High organic carbon content and a decrease in radiolarians at the end of the Permian in a newly discovered continuous pelagic section: A coincidence?

Carbon-isotope stratigraphy across the Permian–Triassic boundary: A review

“…For the P-T boundary, widespread anoxic conditions occurred during the deposition of several successions (e.g., Wignall and Hallam, 1992;Isozaki, 1994Isozaki, , 1997Kajiwara et al, 1994;Knoll et al, 1996;Wignall and Twitchett, 1996;Wignall et al, 1998;Kato et al, 2002;Kidder and Worsley, 2004;Nielsen and Shen, 2004;Grice et al, 2005;Kump et al, 2005;Riccardi et al, 2006Riccardi et al, , 2007Hays et al, 2007;Xie et al, 2007a;Algeo et al, 2008;Grasby and Beauchamp, 2009;Takahashi et al, 2009). Anoxic conditions, in terms analogous to Tyson and Pearson (1991), are indicated by the presence of compounds or alteration products of green sulphur bacteria from the shallow-marine photic zone in the Hovea 3 core (W-Australia) (Grice et al, 2005).…”

An 80 million year oceanic redox history from Permian to Jurassic pelagic sediments of the Mino-Tamba terrane, SW Japan, and the origin of four mass extinctions

“…Bedded radiolarian cherts are the dominant lithology at this time but they are interrupted, in the uppermost Permian, by the development of a siliceous claystone (with variable amounts of clay minerals) known as the Toishi facies (Kuwahara et al, 1991;Musashino, 1993). This is overlain by a thin black shale unit that, on the basis of its conodont fauna, belongs to the basal Griesbachian Stage (Yamakita et al, 1999), although the discovery of Clarkina in the basal part of the black shale from the North Kitakami Belt suggests that the Permian-Triassic boundary (PTB) probably lies within the lower part of the black shale (Takahashi et al, 2009a). The remainder of the Lower Triassic succession sees the return of Toishi facies around the Griesbachian/ Dienerian boundary.…”

“…this section although Yao and Kuwahara (1997) found radiolaria from red cherts higher in the section indicative of a late Early Triassic/early Middle Triassic age. A Griesbachian age is assumed for the Momotaro strata because better-dated sections of similar lithology yield conodonts of this Stage (Yamakita et al, 1999;Takahashi et al, 2009a). SEM examination of the dolomite horizons at Momotaro shows them to be composed almost exclusively of dolomite rhombs (up to 50 μm in diameter), suggesting that they have grown displacively in the sediment rather than occluding sediment as they formed.…”

Reply to the Comments of Kato and Isozaki on “Evaluation of palaeo-oxygenation of the ocean bottom across the Permian–Triassic boundary” by Y. Kakuwa [Global Planet. Change 63 (2008) 40–56]: Was the Late Permian deep-superocean really oxic?

“…On this contradiction, Kato et al (2002) mentioned that they could not detect a brief occurrence of oxic condition at the suspected PTB presented by Kajiwara et al (1994). The sedimentation of carbonaceous claystone continued from the Latest Changhsingian (Takahashi et al, 2009) to the early Smithian (Yamakita and Kadota, 2001), and the duration is never "brief".…”