Approximately 74 ka, Toba caldera in Sumatra, Indonesia, erupted in one of the most catastrophic supereruptions in Earth's history. Resurgent uplift of the caldera floor raised Samosir Island 700 m above Lake Toba, exposing valuable lake sediments. To constrain sediment chronology, we collected 173 discrete paleomagnetic 8 cm3 cubes and 15 radiocarbon samples from six sections across the island. Bulk organic 14C ages provide an initial chronostratigraphic framework ranging from ~12 to 46 ka. Natural and laboratory magnetizations were studied using alternating field demagnetization. A generally well-defined primary magnetization is isolated using principal component analysis. Comparison of inclination, and to a lesser degree declination, across independently dated sections suggests paleomagnetic secular variation (PSV) is recorded. Average inclination of −6° is more negative than a geocentric axial dipole would predict, but consistent with an eastward extension of the negative inclination anomaly observed in the western equatorial Pacific. The 14C- and PSV-derived age model constrains resurgent uplift, confirming faster uplift rates to the east and slower rates to the west, while suggesting that fault blocks moved differentially from each other within a generally trapdoor-type configuration.

中文翻译：

---

印度尼西亚多巴火山口沙摩西岛湖泊沉积物的古地磁观测及其晚更新世复苏

印度尼西亚苏门答腊岛约 74 ka 的多巴火山口喷发，这是地球历史上最具灾难性的超级喷发之一。火山口地面的重新隆起将沙摩西岛抬高到多巴湖上方 700 米处，暴露出宝贵的湖泊沉积物。为了限制沉积物年代学，我们收集了 173 个离散的古地磁 8 cm3立方体和来自全岛六个部分的 15 个放射性碳样本。散装有机14C 年龄提供了一个初始年代地层框架，范围从~12 到 46 ka。使用交变场退磁研究了自然磁化和实验室磁化。使用主成分分析来隔离通常定义明确的初级磁化强度。对独立年代剖面的倾角和较小程度的偏角进行比较表明，记录了古地磁长期变化（PSV）。-6°的平均倾角比地心轴向偶极子预测的更负，但与在赤道西太平洋观察到的负倾角异常向东延伸一致。这14C 和 PSV 衍生的年龄模型限制了复苏的隆起，证实了东部较快的隆起速度和西部较慢的速度，同时表明断块在通常的活板门型配置中彼此移动不同。