The Taho Formation in western Shikoku Island, Japan, consists of Triassic carbonates that formed on a seamount in the Panthalassic Ocean. In order to investigate the stratigraphy and paleoceanography of this carbonate succession, we analyzed the biostratigraphy and chemostratigraphy of a 17.6 m‐thick section of the upper Taho Formation at the stratotype area in Tahokamigumi, Seiyo City. This section comprises bioclastic limestone containing Triassic bivalves, ammonoids, and conodonts. We recognized six conodont zones (in ascending order): the Novispathodus pingdingshanensis, Novispathodus brevissimus, Triassospathodus symmetricus, Triassospathodus homeri, Chiosella timorensis, and Magnigondolella cf. alexanderi zones. Thus, the studied carbonate succession is latest Smithian to Aegean in age. A δ¹³C profile of this section shows elevated values during the lowest Spathian followed by a gradual negative excursion, a subsequent positive excursion near the Spathian–Aegean boundary, and relatively constant values during the Aegean. The characteristic series of negative and positive excursions correlates with other δ¹³C records for this period, including the peak of the upper Smithian–lowest Spathian positive excursion (P3), lower to middle Spathian negative excursion (N4), and middle Spathian–lowest Aegean positive excursion (P4). This represents a new high‐resolution Spathian–Aegean δ¹³C record of the Panthalassic Ocean, for which ages are constrained by conodont biostratigraphy. The Taho δ¹³C profile exhibits a consistent positive offset of ~2 ‰ as compared with those from other regions (i.e., mostly in the Tethyan Ocean). This can be explained by preferential removal of ¹²C from seawater during photosynthesis and calcification by marine organisms over the platform, and/or the relatively high δ¹³C values of dissolved inorganic carbon in the Panthalassic Ocean due to less influence of ¹²C‐enriched terrestrial waters and high marine organic production/burial as compared with the more restricted Tethyan Ocean.

中文翻译：

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喀尔巴阡山脉至爱琴海（下三叠纪上至中三叠纪下）碳同位素地层，受碳酸盐岩在泛海基底海形成的中洋海山顶部的碳酸盐牙形石生物地层学的约束

日本四国岛西部的Taho组由三叠系碳酸盐组成，该碳酸盐形成于Panthalassic海洋的海山上。为了调查该碳酸盐岩层序的地层学和古海洋学，我们分析了西洋市Tahokamigumi地区平流型地区上层Taho组17.6 m厚断层的生物地层和化学地层学。本部分包括含有三叠纪双壳类，铵盐和牙形石的生物碎屑灰岩。我们认识6条牙形石带（升序）：在Novispathodus pingdingshanensis，Novispathodus brevissimus，Triassospathodus symmetricus，Triassospathodus homeri，Chiosella timorensis和大花木兰参 亚历山大地区。因此，研究的碳酸盐演替时代是史密斯时代至爱琴海时代的最新成果。甲δ ¹³的这部分显示C型期间Spathian随后爱琴海期间逐渐负偏移时，Spathian爱琴海边界附近的随后的正偏移，以及相对恒定的值中的最低值升高。特征系列的负和正偏移相关因素与其它δ ¹³ Ç记录此期间，包括上斯密-最低Spathian正偏移（P3）的峰值，降低到中间Spathian负偏移（N4），和中间Spathian-最低爱琴海正面偏移（P4）。这代表了一个新的高清晰度Spathian爱琴海δ ¹³Panthalassic海洋的C记录，其年龄受到牙形体生物地层学的限制。所述TAHOδ ¹³ C型表现出一致的阳性〜2的偏移‰与来自其他区域（即，大部分是在特提斯洋）进行比较。这可以通过优先移除的说明¹²从海水Ç光合作用和钙化期间由海洋生物在平台上，和/或相对高的δ ¹³在Panthalassic海洋溶解的无机碳的C值由于影响少¹² C-富集与更受限制的特提斯洋相比，陆地水和海洋有机产品的生产/埋葬量较高。