王曦谦^1,2,,
高永利^3,,,
王甜莉^1,2,
程鹏^1,4,
臧婧杰¹,
GearySchindel⁵,
李东^1,2,
李云霞^3,6,
谭亮成^1,7,8,,
1. 中国科学院地球环境研究所, 黄土与第四纪地质国家重点实验室, 陕西 西安 710061
2. 中国科学院大学, 北京 100049
3. Department of Geological Sciences, University of Texas at San Antonio, San Antonio 78249, USA
4. 西安加速器质谱中心, 陕西 西安 710061
5. Edwards Aquifer Authority, San Antonio 78215, USA
6. 湖南师范大学资源与环境科学学院, 湖南 长沙 410081
7. 中国科学院第四纪科学与全球变化卓越研究中心, 陕西 西安 710061
8. 西安交通大学全球环境变化研究院, 陕西 西安 710049

基金项目: 国家自然科学基金重大项目(批准号:41991252)和中国国家留学基金委项目(批准号:201504910210)共同资助


详细信息

作者简介: 王曦谦, 女, 25岁, 硕士研究生, 第四纪地质学专业, E-mail:wangxq@ieecas.cn

通讯作者: 高永利, E-mail:yongli.gao@utsa.edu; 谭亮成, E-mail:tanlch@ieecas.cn

中图分类号: P593

收稿日期:2020-02-02
修回日期:2020-05-16
刊出日期:2020-07-30

Application of bat guano deposits in paleoenvironment research

Wang Xiqian^1,2,,
Gao Yongli^3,,,
Wang Tianli^1,2,
Cheng Peng^1,4,
Zang Jingjie¹,
Geary Schindel⁵,
Li Dong^1,2,
Li Yunxia^3,6,
Tan Liangcheng^1,7,8,,
1. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, Shaanxi
2. University of Chinese Academy of Sciences, Beijing 100049
3. Department of Geological Sciences, University of Texas at San Antonio, San Antonio 78249, USA
4. Xi'an Accelerator Mass Spectrometry Center, Xi'an 710061, Shaanxi
5. Edwards Aquifer Authority, San Antonio 78215, USA
6. College of Resources and Environment Sciences, Hunan Normal University, Changsha 410081, Hunan
7. Center for Excellence in Quaternary Science and Global Change, Chinese Academy of Sciences, Xi'an 710061, Shaanxi
8. Institute of Global Environmental Change, Xi'an Jiaotong University, Xi'an 710049, Shaanxi


More Information

Corresponding authors: Gao Yongli,E-mail:yongli.gao@utsa.edu ; Tan Liangcheng,E-mail:tanlch@ieecas.cn

MSC: P593

--> Received Date: 02 February 2020
Revised Date: 16 May 2020
Publish Date: 30 July 2020


摘要
摘要:蝙蝠粪堆积物是洞穴沉积物的一种，由蝙蝠排泄后在洞穴底部堆积而成。由于蝙蝠食物来源单一，以洞穴周边动植物为食，动植物受气候变化影响，并通过食物链进入蝙蝠粪，因此蝙蝠粪中包含有丰富的过去环境变化信息，其沉积序列可以用来进行古环境重建。蝙蝠粪在古环境研究中的优点在于蝙蝠粪在热带和亚热带地区沉积速率快，记录的环境信息多样，并可以通过加速器质谱¹⁴C定年获得高精度年代，是一种很好的环境记录载体。尽管从20世纪80年代开始，就有****逐步关注蝙蝠粪研究，但当时各项指标所指示的意义不太明确，研究范围较为局限，随后研究开展得较少，关注度也不高。本文梳理了目前全球蝙蝠粪研究现状，讨论了蝙蝠粪中可以用来重建古环境的各种代用指标及其指示意义；最后，介绍了我们在美国得克萨斯州Devil's Sinkhole蝙蝠粪的初步研究结果，并对这一研究载体的未来发展方向进行展望。
关键词: 洞穴蝙蝠粪/
代用指标/
古环境/
古气候/
Devil's Sinkhole

