Knowledge Resource Center for Ecological Environment in Arid Area
| 晚渐新世亚洲内陆降温与干旱化 | |
| 其他题名 | Synchronous drying and cooling in Asian Interior during Late Oligocene |
| 董欣欣 | |
| 出版年 | 2013 |
| 学位类型 | 博士 |
| 导师 | 丁仲礼 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 亚洲内陆干旱区——全球最大的中纬度干旱区，通过释放粉尘对大气辐射平衡和海洋生物产率具有重要影响。前人研究表明，亚洲内陆干旱格局在晚渐新世－早中新世时期发生了转型，但由于缺乏高分辨率古气候记录，各种气候动力因素对该转型的作用及其相互关联还不清楚。本文选择天山北麓金沟河剖面的安集海河组湖相沉积序列为研究对象，详细分析了介形虫组合、介壳氧同位素组成、蒸发盐含量、总有机碳／总氮(TOC/TN)比值及粒度分布，基于已有的古地磁年代标尺，重建了研究区晚渐新世时期的气候变化历史，探讨了28.0 －23.3 Ma亚洲内陆干旱环境演变的特征及驱动因子。结果显示： (1) 28.0 － 23.8 Ma，介形虫组合以暖水种布氏土星介(Ilycypirs bradyi)和土星介未定种(Ilyocypris sp.)为主，石膏含量较低；28.0 – 24.0 Ma，介壳氧同位素组成值较小；28.0－24.2 Ma，TOC/TN比值在10左右波动；这些数据表明，在此阶段研究区气候相对暖湿。 (2) 23.8 Ma，冷水种纯净假玻璃介(Pseudocandona albicans)和疏忽玻璃介(Candona cf. neglecta)取代了之前的土星介，石膏含量急剧增加；24.0 Ma，介壳氧同位素组成值明显增大；24.2 Ma，TOC/TN比值降至8以下；这些数据表明，在24.2－23.8 Ma期间区域气候显著变冷、变干。 (3) 本文多指标序列与全球气候记录对比暗示，24.2－23.8 Ma亚洲内陆显著变冷可能是对渐新世－中新世之交的全球降温事件Mi1的响应；而干旱化加剧可能与降温导致的大气持水能力下降以及副特提斯洋向西撤退有关。 (4) 气候代用记录与同一剖面反映区域构造变动的岩石磁学记录对比暗示，渐新世末研究区气候由相对暖湿向显著冷干的转变早于天山山脉抬升，这意味着在渐新世－中新世转变期，天山地区气候演化与区域构造隆升之间不存在因果关联。 |
| 英文摘要 | Aridification of Asian Interior during Late Oligocene and Early Miocene has been documented by numerous eolian records from the North Pacific and Asian Interior. However, direct evidence of aridity from the interior of the arid zone is still rather scarce. To better reconstruct the climate history in Asian Interior during Late Oligocene, we have analyzed ostracod assemblages, gypsum content, C/N ratio and oxygen isotope of ostracod shell carbonate in the sediments from the lacustrine Jingou River section in the northern Tian Shan range. Our results show following conclusions. (1) From 28.0 to 23.8 Ma, Ilyocypris bradyi, Ilyocypris cornea and Ilyocypris sp. were prevailing species, gypsum content was low. The δ18O values of ostracod shells were low too between 28.0 and 23.8 Ma. C/N ratios fluctuated around 10 from 28.0 to 24.2 Ma. All four proxies together indicate that the climate was warm and semi-humid during this period. (2) The cold-water species Candona cf. neglecta and Pseudocandona albicans completely replaced warm-water species at 23.8 Ma. At the same time, gypsum content substantially increased. δ18O values of ostracod shells rapidly increased since 24.0 Ma and C/N ratios decreased to 8 or smaller from 24.2 Ma on. These proxies suggest that terrestrial cooling and drying may have occurred during 24.2 - 23.8 Ma. (3) Comparisons between local and global climate records imply that Asian Interior cooling event from 24.2 to 23.8 Ma may be the response to global cooling event close to O/M boundary, while aridification of Asian Interior during that time might be resulted from the decline of atmospheric water-holding capacity caused by global cooling and the westward retreat of Paratethys Sea. (4) Comparing our multi-proxy climate records to grain-size change and anisotropy of magnetic susceptibility (AMS), we find that cooling and drying event preceded Tian Shan uplift around that time. Therefore the climate events which we found had no linkage with regional tectonism. |
| 中文关键词 | 亚洲内陆 ; 干旱化 ; 降温 ; 介形虫 ; 晚渐新世 |
| 英文关键词 | Asian Interior aridification cooling ostracod Late Oligocene |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 第四纪地质学 |
| 来源机构 | 中国科学院地质与地球物理研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287218 |
| 推荐引用方式 GB/T 7714 | 董欣欣. 晚渐新世亚洲内陆降温与干旱化[D]. 中国科学院大学,2013. |
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