| The zone of the Eastern Yumu Mountain is distribute over Zhangye,Gansu province. The geomorphic development of the river landform and tectonic is intense. People used to study less of the river in the Eastern Yumu Mountain, also the south of Black river, and we are lacking of river terraces at different levels of height and accurate dating data. This paper mainly studied the river geomorphology features and its new tectonic movement by actual measuring river valley profile and terrace elevation and collecting the river terrace’s samples of optical stimulated luminescence dating time in field, and then analyzing the data that had in laboratory by combining the working achievement of former people. Following is the cognizant results:We got the river terraces of morphological characteristics of the study area by measured section of river terraces. The study result found that the terrace development highest series is 6 level terrace. We got the statistics of the three river terraces’ elevation data, mapped the river elevation, calculated the Hongshui river’s terraces in different stages and different positions at all levels of terrace uplift rate. We can generally be inferred that the tectonic movement of Hongshui river have the trend of weakened to enhanced then weakened from the early late Pleistocene to a whole new Holocene. From that, we can calculate that the west section of bay of Hongshui river’s terraces uplift rate is maximum, and also is where the tectonic move strongest.By using the optical luminescence dating method, we got that the T1-T5 age of Hongshui river were: 6.53 ± 0.61 ka.BP, 25.67 ± 1.72 ka.BP, 40.33 ± 4.33 ka.BP, 94.70 ± 6.14 ka.BP, ka.BP, 114.77 ± 4.54 ka.BP,and its corresponding geological age is from the mid to late Pleistocene-Holocene.The fault scarp of West Bay Highway development is fault rupturing off the second, three, four terraces. From differential GPS for West Bay Highway micro-topography measurement, we drawn a contour map and a perspective view of it, and by analyzing and calculating the average vertical displacement of the second, three, four terraces fault scarp, we got the following data: 10.818 m, 17.426 m and 24.692 m. The average thrust rates were 0.421 mm / a, 1.432 mm / a, 0.261 mm / a.From the paper, we divided into five new tectonic movement of the times. In the time of Mid-Pliocene- Early Pleistocene, the planation surface is deformation, and the tertiary strata fold deformation occurred. At the early pleistocene- early middle Pleistocene time, the tertiary is folded and deformed, the Yumen conglomerate is not conformity above the tertiary strata. At the time of Middle Pleistocene, Yumu mountain strongly uplifted, the river incised to terraces, and that makes the Liyuan river T5, and Black river T6 formed. At the time of Late Pleistocene early- late, the West Bay Highway’s fault in the study area was dislocated the terraces and then the scarp developed. From Middle Holocene time to now, the river incised terraces to T0 and T1. |
PDF Full Text Request