本文選題：烏蘭布和沙漠　切入點：鉆孔巖芯　出處：《蘭州大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：位于內(nèi)蒙古高原的西南部的烏蘭布和沙漠,是中國北方主要的沙漠之一,也是北半球重要的粉塵源區(qū)。該沙漠北部主要為固定沙丘和沙壟為主,南部主要為高大沙丘及金字塔形沙丘組成。對于烏蘭布和沙漠南部高大沙丘區(qū)的環(huán)境變化,由于缺乏可靠的沉積記錄和足夠的年齡數(shù)據(jù)支持,沙漠環(huán)境變化及沙漠形成演化過程目前還不清楚。本研究通過在烏蘭布和南部高大沙丘核心區(qū)開展沙漠鉆探,獲得一根120.5 m長的沙漠鉆孔巖芯(WL12ZK-1巖芯)。對巖芯開展了詳細的沉積地層描述。使用石英光釋光測年和鉀長石多步法紅外后紅外釋光測年方法,建立鉆孔巖芯的年齡框架。使用古環(huán)境代用指標(粒度、燒失量、孢粉、介形蟲)對WL12ZK-1鉆孔記錄的環(huán)境變化進行了分析,以便重建該地區(qū)的環(huán)境變化。石英光釋光性質(zhì)(包括劑量恢復(fù)實驗,釋光信號特征)檢驗,結(jié)果表明對小于6萬年的年輕樣品石英光釋光測年方法是可靠的。鉀長石釋光測年的結(jié)果可靠性通過內(nèi)部信號檢驗和鉀長石年齡—激發(fā)溫度坪區(qū)實驗檢驗。鉀長石和石英測年結(jié)果的對比也進一步指示了年齡框架的可靠性。結(jié)合之前沙漠北部已有的WL10ZK-1和WL10ZK-2鉆孔巖芯沉積記錄,烏蘭布和沙漠南部鉆孔巖芯W(wǎng)L12ZK-1古環(huán)境代用指標和年齡結(jié)果表明烏蘭布和沙漠地區(qū)干旱環(huán)境在中晚更新世就已經(jīng)形成,沙漠沙丘沙環(huán)境至少在~230 ka以前就已經(jīng)形成,該地區(qū)植被自此以來主要是沙漠植被和草甸植被。在約155 ka前開始在該地區(qū)形成了由黃河作為主要補給水源的古大湖,古湖泊環(huán)境可能一直持續(xù)到~87 ka前后,古湖泊可能經(jīng)歷了多次湖面進退波動,孢粉分析表明古湖泊周圍主要生長著草甸植物。在~87 ka之后,烏蘭布和沙漠地區(qū)古湖泊消失,沙漠環(huán)境再次形成,在末次冰期該地區(qū)很可能沒有任何穩(wěn)定的古大湖發(fā)育。烏蘭布和沙漠南部末次冰期至全新世早期沙漠環(huán)境穩(wěn)定存在,干旱環(huán)境持續(xù)至今。內(nèi)蒙古高原南部的沙漠在末次間冰期、全新世早期和距今約2 ka以來發(fā)生了進一步擴張。研究結(jié)果表明構(gòu)造活動和氣候變化是更新世中期以來內(nèi)蒙古南部沙漠形成的主要原因,此外晚全新世的人類活動可能促進了沙漠的進一步擴張。
[Abstract]:The Wu Lan Buhe Desert, located in the southwest of Inner Mongolia Plateau, is one of the major deserts in northern China and an important dust source in the Northern Hemisphere. The northern part of the desert is dominated by fixed sand dunes and ridges. The south is mainly composed of tall sand dunes and pyramidal dunes. For the environmental changes in the high sand dunes in the southern part of the Wu Lan Buhe Desert, due to the lack of reliable sedimentary records and sufficient age data, It is not clear how the desert environment changes and the desert formation and evolvement. This study carried out desert drilling in the core area of Wu Lan Buhe and high sand dunes in the south. A 120.5 m long desert drilled core WL12ZK-1 core has been obtained. Detailed sedimentary strata description has been carried out on the core. The methods of quartz photoluminescence dating and potassium feldspar multistep infrared post-infrared luminescence dating have been used. The age frame of borehole core was established. The environmental changes of WL12ZK-1 borehole records were analyzed by using paleoenvironment substitute indexes (granularity, loss of fire, sporopollen, ostracoda). In order to reconstruct the environmental changes in the area. Quartz photoluminescence properties (including dose recovery experiments, luminescent signal characteristics) tests, The results show that the method of quartz photoluminescence dating for younger samples of less than 60,000 years is reliable. The reliability of potassium feldspar dating results is verified by internal signal test and potassium feldspar age-excitation temperature plateau test. The comparison of stone and quartz dating results also further indicates the reliability of the age framework. Combined with previous WL10ZK-1 and WL10ZK-2 drilled core sediment records in the northern part of the desert, The substitution index and age of WL12ZK-1 in the core of the southern Wu Lan Bohe Desert indicate that the arid environment in the area of Wu Lan Buhe has been formed in the middle and late Pleistocene, and the sand environment in the desert dunes was formed at least 230ka ago. Since then, the vegetation in this area has been mainly desert vegetation and meadow vegetation. About 155 ka ago, the ancient Great Lakes were formed in the region, where the Yellow River is the main source of water supply, and the ancient lake environment may last until about 87 ka. The ancient lakes may have experienced many fluctuations in the lake surface, and pollen analysis showed that there were mainly meadow plants around the ancient lakes. After 87 ka, the ancient lakes of Wu Lan Buhe desert area disappeared and the desert environment was formed again. During the last glacial period, there was probably no stable paleolake development in this area. The desert environment in the southern part of Wu Lan Buhe Desert remained stable from the last glacial period to the early Holocene, and the arid environment continued to this day. The desert in the southern Inner Mongolia Plateau was in the last interglacial period. The results show that tectonic activity and climate change are the main causes of desert formation in southern Inner Mongolia since the middle Pleistocene. In addition, human activities in the late Holocene may have contributed to the further expansion of the desert.
【學(xué)位授予單位】：蘭州大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P534.63

【參考文獻】

相關(guān)期刊論文 前2條

1 ;Sedimentary documents and Optically Stimulated Luminescence (OSL) dating for formation of the present landform of the northern Ulan Buh Desert,northern China[J];Science China(Earth Sciences);2010年11期

2 ;Uplift of the Tibetan Plateau and environmental changes[J];Chinese Science Bulletin;1999年23期

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本文編號：1566444