新生代地磁漂移研究若干进展

A review of Cenozoic geomagnetic excursions

地磁漂移事件的成因及发生规律是地学研究热点,是古地磁学科在这个世纪可能为地球科学贡献新理论的一个突破口。在回顾地磁漂移研究历史的基础上,对新生代地磁漂移记录及其时代进行了概述,从地磁漂移的成因、地磁漂移事件与地磁场强度的关系、地磁场漂移期间地磁场形态学研究等几个方面对过去的研究进行了总结。最后,提出未来研究需关注沉积速率较高的河湖相沉积物,通过多种手段生成不同地理位置的可靠地磁漂移记录,利用轨道调谐手段准确限定时代等,才能获得对新生代地磁漂移规律的全面认识。

Driving mechanisms and occurrence frequency of Cenozoic geomagnetic excursions are key questions in geosciences,of which a clear answer might bring about a breakthrough in understanding the behavior of the Earth’s core.Researches on geomagnetic excursions mainly focus on the period of Quaternary.Although there are some reports on pre-Quaternary excursions from marine sediments,precise knowledge of timing,duration,and field behavior associated with these excursions are lacking due to the low sedimentation rate of deep-sea sediments.Hereby we made a brief review of past studies on geomagnetic excursions,upon which we sorted out several problems that need to be solved in future study,such as the origin of geomagnetic excursions,the relationship between occurrence timing and paleointensity variation,the age and duration of geomagnetic excursions,and the field behavior during excursions.Learnt from the successful geomagnetic excursion cases in the Quaternary period,future research should focus more on terrestrial fluvial-lacustrine sediments with high sedimentation rates,and it is essential to learn geomagnetic excursion records at different locations.Particularly,tuning paleoclimatic records to shorter orbital parameters such as precession or semi-precession are suggested giving better estimates for the duration of geomagnetic excursions.The tropical and subtropical areas tend to have strong precession or semi-precession signals.It is recommended,therefore,putting these areas as the priority areas to study the details of excursions during the Tertiary.