Middle Devonian conodonts of the Southern Verkhoyansk Region

Givetian conodonts demonstrate a wide geographical distribution and are instrumental in establishing biostratigraphic correlations at both regional and global levels. Nevertheless, their study in the Southern Verkhoyansk Region has only recently begun. I initially identified these conodonts in Tikhii Creek basin situated on the right bank of the first left tributary of Komar Creek, adjacent to the Vostochnaya Khandyga River, the Sette-Daban Range. In this area, the gypsum-bearing sediments of the Tikhiiskaya Suite underlie the carbonate Zagadochninskaya Suite. During a state-funded geological survey, these suites were classified as the Burkhalinskaya series. Geologists assigned the conglomerates at the base of the Tikhiiskaya Suite and the variegated sediments overlain by basalt to the Givetian Stage. This study suggests that the boundary between the Lower and Middle Devonian periods should be delineated at the base of the conglomerate strata, while the variegated volcanic strata capped by basalt should be classified within the Emsian Stage of the Lower Devonian. The findings related to five taxa of conodonts, which belong to two successive complexes originating from the boundary deposits of the Eifelian and Givetian Stages found along Komar Creek, are reported for the first time. The lower complex, distinguished by the presence of conodonts such as Dvorakia sp., Icriodus expansus Branson and Mehl (1938), Polygnathus parawebbi Chatterton (1974), P. costatus subspecies A, P. parawebbi, and Neopanderodus pearleneatus (Ziegler and Lindström 1971), is identified within the Upper Eiffelian Stage. Conversely, the upper complex, which includes subspecies Polygnathus linguiformis linguiformis Hinde (1879) and P. xylus xylus Stauffer (1940), is indicative of the Givetian Stage. The boundary between the Eiffelian and Givetian Stages in the Tikhii-Komar section is likely situated between beds 5 and 6. Consequently, based on the conodont data, the Tikhiiskaya Suite should be classified as Eiffelian in age. Presumably, the basal layers of the Zagadochninskaya Suite correspond to this same geological stage.