A REVIEW OF PALAEOCLIMATIC IMPLICATIONS FROM LAMINATED TUFA AND TRAVERTINE
层状钙华及其地球化学指标的古气候/环境意义

It is wildly accepted that tufa and travertine with laminae can be used for high-resolution reconstruction of Quaternary paleoclimate.Alternating laminae of dense micrite and porous calcites,combined with stable isotope(δ18 O and δ13 C )and trace elements from recent tufa show seasonal changes which reflect the climatic information.These alternating laminae have been interpreted to represent seasonally controlled differences in the rate of calcification and/or biotic activity of microbes.Variability in δ18 O is driven mainly by changes in water temperature and the δ18 O value of the recharging water,while evaporation,especially in arid climates,also needs to be accounted.Variability in δ13 C reflects principally the relative contribution of isotopically different carbon origins to dissolved inorganic carbon(DIC).CO2 degassing as well as aquatic photosynthesis can take up 12 C-enriched CO2 in water and thus leave isotopically heavier DIC,which can also be given rise to by precipitation of calcite along the stream or river flow path.Meanwhile,the contents of trace element(e.g.Mg,Ba,Sr)in tufa are supposed to be related to temperature,their concentration in water and rainfall.However,whether aggrading neomorphism and reprecipitation change isotope record of tufa,and reliable chronologies need further research.In a word,as these deposits accumulate rapidly,laminated tufas and travertines offer an excellent opportunity to study seasonality in Quaternary palaeoclimate,and may become a promising record in future research.