The Preliminary Study On Cosmic Ray Flux Inversion And Deposition Process Of¹⁰Be In Modern Endogenic Travertine At Baishuitai,Yunnan

Precise knowledge of changes in solar activity through time is a prerequisite for testing the hypothesis of a solar influence on climate and distinguishing natural from anthropogenic climate change.Travertine is a long-term geological carrier with high resolution of year and quarter.The record of 10Be in travertine is a potential indicator of the construction of past solar activity.However,10Be record in travertine is likely to be disturbed by various factors in deposition process.Therefore it can not truly reflect the 10Be signals generated by cosmic ray and atmosphere which modulated by solar activity.And it reduces the credibility of reconstruction.Clarifying the deposition process of 10Be in travertine and extracting the 10Be signals generated by atmosphere from travertine are the prerequisites and basis of tracing research by which research on 10Be in travertine has not been reported neither domestic nor aboard for now.For the first time,the 10Be in endogenic travertine of Baishuitai,Yunnan was extracted and tested.We attempted to limit the deposition process of 10Be in white travertine with carbon and oxygen isotopes,trace elements,local meteoric data,neutron monitoring data reflecting cosmic ray intensity.And the tracing study of 10Be in white travertine is discussed.The following conclusions were obtained through the study:1.The ?13C in travertine varies from 3.268 ‰ to 13.122 ‰,average 5.981 ‰.Due to the apparently positive value,it is the geothermal travertine.The ?18O in travertine varies from-14.120‰ to-11.775 ‰,average-12.856 ‰.It was found that both ?13C and ?18O values of the endogenic travertine were lower in the warm rainy season and higher in the cold dry season,which presented obvious seasonal variations.The carbon and oxygen isotopes in the white travertine had well correlation,which may indicate both of them were controlled by the same process or factor.2.Combing with the local historical data,it confirmed that the extreme droughts correspond to the maxima of ?13C and ?180 in 2005 and 2011 to 2013.The maxima of 813C and 8180 in the travertine indicate the events of drought,which is consistent with the predecessors' research results.3.The content of Ca,Ba and Sr in white travertine was similar to brown travertine,which were mainly from underground water.The content of Al,Cr,K,Fe,Mn and Ni in brown travertine was richness,which were mainly from overland flow.It was found that overland flow resulted from precipitation may control the variations of Al,Fe,K,Sr/Ba and ?13C in brown travertine on the inter-annual scale.And temperature was likely to control the variations of Sr/Ba and ?13C in white travertine on the inter-annual scale through the Pearson correlation analysis between elements and other indicators.4.The 10Be concentration in white travertine varied from 3.06 ± 0.57 t0 8.60 ±1.17 × 10^5 atoms/g,average 4.91 ± 0.86 X 10^5 atoms/g.The 10Be concentration in white travertine was 100 to 1000 times lower than loess-paleosol,marine sediment and lake sediment,whereas the 10Be concentration in white travertine was 10 times higher than ice core.5.The '0Be storaged in white travertine mainly come from atmospheric precipitation and underground water(indirect atmospheric precipitation),which reflects the 10Be signals generated by cosmic ray and atmosphere which modulated by solar activity.After precipitation,10Be is very likely to be adsorbed onto clay minerals and organic matter.And it will participate in the deposition of travertine through overland flow.Due to the similar process in ground between 10Be and both clay minerals and organic matter.Therefore,it is reasonable to regard K(represented clay minerals)and TOC(represented organic matter)as the substitute indicator to revise the effect of climate and environment of 10Be in white travertine.6.The result presented negative correlation through the Pearson correlation analysis between natural 10Be record in white travertine and NM(r=-0.22,p=0.63,n=7).However,it was represented remarkable positive correlation between revised 10Be record and NM(r=0.85,p=0.03,n=6).The similar trend between revised 10Be record and NM in a 7-years series was about 50%,which indicated a large potential for tracing research of 10Be in white travertine.The study of longer series in both white travertine and brown traverine will contribute to exploit this potential.