摘要
环渤海泥质海岸带近30年来获得的600余个放射性碳测年数据,确定了该地区晚更新世晚期以来的基本年代地层序列。但是,对14C数据的系统校正,迄未得到应有的重视,致使在应用14C数据解释地层和地质现象的年代时,存在着一定程度的混乱。文章对作者自己所采集和由国内外有关实验室测定的126个14C数据进行了系统校正,主要步骤包括分馏效应、地区性海洋贮存库效应及大气14C含量变化校正等。建议以-2.68‰PDB作为环渤海晚更新世晚期以来半咸水和开放浅海区(潮间带与潮下带上部)贝壳的地区性δ13C平均值。另外,讨论了在地区性海洋贮存库效应值获得之前的1990年代,以MARINE 93与INTCAL 93程序的平均校正年龄近似地视作该地区贝壳的校正值,以抵消这一类地区小型水体与大气迅速进行14CO2交换而对年龄值的影响。CALIB 4.4校正结果表明,前述近似校正是可行的,其结果仍可沿用。文章经统一校正的年龄,最大限度地接近其太阳历纪年的"真实"年龄,从而有助于更加准确地重建该地区的晚更新世晚期以来的地质年代史,并可与考古纪年及其他测年方法获得的绝对年龄直接对比。
As one of the most important methods for the Late Pleistocene and Holocene chronology, radiocarbon dating, with ca. 600 data accumulated in the last three decades, has set up an essential chronostratigraphic framework on the CBS Coast ( Circum-Bohai Sea-Coast) . However, systematic calibration for those 14C dates has long been neglected and, consequently, confusions have existed for explaining the timeframe of stratigraphy obtained. This paper gives a systematic calibration for 126 data, being collected by the authors and dated by several domestic and foreign laboratories. The major methods include the corrections for isotope fractionation, the (regional) marine reservoir effect, and the fluctuations of atmospheric 14C activity. The results suggest -2. 68‰ PDB as being the regional value for δ13C for those molluscan shells, including foraminifera/ostrocode from the brackish water masses and open shallow sea (i.e. the intertidal and the upper part of the subtidal) for the period since the late Late Pleistocene. Furthermore, this paper assesses a proxy method using arithmetic average, calculated from both MARINE 93 and INTCAL 93 programs, as being an approximate calibrated age for shell samples in 1990's, during which the regional marine reservoir value (△R) had not been set up, in order to offset a reliable rapid exchange of 14CO2 in between the small/shallow water reservoirs and the contemporaneous atmosphere. CALIB 4.4 correction indicates that the method is feasible, and the results can be used continuously. Such calibrated ages, given by CALIB versions, are close to the calendrical true ages in full play. Thus, this is beneficial to better reconstructing the regional geochronologic history since the late Late Pleistocene and such calibrated ages can be compared directly with the archaeological evidence and other absolute dating results as well.
出处
《第四纪研究》
CAS
CSCD
北大核心
2004年第6期601-613,共13页
Quaternary Sciences
基金
比利时政府ABOS奖学金(批准号:904967)中国地质调查局国土资源大调查项目(批准号:199614
199201054和1300013051)共同资助
关键词
环渤海海岸带
放射性碳测年
系统校正
the Circum-Bohai Sea-Coasts, radiocarbon dating, systematic calibration
