【作者】 杨望暾；

【导师】 姜常义；

【作者基本信息】 长安大学 ， 构造地质学， 2016， 博士

【摘要】 丹霞地貌作为地貌学一个新的研究领域,已经走过80年的研究历程,自上世纪30年代末陈国达先生提出丹霞地貌的概念以后,在该领域的研究经历了三个阶段,分别为初创阶段、成型阶段和发展阶段,现阶段已经取得了阶段性成果。但大部分是从地貌景观资源开发角度出发,少数学者所做的成因方面的研究,而从构造地质学、沉积学的角度对其形成机理研究一直是薄弱环节,针对某一较大区域内赋存的丹霞地貌,还没有从其成因的根本要素进行深入研究,利用系统性的思想方法还不成熟。本文选取我国鄂尔多斯盆地西南缘丹霞地貌作为研究对象,利用该区域ETM+遥感影像数据解译的结果,进一步进行野外实际调查和实体验证,在该区域西南边缘查找并圈定3处丹霞地貌富集区域。同时以现代地貌学发展的最新理论为指导,采取野外考察和文献研读、岩石野外采样和室内分析鉴定、系统研究和专题研究,对鄂尔多斯盆地西南缘丹霞地貌形成机制进行系统研究。着重对鄂尔多斯盆地西南缘丹霞地貌构造背景、沉积环境、地层岩性、构造运动等要素进行研究,对鄂尔多斯盆地西南缘丹霞地貌发育特征及形成机制提出了新的观点和认识。(1)从鄂尔多斯盆地西南缘丹霞地貌景观的发育阶段来看,经历了红色盆地的形成、沉积的红色地层构造抬升、节理裂隙密集发育、崩塌及差异风化作用共同作用完成了丹霞地貌的形成的不同阶段。丹霞地貌所在区域发生了沉降运动后,普遍接受了沉积,末期盆地抬升,不同区域地层发生了一系列的断裂和褶皱,导致节理发育,对地质体进行切割,进而发生岩层崩塌及差异风化作用,最终形成了现今的丰富多样的丹霞地貌景观。岩性薄片鉴定表明:鄂尔多斯盆地西南缘丹霞地貌分布砾石中成分以石英为主,其硬度和抗风化能力高,成为该区域丹霞地貌骨架。而该区砂岩岩层中的胶结物主要为钙质,容易被溶蚀,导致该区丹霞崖壁出现大量洞穴和槽龛。这三处丹霞地貌区都经历了多次间歇性地壳抬升,地貌发育过程清晰,形态结构完整,以圆顶密集式壮年期丹霞峰丛峰林为最大特色,该地域丹霞地貌发育与冲积扇沉积相关系密切,其亚相、微相类型对丹霞地貌发育起到重要的作用。(2)通过野外调查和岩矿鉴定,对构成铜川照金-香山丹霞地貌红层沉积的岩层岩性、岩石学特征、沉积特征及古流向分析,认定这些砾岩是干旱环境下山麓洪积扇—河流相粗碎屑岩沉积,水动力条件较强,砾石成分复杂,以花岗岩、石英岩、变质火山岩等为主,砾石分选普遍较差,磨圆一般,呈次棱角—次圆状,风化程度低。依据古水流方向,判定其物源主要来自北秦岭。根据这些特征及沉积—构造演化分析,证明铜川地区早白垩世接受沉积,而渭北隆起发育时限为早白垩世末期以后;在早白垩世时期,现今的渭河地区应为鄂尔多斯盆地与秦岭山脉之间的过渡地带,进而认定早白垩世时期鄂尔多斯原始盆地沉积南界至少在现在渭河地区甚至已达秦岭北麓,铜川照金-香山丹霞地貌反映了鄂尔多斯盆地与秦岭造山带的盆山关系。(3)通过对构成平凉崆峒山丹霞地貌红层沉积岩层岩性、岩石学特征、沉积特征及古流向分析,认为塑造平凉崆峒山地区丹霞地貌的地层主要包括两套,分别为上三叠统崆峒山组和的下白垩统三桥组;依据古水流方向,表明崆峒山晚三叠世沉积期主要以西南和南部物源为主,主要源于秦祁造山带。其中崆峒山地区下白垩统三桥组砾岩岩性单一,属山麓相堆积物。砾石磨圆度差异较大,从浑圆状到棱角状均有,分选极差,砾径大小不等。砾石成分统计结果表明,砾石成分以灰岩,砂岩、粉砂岩为主。根据这些特征及沉积—构造演化分析判定早白垩世沉积期六盘山盆地的东侧存在一古隆起向六盘山盆地提供物源,它不仅构成早白垩世六盘山盆地的东部沉积边界,而且将六盘山盆地和鄂尔多斯盆地分隔开来。(4)通过对构成固原火石寨丹霞地貌红层沉积岩层岩性、岩石学特征、沉积特征及古流向分析,认定这些砾岩是干旱环境下山麓洪积扇—河流相粗碎屑岩沉积,岩性简单,由灰紫色及紫色块状砾岩组成,砾石主要成分为石英岩、钾长花岗岩及花岗闪长岩,其底部砾岩粒径大于上部粒径,具有下粗上细的正旋回沉积特征,砾石排列无序。依据古水流方向,判定其物源主要来自北祁连造山带。根据这些特征及沉积—构造演化分析,得出在这一时期火石寨地区是六盘山盆地的沉积中心。通过本次研究可以得出,鄂尔多斯盆地西南缘的丹霞地貌发育与其发育位置的构造特征、地层沉积厚度、岩性、岩石成分、岩相、古气候及断层与节理发育的强度等均有密切的相关性,这些因素对该地区丹霞地貌的形成演化起到了控制作用,同时,也决定这一区域丹霞地貌景观的成景因素。由于各要素在不同地点表现形式不同,使该区域内不同地点发育各具特征的丹霞地貌景观组合,同时,这一区域是我国西北与东南丹霞地貌发育区的过渡地带,是我国丹霞地貌发育的特殊区域。更多还原

【Abstract】 Danxia landform as a geomorphology’s new field, has gone through 80 years of research history. Since the end of the 30’s of last century, Mr. Chen Guoda put forward the Danxia landform. The research has become increasingly mature now through the three stages of start-up, formation and development.But most of them are from the perspective of the landscape resources development point of view. A few scholars do the research on the causes,and from the angle of structural geology, sedimentology study of its formation mechanism has been a weak link. The basic elements of the formation of Danxia landform are not clear,and the basic elements of the formation of Danxia landform are not systematic.In this paper, the Danxia landform in the southwestern margin of Ordos Basin is selected as the research object in this paper. Through the interpretation of ETM+ remote sensing data and field investigation and verification in the southwestern margin of Ordos Basin, find and delineate three Danxia landforms concentrated area in the southwest margin of the basin.Also in the new theory of modern geomorphology development as a guide, take the field investigation and literature reading, rock field sampling and indoor analysis and identification,system research and special studies, to study the formation mechanism of Danxia Landform in southwestern margin of Ordos Basin. Emphatically for the elements of Ordos Basin in the southwest margin of Danxia tectonic background, sedimentary environment, lithology,tectonic movement, etc. A new view and understanding of the characteristics and formation mechanism of Danxia landform in the southwestern margin of Ordos Basin are presented.