High-resolution upper Maastrichtian carbon isotope stratigraphy of terrestrial organic matter from northern Japan
High-resolution upper Maastrichtian carbon isotope stratigraphy of terrestrial organic matter from northern Japan
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日本北部陆地有机质的高分辨率上马斯特里赫特碳同位素地层学
DOI：
10.1127/nos/2021/0652
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发表时间：
2022
影响因子：
2.2
通讯作者：
M.
中科院分区：
文献类型：
--
作者：
Nifuku;K.;Naruse;H.;& Ikehara;M.
建立了日本北方北海道东部根室群MaastrichtianSenpohshi组上部陆源有机质的高分辨率稳定碳同位素地层学。仙坡石组厚约1300 m，主要为沿着北太平洋地区活动边缘沉积的半远洋泥岩。从地层中提取的干酪根样品的显微镜观察显示存在沉积有机质（SOM），主要是植物碎屑和少量的非荧光无定形有机物，表明材料的陆生高等植物起源。干酪根样品的氢/碳原子比表明煤化等级为无烟煤阶段或以下。因此，稳定的碳同位素值的散装SOM获得的Senpohshi组代表未修改的，原始的陆生有机质的价值。该地层重建的稳定碳同位素剖面提供了第一个高分辨率的马斯特里赫特中期事件（MME）的陆地记录，这是可比的高分辨率海洋碳同位素数据从其他部分。海相记录所确定的碳同位素特征在地层中，特别是在事件的中上部的陆地数据中得到了认可。然而，陆地记录显示的差异，海洋数据在MME的下部，这表明在北太平洋地区的内陆环境的局部变化。这项研究通过建立详细的陆地物质碳同位素记录，为研究马斯特里赫特晚期的环境变化提供了新的视角。
High-resolution stable carbon isotope stratigraphy of terrestrial organic matter was established for the upper Maastrichtian Senpohshi Formation of the Nemuro Group in eastern Hokkaido, northern Japan. The Senpohshi Formation, approximately 1, 300 m thick, is dominated by hemipelagic mudstone deposited along an active margin in the North Pacific region. Microscopic observations of extracted kerogen samples from the formation revealed the presence of sedimentary organic matter (SOM), predominantly phytoclasts and a minor amount of non-fluorescent amorphous organic matter, indicating material of a terrestrial higher plant origin. The atomic hydrogen/carbon ratios of the kerogen samples indicated a coalification rank at the anthracite stage or below. Therefore, the stable carbon isotope values of the bulk SOM obtained for the Senpohshi Formation represent the unmodified, original values of terrestrial organic matter. The stable carbon isotope profile reconstructed for the formation provides the first high-resolution terrestrial record of the Mid-Maastrichtian Event (MME), which is comparable to high-resolution marine carbon isotope data from other sections. The carbon isotopic signatures defined by the marine records are recognized in the terrestrial data from the formation, especially in middle to upper part of the event. However, the terrestrial record showed a discrepancy from the marine data in the lower part of the MME, suggesting local variation of the hinterland environment in the North Pacific region. This study provides new insight into environmental changes during the late Maastrichtian by establishing a detailed carbon isotope record of terrestrial materials.