摘要
通过对我国西南地区3个洞穴9根大型石笋272个初始234U/238U数据的分析研究,发现石笋初始234U/238U值长尺度变化与海洋沉积SPECMAP曲线δ18O记录有一定的正相关关系,与北纬25°夏季太阳辐射能量变化曲线呈一定的负相关关系,石笋初始234U/238U值的变化在冰期时波动强烈,而在间冰期波动相对平缓,在间冰期和冰期(间冰阶和冰阶)转化阶段该值呈跳跃状态变化。末次冰期及全新世阶段石笋初始234U/238U变化记录了该时段内的BA暖期和YD突变冷事件;全新世8200 a BP、7200 a BP、5200 a BP、4200 a BP、2800 a BP、1400 a BP发生的几次较强冷事件在石笋初始234U/238U值都有相应记录,并且和长尺度的变化规律一致,冷事件发生时石笋初始234U/238U值偏重,暖期偏轻。封闭系统形成的洞穴石笋初始234U/238U变化类似于同地区洞穴石笋的δ18O对气候变化的记录特征,在我国西南地区两者与夏季风变化的强弱呈现一种负相关的关系,洞穴石笋初始234U/238U值可以作为一个有用的古气候替代指标来研究古降水的变化。
This paper focuses on the relationship between initial ^234U/^238U in stalagmites and paleoclimate reconstructions based on 272 precise ICP-MS ^230Th data collected from nine big stalagmites in the Dongge Cave （ 108°5′E, 25°17′N ）, Yamen Cave （ 107°54′E, 25°29′N ） and Lianhua Cave （109°32′E, 29°08′N） in southwestern China. The initial ^234U/^238U ratios in stalagmites have a parallel relation to δ^18O records of SPECMAP and keep a negative relation to summer insolation for 25°N in long term records. The （^234U/^238U）0 in stalagmites fluctuated slowly during interglacial periods and intensively in glacial periods; during transitional stage between glacial and interglacial, the （^234U/^238U）0 in stalagmites shifted sharply. The （^234U/^238U）0 in stalagmites records BA warm events and YD chili events from the Last Glacial to Holocene, which is consistent with the long term （^234U/^238U）0 records, with heavier ratioes of stalagmites during chilling events and lighter ratioes of stalagmites during warm events. Initial ^234U/^238U ratios of stalagmites formed in a closed cave system are similar to δ^18O values of the cave stalagmites from the same area, in contrast, the both in the southwestern regions of China display weak negative relationship with summer monsoon changes. （^234U/^238U）0 in stalagmites may be used as a useful proxy for long-term records of paleoprecipitation.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2008年第5期692-701,共10页
Acta Geologica Sinica
基金
国家自然科学基金项目(编号40231008、90511004、40672165、40772216)
中国博士后科学基金
西南大学自然地理学重点学科基金资助成果
