东亚季风区石笋δ13C是否记录植被变化:从川东北石笋记录的Heinrich事件说起  

Can speleothem δ13C record vegetation changes in the East Asia summer monsoon regime? A story starting from Heinrich events recorded by speleothems from northeast Sichuan in Central China

作　　者：程珂 谢宇 刘粤峰 李汉杰[1] 潘晨光 彭小桃 刘淑华[1] 陈琼[1] 周厚云[1] Cheng Ke;Xie Yu;Liu Yuefeng;Li Hanjie;Pan Chenguang;Peng Xiaotao;Liu Shuhua;Chen Qiong;Zhou Houyun(School of Geography, South China Normal University, Guangzhou 510631, Guangdong)

机构地区：[1]华南师范大学地理科学学院,广东广州510631

出　　处：《第四纪研究》2019年第4期837-844,共8页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:41473093和41271212)资助.

摘　　要：以往的研究中一般认为石笋δ13C变化的影响因素复杂,但在大多数报道中地表植被仍被认为是影响石笋δ13C变化的主要因素之一.本文综合国内外已发表的模拟试验研究结果及川东北地区已发表和未发表的石笋δ18O-δ13C数据,特别是Heinrich事件中石笋δ18O-δ13C的表现,指出地表植被不一定是影响石笋δ13C变化的主要因素,洞穴水文(如地下水流速、滴水速率、水文化学,等等)的变化可以解释通常观察到的石笋δ13C变化.植被变化的效应可以叠加在洞穴水文变化的效应上.洞穴系统的水文变化复杂性可能是造成石笋δ13C变化呈现较复杂特征的主要原因.It is generally accepted in previous studies that the speleothem δ13C record is complicated by a series of factors. Nevertheless, vegetation was usually reported in most studies to be one of the main factors affecting the speleothem δ13C record. In this study, speleothem δ18O and δ13C data from northeast Sichuan in Central China (including both published and unpublished), especially the variations of the δ18O and δ13C records during four Heinrich events (H1, H3, H4 and H5), and the results of modeling simulations were combined to analyze the effect of vegetation on the speleothem δ13C records. All the four δ18O records showed remarkable positive excursions during Heinrich events, but the related δ13C records didn't. Changes in the vegetation probably caused by the speleothem-δ18O-derived drier climates left little imprint on the four δ13C records during these Heinrich events including the most serious H1 since the Late Pleistocene. It is inferred that vegetation may not be the major factor causing speleothem δ13C variations. This is in accordance with the results of modeling simulations which indicated that changes in the hydrology of a karst cave system was capable of explaining the δ13C variations usually observed in speleothems. Changes in the hydrology of a karst cave system may be caused by rainfall. It may also be caused by other factors such as modification of the fractures and fissures in the epi-karst system overlying a cave, which usually leads to the dissimilarity between the speleothem δ18O and δ13C records as is observed in the four speleothems in NE Sichuan in Central China. Changes in the vegetation may alter the cave hydrology and superimpose its effects on the speleothem δ13C record in the same direction as rainfall. The hydrological complexity of a karst cave system may explain the complicated variations of the speleothem δ13C records.

关 键 词：石笋 稳定碳同位素 植被 洞穴系统水文变化 

分 类 号：P597[天文地球—地球化学] P534.63[天文地球—地质学]