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近年来,U_(37)~(K’)长链烯酮古温度指标已被越来越多地应用于湖泊沉积物的研究中。综合分析我国西风区的湖泊沉积物记录,U_(37)~(K’)对全新世暖期的记录存在较大差异,甚至有高达0.9的异常值出现,即湖泊表层水温在全新世超过30℃,这在气候意义上很难解释。为了更好地理解U_(37)~(K’)在西北干旱区湖泊沉积物中的应用条件,文章对玛纳斯湖西岸的三处晚全新世湖滨沉积物钻孔进行了有机地球化学分析,首次确认了新疆玛纳斯湖湖泊沉积物中存在长链烯酮。通过分析U_(37)~(K’)记录与长链烯酮含量的关系,并与其他西风区湖泊烯酮记录进行对比,发现长链烯酮的含量与干旱区湖泊的湖水位变化存在一定的关系,即长链烯酮含量的高低指示着湖水位的高低;同时,U_(37)~(K’)记录与长链烯酮含量也存在一定的联系;异常高的U_(37)~(K’)值总是伴随着较低的烯酮含量(<100ng/g干样),即产生于湖滨相或湖泊接近于干涸状态。由此,本文认为湖水位较低时,湖泊水体差异升温和长链烯酮的选择性分解可能是导致较高U_(37)~(K’)出现的原因;这样的U_(37)~(K’)记录是不可靠的,不能用于定量计算古温度,但仍可用于反应冷暖趋势的变化。
In recent years, the ancient temperature index of U_ (37) ~ (K ’) long-alkenone has been used more and more in the study of lake sediments. Based on a comprehensive analysis of the records of lake sediments in the westerly region of China, the records of U_ (37) ~ (K ’) have a great difference in the Holocene, and even up to 0.9 anomalies, ie, ℃, which is difficult to explain in the climate sense. In order to better understand the application conditions of U_ (37) ~ (K ’) in lacustrine sediments in northwestern arid regions, three geochronological analyzes of sediments in the Late Holocene lakeshore in the west bank of Manas Lake were carried out. , For the first time confirms the existence of long-chain ketene in the sediments of Manas Lake in Xinjiang. By analyzing the relationship between U_ (37) ~ (K ’) records and long-chain ketene content, and comparing with the other kefir records of lake westerlies, it was found that the content of long-chain ketene and the lake water level in arid areas varied The relationship between the content of long-chain ketene and the content of long-chain ketene also showed a certain relationship with the level of lake water. At the same time, the U_ (37) ~ (K ’ (K ’) values are always accompanied by a lower ketene content (<100 ng / g dry sample), ie from lakeshore facies or lakes close to dry state. Therefore, we conclude that the difference of lake water temperature and selective decomposition of long-chain ketene may be the reason for the higher occurrence of U_ (37) ~ (K ’) when the lake water level is low. Such U_ (37) ~ ( K ’) records are unreliable and can not be used to quantify palaeontlines, but can still be used to reflect changes in the cool / warm trend.