潘进疆^1,2,,
黄俊华^2,,,
张蕊³,
黄春菊⁴,
刘犟嗣⁴
1. 西南大学地理科学学院, 岩溶环境重庆市重点实验室, 重庆 400715
2. 中国地质大学(武汉)地质过程与矿产资源国家重点实验室, 湖北 武汉 430078
3. 湖北师范大学城市与环境学院, 湖北 黄石 435002
4. 中国地质大学(武汉)生物地质与环境地质国家重点实验室, 湖北 武汉 430078

基金项目: 国家自然科学基金项目（批准号：41773135）、国家自然科学基金青年项目（批准号：40902188）、湖北省自然科学基金项目（批准号：2018CFB398）、中国地质大学（武汉）中央高校基础研究基金项目（批准号：CUGCJ1807和CUGL180813）和西南大学中央高校基本科研业务费项目（批准号：XDJK2020C012）共同资助


详细信息

作者简介: 潘进疆, 男, 29岁, 实验师, 地球化学与古气候变化研究, E-mail: jinjiangpan@swu.edu.cn

通讯作者: 黄俊华, E-mail: jhhuang@cug.edu.cn

中图分类号: P593;P941.78

收稿日期:2020-12-31
修回日期:2021-04-29
刊出日期:2021-07-30

The variation of carbon and nitrogen isotopic compositions in the Dajiuhu sediments and climate changes since Late Pleistocene in the western Hubei of Central China

PAN Jinjiang^1,2,,
HUANG Junhua^2,,,
ZHANG Rui³,
HUANG Chunju⁴,
LIU Jiangsi⁴
1. Chongqing Key Laboratory of Karst Environment, School of Geography Sciences, Southwest University, Chongqing 400715
2. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences(Wuhan), Wuhan 430078, Hubei
3. College of Urban and Environmental Sciences, Hubei Normal University, Huangshi 435002, Hubei
4. State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences(Wuhan), Wuhan 430078, Hubei


More Information

Corresponding author: HUANG Junhua,E-mail:jhhuang@cug.edu.cn

MSC: P593;P941.78

--> Received Date: 31 December 2020
Revised Date: 29 April 2021
Publish Date: 30 July 2021


摘要
摘要:通过对神农架大九湖DJH-ZK8孔岩芯上部739cm的沉积物样品进行高分辨率总有机碳（TOC）、总氮（TN）、C/N、δ¹³C_org以及δ¹⁵N的测定和分析，结合天文调谐确立的年代框架及沉积物岩性特征分析，探讨了大九湖湿地98.5ka B.P.以来的气候的演变历史及驱动因素。结果表明：1）湿地沉积相态的转变是控制TOC、TN的最重要因素。C/N值的有规律的波动，表明不同的沉积阶段有机质的来源不一样。C/N的低值对应湖相沉积，水生植物发育；C/N的高值对应陆生环境，陆生植物发育；C/N在一定程度上可以反映湿地的水文状态。TN和TOC呈现显著的正相关性，有机质中的碳、氮来源具有一致性，碳、氮具有类似的生物地球化学过程。2）与深海氧同位素记录对比发现大九湖湿地98.5ka B.P.以来的气候演变阶段可较好的与深海氧同位素MIS5中后期（98.5~71.0ka B.P.）、MIS4（71~57ka B.P.）、MIS3（57~29ka B.P.）、MIS2（29~14ka B.P.）和MIS1（14ka B.P.至今）阶段对应。3）大九湖湿地沉积物的δ¹³C_org值和δ¹⁵N值在冰期更偏正，间冰期时偏负，湿地植被的演替是影响δ¹³C_org值、δ¹⁵N值的最直接因素。4）DJH-ZK8孔沉积物有机地化指标与三宝/葫芦洞石笋高分辨率气候记录以及北半球夏季日照量曲线变化趋势具有较好的一致性，但在部分时段又有明显差异，说明大九湖湿地的气候变化主要由北半球太阳辐射量变化驱动，其气候和环境演变信息既响应了全球性变化又有区域特征。
关键词: 大九湖/
泥炭/
有机地球化学/
同位素/
岁差/
气候变化