Abstract:Bat guano is fecal excrement from bats. Guano accumulates beneath bat roost sites and is commonly found in attics, beneath bridges, and in caves where the large volumes can accumulate over time. Most bats forage for food near their roost sites and thick deposits of guano can record changes in climate that affect food sources. Guano contains a rich information source of paleoenvironment changes and the sedimentary sequence, which can be used to reconstruct the paleoenvironment. This paper reviews the current status of bat guano research worldwide and discusses various proxies and their significance for use in reconstructing paleoenvironments.
Since the 1980s, scientists noticed the potential of bat guano in paleoenvironment studies. So far, the studying regions of bat guano mainly located in southwestern Romania, southwestern United States, and southeast Asia. The currently applied geochemical proxies of bat guano in the paleoenvironment are isotopes, such as carbon, nitrogen, and hydrogen isotopes, and elements such as copper, lead, and cadmium. The organic carbon in bat guano is from phytophagous insects. As a result, carbon isotope could reflect regional vegetation changes, which are controlled by climate. The main source of nitrogen in bat guano is the inorganic nitrogen storage in soil. The opening and closing of the nitrogen cycle in soil could affect the δ¹⁵N values of bat guano, so it can indicate the regional nitrogen circulation process. Deuterium in bat guano inherits from the natural water body, which comes into bat guano through the food chain. So, it can reflect the metabolism processes of the insect bat eaten, the evaporation and other isotopic fractionation processes during precipitation. The heavy metals in bat guano come from cave bedrock and the overlying soil, and some also resulted from human activities. As a result, they can record the changes in the guano deposition rate and local environmental pollution. For example, Wurster et al. (2010) measured the element ratios, δ¹³C, δ¹⁵N and δD of the bat guano deposits in Bat Cave from the Grand Canyon of the United States. They suggested the ratios of C/N and N/H, as well as δ¹³C and δD values consistently reveal a cooler and wetter climate in the Late Pleistocene than that during the Holocene. O'shea et al. (2001) found organic pollutants and mercury deposits in the bat guano deposits, which was close to the Rocky mountain, recorded the pollution from the local military factory.
Because of the richness of organic materials, accurate age can usually be obtained by using AMS¹⁴C dating of the total organic carbon from bat guano. However, the acidic materials in the excrement might corrode the bedrock, resulting in the dead carbon effect on bat guano, especially for those experienced diageneses. To solve this problem, it is better to extract lipid extracts, saturated hydrocarbon components, and insect chitin in bat guano for AMS¹⁴C dating.
This article also briefly introduces our bat guano study at Devil's Sinkhole in Texas, USA. Texas is located in the subtropical climate zone, with mild to warm winters and hot summers. Precipitation in the region is not evenly distributed and is mainly concentrated in the early spring and early autumn. Devil's Sinkhole (30.062°N, 100.103°W) is about 107 m deep, 15 m wide at the top and 97 m wide at the bottom. The top (1~9 cm) samples collected at the site were loose and grayish brown. The middle section (10~15 cm) was light brown. The lower section (15.5~23.0 cm) was relatively compact, and the areas in contact with the bedrock were dark tan. We selected the top and bottom samples and preformed AMS¹⁴C dating of the total organic carbon from the samples at the Xi'an accelerator mass spectrometry center. Results show that the age of the bottom samples ranges from 695~739 cal.a B.P. and the top samples are modern deposits. Further proxy analysis and chronological work are in progress.
Finally, the future direction of guano studies is discussed. More reliably geochemical and biological proxies are suggested to develop in guano studies. It is also important to separate the anthropogenic and natural influences on different proxies of guano. Applying the recently developed DNA technology to study the changes in bat species and cave biological communities could be another important direction.
Key words:guano/
proxy/
paleoenvironment/
paleoclimate/
Devil's Sinkhole



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