巴丹吉林沙漠与腾格里沙漠沉积物特征的对比研究

【作者】 李恩菊；

【导师】 董治宝；

【作者基本信息】 陕西师范大学 ， 自然地理学， 2011， 博士

【摘要】 巴丹吉林沙漠和腾格里沙漠位于中国西北干旱荒漠区,两者以雅布赖山为界,行政区划属内蒙古阿拉善盟。两沙漠的地貌景观各具特色,为研究风沙地貌的理想区域,长期以来引起了国内外学者的关注。有关巴丹吉林沙漠的研究主要集中在地貌形态、沙山成因、沙漠地下水及湖泊水来源、沙漠形成年代等方面。关于腾格里沙漠的研究主要集中在该沙漠的东南部,内容涉及沙漠的形成演化史、风沙沉积物、风沙物理及沉积构造等方面。但关于两个沙漠沉积物的系统性研究很少,更没有关于两沙漠沉积物的对比研究。风沙沉积物特征的研究,对确定风沙沉积环境、探索其物源及风沙地貌的形成过程均有着重要的意义。本论文在借助大量详实的野外观测及采样的基础上,对比研究了巴丹吉林-腾格里沙漠地表、典型沉积层位、典型沙丘及断面上沉积物的粒度特征、矿物组成和地球化学元素等内容,为探讨两个沙漠沙物质来源及形成机理提供了重要的依据。本论文获得的主要结论为：1.巴丹吉林-腾格里沙漠沉积物的粒度分析结果(1)沉积物的颗粒级配分析表明两沙漠地表沉积物的颗粒组成均以中沙和细沙为主,且巴丹吉林沙漠地表沉积物稍粗于腾格里沙漠。两沙漠不同类型沙丘及不同地貌部位的沙粒级配存在一定的差异：巴丹吉林沙漠的流动沙丘和灌丛沙丘沙粒均以细沙和中沙为主,平沙地和丘间地以粗沙和中沙为主；而腾格里沙漠所有类型沙丘、沙梁和丘间地的沙粒则均以细沙和中沙为主。两沙漠不同沉积层位即垂直剖面上的沙粒粒度组成极为接近,均以细沙和中沙为主。两沙漠沙粒频率分布曲线型态均主要表现为单峰型,但峰值粒径范围存在一定差异,即巴丹吉林沙漠的颗粒频率分布曲线上的峰值粒径范围较广,而腾格里沙漠则相对集中。(2)粒度参数的分析结果显示：巴丹吉林沙漠地表和垂直剖面上沉积物的平均粒径均粗于腾格里沙漠,而典型沙丘表层颗粒则细于腾格里沙漠；两沙漠沉积物为分选好至分选较好,且巴丹吉林沙漠地表和垂直剖面上的颗粒分选较腾格里沙漠的稍差,而典型沙丘表层沉积物的分选程度则稍好于腾格里沙漠；两沙漠沙粒均为近对称中等峰态分布。(3)两沙漠沉积物粒度的区域分布规律均较差,但腾格里沙漠沉积物粒度的区域分布规律稍好于巴丹吉林沙漠。2.巴丹吉林-腾格里沙漠沉积物的矿物分析结果(1)巴丹吉林-腾格里沙漠主要轻矿物均以石英和长石为主,但巴丹吉林沙漠地表沉积物中轻矿物的比重稍低于腾格里沙漠,且轻矿物成分成熟度也稍低于腾格里沙漠。(2)巴丹吉林沙漠轻矿物成分成熟度表现为无规律性和反规律性,而腾格里沙漠轻矿物分布则存在一定的区域规律性,即沿主导风向,轻矿物成分成熟度自西北向东南逐渐变好。(3)巴丹吉林-腾格里沙漠主要重矿物的种类一致,但巴丹吉林沙漠重矿物的含量比重稍高于腾格里沙漠,且巴丹吉林沙漠沉积物的风化程度稍弱于腾格里沙漠,两沙漠的沙丘迎风坡沉积物的风化程度均好于沙丘背风坡。(4)巴丹吉林沙漠磷灰石的风化程度较腾格里沙漠弱,两沙漠物源区性质非常接近,其源岩均为拥有富含石榴子石的基性酸性岩类,两沙漠沉积物的重矿物成熟度均不高。3.巴丹吉林-腾格里沙漠沉积物的元素地球化学分析结果(1)巴丹吉林-腾格里沙漠所含主要常量元素的种类相同,均以SiO2和A1203平均含量较高,除CaO巴丹吉林沙漠相比腾格里沙漠富集外,其他常量元素含量均与腾格里沙漠相接近。与上陆壳(UCC)平均化学成分相比,除Si02外两沙漠其余常量元素均相对亏损。两沙漠不同区域断面上常量元素的曲线分布特征较为一致,但腾格里沙漠沙常量元素的空间分布规律相比巴丹吉林沙漠显著。(2)巴丹吉林-腾格里沙漠均以Ba元素含量最为丰富,Sr、Co、Cr、Zr和Rb等微量元素平均含量均相对较多,其他微量元素平均含量均较少,除Cu的含量在两沙漠稍有差异外,其余微量元素的平均含量差别不大。与上陆壳(UCC)平均化学成分相比,两沙漠Co和Cr元素相对富集,Ba和Ni元素与UCC含量相当,其他微量元素则表现为迁移淋失。两沙漠不同区域断面微量元素的曲线分布特征较为相似,且区域规律性均不显著。(3)巴丹吉林-腾格里沙漠沙物质的化学组成虽有差异但差异很小,两沙漠的沉积物均具有很好的均质性,均处在大陆风化的初级阶段,其中腾格里沙漠所经受的化学风化程度稍强于巴丹吉林沙漠。4.堆积区规律性好于侵蚀区通过对巴丹吉林沙漠和腾格里沙漠沉积物特征的区域对比研究,得出腾格里沙漠沉积物的区域规律性稍好于巴丹吉林沙漠,可见,距离沙源越远,规律性越好。可以推断,在我国西北干旱区,越靠近东南方向,沉积物的区域规律性会变得越好,这就是堆积区规律性好于侵蚀区。本文通过对巴丹吉林-腾格里沙漠沉积物的粒度特征、矿物和地球化学元素的对比研究,得出两沙漠沉积物特征的异同,对探讨其物源及物质形成过程反演以及风成环境的恢复和重建提供了可靠依据。更多还原

