自然资源部岩岩溶动力学重点实验室

洞穴石笋沉积旋回主要特征的古气候环境研究

2009-04-10KDL 2301

A Paleoclimate Environment Study on the Main Characteristics of Sedimentary Cycles in Stalagmite

 

AbstractWe summarize the characteristics of sedimentary cyclescycle interface types of some stalagmites and related significances in climatic, environmental and geological sciences. Before that, the components and structures or some typical large stalagmite in southern China were studied: Also 210 isotopic samples ofδ13C, δ18O, 20 samples for U series dating in D10 and some related trace elements were analyzed comparatively. According to the colors reflected by different impurities in carbonate, the lamina features and isotopic components of stalagmite in D10, three cycling features which are accordant parallel, unaccordant parallel and unaccordant unparallel can be divided. 19 sedimentary cycles can be identified. The average δ13C, δ18O value-3.91PDB and-6.97PDB respectively represent the threshold value. which indicate the evolution of co1d and warm climate. Consequently, if the isotopic value is higher than the threshold va1ue, it means the climate is in favor of cold conditions. According to the isotopic and cycle characteristics of the sedimentary, it is considered preliminarily that the 19 cycles deposited during the years from 352930 to 99410 in Libo area indicate a relatively complete process of the climate evolution in the fifth Ice Age of the Quaternary Ice Age series in China. The 50000 years which is calculated from cycle 10 to cyc1e 15 is surmised as a continuous freezing glacial maximum. The cycle 1 and cycle 16 represents probably interglacial period which was relative warmer. Furthermorethere also existed 50000 or 100000 years sca1e climatic cycle during the period. It is demonstrated that there was glacial period in Libo area from 350000 to l00000 years age. The prophase about 170000 years was frigid climate, and during 350000 years and 250000 years period was even more frigid, however the ecological environment evolved normally. The metaphase about 50000 years was extremely frigid and the ecological environment evolved in favor of the arctic weather. The late stage about 30000 years represented an extreme climate in which the abrupt change between cold climate and warm climate occurred frequently, the normal and mutational succession coexisted

Key wordsstalagmite; cycle; Paleoenvironment;δ13C andδ18O; Dongge cave
[ ]  通过对我国南方大型石笋组分、结构构造的观测和董哥洞10(D10)石笋210件碳、氧同位素组成、20U 系测年数据,以及部分微()量元素的分析对比,概述了石笋沉积旋回性特征、旋回界面类型和相关的气候、环境、地质意义 以组成D10石笋的碳酸盐含碳质、黏土矿物,呈黑灰、灰黄、灰白、灰等色泽匹配、纹层厚及组合、层面呈拱形或平直分别组合或转变、构造类型、碳氧同位素组成及其组合,呈协调平行、不协调同向、不协调反向变化三类型若干亚类等,旋回性特征,确定了19个沉积旋回。根据δ13C平均值为~3.91PDB δ18O-6.97PDB分别为冷暖气候演变的临界()值,δ13C或δ18O临界值者的偏重是冷,<临界值的偏轻是热。以δ13C、δ18O组成(1)和组合变化类型和上述旋回性特征,结合层面构造呈渐变过渡或突变,以及20个同位素年龄数据,初步认定荔波地区35293099410年间沉积的19旋回,是一个较完整的冰期气候演化过程,属我国第四纪冰期系列的第五冰期,⑩旋回顶180695(推算)~⑤旋回顶129890年,约5万多年是连续严寒的盛冰期,①、⑩分别可能是冰期早、晚时段相对温暖的间冰期。期间冷暖变化有5万年级的、10万年级的气候旋回。论证了荔波地区3510万年间是冰期气候环境,前期17万年寒冷的气候环境,期间35万年、25万年前后更严寒,但生态基本保持正常演变的面貌,中期5万多年为极寒冷的气候环境,生态向适应冷气候环境演化,晚期3万多年为冷暖频繁突()变的恶劣气候,期间生态面貌复杂,正常演替与残存、突变演替并存。

[关键词] 石笋;沉积旋回;古气候环境;碳氧同位素;贵州董哥洞
全文检索