NOAA/WDS Paleoclimatology - Stoner et al. 2007 North Iceland Shelf MD99-2269 Holocene Paleomagnetic Secular Variation Data

We report the intercalibration of paleomagnetic secular variation (PSV) and radiocarbon dates of two expanded postglacial sediment cores from geographically proximal, but oceanographically and sedimentologically contrasting settings. The objective is to improve relative correlation and chronology over what can be achieved with either method alone. Core MD99-2269 was taken from the Húnaflóaáll Trough on the north Iceland shelf. Core MD99-2322 was collected from the Kangerlussuaq Trough on the east Greenland margin. Both cores are well dated, with 27 and 20 accelerator mass spectrometry 14C dates for cores 2269 and 2322, respectively. Paleomagnetic measurements made on u channel samples document a strong, stable, single-component magnetization. The temporal similarities of paleomagnetic inclination and declination records are shown using each core's independent calibrated radiocarbon age model. Comparison of the PSV records reveals that the relative correlation between the two cores could be further improved. Starting in the depth domain, tie points initially based on calibrated 14C dates are either adjusted or added to maximize PSV correlations. Radiocarbon dates from both cores are then combined on a common depth scale resulting from the PSV correlation. Support for the correlation comes from the consistent interweaving of dates, correct alignment of the Saksunarvatn tephra, and the improved correlation of paleoceanographic proxy data (percent carbonate). These results demonstrate that PSV correlation used in conjunction with 14C dates can improve relative correlation and also regional chronologies by allowing dates from various stratigraphic sequences to be combined into a single, higher dating density, age-to-depth model.

本研究报道了两份采自地理邻近但海洋学与沉积学特征迥异站位的冰期后厚层沉积岩芯的古地磁长期变化（paleomagnetic secular variation, PSV）与放射性碳定年结果的互校准工作。本研究的目标为相较于单一方法所能实现的效果，进一步优化相对地层对比与区域年代框架的构建精度。岩芯MD99-2269采自冰岛北部陆架的胡纳弗洛厄槽（Húnaflóaáll Trough），岩芯MD99-2322则采集于格陵兰东部陆缘的康克鲁斯瓦格槽（Kangerlussuaq Trough）。两份岩芯均具备高质量年代数据：岩芯2269与2322分别拥有27例和20例加速器质谱（accelerator mass spectrometry）14C定年数据。对u通道（u channel）样品开展的古地磁测量结果显示，其磁化信号具有强而稳定的单组分特征。依托两份岩芯各自独立的校准放射性碳年代模型，可证实其古地磁倾角与偏角记录在时间序列上具有高度相似性。对两份岩芯的古地磁长期变化记录的对比分析表明，二者的相对地层对比精度仍有提升空间。以深度域为切入点，最初基于校准放射性碳定年结果建立的对比控制点可通过调整或新增的方式，以最大化古地磁长期变化记录的相关性。随后，依托古地磁长期变化对比得到的统一深度标尺，可将两份岩芯的放射性碳定年数据整合为一体。该对比结果的佐证包括：定年数据的一致性交织匹配、萨库纳瓦特火山碎屑层（Saksunarvatn tephra）的精准就位，以及古海洋代用指标（碳酸盐含量）对比精度的提升。本研究结果证实，将古地磁长期变化对比与放射性碳定年结合使用，可通过将不同地层序列的定年数据整合为单一、更高定年密度的年代-深度模型，同时优化相对地层对比精度与区域年代框架。