyal facies of meso Tethys ocean basin; it was a suit of flysch clastic deposits of deepwater in fore-arc basin of passive continental margin. The tectonic evolution was divided into basin spreading period (basin spreading stage), and basin subduction period (southward subduction stage, bilateral subduction stage), and the Mugagangri Group can be divided into three lithology groups.
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2015, Vol. 2 
