Research On Historical Events Of Rocky Desertification Based On Speleothem Records

Using stalagmites and tubular stalactite to rebuildpaleoclimate has a long history,also there are a lot of achievementsof using documented to rebuilt paleoclimate.But there are fewresearch on historical events of the evolution of rockydesertification.This research rebuilds the paleoclimate of theSouthwest China of1240a-2000a by making a comparative analysis ofδ18O and δ13C of stalagmites and tubular stalactite in Zhijincave,based on the literature of Ming Dynasty and Qing Dynasty,andinvestigates the development of rocky desertification. Main tasksinclude:(1) By comparing the result of measuring the stalagmite andtubular stalactite to the literature, it’s found that the recordsof the stalagmite and tubular stalactite which taken from the Zhijincave are in accord with the history. After discoursing the changeof wet-dry conditions of1240a to2000a, and the comparativelystudying between the stalagmite ZJD-21and tubular stalactiteZJD-9C, the result indicates that different karst systems didn’tresult in discrepant deviation of δ13C and δ18O.The records ofdifferent speleothems can corroborate and calibrate each other, sothat they will be more consecutive and credible.Choosing thedifferent speleothems(stalagmite and tubular stalactite were chosen in this study) also can avoid inaccuracy coursed by thesimilar reasons. But the effect of the microclimate and the delaycaused by which the speleothems are reflecting the surfaceclimate,may lead to the malposition of the speleothems records andthe surface climate events in short time,and affect theenvironmental records keept in speleothems.(2) With the creation of this paper and the collection ofrelated materials, it can be found that the ancient materials arevery accurate in recording the climate and easy to be drawn, andafter selecting and calibrating, these materials can reflect theregional climate objectively and exactly. The historical record ofthe climate of Guizhou Province is not complete, the lack of therecord of many regions and ages is now a big trouble for us to studythe ancient climate of Guizhou with documents and other materials.As the studying method and the research tools are developing, thematerials are increasing continuously, we can use the climaterecords saved in the valuable history materials comprehensively andsystematically and maximize their value.(3) By comparing the historical records with the oxygen isotopeof stalagmite ZJD-21and tubular stalactite ZJD-9C from Zhijin cave,we illustrate that the oxygen isotope records can be used to analyseand explore local climate situation. Meanwhile, we also find that carbonate isotope positively correlates with oxygen isotope in mosttime and negatively in individual time, it’s considered as theresult of rocky desertification according to deduction,we provethis viewpoint with series discussion.The establishment of thisviewpoint provides a new method for future,the usage of this methodbrings great reference of the correction of paleoclimate recordsand the new possibility of the research on regional climate.(4) We divide the history stage of rocky desertification from1240into several phases including incubation period, occurrenceperiod, development period, swing period and blowout period,andinvestigate the time series of rocky desertification,then describethe climate of corresponding period to infer the rockydesertification in this period,thereby getting the series of theevolution of rocky desertification. We make a try to rebuild timeseries of rocky desertification by comparing cave sediment recordswith literature, so that the new possibility of the study of timeseries of rocky desertification can be found.