【Abstract】 Badain Jaran Desert and Tengger Desert are located in the arid area of northwest China. They are bounded by the Yabulai mountain and belong to Alashan League, Inner Mongolia. As their unique geomorphology, it is recognized as the ideal region to study the aeolian geomorphology, hence draw a great attention of the scholars at home and abroad. The studies of Badain Jaran Desert mainly focused on geomorphology, genesis, source of the groundwater and geochronology, et al. The studies of Tengger Desert were mainly done in the southeast area of the desert, focused on genesis and evolution of the desert, aeolian deposits, aeolian physics, sedimentary structure, et al. However, the systematic studies on the material composition are still very little, not to say the contrastive study of the aeolian deposits in the both deserts. The studies on the characteristics of aeolian deposits make great sense in the determining of aeolian sedimentary environment, exploring the source of the aeolian deposits and the evolution of the aeolian geomorphology. In order to do the research, the author collected the samples in the typical surface, different sedimentary layers, typical dune and cross-section of the Badain Jaran Desert and Tengger Desert. And made a comparative study of the representative samples from the characteristic of grain size, mineral composition, and geochemical element and so on, and analysed the similarities and differences of the deposits in the two deserts. These provide an important basis to investigate the source and formation of the sand in the two deserts. The main conclusions are following:1.The grain size analysis results of the deposits in the Badain Jaran-Tengger Deserts(1) The grain size composition analysis shows that the sediments of the two deserts are mainly comprised of medium and fine sand, and the surface sediments of Badain Jaran Desert are slightly coarser than that of Tengger Desert. The grain size composition of different type of dunes and different landform positions of the two deserts are different:mobile dunes and shrub canopy dunes of Badain Jaran Desert are mainly composed of fine and medium sand, but flat sandy land and inter-dunes are mainly composed of coarse and medium sand; while all the dunes,ridges,and inter-dunes of Tengger Desert are primarily composed of fine and medium sand.It is similar to the grain size composition in different sedimentary layers namely the vertical section of the two deserts, which are primarily composed by fine and medium sand.The frequency curve is mainly unimodal for dune sands of both deserts, but there are some differences of the peaks’range of grain size, that is the peaks’range of Badain Jaran Desert is broad, while the Tengger Desert is relatively concentrate.(2) grain size parameters shows that the Badain Jaran Desert’s mean grain size of the surface deposits and the longitudinal profile of typical dunes is coarser than that of Tengger Desert, while the surface grain size of typical dunes is finer than that of Tengger Desert. The sorting parameters show that the sediments from the two deserts are better sorted to well sorted with a distribution of near symmetric skewness and mesokurtic.The sediments from the surface and longitudinal profile of Badain Jaran Desert is slightly worse sorted than that of Tengger Desert, while it is slightly better sorted of the sediments from the surface of typical dunes than that of Tengger Desert.(3) From a regional perspective, The grain size parameters of the sediments from the both deserts have no distinct regional change, but the Tengger Desert is slightly better than the Badain Jaran Desert.2.The mineral assemblages of sands in the Badain Jaran-Tengger Desert(1) The main light minerals in Badain Jaran Desert and Tengger Desert are mainly comprised of quartz and feldspar, but the content proportion of the light minerals of surface sediments in Badain Jaran Desert is slightly lower than that of Tengger Desert, and the Light mineral composition maturity in Tengger Desert is also slightly lower than that of Badain Jaran Desert.