科研之友
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摘要
Yardang is a typical wind erosion landform which is widely distributed in the world. Because of its various forms and volatility,Yardang's morphological characteristics attract people's long-term attention. How to accurately and quantitatively describe the Yardang morphology has been discussed enthusiastically and with a lot of questions still remained. The Lop Nur area is located in the eastern part of the Tarim Basin in Xinjiang,China. Although there are a large number of Yardangs in the area and the morphological types are abundant, there is a lack of detailed description of the Yardang morphology in Lop Nur area. Through the field investigation of wind erosion landforms in Lop Nur area and the aerial surveying using unmanned aerial vehicle (UAV), this paper finds that there is a new morphological combination of Yardangs in the Lop Nur area-the Yardangs which have common pedestal. It is observed on the high wind erosion ridges that there are often platform surfaces on the top of the ridges. On this flat platform surfaces there are many streamlined wind erosion tiny-hills, and they are very similar to Yardang. Under the platform surfaces, the wind erosion ridges are surrounded by cliffs which is like a pedestal, then we call this part of the ridges as pedestal body. The streamlined wind erosion tiny-hills on the same platform surfaces is called the common pedestal Yardangs, and the Yardangs which have common pedestal is the combination of Yardangs and the pedestal body. The measurement and analysis of the Yardangs morphological parameters were carried out on the common pedestal Yardangs and the pedestal bodies separately. The results shows that firstly, the values of length-width (L/W) ratio of Yardangs which have common pedestal are mainly sit in the range between 3 : 1 and 5 : 1, very similar to the whale-back or other streamline-appearance Yardangs, showing that the common pedestal Yardangs undergoing the same wind erosion processing as the whale-back or other streamline-appearance Yardangs. They were all shaped gradually under the single-wind-direction erosion circumstance. Secondly,the Yardangs which have common pedestal are morphological combination of Yardangs. This phenomenon is essentially a wind erosion ridge-mound phenomenon when wind broke the former deep and strong wind-erosion-resistance stratum and cut it into less wind-erosion-resistance strata, and thus the strata of different thicknesses and different wind-erosion-resistance levels appeared alternately in the vertical direction which together with the single direction wind erosion produced this phenomenon as two important factors. Lastly, the measurement results shows the Yardangs which have common pedestal made the Yardang morphological characteristics become even more complex and fluctuated, especially in the description of the Yardang spatial distribution pattern. Through the interpretation and quantitative analysis, we expect this phenomenon would attract one's attention. By taking it into consideration,analysis of Yardangs which have common pedestal may help us improve the Yardangs' morphological measurement, understand more a-bout Yardangs development and discuss the various causes of Yardangs' morphological diversity.
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