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

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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

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