Sediments from the semi-enclosed Japan Sea are sensitive to paleoclimatic perturbations and they offer great opportunities for many regional and global paleoceanographic and paleoclimatic studies. These studies often require a robust chronology. However, due to rare preservation of calcareous microfossils and drastic changes in surface water salinity during glacial lowstands, the construction of a traditional oxygen isotope stratigraphy for Japan Sea sediments is often difficult. Here, we use sediments recovered at Integrated Ocean Drilling Program (IODP) Expedition 346 Site U1424 to build an integrated Pliocene-Pleistocene reference magnetostratigraphy and tephrostratigraphy for sedimentary sequences from the region. Rock magnetic experiments indicate that magnetic remanence of Site U1424 sediments are carried primarily by (titano)magnetite with small contributions from high coercivity minerals (e.g., hematite) and possibly iron sulphides (pyrrhotite and/or greigite). Dark-colored sediments appear to contain less (titano)magnetite probably due to reductive diagenesis under euxinic conditions. Natural remanent magnetization (NRM) of u-channel samples covering a continuous ~ 167.6 m sediment sequence at Site U1424 was repeatedly measured at 1 cm intervals before and after stepwise demagnetization. Despite lower NRM intensity in dark-colored sediments, NRM directional data from both dark- and light-colored sediments are considered suitable for the construction of magnetostratigraphy. Site U1424 sediments clearly recorded the majority of the polarity chrons and subchrons within the last ~ 4.89 Myr, with the Cobb Mountain subchron, the end of Kaena subchron, and the onset of Nunivak subchron less well preserved. Sixteen tephra layers from the site were sampled for chemical composition analyses and the results were correlated to reference tephrostratigraphy of the region. Ages of the identified tephras are consistent with and can be well integrated with the magnetostratigraphy. The resulting age model suggests that sedimentation rates at Site U1424 range between ~ 1.7 and 7.6 cm/kyr with an average of ~ 3.3 cm/kyr. The acquired magnetostratigraphy and tephrostratigraphy at Site U1424 provide a reference chronology that can be correlated with and transferred to other sediment sequences in the region to study paleoceanographic and paleoclimatic changes of the region as well as their links to other regional and global changes.

Graphical abstract

中文翻译：

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IODP站点U1424（日本大和盆地）深海沉积物的上新世—更新世磁地层学和斜生地层学

半封闭日本海的沉积物对古气候扰动敏感，为许多区域和全球古海洋学和古气候研究提供了巨大的机会。这些研究通常需要可靠的时间顺序。然而，由于冰川低潮期钙质微化石的稀有保存和地表水盐度的急剧变化，通常难以为日本海沉积物构造传统的氧同位素地层。在这里，我们使用在综合海洋钻探计划（IODP）346号站点U1424上回收的沉积物，为该地区的沉积序列建立了上新世-更新世参考地层和地层。岩石磁性实验表明，U1424站点沉积物的剩磁主要由（钛铁矿）磁铁矿携带，而高矫顽力矿物（例如赤铁矿）和可能的硫化铁（硫铁矿和/或钙铁矿）贡献很小。深色沉积物似乎含有较少的（钛铁矿）磁铁矿，这可能是由于在富氧条件下还原成岩作用所致。在逐步消磁之前和之后，以1 cm的间隔重复测量覆盖U1624站点连续〜167.6 m沉积物序列的u通道样本的自然剩磁（NRM）。尽管深色沉积物中的NRM强度较低，但深色和浅色沉积物中的NRM方向数据都被认为适合于磁地层学的构造。U1424站点的沉积物清楚地记录了最后一个〜4.89 Myr内的大多数极性年代和子年代，其中Cobb山子年代，Kaena子年代末和Nunivak子年代的开始保存得不好。对该地点的16个特非拉岩层进行了采样，以进行化学成分分析，并将结果与​​该地区的特制地貌相关。鉴定出的特弗拉斯的年龄与地磁地层学一致并且可以很好地整合在一起。最终的年龄模型表明，U1424站点的沉积速率介于1.7至7.6 cm / kyr之间，平均约为3.3 cm / kyr。

图形概要