Study On The Formation Of Travertine Annual Laminae Controled By Climatic And Environmental Factors

The information of climatic and environmental change in the past is very important as we human pay more and more attention to the environments that surround us.The intentions require higher time resolution so as to find out how climate and environment change,revealing the regulation of the climate evolution, and the direction of the future climate change.So the tufa as a proxy of climate inspired great interests of scholars.Records from annually banded ice sheets and reef corals have provided high-resolution evidence of climate change and related phenomena. Unfortunately, these paleoclimatic media cannot be directly used to help predict climates for terrestrial areas,owing to their limited geographic distribution.Suitable terrestrial paleoclimate media are needed to help understand past climates and to try to forecast the impact of future climates on human society.Previous studies of terrestrial paleoclimates have entailed research on lake deposits, loess-paleosol sequences,and speleothems.Such studies have implied paleoclimates from sedimentological (deposition rate and grain size) and geochemical (stable isotope and trace element) proxies.Furthermore,several studies,especially of speleothems,have demonstrated high-resolution records that have potential as annual to subannual records of change in humidity and temperature.Tufa, a freshwater carbonate,is another promising material for high-resolution subannual paleoclimate studies, because tufas have high deposition rates and some have annual laminations.The deposition rate of travertine reachs 1-20mm per year,consisting of abundant microbanding layers.The thickness and the width of the micro-banding of single band are enough for analyzing stable isotopes and trace elements so that can achieve the higher resolution of season or month in paleoclimate reconstruction with travertine.Tufas are calcite deposits that are ubiquitous in areas underlain by limestone in temperate to tropical climates.Calcite precipitates because of CO2 degassing when CaCO3-supersaturated...