中国盐湖沉积年代学研究进展

盐湖沉积记录了区域气候和水文变化,是重要的古气候研究对象。年代学是盐湖古气候研究最重要的一项内容,是后续工作的基础。盐湖沉积最常用的定年方法有14C定年、铀系定年、光释光(OSL)定年、古地磁定年。受各种定年方法自身局限性以及盐湖沉积特殊性的制约,存在不同方法测出的年龄差异较大的现象。准确测定盐湖沉积的年代还较为困难,一定程度限制了盐湖古气候研究的发展。最新研究表明,由于盐湖沉积有机质含量低,易受现代碳的污染,14C测年中存在复杂的碳库效应,其14C年代老于30 cal ka BP时,测出的年龄可能被低估,需谨慎对待。未来需要加强铀系定年和光释光定年等方法在盐湖沉积中的基础研究,并开发新的更好的测年方法,提高盐湖沉积测年的准确度,为深入开展盐湖古气候变化及成盐成矿规律研究提供坚实基础。

Progress on Dating Deposits from Salt Lake in China

:Salt lake deposit records regional climatic and hydrological changes during the past.Thus,it is an important archive for paleoclimatic study.Geochronological study is very important for reconstructing the past climate change recorded in salt lake.At present,¹⁴C dating,uranium-series dating,OSL (optically stimulated luminescence) dating and paleomagnetic dating are the most common methods to date deposits from salt lake.Due to limitations of the above dating methods and characteristics of salt lake deposits,past researches show that chronological results derived by different dating methods are sometimes inconsistent.Accurate dating of deposits from salt lake is still difficult.Therefore,the paleoclimate study on salt lakes has been hampered.Organic matter is few in the deposits from salt lakes,and it can be easily contaminated by modern carbon.The ¹⁴C ages of salt lake deposits are usually influenced by complicated carbon reservoir effect.The latest researches show that the ¹⁴C ages are probably underestimated when the ¹⁴C ages are older than 30 cal ka BP.Basic study for uranium-series and OSL dating methods,and exploitation of new better methods to improve the accuracy of dating results in deposits from salt lake,will help to establish a robust foundation for paleoclimatic reconstruction in the future.