Advance in the Study of Palaeo-climate Reconstruction from Stable Isotope Variations in Speleothems

Speleothems are now regarded as valuable archives of continental climatic conditions on the continents,offering a number of advantages relative to other continental climate proxy recorders such as lake sediments and peat cores.They are ideal materials for precise U-series dating,yielding ages in calendar years,thereby circumventing the radiocarbon calibration problems associated with most other continental records.Speleothem data sets are nottuned,and their independent chronology offers opportunities to provide the chronologic benchmark for correlating and calibrating climate variability.Under equilibrium condition,the stalagmite δ18O is mainly controlled by local climate,normally by the precipitation in monsoon areas or temperature in Europe.Using the cave marine and cave ice core correlations,it can provide all three records with an accurate time scale for the last four Glacial/Interglacial cycles,which in turn can provide important insights into the global link and forcing mechanism.Although the influence factors on δ13C may be more complicated,carbon isotope signatures are mainly controlled by the C3/C4 ratio of the local vegetation or biogenic CO2 supply by the soil,which is in turn affected by temperature and secondarily rainfall amount.The literature is reviewed briefly to provide for all readers a sense of the current research work of the stable isotope of speleothem,and provide some pointers for future research directions.