(1)Ordos Basin on the southwestern margin of the Danxia landform basin formation,sedimentary tectonic uplift, joint fissure development, collapse cause Wai Valley, peak cluster and cliff development, lead to differences in bedrock weathering collapse and weathering and denudation handling this a series of process. Danxia landform area where the settlement movement, it was generally accepted deposition, at the end of the basin was uplifted, different regional stratigraphic occurred a series of faults and folds, and joints is developed,accelerating the cutting of the geological body, but also accelerate the geological body is cut after the rock layers collapse process. Lithologic sheet identification shows that the main component of Danxia landform in the southwest margin of Ordos Basin is mainly composed of quartz, its hardness and anti weathering ability is high, and it has become the framework ofDanxia landform in this area.The three Danxia landform area have undergone several intermittent crustal uplift, the process of landform development clear and intact structure. In a dome of intensive maturity characteristics of the largest peak Danxia peak cluster. The landform development of Danxia is closely related to alluvial fan sedimentary facies.Its sub phase and micro phase type play an important role in the control of Danxia landform development.(2)Through field investigation and rock mineral identification, to constitute the according to golden hill Danxia landform red layer deposited product conglomerate gravel group and lithology, sedimentary characteristics and paleocurrent direction analysis, identified the conglomerate is arid environment down in piedmont alluvial fan fluvial phase coarse clastic sedimentary rocks, hydrodynamic conditions strong, gravel composition complex,dominated by granite, quartz rock and metamorphic volcanic rocks, gravel sorting is generally poor, rounded generally, a sub angular, sub rounded shape and low degree weathering.According to the direction of the ancient water flow, it is determined that the provenance is mainly from North Qinling Mountains. According to an analysis of the characteristics and sedimentary- tectonic evolution that Tongchuan area during the early Cretaceous deposition and Wei northern uplift of the development time was the end of the early Cretaceous later. In the early Cretaceous period, the Weihe area is a transition zone between Ordos basin and the Qinling Mountains mountains, then identification of Early Cretaceous sedimentary basin in South Erdos original circles at least in the Weihe region now even reached North Qinling Mountains. The Tongchuan Danxia landform reflects the relationship between the Ordos Basin and the Qinling Mountains orogenic belt.