High-resolution foraminiferal biostratigraphy across the Moscovian/Kasimovian boundary

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In the present research, I studied high-resolution foraminiferal biostratigraphy across the Moscovian/Kasimovian boundary in the Kalinovo section of the Donets Basin, Ukraine, and the Zhongdi section of the Yangtze Platform, China.In the Kalinovo section, the following 12 limestones covering a Moscovian-Kasimovian boundary interval are examined : N_2, N_3, N_3^1, N_3^2, N_3^3, N_5^1, O_1, O_1^1, O_1^2, O_2, O_3, and O_4. In N_2, typical late Moscovian fusuline genera such as Taitzehoella and Fusulina are found. N_3 yields Quasifusulinoides and primitive Protritivcites, suggesting a latest Moscovian age. N_3^3 records the occurrence of Protriticites similar to P. pseudomontiparus and/or P. subschwagerinoides, and is probably already of traditional, early Kasimovian. O_1 is dominated by Obsoletes and Quasifusulinoides, together with rare, primitive Montiparus. This level is possibly correlated to the early part of the traditional, middle Kasimovian. O_2 is rich in typical Montiparus, and … More is assignable to the traditional, middle Kasimovian. In the Kalinovo section, therefore, the traditional base of the Kasimovian can be placed somewhere within the N_3-N_3^3 interval. In Donets, ldiognathodus sagittalis, a current potential marker conodont species for the base of the Kasimovian, occurs first in O_1. Thus, this level is several depositional cycles higher than the traditional base of the Kasimovian.In the latest Moscovian-Kasimovian of the Zhongdi section, five fusuline zones were established: in ascending order, they are the Fusulinella-Fusulina, Protriticites sp. A, Protriticites sp. B, Montiparus, and Triticites Zones. Of them, the Protriticites sp. A Zone records the occurrence of primitive Protriticites that bears fine perforations in its spirotheca. In contrast, advanced Protriticites with definitely coarse perforations comparable with rudimentary keriotheca are found in the Protriticites sp. B Zone. These lines of evidence suggest that the base of the Kasimovian in the Zhongdi section almost coincides with the boundary between the Protriticites sp. A Zone and Protriticites sp. B Zone. Less