马兰黄土中Laschamp地磁漂移的10Be记录与古地磁测试结果的初步对比

10Be evidence for the Laschamp excursion in Malan loess and its preliminary comparison with that of paleogeomagnetic study

关键词:  Laschamp地磁场漂移  马兰黄土  ¹⁰Be 记录  剩磁获得过程

Key words:  Laschamp excursion  Malan loess  ¹⁰Be  remanence acquisition process

摘要:

Laschamp地磁场漂移事件发生的确切年代(～42 ka BP) 已通过相对独立的同位素定年手段确定，并被证实具有全球性特征。但这一事件在我国马兰黄土地层中的记录存在着明显的空间差异。本文初步对比了最近发表的黄土高原洛川剖面¹⁰Be记录的Laschamp漂移信息和前人根据该剖面古地磁参数异常结合Heinrich冷事件所确定的Laschamp记录层位结果，进一步证实了这一地磁漂移事件在马兰黄土地层中记录的真实性. 同时初步对比也显示根据¹⁰Be产率异常增高对应的磁场强度低值确定的Lashcamp层位偏上，而古地磁异常确定的Laschamp层位相对偏下约76 cm。排除因采样剖面分辨率不同的可能影响，两种手段记录同一地磁漂移事件的显著层位差异具有指示意义，可能为未来研究黄土-古土壤序列沉积剩磁获得过程提供新的途径。

Abstract:

The Laschamp geomagnetic excursion event with reliable age of 42 ka BP deriving from the independent isotope dating method, has been proved to exhibit the global nature. However, there exists clear spatial discrepancy of the record for this event in the Malan loess strata in Chinese loess sections. In this paper, the recently published ¹⁰Be tracing study on Laschamp excursion in Luochuan section is preliminarily compared with that of the previous records for this event by the combination analysis of abnormal paleomagnetic parameters with the cold Heinrich events, which further confirms the reliability of this geomagnetic event records in the Malan loess strata. In addition, the preliminary comparison also suggests that there is a offset of 76 cm for the position of Laschamp excursion recording by the abnormal ¹⁰Be production rate with low magnetic field strength and the paleomagnetic anomalies respectively. The geomagnetic results for the Laschamp excursion is downwards shifted compared with that of the ¹⁰Be records. Therefore, the obvious offset for the same geomagnetic event by ¹⁰Be tracing and paleomagnetic measurement is of importance, if the possible effects from sampling resolution difference in two independent studies can be neglected. It may provide a potential way to improve our understandings on the sedimentary remanence acquisition process for Chinese loess-paleosol sequence.