Perspectives in carbonate paleoclimatology

Abstract

Sedimentary carbonate is the most successful material in paleoclimatological researches. Researches in this field are now challenging to extract high-resolution and quantitative records of millennial-century scales in order to predict the climatic changes due to global warming. The most promising study material is a reef coral, which records temperature (and salinity) changes in its annually-laminated aragonitic skeleton. Data from coral climatology and annually-laminated polar ice cores would contribute to climate prediction although the information is geographically limited in only tropical and polar areas.For the information from temperate-subtropical climatic belts, carbonate paleoclimatology using speleothems is effective. Oxygen and carbon isotopic signatures of speleothems are now treated as possible proxies of water temperature and vegetation. Another promising material for the study on temperate-subtropical areas is a tufa, a calcitic deposit in freshwater environments of limestone areas. The tufa commonly shows annual laminations and advances to speleothems in its larger depositional rate (several millimeters per year) that allows higher analytical resolution. This study represents that rainfall events were recoded in a Japanese tufa deposit.