西太平洋卡罗琳海域沉积速率:来自3种测年方法的限定

Sedimentation rate obtained by multiple chronological analysis in Caroline area of the western Pacific Ocean

为了更好地认识西太平洋暖池区北部卡罗琳海域沉积速率的变化,利用放射性碳测试(14C)、氧同位素及古地磁方法对采自西太平洋卡罗琳地区一根长217 cm的柱状样开展了综合年代学分析。14C数据获取了样品上部44.3 ka BP以来的年代数据,在此基础上利用氧同位素及古地磁相对强度数据建立了该柱125 cm至表层的年代框架,对应为MIS4期(约8万年)以来的沉积。进一步分析发现本柱在126~127 cm处存在明显沉积间断,虽然该处已超出^(14)C测年范围,但古地磁测试结果表明该柱位于布容正极性时期,同时古地磁强度与氧同位素的变化关系为沉积间断以下年代数据获取提供了可信的证据,表明该阶段对应距今13万年至18万年时期。本柱沉积速率在沉积间断前后均较为一致,为1~2 cm/ka。同时对比不同方法获取的沉积速率之间差异后,发现个别层位可能由于较高的有孔虫破壳率,导致14C值存在较大偏差。

In order to better understand the sedimentary rate changes in the Caroline area which is located in the north of West Pacific Warm Pool,a comprehensive dating method was carried out by using radiocarbon testing(^(14)C),oxygen isotope and paleomagnetism on a gravity core from the Caroline area of the western Pacific Ocean.^(14)C data provide the age of the upper section since 44.3 ka BP for this core.Subsequently,the age frame-work since MIS4(about 80 ka)which corresponds to the depth of 125 cm was established by using oxygen isotope and relative paleointensity(RPI)data,while the upper part also considered the ^(14)C data.Further analysis revealed that there was an obvious sedimentary discontinuity at the depth of 126 cm to 127 cm in this core,although it has been beyond the range of ^(14)C dating,but the paleomagnetic results show that the core formed in Brunhes period,and the relationship between RPI and oxygen isotope data under the hiatus provide a robust evidence that the age is from 180 ka to 130 ka in the bottom.At the end the deposition rate of the core was obtained,which is 1 cm/ka to 2 cm/ka,and it is consistent before and after the deposition hiatus.At the same time,the disparity of the deposition rate for each dating method indicated that there was a large deviation of ^(14)C data in one layer maybe due to the high rate of foraminiferal shell breaking.