中国科学院海洋研究所机构知识库

本文以西菲律宾海中依托国际海洋全球变化计划（IMAGES）所采集到的MD06-3052站位和东阿拉伯海中基于国际大洋发现计划（IODP）所获取的U1456站位沉积物为研究对象，对其有机质稳定碳同位素组成（δ¹³C_org）进行了测试，再结合上述站位已发表的相关数据如总有机碳含量、总氮含量、生物硅含量、质量堆积速率以及粘土矿物、常/微量元素和Sr-Nd同位素组成等开展了综合研究，由此来重建了第四纪轨道时间尺度上东亚-南亚季风区海洋沉积物中有机质的定量源-汇过程，并探讨了不同来源有机碳在海底中埋藏演化的影响因素，进而对比分析了两种不同区域的陆表风化和剥蚀及深海有机碳埋藏过程及其在全球碳循环中的意义。

156 ka以来西菲律宾海中MD06-3052站位的δ¹³C_org值在-27.44‰和-18.59‰之间波动，其平均值为-22.21‰，且呈现出冰期相对偏负而间冰期相对偏正的变化特征。所研究有机质的具体来源包括海洋生物和陆地C3植物，在冰期和间冰期阶段分别以陆源（平均约为67%）和海源（平均约为83%）有机质的贡献为主。陆源有机碳含量和质量堆积速率的变化趋势与总有机碳相应指标间非常一致，均具有冰期高而间冰期低的特征，表明研究区冰期阶段总有机碳通量增加的最主要原因是海平面下降所引起的大陆架出露及其上松散硅酸盐沉积物的强物理剥蚀作用。

700 ka以来东阿拉伯海中U1456站位δ¹³C_org值的变化范围为-23.74‰至-18.08‰，其平均值为-20.31‰，并具有一定的冰期-间冰期旋回特征。该有机质来源包括海洋生物（23-52%）和陆地上C3植物（21.5-68.5%）及C4植物（12-49%）的混合。冰期阶段陆源有机碳和海源有机碳的质量堆积速率均较高，这与喜马拉雅地区冰川扩张和印度夏季风减弱有关。C3和C4植物贡献比例的变化也表现出冰期-间冰期旋回的特征。其中C4植物在冰期时贡献比例增大的原因是季风降水减少所导致的喜马拉雅地区的干旱气候，从而更适宜于C4植被的生长。

结合研究区内其他岩芯的相关记录可知：冰期阶段热带西太平洋出露大陆架上硅酸盐沉积物的再次风化剥蚀作用及与其伴随的海底有机碳埋藏是当时全球碳循环中的一个重要且普遍的过程；此外，喜马拉雅山脉的强陆表物理剥蚀作用所引起的其周围边缘海中有机碳埋藏量的增多也在当时全球的碳循环中扮演着重要角色。综上可见，印-太暖池周边陆表的上述风化剥蚀作用及与之相关的海底有机碳埋藏过程对第四纪冰期时的全球碳循环具有重要的贡献，进而对当时大气中CO₂浓度的降低及全球变冷有着积极的促进作用。

The stable carbon isotopic composition of organic matter (δ¹³C_org) in the sediments at site MD06-3052 from the International Marine Past Global Change Study (IMAGES) in the western Philippine Sea and site U1456 from the International Ocean Discovery Program (IODP) in the eastern Arabian Sea were measured, combined with the published data from the same cores including total organic carbon content, total nitrogen content, biogenic silica content, mass accumulation rate, clay minerals, major and trace elements, and Sr-Nd isotopic compositions, to constrain the quantitative source-to-sink processes of organic matter in sediments in the East Asian-South Asian monsoon region on the orbital scale during Quaternary, and to discuss the influencing factors of organic carbon burial evolution from different sources, thus to compare and analyze the continental weathering and erosion and deep-sea organic carbon burial processes in two different regions and their significances in the global carbon cycle.

The δ¹³C_org values at site MD06-3052 in the western Philippine Sea since 156 ka fluctuated between -27.44‰ and -18.59‰, with an average value of -22.21‰, and are characterized by a variation characteristic of relatively negative values during glacial periods and relatively positive values during interglacial periods. The sources of the organic matter include marine organisms and terrestrial C3 plants, dominated by terrestrial provenance (about 67% on average) and marine provenance (average 83%) during glacial and interglacial periods, respectively. The variation trends of content and mass accumulation rate of terrigenous organic carbon are very consistent with the corresponding indicators of total organic carbon, characterized by higher values during glacial periods and lower values during interglacial periods, indicating that the main reason for the increased organic carbon burial in the glacial periods is continental shelf exposure caused by the decrease of sea level and the strong weathering and erosion of loose silicate sediments on it.

The δ¹³C_org values at site U1456 in the eastern Arabian Sea since 700 ka range from -18.08‰ to -23.74‰, with an average value of -20.31‰, and is characterized by a certain glacial-interglacial cycle. Sources of organic matter include a mixture of marine organisms (23-52%) and terrestrial C3 plants (21.5-68.5%) and C4 plants (12-49%). The mass accumulation rates of terrigenous and marine organic carbon are higher during the glacial periods, which is related to the glaciers expanding in Himalayan and the weakening of the Indian summer monsoon. The variations of contribution ratios for C3 and C4 plants show the characteristics of a glacial-interglacial cycle. The reason for the increased contribution of C4 plants during the glacial periods is the arid climate in the Himalayas caused by reduction of monsoon precipitation, which is more suitable for the growth of C4 vegetation.

Combined with the records of other cores in the study area, the weathering and erosion of silicate sediments on the exposed continental shelf and the associated organic carbon burial in the seabed at the tropical western Pacific during the glacial periods were an important and common process in the global carbon cycle at these times. In addition, the increase of organic carbon burial in marginal seas caused by strong continental surface erosion of the Himalayas also played an important role in the global carbon cycle at these times. In conclusion, the weathering and erosion of the continental surface around the Indo-Pacific warm pool and its associated organic carbon burial process contribute significantly to the global carbon cycle during the Quaternary glacial periods, and thus contribute positively to the reduction of atmospheric CO₂ concentration and global cooling.

第1章 引言 1

1.1 选题背景及意义 1

1.2 国内外研究现状 5

1.2.1 冰期-间冰期中的碳循环 5

1.2.2 有机质来源 7

第2章 区域地质概况 11

2.1 西菲律宾海地质概况 11

2.1.1 西菲律宾海地质背景 11

2.1.2 西菲律宾海气候特征 13

2.1.3 西菲律宾海水文特征 14

2.2 阿拉伯海地质概况 16

2.2.1 阿拉伯海地质背景 16

2.2.2 阿拉伯海气候特征 18

2.2.3 阿拉伯海水文特征 19

第3章 研究材料与方法 22

3.1 研究材料 22

3.1.1 MD06-3052岩芯 23

3.1.2 IODP U1456岩芯 24

3.2 研究方法 27

3.2.1 有机质稳定碳同位素分析 27

3.2.2 有机碳来源贡献比例计算 28

3.2.3 质量堆积速率计算 29

第4章 156 ka以来西菲律宾海有机质来源及其控制因素 30

4.1 有机质碳同位素组成变化特征 30

4.2 有机质来源 31

4.3 控制因素 34

4.4 碳循环效应 36

第5章 700 ka以来东阿拉伯海有机质来源及其控制因素 39

5.1 有机质碳同位素组成变化特征 39

5.2 有机质来源 40

5.3 控制因素 43

5.4 碳循环效应 51

第6章 结论与展望 55

参考文献 57

致谢 71

作者简历及攻读学位期间发表的学术论文与研究成果 73