金字塔沙丘粒度变化及表面过程的初步研究

doi:10.7522/j.issn.1000-694X.2013.00235

摘要/Abstract

摘要：

莫高窟顶金字塔沙丘粒径集中分布在2.44～2.94 Φ,属细砂。标准差介于0.24～0.65之间,偏度在0.03～0.31,属于正偏级。峰度在0.78～1.72,介于宽峰态至尖峰态。沙粒粒径级配是风况、地貌与沙物质相互均衡作用的结果。金字塔沙丘存在着沙臂顶部沙最细或最粗两种粒度模式。金字塔沙丘沙丘主臂(WNW—ESE)属于在双向风环境作用下,类似于横向沙丘粒度变化模式,两坡下部以风蚀为主,丘顶附近以堆积过程为主,导致沙臂两坡粒径与分选性由下而上变细与变好。频率高、风速不大的局地气流,可将大量细沙物质搬运到金字塔沙丘主臂,造成丘底到丘顶的粒度变化不大。副臂(SW)受较强NW风力作用,具有横向及纵向沙丘粒度变化模式,整个坡面处于风蚀状态,沙臂顶部风蚀最为强烈,导致从底部到顶部的粒度逐渐由细变粗。

关键词: 莫高窟, 金字塔沙丘, 主臂, 副臂, 粒度, 表面过程

Abstract:

The pyramid dune at the top of the Mogao Grottoes is composed of fine sands with a diameter between 2.44 Φ and 2.94 Φ and a standard deviation in 0.24-0.65. The skewness varying between 0.03 and 0.31 with a mean value of 0.11 indicates that the sands belonging positive skews. The kurtosis is between 0.78 and 1.72 with a mean value of 1.28 ranging from broad to narrow scare. The pattern of grain size characteristic of the main arm (NWW-ESE direction) is similar to that of the transverse dune. Erosion is occurred at the toe and deposition around the dune top. Abundant fine blown sand is moved toward the crest of main arms by the frequent local wind with low speed, leading to homegeny grain size distributions at the toe and the top. The secondary arm (SW direction) is controlled by stronger NW wind regime and its grain size distribution pattern is similar to longitudinal dune. The whole slope, especially the dune top, suffers erosion and the diameter of sand increases from the toe to the top.

Key words: Mogao Grottoes, pyramid dune, main arm, secondary arm, grain size, surface process

中图分类号:

P931.3

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.

ZHANG Wei-min. Grain Size and Surface Processes of the Pyramid Dune in the Mogao Grottoes of China[J]. JOURNAL OF DESERT RESEARCH, 2013, 33(6): 1615-1621.

参考文献

[1]Vincent P J.Particle size variation over a transverse dune in the Nefud as Sirr,central Saudi Arabia[J].Journal of Arid Environments,1984,7(4):329-336.

[2]陈渭南,雷加强.塔克拉玛干沙漠新月形沙丘不同部位的粒度特征[J].干旱区资源与环境,1992,6(2):101-109.

[3]哈斯,庄燕美,王蕾,等.毛乌素沙地南缘横向沙丘粒度分布及其对风向变化的响应[J].地理科学进展,2006,25(6):42-50.

[4]张春来,郭青振,邹学勇,等.新月形沙丘迎风坡形态及沉积物对表面气流的响应[J].中国沙漠,1999,19(4):359-363.

[5]董玉祥,马骏,黄德全.福建长乐海岸横向前丘表面粒度分异研究[J].沉积学报,2008,26(5):813-819.

[6]Folk R L.Longitudinal dunes of the northwestern edge of the Simpson Desert,Northern territory,Australia,1.Geomorphology and grain size relationships[J].Sedimentology,1971,16(1/2):5-54.

[7]Livingstone I,Warren A.Aeolian Geomorphology-An Introduction[M].London:Addison Wesly Longman Limited,1996:211.

[8]李志忠,关有志,孙忠,等.塔克拉玛干沙漠腹地纵向沙垄的粒度分布特征[J].干旱区研究,1996,13(2):37-43.

[9]李振山,陈广庭,冯起,等.塔克拉玛干沙漠腹地纵向沙垄表面沙物质粒度特征[J].干旱区资源与环境,1998,12(1):21-28.

[10]哈斯.腾格里沙漠东南缘格状沙丘粒度特征与成因探讨[J].地理研究,1998,17(2):178-185.

[11]Lancaster N.Geomorphology of Desert Dunes[M].London: Routaledge,1995:526.

[12]Lancaster N.The Namib Sand Sea[M].Netherland: Balkema,1989:46-74.

[13]何清,杨兴华,霍文,等.库姆塔格沙漠粒度分布特征及环境意义[J].中国沙漠,2009,29(1):18-22.

[14]钱广强,董治宝,罗万银,等.巴丹吉林沙漠地表沉积物粒度特征及区域差[J].中国沙漠,2011,31(6):1357-1364.

[15]Watson A.Grain-size variations on a longitudinal dune and a barchan dune [J].Sedimentary Geology,1986,46(1):49-66.

[16]Thomas D S G.Analysis of linear dune sediment-form relationships in the Kalahari dune desert[J].Earth Surface Processes and Landforms,1988,13(6):545-553.

[17]Sneh A,Weissbrod T.Size-frequency distribution on longitudinal dune ripple flank sands compared to that of slipface sands of various dune types[J].Sedimentology,1983,30(5):717-726.

[18]Livingstone I.Temporal trends in grain-size measures on a linear sand dune[J].Sedimentology,1989,36:1017-1022.

[19]Fryberger S G.Dune forms and wind regime [M]//Makee E D.A Study of Global Sand Seas.Washington,USA:United States Geological Survey and United States National Aeronautics and Space Administration,1979:137-169.

[20]Wang T,Zhang W M,Dong Z B,et al.The dynamic characteristics and migration of a pyramid dune[J].Sedimentology,2005,52(2):429-440.

[21]Folk R L,Ward W C.Brazos River bar:a study in the significance of grain size parameters[J].Journal of Sedimentary Petrology,1957,27(1):3-26.

[22]Lancaster N.Star dunes[J].Progress in Physical Geography,1989,13(1):67-91.

[23]Pye K,Tsoar H.Eolian Sand Deposits[M].London:Unwin Hyman,1990:152-253.

[24]Burkinshaw J R,Rust I C.Aeolian dynamics on the windward slope of a reversing transverse dune Alexandria coastal dunefield,South Africa[M]//Pye K.The Dynamics and Environmental Contest of Aeolian Sedimentary Systems.London,UK:Geological Society of London,1993:13-21.