The clastic rocks of the Maoniushan Formation in Maoniushan area along the northern margin of the Qaidam terrane is a suit of nonmarine sedimentary rocks that deposited in the alluvial fan and fan-delta environments. The alluvial fan deposits, conglomerate to coarse-grained sandstone association, are primarily located in the SE. The fan delta deposits are mainly distributed in the NW and consist of sandstone and mudstone. Paleocurrent analysis indicates that the Maoniushan Formation deposits originated from an ancient uplift which located in the SE primarily, but some deposits of fan delta were drived from NW and NE. In combination with synchronic lacustrine and shallow-marine sediments in the southwest of the study area, the spatial changes of these sedimentary facies suggest that a NW-striking paleoslope should exist along the north margin of the Qaidam terrane in the late Silurian-early Devonian and the north side uplifted in the later period. Comparison between detrital components and regional rock assenblages demonstrates that the clastic sediments of the Maoniushan Formation mainly derived from the Tanjianshan Group. Sedimentary sequence and regional tectonic evolution coevally suggest that the Maoniushan Formation deposited within a graben basin in a convergent setting which was formed by the northward subduction of the Qaidam terrane.