粒度和磁化率反映的中晚全新世以來瑪曲高原的沙漠化演化
發(fā)布時(shí)間：2018-09-12 18:51
【摘要】：瑪曲高原位于青藏高原東端,深受高原氣候和東部季風(fēng)氣候的影響,廣泛存在著風(fēng)成沉積物,因此較完整地保存了黃土-古土壤-古風(fēng)成砂的沉積序列,加之其處于黃土高原和青藏高原的過渡地帶,氣候環(huán)境變化更為敏感�，斍咴F(xiàn)代沙漠化是在地質(zhì)歷史的基礎(chǔ)上一個(gè)古砂翻新的過程,本文在瑪曲高原東部選取了典型的黃土-古土壤-古風(fēng)成砂沉積序列OL剖面和MO剖面作為研究對(duì)象,在高密度采樣和14C定年的基礎(chǔ)上,對(duì)兩個(gè)剖面的沉積相、年代、磁化率、有機(jī)質(zhì)、粒度及其參數(shù)等氣候代用指標(biāo)進(jìn)行對(duì)比分析,借鑒前人對(duì)青藏高原全新世已取得的研究成果基礎(chǔ)之上,與其它典型區(qū)域進(jìn)行對(duì)比分析,以便填補(bǔ)瑪曲高原地質(zhì)時(shí)期沙漠化過程研究的空白,從而探討氣候變化和風(fēng)沙活動(dòng)的關(guān)系,此研究對(duì)豐富瑪曲高原古環(huán)境及古氣候變化、沙漠化形成演化等方面理論具有重要意義,可為現(xiàn)代沙漠化防治提供理論依據(jù)和實(shí)踐指導(dǎo)。研究結(jié)果表明:(1)瑪曲高原中晚全新世以來氣候變化呈現(xiàn)冷干-溫濕-涼干的變化趨勢(shì),風(fēng)沙活動(dòng)經(jīng)歷了強(qiáng)-弱-較強(qiáng)的演變。(2)古土壤發(fā)育時(shí)期氣候溫濕,古風(fēng)成砂層氣候相對(duì)冷干,黃土沉積時(shí)期氣候由溫濕向冷干過渡。(3)瑪曲高原中晚全新世以來的風(fēng)沙活動(dòng)主要經(jīng)歷了以下四個(gè)階段:1)4.6ka B.P.以前,氣候以冷干為主,冬季風(fēng)較強(qiáng)盛,風(fēng)沙活動(dòng)強(qiáng),沙漠化程度加快;2)4.6~4.3 ka B.P.為氣候涼潤(rùn)期,冬季風(fēng)較弱,風(fēng)沙活動(dòng)較上一時(shí)期弱,沙漠化程度弱;3)4.3~0.3 ka B.P.為氣候溫濕期,夏季風(fēng)較強(qiáng),風(fēng)沙活動(dòng)弱,沙漠化程度很弱,這一時(shí)期可分為三個(gè)小階段,即a階段(4.3~3.6 ka B.P.)為氣候由涼潤(rùn)向溫濕過渡期,風(fēng)沙活動(dòng)由強(qiáng)變?nèi)?發(fā)育了較弱的古土壤;b階段(3.6~3.5 ka B.P.)為氣候涼潤(rùn)期,風(fēng)沙活動(dòng)較a階段強(qiáng),沉積了黃土;c階段(3.5~0.3 ka B.P.)為氣候溫濕期,夏季風(fēng)較強(qiáng),風(fēng)沙活動(dòng)弱,發(fā)育了較厚的古土壤;4)0.3ka B.P.為氣候涼干期,冬季風(fēng)較弱,風(fēng)沙活動(dòng)較弱,沙漠化程度較弱。(4)中晚全新世以來瑪曲高原氣候變化遵循“冷干強(qiáng)風(fēng)-溫濕弱風(fēng)”的變化模式。通過對(duì)比分析發(fā)現(xiàn)瑪曲高原中晚全新世以來的氣候變化與青藏高原東北部乃至全球的氣候變化都具有同步性。氣候代用指標(biāo)反映了瑪曲高原中晚全新世以來分別在3.57 ka B.P.、3.47 ka B.P.、2.90 ka B.P.、2.50 ka B.P.、2.03 ka B.P.、1.84 ka B.P.、1.57 ka B.P.、1.30 ka B.P.、0.98 ka B.P.、0.80 ka B.P.、0.62 ka B.P.左右發(fā)生了11次較大的冷事件。其中3.57 ka B.P.與青海湖周邊地區(qū)約3.5 ka B.P.以涼干氣候?yàn)橹鳌L(fēng)沙活動(dòng)增強(qiáng)相一致;3.47 ka B.P.、2.90 ka B.P.、2.50 ka B.P.的冷事件與3.37 ka B.P.、2.96 ka B.P.、2.49 ka B.P.發(fā)生在青海湖周邊地區(qū)的強(qiáng)風(fēng)沙活動(dòng)相對(duì)應(yīng);2.96 ka B.P.的冷事件也與北大西洋在3.0 ka B.P.的寒冷事件具有很高的一致性;1.57 ka B.P.的氣候變冷與甘青毗鄰草原地區(qū)1.5 ka B.P.氣候冷干對(duì)應(yīng)良好;1.30 ka B.P.、0.80 ka B.P.和0.62 ka B.P.的冷事件與青藏高原東北部共和盆地在1.40 ka B.P.左右、0.8~0.5 ka B.P.處于寒冷階段相一致。
[Abstract]:The Maqu Plateau is located in the eastern end of the Qinghai-Tibet Plateau. It is deeply influenced by the plateau climate and the eastern monsoon climate. There are widely aeolian sediments. Therefore, the depositional sequence of loess-palaeosol-aeolian sand has been preserved relatively intact. In addition, the Maqu Plateau is in the transition zone between the Loess Plateau and the Qinghai-Tibet Plateau. Desertification is a process of retrofitting ancient sand on the basis of geological history. In this paper, OL and MO sections of typical loess-paleosol-aeolian sand sedimentary sequences are selected as the research objects in the eastern part of Maqu plateau. On the basis of high-density sampling and 14C dating, sedimentary facies, age, magnetic susceptibility, organic matter, grain size and their distribution in the two sections are studied. In