地形在高大金字塔沙山形成发育过程中的作用——以敦煌鸣沙山-月牙泉地区为例

doi:10.7522/j.issn.1000-694X.2015.00268

摘要/Abstract

摘要： 地形在金字塔沙山形成发育过程中起着重要的作用。金字塔沙山通常形成于山前地带，应属于地形屏障影响下形成的一种沙丘类型。首先，上升气流的发育是山前风阻区气流的主要特征，地形屏障是上升气流发生发展的主要原因。沙山的坡脚、坡中及坡顶分别是上升气流的启动区、发育区及衰退区。上升气流是沙山增高增大发育的主要机制。其次，金字塔沙山多发育于局地环流发育较强的地带，局地环流与区域风况配置是形成复杂沙丘类型的重要因素。本区局地环流偏南风不仅持续时间长，且受到鸣沙山微地形的影响，下坡气流较强。实地观测结果破解了常规气候台观测数据难以揭示上升气流及局地环流对金字塔沙丘形成发育的影响。第三，下附地形在沙山形成发育过程中决定着沙丘发育的“临界尺度”，即丘体达到“临界尺度”的时候，坡面上升气流及风速放大作用逐渐显现，促使丘体增高增大发育，随着沙丘形态与上升气流的互馈作用进一步增强，金字塔沙丘逐渐形成演化为高大沙山。实地观测进一步证实了金字塔沙山是纵向（横向）沙丘形变的一种形式。并提出了金字塔沙山在地形条件下形成演化的一种新模式。

关键词: 金字塔沙山, 地形屏障, 上升气流, 局地环流, 鸣沙山

Abstract: Topographic barriers play an important role in the development process of pyramidal mega-dunes. Pyramid mega-dunes usually develop in front of mountains, and they belong to dunes controlled by topography. Firstly, vertical airflow is a main characteristic of airflow in mountain front wind shadow area. The lower, middle, and top locations of the east-oriented side corresponded to the vertical airflow initiation, development, and recession zones, respectively. Vertical airflow is the main driving mechanism of the upward growth of mega-dunes. Secondly, pyramidal dunes usually develop in areas with strong local air circulation. Local air circulation and regional wind regime consist of three wind directions which contribute to the maintenance and development of complex dunes (pyramidal dunes). The local air circulation-southerly wind in the study area has high frequency and long duration, and the downhill flow is strong. Thirdly, microreliefs, such as unaka soils and bench terraces, are similar to a "rock core", serving as the function of "minimum survival size". When the dune body reaches the so-called "minimum survival size", the vertical airflow begins to develop, making pyramidal dunes to develop to a certain height with a large volume and the end result is a pyramidal mega-dune. Our results also indicate that pyramidal mega-dunes develop from liner dunes controlled by topography.

Key words: pyramidal mega-dunes, topographic barriers, vertical airflow, local air circulation, Mingsha Mountain

中图分类号:

P931.3

张伟民, 谭立海, 边凯, 牛清河. 地形在高大金字塔沙山形成发育过程中的作用——以敦煌鸣沙山-月牙泉地区为例[J]. 中国沙漠, 2016, 36(5): 1207-1215.

Zhang Weimin, Tan Lihai, Bian Kai, Niu Qinghe. The Role of Topographic Barriers in Pyramidal Mega-dune Development: a case study in Mingsha Mountain, Dunhuang, China[J]. JOURNAL OF DESERT RESEARCH, 2016, 36(5): 1207-1215.

参考文献

[1] Cooke R U,Warren A.Geomorphology in Deserts[M].London,UK:Batsford,1973.
[2] Wilson I G.Aeolian bedforms-their development and origins[J].Sedimentology,1972,19(3/4):173-210.
[3] Nielson J,Kocurek G.Surface processes,deposits,and development of star dunes:Dumont dune field,California[J].Geological Society of America Bulletin,1987,99(2):177-186.
[4] N Lancaster.Controls of dune morphology in the Namib Sand Sea[J].Developments in Sedimentology,1983:261-289.
[5] Lancaster N.Star dunes[J].Progress in Physical Geography,1989,13(1):67-91.
[6] Tsoar H.Dynamic processes acting on a longitudinal (seif) sand dune[J].Sedimentology,1983,30(4):567-578
[7] Pye K,Tsoar H.Study on Aeolian sand landforms of Taklimakan Desert[M].London,UK:Unwin Hyman,1990.
[8] Qu J J,Gong G G,Wen Z X,et al.Sand drift encroachment in the Dunhuang Mogao Grottoes District and its control[J].Science in China Series D-Earth Sciences,1997,40(2):197-206.
[9] Zhang W M,Qu J J,Dong Z B,et al.The airflow field and dynamic processes of pyramid dunes[J].Journal of Arid Environments,2000,45(4):357-368.
[10] Wang T,Zhang W M,Dong Z B,et al.The dynamic characteristics and migration of a pyramid dune[J].Sedimentology,2005,52(3):429-440.
[11] Lancaster N.The dynamics of star dunes:an example from the Gran Desierto,Mexico[J].Sedimentology,1989,36(2):273-289.
[12] Chen J S,Li L,Wang J Y,et al.Water resources:groundwater maintains dune landscape[J].Nature,2004,432(7016):459-460.
[13] Zhang D G,Narteau C,Rozier O,et al.Morphology and dynamics of star dunes from numerical modelling[J].Nature Geoscience,2012,5(7):463-467.
[14] Lancaster N.Palaeoclimatic evidence from sand seas[J].Palaeogeography Palaeoclimatology Palaeoecology,1990,76:279-290.
[15] Koji K.Wind tunnel and field studies of stagnant flow upstream of a ridge[J].Journal of the Meteorological Society of Japan,1977:193-204.
[16] Mainguet M,Callot Y.L'erg de Fachi-Bilma,Tchad-Niger:contribution à la connaissance de la dynamique des ergs et des dunes des zones arides chaudes[M].L'erg de Fachi-Bilma,Tchad-Niger:contribution à la connaissance de la dynamique des ergs et des dunes des zones arides chaudes,1978.
[17] McKee E D.Sedimentary structures in dunes of the Namib Desert,South West Africa[J].Geological Society of America Special Papers,1982:1-2.
[18] Tsoar H.Wind Tunnel Modeling of Echo and Climbing Dunes[J].Developments in Sedimentology,1983:247-259.
[19] 张伟民.金字塔沙丘粒度变化及表面过程的初步研究[J].中国沙漠,2013,33(6):1615-1621.
[20] Bristow C S,Bailey S D,Lancaster N.The sedimentary structure of linear sand dunes[J].Nature,2000,406(6791):56-59.
[21] 屈建军,凌裕泉,张伟民,等.金字塔沙丘形成机制的初步观测与研究[J].中国沙漠,1992,12(4):20-28.
[22] Breed C S,Grow T.Morphology and distribution of dunes in sand seas observed by remote sensing[M]//A Study of Global Sand Seas.USGS Professional Paper.1979:253-303.
[23] Wilson I G.Ergs[J].Sedimentary Geology,1973,10:77-106.
[24] Sharp R P.Kelso Dunes,Mojave Desert,California[J].Geological Society of America Bulletin,1966,77(10):1045-1073.
[25] 孙显科,吕亚军,张大治,等.成沙地地形1/10定律的研究与敦煌鸣沙山成因的猜想[J].中国沙漠,2006,26(5):704-709
[26] Gautier E F.The Sahara-the Great Desert[M].New York,USA:Columbia University Press,1935.
[27] 张伟民,李孝泽,屈建军,等.金字塔沙丘地表气流场及其动力学过程研究[J].中国沙漠,1998,18(3):215-220.