Mechanism Study Of Oxygen And Hydrogen Isotope In Karst Records Based On Modern Process Monitoring Of Jiguan Cave And Multi-proxy Stalagmite Records In Western Henan During 1000 A A.D

Thinking out of box, the exploring to the unknown world is alwaysthe original dream of human being, the search for truth is always the ultimate meaning of human wisdom. Global change research has become an important pivot of human life and high hope for the future. The earth still operates in his natural way, but mankind is faced with increasingly complex problems, climate warming, frequent occurrences of extreme weather events, water resources, environmental degradation and disaster-prone, and so on. In order to get the scientific analysis of the forming principle and variation, seeking advantages and avoiding disadvantages, we should learn the greater insight into past global changes, more comprehensive knowledge and understanding. Stalagmite in the cave because of its wide distribution, alternative indicators of wealth, little outside interference, growth mechanism of external climate-sensitive, can establish a precise timescale, a wide range of available recording time as well as lower cost of sampling and other geological record is no substitute for a clear advantage while people pay more and more attention. Its alternative indicators of paleoclimate have oxygen and carbon isotope and trace element, rate of deposition, stalagmite microlayer, but the oxygen isotopes as cave researchers are most concerned about at present, and the most widely used one of many environmental indicators, which matured. But because of the impact of the multiplicity of factors and spatio-temporal differences, makes the interpretation of the indicators there are more disputes, it is necessary through regional research and modern monitoring mechanism further more comprehensive interpretation and argumentation. Variations in speleothem oxygen-isotope values (δ18O) result from a complicated interplay of environmental controls and processes in the ocean, atmosphere, and cave system. As such, the controls on speleothem δ18O values are extremely complex. An understanding of the processes that control equilibrium fractionation of oxygen isotopes in water and carbonate species is essential for the proper interpretation of speleothem δ18O, and is best complemented by study of site-specific cave processes. Hence, the oxygen isotopic compositions of the meteoric precipitation, cave drip water and modern calcite deposition from an in situ multiyear(October 2009-March 2015)monitoring program in Jiguan Cave have been examined.(1)The Jiguan cave(33°46’N,111°34’E; 900m a.s.1. at the entrance) is located in Cambrian limestone hostrock 4 km southwest of the city of Luanchuan HenanProvince, the oxygen isotopic compositions of the meteoric precipitation, cave drip water and modern calcite deposition from an insitu multiyear(October 2009-March 2015) monitoring program in Jiguan Cave have been examined. An understanding of the processes that control equilibrium fractionation of oxygen isotopes in water and carbonate species is essential for the proper interpretation of speleothem δ18Oδ, and is best complemented by study of site-specific cave processes. Studies have shown that: The δ18O of meteoric precipitation ranged from 1.2‰～-16.1‰, and the average of the weighted δ18O in summer is-9.29%o; The δ18O of drip water ranged from-7.3‰～-11.9‰, and the average is-8.90‰; The δ18O of modern calcite depositions varied between -6.6‰～-10.1%o, and the average is-8.70%o. The seasonalvariation of three indexes is clear and coincident, showing the increase of stable isotope values during the winter season and the decrease of stable isotope values during the summer monsoon season. Seasonal variation characteristics of δ18O in cave drip water are consistent with the rainfall of Luanchuan. The months that appear the maximum and minimum of δ18O in cave drip water and so does the rainfall. This suggests that cave drip water inheritances and reflects the seasonal δ18O variation characteristics especially the summer rainfall very well. Seasonal variation characteristics of δ18O in cave drip water could indicate the seasonal variation characteristics in precipitation. The two cave drip water points have the same http://dict.youdao. com/search? q=%E7%9B%B8%E4 %B8%80%E8%87%B4&keyfrom=fanyi.smartResult-#variation range arid average value and similar variation tendency basically, this indicates that the two cave drip water may be from the same water source and the differences are the transmission pipe lines.(2)The equation of local meteoric water line (LMWL) was established,δD=7.79δ18O+7.91 (r=0.96, P<0.01), and it is similar to the global meteoric water line (GMWL).(3)The amount effect on precipitation δ18O is relatively weak, but it is sensitive to circulation effect. During the El Nino event(2009/2010) in the monitoring period, the West Pacific subtropical high becomes strong and subsequently extends southwestward. The water vapor from the Western Pacific increases, which results in the heavier oxygen isotope in the local meteoric precipitation, cave drip water and modern calcite depositions, because of the short trajectory associated with the water vapor. In contrast, during theLa Nina event(2010/2011) in the monitoring period, the lighter isotopic composition is found in the local meteoric precipitation, cave drip water and modern calcite depositions. The deuterium excess(d) values also showed the characteristics of being high when El Nino occurred and low when La Nina happened.In 2013, the vast majority of the monitored climate variables reported here maintained trends established in recent decades. ENSO was in a neutral state during the entire year, remaining mostly on the cool side of neutral with modest impacts on regional weather patterns around the world. This follows several years dominated by the effects of either La Nina or El Nino events. Whether 2014 is identified as El Nino years or not still remains controversial,but SOI index is so biased to-1.64in March 2014 spring, most likelyfor El Nino years, so although itsnormal precipitation, but itsdeuterium and oxygen isotopes isbiased-6.71, echoing the events of2010, oxygen isotopes and moisturesources closer. But itsinterpretation would still needother meteorological data analysisin 2014 and 2015.(3)Seasonal variation characteristics of δ18O in modern spelethems are consistent with the rainfall of Luanchuan and cave drip water. This suggests that the variation of δ18O in modern spelethems could reflect the variation of δ18O in cave drip water and rainfall; it also could reflect the amount of precipitation especially the δ18O variation of summer rainfall and the change of summer monsoon intensity to certain extent. Under the polarizing microscope we found that the crystal structure of modern spelethems are all calcite deposition, and the amount has a seasonal variation characteristic, much in fall and winter, small in spring and summer.(4)The δ18O ofthe stalagmite of DSY1201, DSY1204 in Jiguan cave, WX42B inWanxiang cave and HS4 in Heshang cave are consistent, both of which haveclear records to the medieval climate anomaly (MWP) andthe little ice age (LIA) and the 20C obvious climaticevents such as global warming and the little ice age(LIA) period presents two other valley.Secondly, DSY1204 stalagmite oxygen isotope whole andMg/Ca and Sr/Ca and Ba/Ca and climatic conditions were positively correlated, andoxygen isotopes emphasizes, Mg/Ca, Sr/Ca and Ba/Ca ratiois high, such as during the little ice age. Preliminaryanalysis shows that Mg/Ca in dry and cold during theearly deposition (PCP), Sr/Ca and Ba/Ca ratio is highand dry and cold periods and related atmospheric dust.