Abstract:The Dajiuhu wetland (31°27'~31°31'N, 109°57'~110°02'E) is of great significance to the study of the environment and climate evolution during the geological history period. Past studies have focused on the peatland's evolution and the relationship between the summer monsoon on centennial-millennial scales. However, the research on the response of vegetation change to environmental evolution in the Dajiuhu wetland still has some deficiencies.
A sediment core(DJH-ZK8) with a depth of 739cm was obtained from the Dajiuhu wetland(31°29'28.17″N, 109°59'39.99″E), of Shennongjia, western Hubei Province, Central China. Samples were taken from this core was at 2cm intervals. The lithological characteristics of the core were analyzed, and the depositional environment of the area was analyzed. Then the astronomical time scale of DJH-ZK8 was established by using the 23-ka precession tuning, thus the 739cm sediment core was deposited during the past 98.5ka B.P. The date of total organic carbon(TOC) content and its stable isotope(δ¹³C_org), total nitrogen(TN) content and its stable isotope(δ¹⁵N), and the total organic carbon and nitrogen ratios(C/N) of sediments were measured to reconstruct the environmental and climate change of Dajiuhu Wetland.
The TOC values of DJH-ZK8 core varied from 0.1%~39.9%, its mean value was 6.8%. The TN values of the core varied from 0.1%~2.2%, and with the average of 0.3%. The C/N ratios in the sediments of Dajiuhu were 1.3~33.6. The δ¹³C_org values varied from -24.2 ‰~-28.9 ‰, and its mean value was -27.5 ‰. The δ¹⁵N values of the core varied from 0.2 ‰~7.6 ‰, its mean value was 2.7 ‰.
In contrast to the deep marine oxygen isotope stages(MIS), the geochemical record of the DJH-ZK8 core showed the environmental evolution over the 98500 years in the Dajiuhu wetland was corresponded with MIS. In the late period of MIS5d(98.5~96.0ka B.P.), the terrestrial plants of wetland were developed, and the climate changed from cold wet to warm dry. During the MIS5c(96~87ka B.P.), the productivity in the wetlands increased, the sedimentary environment was stable, and the climate was warm and dry. MIS5b(87~82ka B.P.), this stage experienced several severe climate fluctuations. The contribution from terrestrial plants to the organic matter of sediments gradually decreased and the contribution from aquatic plants to organic matter gradually increased, the lake began to develop and the climate was cold and wet. MIS5a(82~71ka B.P.), organic matter of sediment mainly came from the lake aquatic plants, the contribution of the terrigenous was small, showed cold climate at that period. In the stage of MIS4 (71~57ka B.P.), the climate was colder and wetter, the precipitation was high, the runoff erosion ability of the basin increases, the organic matter was preserved better, which was mainly exogenous land source input, while the lake was less productive. The climate at the MIS3 (49~29ka B.P.) stage was unstable. During this period, there were many sudden climate events and short-term alternating cold and warm processes. In the early stage of MIS3 in Dajiuhu wetland, sediment organic matter was mainly provided by aquatic plants, and surface runoff weakened. The contribution of terrigenous input to sediment organic matter decreased, precipitation decreased, and the climate changed from cold to wet. During the middle period of MIS3 (49~40ka B.P.), the lake was degraded to a marsh wetland, but the climate was unstable during this period, and the cold and warm waves fluctuated frequently. In the late stage of MIS3 (40~29ka B.P.), the environment was stable, the climate was warm and humid. For the stage of MIS2 (29~14ka B.P.), peat deposited in the early stages, and turned into a greyish-blue silt of the lake phase later. The continuous cooling and drying tendency affected the peat accumulation and eventually stopped development and turned into lakes. The MIS1(from 14ka B.P. to the present) stage included the late glaciation and the whole Holocene. After entering the Holocene, the contribution of terrestrial plants to the organic matter of sediments increased, the climate entered a warmer period, precipitation increased, and runoff erosion increased. After the Mid-Holocene, the lake gradually disappeared, the water in the wetland decreased, peat began to develop, and the climate was relatively dry before the fluctuation.
The climate and environmental evolution since the Late Pleistocene recorded in the sediments of the Dajiuhu Wetland shows good agreement with the high-resolution stalagmite δ¹⁸O from the Sanbao/Hulu caves and the variation trend of the Northern Hemisphere summer insolation 65°N(NHSI), which indicates that the climate changes in the Dajiuhu Basin have a very good respond to the global climate changes. The change is dominantly and directly to changes in Northern Hemisphere summer insolation, while it is also affected by the regional climate and environment.
Key words:Dajiuhu/
peat/
organic geochemistry/
isotope/
precession-forced/
climate change



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