order to fill in the blank of the study on the desertification process in the geological period of the Maqu plateau and to explore the relationship between climate change and aeolian sand activity, this study enriches the Maqu plateau by comparing and analyzing the climate substitution indexes such as parameters and other climate substitution indexes, drawing lessons from the research achievements of predecessors on the Holocene of the Qinghai-Tibet Plateau and other typical regions. The results show that: (1) Since the middle and late Holocene, the climate change in the Maqu Plateau has shown a trend of cold-dry, warm-humid, cool-dry, and the aeolian sand activity has experienced a strong-weak-strong trend. (3) Sandstorm activities in the Maqu Plateau since the Middle and Late Holocene have mainly undergone the following four stages: (1) before 4.6 Ka B.P., the climate was mainly cold and dry, with strong winter wind, strong aeolian sand activity and desertification. 2) 4.6-4.3 Ka B.P. is a cool and humid period with weak winter monsoon, weak aeolian sand activity and weak desertification degree; 3) 4.3-0.3 Ka B.P. is a warm and humid period with strong summer monsoon, weak aeolian sand activity and weak desertification degree. The period can be divided into three small stages, i.e. stage a (4.3-3.6 Ka B.P.) is a transition from cool to warm and humid climate. During the transitional period, the aeolian sand activity changed from strong to weak and developed weak paleosols; stage B (3.6-3.5 Ka B.P.) was a cool and humid period, and aeolian sand activity was stronger than stage a, thus depositing loess; stage C (3.5-0.3 Ka B.P.) was a warm and humid period with strong summer monsoon and weak aeolian sand activity, and developed thick paleosols; and stage 4) 0.3 Ka B.P. was a cool and dry period with weak winter wind and weak wind. The climate change of the Maqu Plateau follows the pattern of "cold-dry strong wind-warm-humid weak wind" since the Middle-Late Holocene. The climate change of the Maqu Plateau since the Middle-Late Holocene is synchronous with the climate change in the northeast of the Qinghai-Tibet Plateau and the whole world. It reflects 11 major cold events since the middle and late Holocene in the Maqu Plateau, including 3.57 Ka B.P., 3.47 Ka B.P., 2.90 Ka B.P., 2.50 Ka B.P., 2.03 Ka B.P., 1.84 Ka B.P., 1.57 Ka B.P., 1.30 Ka B.P., 0.98 Ka B.P., 0.80 Ka B.P., 0.62 Ka B.P., 3.57 Ka B.P. and 3.5 Ka B.P. around the Qinghai Lake. The cold events of 3.47 Ka B.P., 2.90 Ka B.P., 2.50 Ka B.P. correspond to the strong wind and sand activities of 3.37 Ka B.P., 2.96 Ka B.P., 2.49 Ka B.P. in the area around Qinghai Lake; the cold events of 2.96 Ka B.P. correspond to the cold events of 3.0 Ka B.P. in the North Atlantic Ocean. The cold events of 1.30 Ka B.P., 0.80 Ka B.P. and 0.62 Ka B.P. coincided with the cold events of 1.40 Ka B.P., 0.8 Ka B.P. and 0.5 Ka B.P. in the Gonghe Basin in the northeastern Qinghai-Tibet Plateau.