(2) From a regional perspective, the light mineral composition maturity shows no regularity and anti-regularity in Badain Jaran Desert. But in Tengger Desert, the light mineral composition maturity shows distinct regional change. That is in the NW-SE cross sections which are parallel to the dominant wind direction, the light mineral composition maturity becoming better.(3) The types of heavy minerals in both Badan Jaran Desert and Tengger Desert are consistent, but the heavy mineral proportion of sediments in Badan Jaran Desert is slightly higher than that in Tengger Desert. And the weathering degree of the sediments in Badan Jaran Desert is slightly weaker than that in Tengger Desert. The weathering degree of the sediments in windward slope is better than that in leeward slope in both Badain Jaran Desert and Tengger Desert.(4) The weathering degree of apatite in Badan Jaran Desert is weaker than that in Tengger Desert. The source area of the both deserts is very close. The source of sand is basisc acid rocks, which is rich of garnet. The mineral maturity in the both deserts is not high3. The geochemical element analysis results(1) Badain Jaran-Tengger Desert contains the same types of the main major elements, both have a high average content of SiO2 and Al2O3, except the CaO enriches in the Badan Jaran Desert compares to the Tengger Desert, the other major elements contents are similar to the Tengger Desert. Compare to the average chemical composition of the upper continental crust (UCC), except the SiO2, the other major elements of both deserts are suffered a relatively loss. The content distribution curves of major elements of different regional cross sections in the both deserts is more consistent, but the spatial distribution regularity of major elements is more remarkable in Tengger Desert than that of Badan Jaran Desert. (2) Both Badain Jaran Desert and Tengger Desert are most abundant in Ba, the average content of trace elements, such as Sr、Go、Cr、Zr、Rb and so on are relatively higher, the content of the other trace elements are relatively less. Except the content of Cu are slightly different in both deserts, the average content of the other trace elements have little difference. Compare to the average chemical composition of the upper continental crust(UCC), both deserts are relatively enrich of Co and Cr. The content of Ba and Ni are equivalent to UCC, the other trace elements show migration and lesching out. The content distribution curves of different regional cross sections in the both deserts are similar, and the regional regularity is not remarkable.(3) There are some difference in the chemical composition of the aeolian deposits in the both deserts, but the difference is tiny. The aeolian deposits of the both deserts are of good homogeneity, which is at the initial stage of continental weathering. The chemical weathering degree in Tengger Desert is slightly stronger than that in the Badain Jaran Desert.4. Through the contrast studies of desert sedimentary characteristic on regional scale between Badain Jaran Desert and Tenger Desert, this paper draw a conclusion that the regional variation law of desert sedimentary in Tengger Desert is slightly superior to that of desert sedimentary in Badain Jaran Desert. It is inferred that the regional precipitation regularity of desert sedimentary become better and better toward the southeast in arid region in northwest China, that is to say, the precipitation regularity in deposit area is superior to that in erosion area.Based on the comparative study of the grain size, mineral and geochemical elements of sediments from Badain Jaran Desert and Tengger Desert, this paper obtained the similarities and differences of aeolian sediments’characteristics in the both deserts. This study can provide reliable basis on the discussion of sand source, the inversion of material forming processes, as well as the restoration and reconstruction of aeolian environment of the two deserts.更多还原