Carbon isotope chemostratigraphy and conodont biostratigraphy around the Smithian–Spathian boundary in the Panthalassan carbonate succession (SW Japan)

Spathian to Aegean (upper Lower Triassic to lower Middle Triassic) carbon isotope stratigraphy constrained by the conodont biostratigraphy of carbonates on top of a mid‐oceanic seamount formed in the Panthalassic Ocean

“…(c). Geological map of the type area of the Taho Formation (modified from Maekawa et al, 2021). (d) Paleogeographic map for the Late Triassic (modified from Martindale et al, 2015).…”

“…These blocks are an important archive of the biotic assemblages and sedimentary evolution of oceanic sediments from the Panthalassic Ocean, and include deep-sea bedded cherts (Matsuda & Isozaki, 1991) and shallow-water carbonates (Wakita, 2019). Blocks found in Tahokamigumi, Seiyo City, western Shikoku Island, are known as the Taho Limestone (Koike, 1994) or Taho Formation (Koike, 1996;Maekawa et al, 2018Maekawa et al, , 2021, and were derived from an atoll/carbonate buildup or an isolated carbonate platform developed on top of a mid-oceanic seamount during the Triassic (Hirsch & Ishida, 2002;Maekawa et al, 2018Maekawa et al, , 2021Musashi et al, 2001) (Figures 1 and 2). These limestone blocks contain abundant, well-preserved marine fossils, such as ammonoids (Bando, 1961(Bando, , 1964Shimizu & Jimbo, 1933;Yehara, 1925), bivalves (Yehara, 1923), gastropods (Nakazawa, 1971), fish remains (Goto et al, 2010;Yamagishi, 2004), and conodonts (Koike, 1981(Koike, , 1988(Koike, , 1992(Koike, , 1994(Koike, , 1996(Koike, , 2004Maekawa et al, 2018Maekawa et al, , 2021.…”

“…Blocks found in Tahokamigumi, Seiyo City, western Shikoku Island, are known as the Taho Limestone (Koike, 1994) or Taho Formation (Koike, 1996;Maekawa et al, 2018Maekawa et al, , 2021, and were derived from an atoll/carbonate buildup or an isolated carbonate platform developed on top of a mid-oceanic seamount during the Triassic (Hirsch & Ishida, 2002;Maekawa et al, 2018Maekawa et al, , 2021Musashi et al, 2001) (Figures 1 and 2). These limestone blocks contain abundant, well-preserved marine fossils, such as ammonoids (Bando, 1961(Bando, , 1964Shimizu & Jimbo, 1933;Yehara, 1925), bivalves (Yehara, 1923), gastropods (Nakazawa, 1971), fish remains (Goto et al, 2010;Yamagishi, 2004), and conodonts (Koike, 1981(Koike, , 1988(Koike, , 1992(Koike, , 1994(Koike, , 1996(Koike, , 2004Maekawa et al, 2018Maekawa et al, , 2021. In contrast to the numerous paleontological studies, there has only been one chemostratigraphic investigation of the Taho Formation (Musashi et al, 2001), which focused on a short negative spike at the Permian-Triassic boundary.…”

“…In addition, most of these studies have been conducted on Tethyan sites/sections. Recently, Maekawa et al (2021) presented a δ 13 C profile constrained by conodont biostratigraphy around the Smithian-Spathian boundary in the Tahogawa Member of the Taho Formation, which represents a Panthalassic carbonate succession. The carbon cycle perturbation recorded in their study sections (E02 and E03 in Figure 1) was correlated to the late Smithian to early Spathian global carbon isotope negative (N3) and following positive (P3) excursions reported for the Tethyan, Panthalassic, and Boreal regions (Figure 3).…”

“…The carbon cycle perturbation recorded in their study sections (E02 and E03 in Figure 1) was correlated to the late Smithian to early Spathian global carbon isotope negative (N3) and following positive (P3) excursions reported for the Tethyan, Panthalassic, and Boreal regions (Figure 3). Here we present a new high-resolution Spathian to Aegean carbon isotope record, which is constrained by conodont biostratigraphy, from section C02 of the Tahogawa Member that is located above the Maekawa et al (2021) study sections, but overlaps for 5 m (Figures 2 and 3). This is the first report of a continuous Spathian to Aegean carbonate carbon isotope stratigraphy from the mid-Panthalassa.…”