【學(xué)位授予單位】：西北師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P534.632;P931.3
本文編號(hào)：2239919
[Abstract]:The Maqu Plateau is located in the eastern end of the Qinghai-Tibet Plateau. It is deeply influenced by the plateau climate and the eastern monsoon climate. There are widely aeolian sediments. Therefore, the depositional sequence of loess-palaeosol-aeolian sand has been preserved relatively intact. In addition, the Maqu Plateau is in the transition zone between the Loess Plateau and the Qinghai-Tibet Plateau. Desertification is a process of retrofitting ancient sand on the basis of geological history. In this paper, OL and MO sections of typical loess-paleosol-aeolian sand sedimentary sequences are selected as the research objects in the eastern part of Maqu plateau. On the basis of high-density sampling and 14C dating, sedimentary facies, age, magnetic susceptibility, organic matter, grain size and their distribution in the two sections are studied. In order to fill in the blank of the study on the desertification process in the geological period of the Maqu plateau and to explore the relationship between climate change and aeolian sand activity, this study enriches the Maqu plateau by comparing and analyzing the climate substitution indexes such as parameters and other climate substitution indexes, drawing lessons from the research achievements of predecessors on the Holocene of the Qinghai-Tibet Plateau and other typical regions. The results show that: (1) Since the middle and late Holocene, the climate change in the Maqu Plateau has shown a trend of cold-dry, warm-humid, cool-dry, and the aeolian sand activity has experienced a strong-weak-strong trend. (3) Sandstorm activities in the Maqu Plateau since the Middle and Late Holocene have mainly undergone the following four stages: (1) before 4.6 Ka B.P., the climate was mainly cold and dry, with strong winter wind, strong aeolian sand activity and desertification. 2) 4.6-4.3 Ka B.P. is a cool and humid period with weak winter monsoon, weak aeolian sand activity and weak desertification degree; 3) 4.3-0.3 Ka B.P. is a warm and humid period with strong summer monsoon, weak aeolian sand activity and weak desertification degree. The period can be divided into three small stages, i.e. stage a (4.3-3.6 Ka B.P.) is a transition from cool to warm and humid climate. During the transitional period, the aeolian sand activity changed from strong to weak and developed weak paleosols; stage B (3.6-3.5 Ka B.P.) was a cool and humid period, and aeolian sand activity was stronger than stage a, thus depositing loess; stage C (3.5-0.3 Ka B.P.) was a warm and humid period with strong summer monsoon and weak aeolian sand activity, and developed thick paleosols; and stage 4) 0.3 Ka B.P. was a cool and dry period with weak winter wind and weak wind. The climate change of the Maqu Plateau follows the pattern of "cold-dry strong wind-warm-humid weak wind" since the Middle-Late Holocene. The climate change of the Maqu Plateau since the Middle-Late Holocene is synchronous with the climate change in the northeast of the Qinghai-Tibet Plateau and the whole world. It reflects 11 major cold events since the middle and late Holocene in the Maqu Plateau, including 3.57 Ka B.P., 3.47 Ka B.P., 2.90 Ka B.P., 2.50 Ka B.P., 2.03 Ka B.P., 1.84 Ka B.P., 1.57 Ka B.P., 1.30 Ka B.P., 0.98 Ka B.P., 0.80 Ka B.P., 0.62 Ka B.P., 3.57 Ka B.P. and 3.5 Ka B.P. around the Qinghai Lake. The cold events of 3.47 Ka B.P., 2.90 Ka B.P., 2.50 Ka B.P. correspond to the strong wind and sand activities of 3.37 Ka B.P., 2.96 Ka B.P., 2.49 Ka B.P. in the area around Qinghai Lake; the cold events of 2.96 Ka B.P. correspond to the cold events of 3.0 Ka B.P. in the North Atlantic Ocean. The cold events of 1.30 Ka B.P., 0.80 Ka B.P. and 0.62 Ka B.P. coincided with the cold events of 1.40 Ka B.P., 0.8 Ka B.P. and 0.5 Ka B.P. in the Gonghe Basin in the northeastern Qinghai-Tibet Plateau.
【學(xué)位授予單位】：西北師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P534.632;P931.3
【參考文獻(xiàn)】
相關(guān)期刊論文 前1條
1 呂厚遠(yuǎn),韓家懋,吳乃琴,郭正堂;中國(guó)現(xiàn)代土壤磁化率分析及其古氣候意義[J];中國(guó)科學(xué)(B輯 化學(xué) 生命科學(xué) 地學(xué));1994年12期
，本文編號(hào)：2239919
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