东海嵊山岛末次冰期黄土有机碳同位素特征及其古环境意义

赵庆; 周立旻; 郑祥民; 王辉; 吕红华; 陈圆圆

doi:10.16562/j.cnki.0256-1492.2022061403

东海嵊山岛末次冰期黄土有机碳同位素特征及其古环境意义

华东师范大学地理科学学院地理信息科学教育部重点实验室，上海 200241

基金项目: 国家自然科学基金面上项目“长江三角洲东延区域风尘黄土次生作用及古环境信息研究”（41871015）

详细信息

作者简介: 赵庆（1982—），男，工程师，博士，主要从事地球化学与古环境研究，E-mail：zhaoq@admin.ecnu.edu.cn

通讯作者: 周立旻（1976—），男，教授，主要从事全球变化领域研究，E-mail：lmzhou@geo.ecnu.edu.cn

中图分类号: P534.63

收稿日期: 2022-06-14

修回日期: 2022-08-31

录用日期: 2022-08-31

刊出日期: 2023-02-28

Characteristics of organic carbon isotope and the paleoenvironmental significances of loess in Shengshan Island during the Last Glacial Period

Key Laboratory of Geographic Information Science of Ministry of Education, School of Geographic Sciences, East China Normal University, Shanghai 200241, China

More Information

Corresponding author: ZHOU Limin, lmzhou@geo.ecnu.edu.cn

Received Date: 14 June 2022

Revised Date: 31 August 2022

Accepted Date: 31 August 2022

Publish Date: 28 February 2023

摘要

摘要:
黄土沉积中有机碳同位素组成与古气候关系密切，对研究区域环境演变具有重要意义。本文聚焦我国东海嵊山岛末次冰期黄土地层，在磁化率和元素地球化学指标特征分析基础上，开展有机碳同位素组成特征研究。研究结果表明：嵊山岛黄土沉积剖面有机碳同位素组成波动范围−21.63‰～−27.56‰，平均值为−24.88‰，剖面有机碳同位素组成波动偏正；利用端元法对嵊山岛黄土沉积环境中C₃/C₄植被相对丰度进行估算，揭示沉积地层记录的植被类型是以C₃型植被为主导，C₄型植被对沉积地层中有机碳同位素的贡献有限；与南京洞穴石笋、苏禄海海洋沉积以及南极Vostok冰芯氧同位素记录对比，显示末次冰期间冰阶时期嵊山岛黄土沉积中有机碳同位素波动是以C₃型植被为主导的植被碳同位素对降水条件改变的响应，降水可能是这一时期黄土沉积中有机碳同位素变化的主要影响因素；在末次冰消期阶段，温度有利于C₄植被的发育，导致区域C₄型植被丰度有所上升，并对沉积地层中有机碳同位素变动的贡献增加。
- 有机碳同位素组成 /
- 末次冰期 /
- 降水 /
- 温度 /
- 嵊山岛黄土
Abstract:
The organic carbon isotope composition in loess deposits is closely related to paleoclimate, which is of great significance to the study of regional environmental evolution. The loess deposit of the Last Glacial Period in Shengshan Island in the East China Sea off the East China was studied. The magnetic susceptibility and element geochemistry were analyzed, based on which the organic carbon isotope composition was scrutinized. Results show that since the Last Glaciation, the organic carbon isotope composition in the loess fluctuated from −21.63‰ to −27.56‰ on average of −24.88‰. In general, the value of organic carbon isotope decreased with the increase in burial depth of the loess. In addition, the relative abundance of C₃/C₄ vegetation in Shengshan Island was estimated by using the end-member method. It was revealed that the C₃ plants dominated in the island since the Last Glacial Period, and C₄ plants were very limited in the contribution to the organic carbon isotope in the loess deposit. In comparison with the oxygen isotope data of the cave stalagmites in Nanjing, marine sediments from Sulu Sea, and Antarctic Vostok ice core, the loess was deposited during the interstage of the Last Glaciation, and the fluctuation in organic carbon isotope value was resulted mainly from the responses of local ancient C₃ plant-dominated vegetation to the variation of precipitation condition. The precipitation was the main influential factor on the organic carbon isotope variation during the period. In the last deglaciation stage, the paleo-temperature favored C₄ plants booming, thus the relative abundance of C₄ plants increased, and so did their contribution to the fluctuation of organic carbon isotopes in the loess deposits in the island.
- organic carbon isotope composition /
- Last Glaciation /
- precipitation /
- temperature /
- Shengshan Island loess

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图 1 采样点示意图

Figure 1.

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图 2 嵊山岛黄土剖面总有机碳含量（a）和有机碳同位素组成特征（b）

Figure 2.

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图 3 嵊山岛黄土沉积中C₄植被相对丰度估算

Figure 3.

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图 4 嵊山岛黄土沉积剖面有机碳同位素与磁化率（a）和总有机碳散点图（b）

Figure 4.

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图 5 嵊山岛黄土沉积剖面有机碳同位素、铷锶比、磁化率、C₄植被丰度变化

Figure 5.

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表 1 嵊山岛黄土剖面光释光年代测定结果

Table 1. OSL (optically stimulated luminescence) dating results of the loess in Shengshan Island

深度/cm	U/(μg/g)	Th/(μg/g)	K/%	实测含水量/%	环境剂量率/(Gy/ka)	等效剂量/Gy	年龄/ka
10	2.83	14.3	1.49	14.45	3.05	1.2±0.3	0.4±0.1
100	2.98	15.1	1.69	11.86	3.34	117±4	35.03±3
150	2.94	14.4	1.56	8.18	3.23	137±8	42.41±4
250	2.93	14.3	1.62	16.49	3.00	152±5	51.67±4

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