Biostratigraphy of the terminal Carboniferous of the lower reaches of the Lena River (Kubalakh section, Russia)

Abstract

The main objective of the study is to solve the question of the age and paleontological characteristics of the Kubalakh Formation of the Upper Paleozoic of the lower reaches of the Lena River. The Kubalakh Formation has been attributed by various researchers either to the Upper Carboniferous or to the base of the Permian according to biostratigraphic data. However, the data on the paleontological characteristics of this straton have been often contradictory. In the course of studying the stratotype of the Kubalakh Formation, which is located near the mouth of the Kubalakh Creek in the lower reaches of the Lena River, the lithological structure of the section was clarified and the representative paleontological material of brachiopods was collected. The following species were identified in the lower part of the Kubalakh Formation: Jakutoproductus protoverkhoyanicus Kaschirzew, Verchojania abramovi Makoshin, Verchojania cf. monstrosus (Ganelin), Cancrinella? alazeica Zavodowsky, and Tornquistia kolymensis Afanasjeva. They all indicate that this part of the formation belongs to the Jakutoproductus protoverkhoyanicus Zone. Brachiopods from the upper part of the Kubalakh Formation were previously assigned to the Jakutoproductus verkhoyanicus Zone of the Khorokytian Regional Stage of the Permian. The results obtained indicate that the lower part of the Kubalakh Formation belongs to the Jakutoproductus protoverkhoyanicus Zone of the Kygyltasian Regional Stage (Gzhelian) of the Verkhoyansk Region. The finding of Verchojania cf. monstrosus (Ganelin) allowed comparing the lower part of the Kubalakh Formation with the Verchojania monstrosus Zone of the Upper Parenian Regional Super Stage of the Upper Carboniferous of the Kolyma-Omolon Region, which revealed that the border between the Kygyltasian and Khorokytian Regional Stages of the Verkhoyansk Region is sub-synchronous with the border between the Parenian and Munugudzhakian Regional Super Stages of the Omolon Massif. The new data expand the understanding of the historical development of biota under the specific (subarctic) conditions of the Eastern Boreal waters at the turn of the Carboniferous and Permian and can be helpful for geological mapping in the region.

Keywords

• upper carboniferous
• biostratigraphy
• brachiopods
• kubalakh formation
• verkhoyansk region