本文選題：XRF巖芯掃描　切入點(diǎn)：粒度　出處：《南京師范大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：末次冰消期以來海平面上升,對人類尤其是沿海地區(qū)人們的生活環(huán)境產(chǎn)生較大的影響。海平面變化的研究已經(jīng)成為全球變化研究的熱點(diǎn)問題之一。長江三角洲因其重要的經(jīng)濟(jì)地位和獨(dú)特的自然地理位置成為我國學(xué)者研究中國東部海平面變化的重要區(qū)域。長江三角洲處于構(gòu)造沉降帶,同時(shí)接收來自長江和錢塘江的河流沉積物,形成了一個(gè)廣闊的近海平原。由于該區(qū)域地勢平坦,極其容易受海面變化的影響,因此難以獲得連續(xù)的、高分辨率的沉積序列。針對上述問題,本研究選取長江三角洲南側(cè)的寧紹平原作為研究區(qū)域,以研究區(qū)內(nèi)的自然鉆孔HMD1401為研究對象,該區(qū)域受到東部舟山群島和北部慈南山脈的屏障作用,沉積環(huán)境穩(wěn)定,沉積地層連續(xù),巖性單一,對研究長江三角洲的地貌演化具有重要的參考價(jià)值。本文通過對HMD1401孔的沉積相分析、年代框架的建立、粒度特征分析、典型元素地球化學(xué)分析,探討寧紹平原末次冰消期以來的地貌與環(huán)境演化過程,主要得出以下結(jié)論:(1)末次冰消期以前(10.7kaB.P.):寧紹平原屬于混雜的坡積物,沉積環(huán)境變化較大。古土壤層(第一硬粘土層)發(fā)育于厚約80cm的砂層之上,極有可能形成于水動(dòng)力不強(qiáng)的靜水環(huán)境。(2) 10.7～9.1 kaB.P.:這個(gè)時(shí)期為潮間帶沉積環(huán)境,水動(dòng)力較強(qiáng),沉積環(huán)境逐漸由陸相沉積轉(zhuǎn)化為海相沉積,寧紹平原由此逐漸進(jìn)入淺海階段。初期10.7～9.6kaB.P.之間應(yīng)屬于偶爾受海水影響的淺水洼地環(huán)境。9.6～9.1kaB.P.之間該區(qū)域可能處于近岸海灣環(huán)境。(3)9.1～6.5 kaB.P.:該階段是海面上升的全盛時(shí)期,海平面快速上升,達(dá)到距今海平面至少-3 m左右的位置。陸源物質(zhì)的輸入也并不是穩(wěn)定的,存在一定的沉積周期。海水淹沒了整個(gè)寧紹平原,僅剩的一些低山和島嶼為河姆渡文化的發(fā)展提供了有限的生存空間。河姆渡早期人類就是在這樣的地貌環(huán)境下生產(chǎn)和生活。(4) 6.5kaB.P.以后:該階段寧紹平原海平面上升速度下降,但沉積物供給仍然豐富,最后成陸作用逐漸超過了海平面上升的速度,逐漸由海相沉積轉(zhuǎn)變?yōu)殛懴喑练e。這為河姆渡文化的進(jìn)一步壯大和繁榮提供了廣闊的空間。并且我們認(rèn)為在6.5 ka B.P.以后多次受到咸潮入侵的影響,而咸潮的入侵對河姆渡文化的發(fā)展必然會(huì)產(chǎn)生一定的負(fù)面影響。為保證研究結(jié)果的準(zhǔn)確性,本文將HMD1401鉆孔的元素掃描研究結(jié)果與HMD03的藻類、孢粉數(shù)據(jù)進(jìn)行對比,發(fā)現(xiàn)海相性元素指標(biāo)Ca和Mn尤其是Ca與溝鞭藻、藜科的變化具有較高的相似性;此外,將HMD1401的元素掃描結(jié)果與TLS13孔的XRD礦物鑒定結(jié)果進(jìn)行對比,發(fā)現(xiàn)Ca和Mn的變化特征與蒙脫石具有一致性。
[Abstract]:Sea level has risen since the last ice age, The study of sea level change has become one of the hot issues in the study of global change. The Yangtze River Delta because of its important economic status and unique self. However, geographical location has become an important area for Chinese scholars to study sea level changes in eastern China. The Yangtze River Delta is located in a tectonic subsidence zone. Receiving river sediments from both the Yangtze and Qiantang rivers at the same time, forming a vast offshore plain. Because the area is flat and extremely vulnerable to changes in the sea, it is difficult to obtain continuity. High-resolution sedimentary sequence. In view of the above problems, the Ningshao Plain in the southern side of the Yangtze River Delta is selected as the study area, and the natural borehole HMD1401 in the study area is taken as the research object. The area is protected by the Zhoushan archipelago in the east and the Zinan Mountains in the north. The sedimentary environment is stable, the sedimentary strata are continuous, and the lithology is single. In this paper, the sedimentary facies of the HMD1401 pore, the establishment of the age frame, the grain size characteristics, the geochemistry of typical elements, and the analysis of the sedimentary facies of the HMD1401 pore are analyzed, which are important for the study of the geomorphological evolution of the Yangtze River Delta. The geomorphology and environmental evolution of Ningshao Plain since the last ice age are discussed. The main conclusions are as follows: before the last ice elimination stage, there were 10.7ka B.P.: Ningshao Plain belongs to mixed slope deposits. The paleosol layer (the first hard clay layer) developed above the sand layer about 80 cm thick, and most likely formed in the hydrodynamic hydrostatic environment.) 10.79.1 kaB.P.: this period is an intertidal sedimentary environment, and the hydrodynamic environment is relatively strong. The sedimentary environment gradually changed from continental to marine. Therefore, the Ningshao Plain gradually entered the shallow water stage, between 10.7 and 9.6kaB.P., which belongs to the shallow water basin environment, which is occasionally affected by seawater. The area may be in the coastal bay environment of 6.5kaB.P.: this stage is the heyday of sea level rise, and the sea level rises rapidly. At least 3 m above sea level, the input of land-based materials is not stable, and there is a certain period of sedimentation. The sea water inundated the whole Ningshao Plain. The remaining low mountains and islands provided a limited living space for the development of the Hemudu culture. It was in this geomorphological environment that the early Hemudu people produced and lived in such a geomorphological environment) 6.5kaB.P.After this stage, the sea level in the Ningshao Plain fell at a rate of decline. But the sediment supply is still abundant, and eventually the land-based process gradually exceeds the rate of sea-level rise. The gradual transition from marine to continental sediments provides a vast space for the further growth and prosperity of the Hemudu culture. And we believe that the saltwater intrusions have affected many times since 6.5 ka B.P. In order to ensure the accuracy of the research results, the elemental scanning results of HMD1401 boreholes are compared with the algae and sporopollen data of HMD03. It was found that the changes of Ca and mn, especially Ca and Verbenidae, were similar to those of Chenopodiaceae. In addition, the elemental scanning results of HMD1401 were compared with the results of XRD mineral identification in TLS13 pore. It is found that the change of Ca and mn is consistent with that of montmorillonite.
【學(xué)位授予單位】：南京師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：P931;P736.2

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