We investigated the deep-sea sedimentary sequence of core MD012422 corresponding to the last 350 ka (since marine isotopic stage, MIS 10) from off Shikoku Island, NW Pacific Ocean, and refined its tephrostratigraphy. We detected many tephras and cryptotephras and correlated them with terrestrial tephras on the basis of the major- and trace-element compositions of their glass shards. Then we cross-checked our results against the reported marine tephrostratigraphy in the NW Pacific area and assessed the relative timing of tephra eruptions and bioevents. Many widespread tephras and cryptotephras originated from the Kyushu volcanic zone (Kuju, Aso, Kakuto, Aira, Ata, and Kikai volcanoes/calderas), along with the Takayama-Ng1 tephra (Tky-Ng1) from Suiendani volcano in central Honshu, were detected in the core. These tephras were used to validate and refine the reported NW Pacific marine tephrostratigraphy and to develop useful time-synchronous markers for this ocean area. Among the tephras, Ata-Torihama (Ata-Th) occurs at the MIS 7/8 transition (ca. 240 ka) and its horizon overlaps with a calcareous nannofossil biohorizon, the first appearance datum (FAD) of Emiliania huxleyi. Ata-Th and this biohorizon are stratigraphically above the Tky-Ng1 (MIS 8/9 transition, 290–300 ka) and Kakuto (Kkt, MIS 9/10 transition, 330–340 ka) tephras, and these tephras have the same stratigraphic relationship with this biohorizon in deep-sea sediments from the East China Sea, off Shikoku Island, and off central Honshu. However, in deep-sea cores from off northern Honshu, an inconsistency between the tephrostratigraphy and the FAD of E. huxleyi has been reported. This inconsistency can be explained by poor preservation of calcareous fossils in the deep waters off northern Honshu, which are more corrosive to calcium carbonate than the shallower waters off Shikoku Island. These findings emphasize the importance of cross-checking biohorizons against tephra horizons and of linking tephras between terrestrial and marine sequences to assess the synchronicity of globally correlated age indicators.

我们调查了西北太平洋四国岛外最后350 ka（自海洋同位素阶段，MIS 10起）对应的MD012422核心深海沉积层序，并细化了其地层。我们根据玻璃碎片的主要和微量元素组成，检测到许多特非拉斯和隐头目，并将它们与陆地特非拉斯相关联。然后，我们将结果与西北太平洋地区报道的海洋岩相地层学进行了交叉核对，并评估了地弗拉火山喷发和生物事件的相对时间。发现了来自九州火山带的许多广泛的特非拉斯和隐头目（九州，阿苏，卡库托，艾拉，阿塔和基凯火山/卡尔德拉斯火山），以及本州中部水谷谷火山的高山-Ng1特弗拉（Tky-Ng1）。在核心。这些特弗拉斯被用于验证和完善已报道的西北太平洋太平洋海相岩石地层学，并为该海域开发有用的时间同步标志。在特非拉斯中，Ata-Torihama（Ata-Th）发生在MIS 7/8过渡处（约240 ka），其地平线与钙质的纳米化石生物地平线（FAD）的第一个出现基准（FAD）重叠。（Emiliania huxleyi）。Ata-Th和这种生物地平线在Tky-Ng1（MIS 8/9过渡，290-300 ka）和Kakuto（Kkt，MIS 9/10过渡，330-340 ka）地层之上，并且这些特弗拉斯具有相同的地层东海，四国岛和本州中部海域深海沉积物中与这种生物地平线的关系。然而，在本州北部海底深部岩心中，地层与E. huxleyi的FAD不一致。已经被报告了。这种不一致的现象可以通过本州北部深水区钙质化石的保存不充分来解释，而钙质化石比四国岛浅水区对碳酸钙的腐蚀性更大。这些发现强调了针对蒂弗拉层层交叉检查生物地平线以及在陆地和海洋序列之间联系蒂弗拉峰以评估全球相关年龄指标的同步性的重要性。