Gravel Morphology of Curvilinear Ridges in the Qaidam Basin and its Paleoenvironmental Significance

Key words: 
• Qaidam Basin /
• Curvilinear ridge /
• Gravel morphology /
• Han River /
• Paleohydrology

Abstract: There are many curvilinear ridges that have similar planforms as rivers in the northern and southwestern Qaidam Basin. To investigate their formation mechanism, [Methods] we carry out statistical and morphological analyses on 21 sets of gravel samples from the curvilinear ridges, and compared them with the gravel layer sediments in the middle reaches of the Han River. [Results and Discussions] Analysis shows that the ratio of round and sub-round gravels in the curvilinear ridges area ranges from 71.6% to 74.0%, and the ratio of discoid gravels ranges from 44.9% to 54.0%. The correlation coefficients of the gravel morphological features between the distribution area of curvilinear ridges in the Qaidam Basin and the sampling area of the middle reaches of the Han River range from 0.688 to 0.7258. [Conclusions] Studies indicate the following: the gravels in the curvilinear ridges are fluvial deposits. And if based on the modern hydrologic parameters of the Qaidam Basin, the paleocurrent velocity, paleo-discharge and paleo-annual runoff rate of the river indicated by the curvilinear ridges are 0.217 m/s, 1.39 m3/s, and 0.1440 × 108 m3, respectively. The paleo-discharge range of the curvilinear ridges of the Qaidam Basin reconstructed based on the channel width is 14-16 m3/s. Accordingly, the paleo-runoff depth is estimated to be about 2 m, and the corresponding paleocurrent velocity, paleo-discharge and paleo-annual runoff rate are about 0.357 m/s, 14.28 m3/s, and 1.4801×108 m3, respectively. Keywords: Qaidam Basin; Curvilinear ridge; Gravel morphology; Han River; Paleohydrology