巴丹吉林沙漠横向沙山沉积GPR雷达探测研究

应用GPR雷达探测技术对巴丹吉林沙漠东南部呼都格吉林和诺日图两个典型横向沙山迎风坡剖面探测结果表明： GPR雷达探测可以清晰地揭示沙山距地面 20～30m 深度内的沉积构造信息，并可模糊地揭示其下的湿砂层部分信息； 该横向沙山迎风坡地貌与沉积自坡底至坡顶可依次划分为底部湖滨草－灌丛沙堆相、下部单一横向沙丘相、中部复合横向沙丘相、顶部星状沙丘相等类型； 横向沙山迎风坡现代沙丘下伏有相当连续且厚度巨大的沉积序列； 沙山内部存在巨厚持水湿砂层，干、湿砂界面大致平行于沙山表面，其深度在沙山中、上部在 20～30m 深度处变化，在沙山下部接近地表； 沙山内部湿沙水分很可能来自降水，并对沙山发育起着重要支持作用； 湖泊水可能主要来自沙山内部水分下渗迁移； 沙山间湖泊可能是沙山或沙漠发育到一定阶段的必然产物。

DEPOSITION OF TRANSVERSE DUNE MOUNTAINS IN BADAIN JARAN DESERT OF CHINA BY GPR-DETECTION

As the most tremendous transverse dune-mountain system in the world,the Badain Jaran Desert is located in the west part of Inner Mongolia Autonomous Region of China.Its formation mechanism has been the desert field problem of concern,in which the geomorphic and sedimentary structures are both basic and key issues.With GPR technique,profile detections had been made on two typical windward slopes of transverse dune-mountain in October of 2007.One is at Hudugo Jaran,and the other Nurtu,both of them were in the southeastern part of the desert,where dune-mountain system is the highest in the whole desert.The Hudugo Jaran slope is as high as 372m above its lake (lake Hudugo Jaran)level,detected in turn with 12.5MHZ(lm between two successive detecting points),25MHZ (lm space between),50MHZ(0.5m space between),100MHZ(0.5m space between),respectively,and the Nurtu slope 421m above its lake(lake Nurtu)level with 50MHZ(1 m space between).Because of the dissimilarity of humidity of sand layer,the probing depth was less than 100m or so,but the effective thickness of structural sand layer detected generally less than 30m.There existed 4 kinds of sedimentary facies according to the relationship of geomorphology and deposition structure in the depth range probed from the bottoms to the top of the whole sections.The first was a facies of fixed dune stabilized by Grass and shrub,which was distributed near the lake shore.The second was a simple transverse dune facies formed dominantly by the foreset laminae of ancient crescent-shaped dune,which was generally located in the lower range of slope,and was exposured as wind erosion plane.The third is a complex facies of ancient muhi-tansverse dune that is usually situated in the upper segment of slope,consisting of different kind of laminae of transverse dune.And the last was a star-shaped dune facies,commonly perched on the top of the dune-mountain,with foreset laminae parallel to corresponding slope planes,and is exposed on both western and eastern slopes.According to the relationship of the layer sequence among all the segments and their inner parts detected,there very likely existed a sandy layer sequence with huge thickness under the slope of winward(i.e.west)side of the transverse dune-mountain,which was covered by modern secondary dunes.There existed wet sandy bodies in the inner parts of the sandy mountain bodies.Humid sandy layer generally happened under the middle and upper slope surfaces by 20～30m.Moisture were exposured on the surface of lower part of the slope.The water content of sand in the internal sand mountain may come mainly from precipitation,and be an important factor to form the sand mountain bodies and the lakes.The lakes of inter dunemountains may have closely related to some certain developing stages of the dunemountains or the sandy desert.