| In recent years, the climate anomalies have occurred from time to time, prompting us to study past climate change. Past climate change is an important part of the global change; the research can provide a theoretical basis for future environmental studies. And because of the climate change in our country is not only affected by the global atmosphere system, but also influenced by the special geographical position, so it has the global general characteristics and the regional characteristics in the meantime. Therefore, the climate and environment changes in our country have great complexity, and his study is in a relatively important position. In recent decades, people use the geological record, such as cave sediments, marine, loess, ice cores, lake, tree rings corals, etc., have achieved fruitful results. Among them, due to high-precision and high-resolution chronology characteristics, cave sediments in the reconstruction of inter-annual and seasonal time scales of climate and environmental change, can not be replaced.This paper takes LM2. LM3stalagmite Laomu cave in Henan Luanchuan as the main research object. Based on analysis and discussion, used oxygen and carbon isotopes and trace elements of stalagmite in Laomu Cave of Luanchuan to restore the past climatic change history of early Holocene. to discuss the possible mechanism. In the meantime the control factors and the climate implication of the trace elements in mother hole are discussed, draws the following conclusion:(1) Using the oxygen and carbon isotope of LM2, LM3stalagmite of Laomu cave Luanchuan in Western Henan rebuilt the evolution trend of Asian monsoon in northern China of early Holocene period, and analyzes the weak monsoon event about early Holocene. According to the analysis of monitoring data, the δ18O variations of stalagmite in western Henan Laomu cave indicate the strength of the monsoon changes; The record of stalagmite oxygen isotope about weak monsoon events in North and South China is not the same:In LM2stalagmites, from10.9ka BP to10.13ka BP, differences variation trends in monsoon evolutionary between northern China stalagmite oxygen isotope record and South stalagmite and Oman stalagmite of Gulf exhibited may be influenced by regional factors; LM2stalagmite δ18O curve has no record of cold event in9.3ka BP, but around9.3-9.6ka BP recorded a cool event, similar to DSY09, Y1, HS-4records, show that in the period of memory existed the weakening of the monsoon events, But because of the complexity of the oxygen isotope transmission, the North and South has a different performance. Two stalagmite δ18O curves recorded8.2ka BP start time. In time, Stalagmite in different parts of Asia monsoon region has consistency. But the Laomu Cave show a staged fall (China "8200phase"), and the amplitude is large, indicating the existence of differences in changes in different regions of the records. This may be coupled with the complexity of the oxygen isotopes transmission in response to climatic events in various spheres in the process Monsoon vapor coupling.Oxygen isotope curve of two stalagmites appear the most negative in8.4-8.5ka BP period, while the GRIP ice core δ18O values appear the most partial at this stage, further inferred, North latitude climate change associated with the strength of the Asian monsoon.(2)The ratio of Luanchuan Cave Stalagmite trace elements Mg/Ca, Sr/Ca, Ba/Ca can better respond to changes in the external climatic conditions.Via the discussion combined trace elements with stable isotope; we can better reconstruct ancient climate change history and restore its pale climate evolution. Two stalagmites of Loam Cave in the early Holocene period, Mg/Ca and δ13C have a positive correlation, CO2degassing caused a decrease of precipitation and pre deposition of carbonate (PCP) may be the main factor leading to this positive correlation. Sr/Ca, Ba/Ca trends show a high degree of consistency, suggesting that there may be affected by the same factors. And their variation trend are similar with δ18O, therefore, inferring Sr/Ca, Ba/Ca controlled by precipitation; while according to the content of elements in bedrock, Sr/Ca and Ba/Ca is also controlled by bedrock, in addition, atmospheric dust and vegetation, overlying soils also is its influencing factors. Sr/Ca, Ba/Ca ratio is affected by many factors, and the dominant factor is not obvious, as the indicator of climate proxy indicators is not obvious. In the event of strong cold event, changes of Sr/Ca, Ba/Ca ratio is decreased first and then increased, and showing the opposite trend with Mg/Ca,δ13C and δ18O trend, May be due to the great changes of temperature, precipitation and conditions have occurred in the strong cold event. In view of the complexity of the changes of trace elements in the karst system, also need to strengthen the mechanism study in the future works. (3)Through the power spectrum analysis of oxygen isotopes in two stalagmite Laomu cave, we found that the main manife stations are solar activity cycle and the ENSO cycle. And two oxygen isotope records of stalagmites and GRIP ice core δ18O is similar, so the Monsoon change in Asia is related to Solar radiation energy fluctuation,the change of High latitude climate and ENSO.The cycle of Carbon isotope and trace element ratios by power spectrum may show the solar activity cycle and the ENSO cycle. Their explanation is consistent with the oxygen isotope factors. However, the specific impact of the mechanism needs further study. |
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