Archaeointensity record of weak field recurrence in Japan: new data from Late Yayoi and Kofun ceramic artifacts
Archaeointensity record of weak field recurrence in Japan: new data from Late Yayoi and Kofun ceramic artifacts
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日本弱场重现的考古强度记录：来自弥生晚期和古坟陶瓷文物的新数据
DOI：
10.1093/gji/ggac498
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发表时间：
2022
影响因子：
2.8
通讯作者：
Gulmini M
中科院分区：
文献类型：
--
作者：
Tema E;Santos Y;Trindade R;Hartmann G A;Hatakeyama T;Terra-Nova F;Matsumoto N;Mitsumoto J;Gulmini M
我们提供来自日本冈山县六个考古遗址的新绝对考古强度数据。研究的材料是来自陶器、陶瓷棺材和埴轮工艺品的年代久远的碎片。他们的时代从公元 160 年到公元 675 年，涵盖了弥生晚期和古坟时期。岩石磁性实验表明，存在磁铁矿和/或钛磁铁矿作为剩磁的主要载体，较高矫顽力矿物的贡献可能较小。经过热退磁实验后，选择磁力最稳定的样品，按照Thellier提出并经Coe修改的双重加热方法进行考古强度分析。进行部分热剩磁 (pTRM) 检查和 pTRM 尾部检查，以监测加热过程中可能发生的化学变化。所有测量值均针对各向异性和冷却速率效应进行了校正。根据严格的选择标准，对来自所有调查的考古遗址的样本进行了成功的考古强度测定。与日本的文献数据相比，新的高质量数据显示出明显较低的强度值。它们还揭示了弥生晚期可能发生的快速长期变化以及公元 630 年左右地磁强度场非常弱的情况。这些值提供了东亚弱强度场可能重现的证据，表明西太平洋异常在古代重现。新数据可能会改变该地区考古磁场模型的解释，尽管仍然需要更多数据来更好地了解日本的长期变化和东亚地磁场行为的时间演变。
We present new absolute archaeointensity data from six archaeological sites situated in the Okayama Prefecture, Japan. The materials studied are well-dated fragments from pottery, ceramic coffins and haniwa artefacts. Their ages range from 160 AD to 675 AD, covering the Late Yayoi and Kofun periods. Rock magnetic experiments suggest the presence of magnetite and/or Ti-magnetite as the main carrier of the remanence, with a possible minor contribution of higher coercivity minerals. After thermal demagnetization experiments, the most magnetically stable samples were selected for archaeointensity analysis performed following the double-heating method proposed by Thellier and modified by Coe. Partial thermoremanent magnetization (pTRM) checks and pTRM tail-checks were performed for monitoring possible chemical alterations during heating. All measurements were corrected for both anisotropy and cooling-rate effects. Successful archaeointensity determinations, following rigorous selection criteria, were obtained for samples from all the investigated archaeological sites. Compared with literature data from Japan, the new high-quality data show significantly lower intensity values. They also reveal possible fast secular variation changes during the Late Yayoi period and very weak geomagnetic intensity field around 630 AD. Such values offer evidence of a possible recurrence of weak intensity field in East Asia, suggesting an ancient recurrence of the West Pacific Anomaly. The new data might change the archaeomagnetic field models interpretations in the area, even though more data are still necessary to better understand the secular variation in Japan and the temporal evolution of the geomagnetic field's behaviour in East Asia.