新仙女木事件在中國內蒙古地區的記錄

The Climate Records Before and After Younger Dryas Event, Inner Mongolia, China

蕭秀璟(Hsiu-Ching Hsiao)

指導教授 ： 宋聖榮

國立臺灣大學/理學院/地質科學研究所/碩士(2011年)

https://doi.org/10.6342/NTU.2011.02877

摘要

我們藉由中國內蒙古地區之必魯圖湖泊 (43°25'12.0' N, 113°46'32.5' E) 為研究對象，以瞭解新仙女木事件在中國北方所造成的氣候型態。此地區之氣候主要受三大系統主控，分別是西伯利亞冷高壓、東亞夏季季風和西風帶，因而對氣候環境變化特別敏感。岩芯總長7.52公尺，根據碳-14定年結果可推得其涵蓋年代範圍是距今8,500∼13,000年前，平均沉積速率為0.167cm/yr。根據礦物相分析結果顯示，沉積物主要由石英、長石、黏土礦物、方解石、白雲石、和菱鎂礦所組成。此外，介形蟲的存在說明了霰石訊號出現所代表的意義。
綜合礦物相結果、有機碳含量、粒徑大小、掃描式電子顯微鏡觀察和磁學參數的分析，可發現在Bølling-Allerød時期，此地區可能受全球氣溫上升的趨勢，而有大量冰水融解並且沖刷至此，帶來大量粗粒沉積物。另外，從粒徑分析結果，此時期劇烈的氣候環境波動造就多次事件型的發生。在新仙女木時期，由於環境的乾旱導致湖體萎縮，進而造成菱鎂礦的沉澱，並且沉積物中泥—粉砂密集互層說明當時環境乾濕變化急遽。進入全新世以後，氣候則轉為潮濕環境，並且水體組成發生改變。此外，根據碳酸鹽類礦物的變化，推斷8,500∼10,200 yr BP為高降水、高蒸發量的環境。

關鍵字

氣候變遷 ； 內蒙古 ； 湖泊沉積物 ； 新仙女木 ； 全新世 ； 菱鎂礦

並列摘要

We collected sediments from the Bilutu Lake (43°25'12.0' N, 113°46'32.5' E) in the center of Inner Mongolia of China to understand climate and environment changes during Younger Dryas Period in northern China. This area is located at the central Asian, where the climate is controlled predominantly by the interaction between the Siberian High, East Asian monsoons and westerly belt. Therefore, this area is considered as a sensitive response for the climate change, so we drilled and analyzed the lake sediments here. The retrieved core from this lake was 7.52 m in length which covered the age ranging from 8.5 to 13 cal. ka BP by C-14 dating, and the average sedimentation rate was estimated as 0.167cm/yr. The X-ray diffraction (XRD) analyses show that the mineral assemblage is predominantly composed of quartz, feldspar, clay minerals, calcite, dolomite and magnesite. In addition, the abundant aragonites indicates the existing of Ostracodas.
Combining the results of XRD, total carbon content (TOC), grain size analyses, field-emission Scanning Electron Microscopy (SEM) observation and magnetic proxies, we conclude the environmental change between 8.5-13 cal. ka BP in northern China. As global temperature rising in the Bølling-Allerød period globally, there were more coarse sediments deposited in this lake by melting glacier. Several events of extreme climate changes were recorded by highly fluctuated variations of grain size. In the Younger Dryas period, dry climate caused the lake to shrink and magnesite deposited. Moreover, the interbedded muds and silts implied rapid environmental changes, and induced an oxidation condition at that time. During the Holocene, the climate became wetter, and the compositions of pore water changed to more brine than before. Meanwhile, according to the variations of carbonate minerals, the climate displayed high fluctuations of precipitation and evaporation between 8,500-10,200 cal. yr BP.

並列關鍵字

Climate change ； Inner Mongolia of China ； Lake sediments ； Younger Dryas ； Holocene ； Magnesite

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