Sequence composition and conodonts of the Kara formation (lower carboniferous) of the Amderma district of the Northern Pay-Khoy

The Kara Shale allochthone of the Pay-Khoy comprises the Middle Paleozoic bathyal deposits. The siliceous and clayey rocks are characteristic for the deposits. The specific feature of the Kara Formation is its carbonate composition. The formation overlays the Late Tournaisian Silovayakha Formation and overlaid by the Karasolova Formation of the Early Bashkirian age. The Kara Formation comprises stratigraphical interval from the Visean through Serpukhovian. The lower part of the formation is composed of carbonate turbidites and contains allochthonous conodont associations including Early Visean Idioprioniodus healdi (Roundy). The middle part of the formation, mainly composed of micritic carbonates, is characterized by the Late Visean conodont association dominated by Gnathodus praebilineatus Belka, Gnathodus bilineatus (Roundy), Lochriea commutata (Branson et Mehl), Pseudognathodus homopunctatus (Ziegler). Absence of the advanced species of Lochriea makes it impossible to detect the Visean/Serpukhovian boundary precisely. The Serpukhovian part of the formation is composed of micritic and hydrothermal carbonates. The Lower Serpukhovian conodont associations are poor. The upper part of the Kara Formation contains the Late Serpukhovian conodonts, including Gnathodus bollandensis (Higgins et Bouckaert). In general Lochriea commutata, Pseudognathodus, and Gnathodus bilineatus group dominate the taxonomically poor conodont associations of the Kara Formation. The sequence, thickness (about 180 m) and age of the Kara Formation of the Amderma District are similar to those of the type section of the formation. The lower part of the Kara Formation is correlated with the gap in the bottom of the Bolvansky Formation of the carbonate parautochton, and the upper part - with the lower part of the Bolvansky Formation.