热带地理 ›› 2016, Vol. 36 ›› Issue (3): 457-467.doi: 10.13284/j.cnki.rddl.002854

• 论文 • 上一篇    下一篇

文石方解石化对文石石笋δ18O记录的影响

张会领1,2,余克服2,3,赵建新4,俸月星4,林玉石5,周 玮4,刘国辉2   

  1. (1.广东海洋大学 海洋工程学院 海洋工程系,广东 湛江 524088;2.中国科学院 南海海洋研究所边缘海地质重点实验室,广州 510301; 3.广西大学 海洋学院,南宁 530004;4.Radiogenic Isotope Laboratory,Department of geology,University of Queensland,Brisbane, Qld 4072,Australia;5.中国地质科学院 岩溶地质研究所岩溶动力学重点实验室,广西 桂林 541004;)
  • 出版日期:2016-05-05 发布日期:2016-05-05
  • 作者简介:张会领(1979―),男,河南平顶山人,讲师,博士,主要从事全新世气候研究,(E-mail)zhanghuiling0375@126.com。
  • 基金资助:
    国家重大科学研究计划(2013CB956102);国家自然科学基金项目(41302281);中国科学院边缘海地质重点实验室开放基金(MSGL15-09)

Process of Calcitization of Aragonite Altering δ18O Records of Aragonite Stalagmites

ZHANG Huiling1,2,YU Kefu2,3,ZHAO Jianxin4,FENG Yuexing4,LIN Yushi5,ZHOU Wei4,LIU Guohui2   

  1. (1.Department of Ocean Engineering,Faculty of Ocean Engineering,Guangdong Ocean University,Zhanjiang 524088,China;2.Key lab of Marginal Sea Geology,South China Sea Institute of Oceanology,CAS,Guangzhou 510301,China;3.School of Ocean,Guangxi University,Nanning 530004,China;4.Radiogenic Isotope Laboratory,Department of Geology,University of Queensland,Brisbane,Qld 4072,Australia; 5.Karst Dynamics Laboratory,Institute of Karst Geology,CAGS,Guilin 541004,China)
  • Online:2016-05-05 Published:2016-05-05

摘要: 近年来,文石石笋成为古气候研究的新材料,但文石的方解石化对文石石笋氧同位素的影响问题仍未很好地解决。选取湖南湘西莲花洞方解石化文石石笋LH5为研究对象,基于18个TIMS-U系年龄和311个δ18O,探讨了方解石化对文石石笋古气候记录的影响。结果表明:1)文石的方解石化会引起文石矿物中所赋存的铀元素流失,造成铀系年龄的倒转,但LH5石笋中下部铀系衰变体系的开放程度较低(<10%),在剔除异常年龄后,仍可构建时间标尺。2)通过末次冰消期气候事件的对比发现:文石的方解石化会导致δ18O的异常波动,末次冰消期其他中国南方石笋记录的气候事件,如B?lling-Aller?d和新仙女木事件等在LH5石笋中都难以确认。而在LH5石笋的中上部文石层段,δ18O波动却能够很好地记录气候的变化。3)洞穴滴水的淋滤被认为是文石方解石化的主要原因之一。但对于LH5石笋而言,洞穴滴水的溅蚀作用可能在文石向方解石转变过程中起到了重要作用。由于在石笋的不同部位受到溅蚀淋滤的强度不同,以及石笋结构的非均一性等原因,导致文石的方解石化不均匀,这也最终造成LH5石笋文石-方解石层段δ18O的非线性变化,失去记录气候变化的能力。

关键词: 文石方解石化, 氧同位素, 文石石笋, 莲花洞

Abstract: The aragonite stalagmite has been used to be a new paleoclimate archive recently, but the problem of how the aragonite to calcite transition affects δ18O of aragonite stalagmites is still a puzzling problem. A stalagmite LH5, which was recovered from the Lianhua Cave, Central China, has been identified by XRD analyzing that its aragonite has partially inverted into calcite in the lower part in which the content of calcite ranges during 10%-27.5%. On the basis of 18 TIMS-U series ages and 311 δ18O measures of stalagmite LH5, this paper studied effects of aragonite to calcite transition on the aragonite stalagmite paleoclimate record. At first, uranium loss of aragonite in the process of aragonite-calcite transition results in radiometric ages deviating from real ages to form reversal ages. Although there are phenomena of aragonite to calcite transition in lower part of stalagmite LH5, low openness of uranium decay system (less than 10%) can’t change TIMS ages greatly which still can be used to set up time scale after eliminating abnormal ages. Secondly, through comparison of climate events during the last deglaciation,this paper revealed the aragonite to calcite transition resulting in abnormal δ18O signals which can’t record any climate events e.g. B?lling-Aller?d and Younger Dryas which have been recorded by the other stalagmites from Southern China. However, during the early Holonece, the aragonite segment of stalagmite LH5, δ18O fluctuations recorded climate change faithfully. Drip water is considered to be one of the main causes of the aragonite to calcite transition. As for stalagmite LH5, the splash erosion of cave water in collapse pit may play an important role in the process of aragonite to calcite transition. Because of intensity of penetrating and leaching of water in different part of aragonite stalagmites and heterogeneity of stalagmites, aragonite to calcite transition in aragonite stalagmite is not linear. It is the nonlinear transition of aragonite to calcite that leads to nonlinear change of δ18O, which results in δ18O signals of stalagmite in which aragonite to calcite transition occurred can’t reflect climate changes.

Key words: calcitization of aragonite, Oxygen stable isotope, aragonite stalagmite, the Lianhua Cave