The Study On Deposition Process,signal Characteristic And Paleo-environmental Significance Of ¹⁰Be In Travertine At Baishuitai,Yunnan

Reconstructing accurate and high-resolution record of past solar activity is vital for us to assess the role of solar forcing on climate variations as well as to understand the physical mechanism of solar variations.Cosmogenic radionuclides(e.g.,¹⁰Be and¹⁴C),produced by the galactic cosmic rays and stored in natural archives such as tree tings,ice cores and lake sediments,have confirmed to be an useful proxy for reconstructing past solar activity.Previous studies from Xu(2017)have shown that travertine¹⁰Be has great potential in reconstructing high resolution solar activity,but it didn't establish a reliable methodology for reconstructing high resolution solar activity.To further reveal the relationship between travertine ¹⁰Be and solar activity,and to improve the methodology for reconstructing high-resolution solar activity by using travertine ¹⁰Be record,we select endogenic travertine from Baishuitai in Yunnan Province as the subject investigated in this study.By collecting the modern travertine and ancient travertine,local spring water,rainwater,new travertine micro-layer samples with field work and observation,combined with geochemical analysis and deposition process simulation,we carry on the systematically studies for the deposition mechanism,signal characteristics and interpretation of paleo-environmental significance of travertine ¹⁰Be.The following conclusions were obtained in this study:(1)Simulation experiments of Be distribution show that¹⁰Be will be removed from spring water and enriched in travertine during the formation of travertine.(2)Carbonated fraction is the main fraction of ¹⁰Be in travertine.The concentration of¹⁰Be in travertine was mainly in the range of 10⁵?10⁶atoms/g.The concentration of ¹⁰Be in Baishuitai travertine has obvious seasonal variation characteristics,that is,high value of ¹⁰Be concentration appears in the dark layers formed in rainy season while low value of¹⁰Be concentration appears in the white layers formed in dry season.(3)It is feasible by using ⁹Be,K and Fe to calibrate the effects of accumulation rate of carbonate,the overland flow and the variation of¹⁰Be scavenging efficiency due to the deposition processes,respectively.Corrected ¹⁰Be record in modern travertine profile provide significant correlation with global ¹⁰Be production rate than the original¹⁰Be record,which suggests that travertine¹⁰Be record do indeed reflect the atmospheric radionuclide production signal.(4)Corrected ¹⁰Be record in ancient travertine profile showed a significant upward trend during the Maunder minimum;it showed 11.4 years of periodic characteristics;and it had a significant positive correlation with the ice core ¹⁰Be records.These indicate that the travertine ¹⁰Be record in Baishuitai mainly reflect the information of atmospheric¹⁰Be production rate modulated by solar activity and can be used to reconstruct the high-resolution past solar activity.(5)Synchronizing travertine ¹⁰Be record and ice core ¹⁰Be record can effectively reduce the error range of age in travertine.(6)There was a response in the recording of travertine ¹⁰Be with a short-term peak near the appearance of supernova outbreak in the study period,which suggests that the short-term peak signal in travertine¹⁰Be record has great potential in tracing extreme extraterrestrial events.