本文選題：江郎山　切入點：方巖組　出處：《東華理工大學》2017年碩士論文　論文類型：學位論文

【摘要】：江郎山發(fā)育典型的老年期丹霞地貌景觀,先后被評為世界自然遺產地和國家5A級旅游景區(qū),本文對構成江郎山丹霞地貌的下白堊統(tǒng)方巖組進行了沉積構造、粒度特征、巖石地球化學特征研究,進而開展其物源分析。主要認識如下:(1)江郎山下白堊統(tǒng)方巖組巖石類型為砂巖、礫巖,礫石成分主要為中酸性火山巖,以凝灰?guī)r為主(熔結凝灰?guī)r、晶屑凝灰?guī)r),其次為硅質巖,分選性普遍較差,礫石扁度介于1.01-4.17,球度為0.54-0.76,磨圓度為20.87%-24.7%。露頭上粒序層理、疊瓦狀構造和沖刷面構造十分發(fā)育。沉積類型以沖積扇和河流沉積為主,其粒度參數(shù)偏度、峰態(tài)、標準偏差指示該區(qū)水動力條件不穩(wěn)定,流速多變但總體具有快速傾泄堆積的特點。(2)方巖組砂巖富硅酸鹽礦物,堿性程度強,貧鋁鐵鎂,親鐵元素偏低,親石元素相對偏高,親稀土相對富集而重稀土相對虧損,Eu的負異常明顯,Sr值相對較低,稀土元素上不同巖石類型總體趨勢基本相同,江郎山下白堊統(tǒng)方巖組的沉積物源主要來自南西和南東方向,風化母巖為中酸性火山巖,總體屬于近源堆積。(3)白堊紀早期,區(qū)域背景由擠壓環(huán)境變成拉張環(huán)境,江郎山所處的峽口盆地成為斷陷盆地,接受附近侏羅系火山巖物質的沉積。在急速式的山洪環(huán)境中,峽口盆地堆積了大量礫巖、砂巖,形成多期次沖積扇。固結成巖后,區(qū)域抬升作用形成大量垂直斷裂,膠結相對不堅固的砂巖在垂直斷裂和風化剝蝕的作用下產生崩塌,而由多期次沖積扇堆積而成的這一部分砂礫巖得到保留。在內、外動力共同的作用下,最終形成現(xiàn)今的江郎山丹霞地貌景觀。通過對該地貌景觀的形成可以看出:丹霞景觀地貌對巖相具有選擇性,沖積扇相是形成丹霞地貌景觀的物質基礎。
[Abstract]:The typical Danxia landform landscape developed in Jianglang Mountain has been appraised as the World Natural Heritage site and the national 5A class tourist area. The sedimentary structure and granularity characteristics of the Lower Cretaceous Fangyan formation, which constitute the Danxia geomorphology of Jianglang Mountain, have been carried out in this paper. The rock types of the Lower Cretaceous calcite formation in Jianglang Mountain are sandstone, conglomerate and gravel mainly composed of intermediate-acid volcanic rocks and tuff (melt-formed tuff). The grained tuff, followed by siliceous rock, is generally poor in sorting, with gravel flatness between 1.01-4.17, sphericity between 0.54-0.76, and grinding roundness of 20.87-24.7.The grain sequence bedding, imbricate structure and scour surface structure on the outcrop are well developed. The sedimentary types are mainly alluvial fans and fluvial deposits. The granularity parameter bias, peak state and standard deviation indicate that the hydrodynamic conditions in this area are unstable, the velocity is variable, but generally has the characteristics of rapid dumping and accumulation.) the sandstone of the Fangyan formation is rich in silicate minerals, strong in alkalinity, poor in aluminum-ferric magnesium, and low in ferriphilic elements. The lithophile elements are relatively high, the relative enrichment of the lipophilic elements is relatively high, and the negative anomaly of the heavy rare earth elements is obviously lower than that of the depleted EU, and the general trend of different rock types on the rare earth elements is basically the same. The sediments of the Lower Cretaceous Fangyan formation in Jianglangshan mainly come from the direction of the south west and south east, and the aeolian parent rock is intermediate acid volcanic rock, which belongs to the near source accumulation. (3) in the early Cretaceous, the regional background changed from the compressional environment to the extensional environment. The Xiakou basin of Jianglang Mountain is a faulted basin, which accepts the deposition of the nearby Jurassic volcanic rocks. In the rapid mountain flood environment, the Xiakou basin accumulates a large number of conglomerates and sandstones, forming multi-stage alluvial fans, and after consolidation of diagenetic rocks, A large number of vertical faults were formed by regional uplift, and the relatively weak cemented sandstone collapsed under the action of vertical faults and weathering and denudation, while this part of sandy gravel, which was accumulated by multi-stage alluvial fans, was retained. Through the formation of the geomorphological landscape, it can be seen that the Danxia landscape is selective to the lithofacies, and the alluvial fan facies is the material basis for the formation of the Danxia landform landscape.
【學位授予單位】：東華理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：P534.53;P512.2

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