(3) Through the analysis on the composition of Pingliang Kongtong mountain Danxia landform red layer sedimentary conglomerate gravel group and lithology, petrology,sedimentary characteristics and paleocurrent direction. That shapes Pingliang Kongtong mountain area of Danxia landform, mainly include two sets, respectively, for the upper Triassic Series Kongtongshan formation and lower Cretaceous Bridge Group. According to the paleocurrent direction, indicating that the Kongtong mountain during Late Triassic sedimentary stage mainly in southwest and southern provenance.The main source in the Qinling Qilian orogenic belt. The Kongtong mountain area of Lower Cretaceous formation lithology is a single bridge, the accumulation phase. Gravel grinding roundness difference is larger, from the muddy garden to angular shape, separation range, Unequal diameter. Gravelcomposition statistics show that the gravel components are mainly dominated by limestone,sandstone and silty sandstone. According to these characteristics and sedimentary- tectonic evolution analysis determination of the early Cretaceous sedimentary period of six mountain in the east side of the basin there is a paleo uplift provenance to six Basin. It not only makes early Cretaceous Liupanshan Basin Deposition to the eastern boundary, and will be separated from the Liupanshan Basin and Ordos Basin.(4)Through to constitute the Guyuan Huoshizhai Danxia landform red layer sedimentary conglomerate product conglomerate gravel group and lithology, sedimentary characteristics and paleocurrent direction analysis, finds that the conglomerate is arid environment down in piedmont alluvial fan fluvial phase coarse clastic sedimentary rocks and pretty close to the source area, single lithologic formation, composed of grey purple, purple red massive conglomerate, gravel composition mainly K-feldspar granite, granite diorite and quartz rock flash, gravel bottom conglomerate particle diameter greater than that of the upper particle size, with finer positive cycle sedimentary characteristics, gravel disordered.According to the direction of the ancient water flow, it is determined that the provenance is mainly from the North Qilian orogenic belt. According to these characteristics and sedimentary- tectonic evolution analysis, it is concluded that in this period the fire Danzhai area is the depositional center of Liupanshan Basin.Research shows that the development of Danxia Landform in southwestern margin of Ordos Basin and the position of the tectonic background, red layer deposition thickness,lithology, rock composition, sedimentary facies, and development of paleoclimate and faults and joints strength were closely related, these factors in interrelated constraints in the process of the formation of the southwestern margin of the basin Dan Xia landforms, together constitute the Danxia Landform in this area the scenery control factors. Due to the elements with different characteristics, they work together to the unique Danxia landform landscape composition in different position of development. At the same time, this area is the transition zone of Danxia Landform Development Zone in Northwest and southeast of China, and it is a special region of Danxia landform development in China.更多还原