东、中亚干旱—半干旱区全新世湖泊沉积ω(TOC)与δ^(13)C_(org)意义的阈值问题

Threshold problem of TOC mass fraction and δ^(13)C_(org) from Holocene lake sediments in arid and semi-arid regions of East and Central Asia

选择了东、中亚干旱-半干旱区14个湖泊全新世沉积物的ω(TOC)和δ^(13)C_(org)纪录,探讨了TOC及其不同沉积阶段对δ^(13)C_(org)变化的影响及两者的关系,为δ^(13)C_(org)在古气候研究中的正确使用提供依据.结果表明:湖泊沉积物δ^(13)C_(org)的变化在一定程度上受控于ω(TOC).该区域湖泊沉积物ω(TOC)相对于δ^(13)C_(org)变化存在相应阈值,不同阈值区间代表TOC的不同沉积模式,不同沉积模式下ω(TOC)和δ^(13)C_(org)的关系不同.ω(TOC)较低或较高时,两者均无对应关系,可能是有机质受到不稳定的沉积环境影响;不同湖泊主导有机碳沉积的模式不同;δ^(13)C_(org)在相应TOC的重沉积埋藏模式下可能与气候变化有关,因此在利用δ^(13)C_(org)解释气候变化时应结合有机质沉积阶段进行分析.

14 TOC mass fraction and δ^13 Corg records were selected from lake sediments in arid and semi-arid regions of East and Central Asia, and the TOC mass fraction and the impact of δ^13Corg changes in their different deposition stages and their relationships were studied, which could provide a basis for the proper use of δ^13Corg in palaeo-climate research. The results showed that the changes in lake sediments δ^13Corg had been controlled by the TOC mass fraction to a certain extent. The TOC mass fraction and the corresponding variations of δ^13Corg possessed corresponding thresholds in those regions. Different threshold ranges represented different depositional patterns of TOC and the relationship between TOC mass fraction and δ^13Corg were different in different depositional models. When the TOC mass fraction became lower or higher, no correspondence between them occurred, probably organic matter was affected by an unstable sedimentary environment. Different deposition patterns of lakes might have caused the organic carbons to be different. δ^13Corg might be related to climate changes under the buried model of organic matter. Therefore, using δ^13Corg to explain climate changes should be combined with data about the sedimentary stage of organic matter.