| 北京延庆古湖正构烷烃分布特征及古气候意义 |
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| 引用本文： | 张慧娟,杨桂芳,陈正洪,武法东,田明中,桑萌.北京延庆古湖正构烷烃分布特征及古气候意义[J].地球科学,2018,43(11):4120-4127. |
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| 作者姓名： | 张慧娟 杨桂芳 陈正洪 武法东 田明中 桑萌 |
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| 作者单位： | 1.中国地质大学地球科学与资源学院, 北京 100083 |
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| 基金项目： | 中央高校经费基本科研业务费优秀教师基金项目2652017216国家自然科学基金专项项目41320003国家自然科学基金专项项目41220001国际合作与交流项目2652017285北京市自然科学基金委项目8162038 |
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| 摘 要： | 为了更好地了解华北平原核心区延庆盆地古气候演化，利用气相色谱仪对北京延庆盆地阜高营剖面湖相沉积物中的正构烷烃进行了检测.结果表明其正构烷烃含量丰富且连续，碳数分布范围为C16~C33，高碳数奇碳优势明显，中链和短链烷烃均无奇偶优势，多以C29或C31为主峰的单峰分布为主，同时存在少量低碳数和高碳数并存的双峰型.延庆古湖有机质以陆生植物为主，包含少量的菌藻类和水生植物.综合ESR年代序列、有机碳同位素（δ13Corg）、长链正构烷烃平均链长（average chain length，ACL）碳优势指数（carbon preference index，CPI）和正构烷烃Paq参数，将延庆盆地晚更新世中期以来的环境演变划分为:56.8~45.6 ka，气候暖湿，湖泊发育良好，湖面较高；45.6~31.5 ka，气候温湿，湖泊发育缓慢，水位略有下降；31.5~20.0 ka，气候冷干，湖泊水位严重下降；20.0~13.4 ka，气候较为干冷，有转暖趋势；13.4~9.2 ka，气候转暖，湖泊有所发育，但水位较低；9.2 ka至今，气候变干，湖泊萎缩.延庆古湖沉积物中正构烷烃参数的变化与古里雅冰心、李家塬黄土、深海氧同位素反映的气候变化较为一致，呈现冰期-间冰期旋回，且受控于同纬度太阳辐射量的变化.
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| 关 键 词： | 正构烷烃 分布特征 湖泊沉积物 古植被 延庆盆地 气候变化 |
| 收稿时间： | 2018-01-17 |
Distribution of n-Alkane Indicative of Paleoclimatic Change in Paleolake of Yanqing,Beijing |
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| Abstract: | N-alkanes in lacustrine sediments could be well preserved and have documented the paleoenvironmental variations. By the aid of GC method, n-alkanes were identified in lacustrine sediments from Fugaoying profile within Yanqing basin of Beijing, one of the core regions in the North China plain, to characterize the paleoclimatic variations in this area. The results show that the n-alkanes with carbon numbers ranging from C16 to C33 exhibit different distribution patterns. Most samples show a single peak with high carbons (C29 or C31 in particular) and have an odd carbon number predominance, while a few have double peaks with lower and high carbons. The middle and short n-alkanes have no obvious carbon number characteristics. The results suggest the organic origin from terrestrial, some algae and few aquatic plants. According to ESR sequence, organic carbon isotope, ACL (average chain length), CPI (carbon preference index), and Paq, alternative paleoclimatic conditions have been reconstructed in the study area since 56.8 ka. From 56.8 to 45.6 ka, the pretty hot-humid climate results in a higher lake level. During 45.6 and 31.5 ka, the climate became warm and humid, producing a slightly declined lake level. After that, cold-dry climate and seriously declined lake level were distinct between 31.5 and 20.0 ka. From 20.0 to 13.4 ka, the climate was cold and dry, but with a warming trend. During 13.4 to 9.2 ka, the climate became warm slightly and the resulted lake level was lower. Since 9.2 ka, the climate became dry, thus leading to a shrunken lake. Distribution of n-alkanes indicates that the paleoclimatic changes of Yanqing basin are basically parallel to summer solar radiation, grain size of Lijiayuan profile, and oxygen isotope records in Guliya core and Sulu Sea, potentially suggesting the control of solar radiation. |
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