A preliminary study on paleomagnetic field intensity variation forthe past 6000 years

在此资助期内，我们购置了一台测量岩石居里温度的高灵敏度磁天平，并完成了校准和调校工作，以便在未来的古强度研究中识别出适合测量古强度的岩石样品。在九州火山区13个测点采集了古地磁样品，其中8个测点获得了可靠性较高的古地磁方向。在九州岛火山区，熔岩的年龄是根据与火山灰层的关系报道的，因此，熔岩的形成年龄不能精确确定。我们认识到，这些不准确的熔岩年龄不适合恢复过去几千年的古强度变化。我们注意到，我们不应该将我们的采样限制在Kujuvolcanic领域，但我们应该改变计划，从熔岩和火山碎屑流中收集样品，这些样品已经报道了碳-14年龄。对这些熔岩和火山碎屑流进行了古强度测量。

During this funding period, a high-sensitivity magnetic balance for measuring a Curietemperature of rocks was purchased and the calibration and adjustment were completed.Using this system, a rock sample which is suitable for paleointensity measurement canbe recognized in the future paleointensity studies. Paleomagnetic sample was collectedat 13 sites of the Kuju volcanic field, and paleomagnetic directions with relatively highreliability were obtained from eight sites. In the Kuju volcanic field, the ages of lavaswere reported based on the relation with volcanic ash layers, and therefore the formationages of lava were not precisely determined. We recognized that these inaccuracies of theages of the lavas were not suitable for recovering the paleointenisty variation for thepast several thousand years. We noticed that we should not limit our sampling to the Kujuvolcanic field, but we should change the plan to collect samples from lavas andpyroclastic-flows for which carbon-14 ages have been reported. Paleointensitymeasurements are being conducted on these lavas and pyroclastic-flows.