现生和化石枫香碳同位素的变化——对古环境重建的指示

1.长安大学 地球科学与资源学院,陕西 西安 710064; 2.中国石油长庆油田分公司 第八采油厂,陕西 西安 710021; 3.中国科学院 南京地质古生物研究所现代古生物学和地层学国家重点实验室,江苏 南京 210008

现生枫香; 化石华枫香; 浙江天台; 中新统嵊县组; 碳同位素; 古环境

Variation in Stable carbon isotope of recent and fossil Liquidambar——Indication for palaeoenvironmental reconstruction
XIAO Liang1,3,AN Yong-fu2,LI Xiang-chuan1,3,GUO Jun-feng1,SUN Nan1,YAO Xiao-yong1,YANG Wang-tun1

(1.School of Earth Science and Resources,Chang'an University,Xi'an 710054,China; 2.Oil Production Plant No.8,Changqing Oilfield Company,Xi'an 710021,China; 3.State Key Laboratory of Palaeobiology and Stratigraphy,Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences,Nanjing 210008,China)

liquidambar formosana; liquidambar miosinica; Tiantai Zhejiang province; Miocene Shengxian Formation; stable carbon isotope; palaeoenvironment

DOI: 10.13800/j.cnki.xakjdxxb.2017.0514

备注

现生植物稳定碳同位素对环境的响应已有大量研究,但是化石植物碳同位素与古环境关系的研究却很少。浙江天台中新统嵊县组中含有大量保存精美的枫香叶片化石(Liquidambar miosinica),为探讨利用化石叶片稳定碳同位素重建古环境提供了可靠材料。首先,分析了采自6个不同地区的现生枫香叶片(Liquidambar formosana)的碳同位素,获得它们的Δ13C值,讨论其与温度、水分条件、光照水平等环境因子的相关关系。其中年极端最高温、年降水量和年日照时数与Δ13C具有显著相关性,R2分别为0.6,0.75和0.80,并建立了线性回归方程,显示出Δ13C随着温度的升高而降低、年降水量的增加而增大,年日照时数的增多而降低。然后,将L.miosinica的Δ13C代入3个回归方程中,计算出浙江天台晚中新世的年极端最高温、年降水量和年日照时数分别为39.2 ℃,1 329 mm,1 938 hrs.其中年降水量与采用其它方法恢复出的值相似,表明结果的可靠性,说明L.miosinica化石叶片碳同位素可以作为重建古环境的有效指示物。将重建出的晚中新世古环境参数进一步与现在的环境进行对比,发现与浙江天台比较相似,表明晚中新世浙东已演化出温暖湿润的亚热带气候。

Stable carbon isotopic response of recent plants to environmental variation has been extensively researched.However,the study on relation between carbon isotope of fossil plants and palaeoenvironments was seldom performed.Abundant well preserved fossil Liquidambar miosinica leaves were collected from the Miocene Shengxian Formation in Tiantai,Zhejiang Province,which provides reliable materials for reconstructing palaeoenvironments using stable carbon isotope of fossil leaves.Firstly,carbon isotopes of recent Liquidambar formosana leaves collected from six different sites were analyzed to obtain their carbon isotopic discrimination values(Δ13C).The correlations between Δ13C and environmental parameters including temperature,water condition,irradiation condition,are established.The notable correlativity is found between Δ13C and annual extremely warmest temperature(EWT),the mean annual precipitation(MAP),annual sunshine duration(ASD),and whose correlation coefficient values(i.e.,R2)are 0.60,0.75 and 0.80,respectively.It shows that Δ13C value is more positive with increase of MAP,but more negative with enrichment of EWT and ASD.Secondly,Δ13C of fossil L.miosinica leaves is substituted into three regression equations established above.The EWT,MAP,and ASD in late Miocene Tiantai,Zhejiang,are counted as 39.2 ℃,1 329 mm and1 938 hrs,respectively.The MAP is similar to that reconstructed from other methods,showing the result here is reliable.It suggests that stable carbon isotope of fossil L.miosinica leaves can be an indicator to reconstruct palaeoenvironment.Moreover,comparing to modern environment,the Late Miocene environment in Tiantai is parallel to that in same place,suggesting the subtropical climate has come into being in the Late Miocene for eastern Zhejiang.