Lithostratigraphic Criteria of the Polar Moraine in Subarctic Regions of European Russia and Typomorphic Features of Garnets and Zircon

Abstract

The results of a comprehensive lithological study of the Upper Neopleistocene polar (Ostashkovo) moraine (textural, structural, and mineral-petrographic features, as well as the chemical composition and typomorphism of garnets and zircons, carried out to identify its lithostratigraphic criteria and substantiate the division and correlation of Quaternary sections are considered. The moraine is widespread only in the northernmost part of the Pechora Lowland, where it forms the day surface relief. The study was carried out in lower reaches of the Pechora River and in coastal outcrops of the Kuya, Chernaya, and Shapkina rivers. The moraine, characterized by a high content of the pelite fraction, has a finer composition than the Middle Neopleistocene moraines widely developed here. The mineralogical spectra of the moraine in the studied area are of the same type and represented by epidote, garnets, amphiboles, siderite, and pyrite. Total amount of pyrite and siderite increases to 20–35% with the permanent dominance of siderite over pyrite. The petrographic spectrum of the polar moraine is characterized by the presence of single fragments of the crinoid–bryozoan limestones (guide boulders of the Novaya Zemlya demolition area), as well as a very consistent orientation of elongated rock fragments, suggesting their delivery from the north-northeast (Pai-Khoi and Novaya Zemlya). It was overlapped only in lower reaches of the Shapkina River by a glacial tongue extending from the northwest (Fennoscandinavia and northern Timan). The presence of garnets in the moraine is related to their supply from metamorphic and certain types of igneous rocks. Based on the ZrO₂/HfO₂ ratio, the predominant mass of zircon grains was formed in mafic and felsic igneous rocks. Zircons from the metamorphic rocks are subordinate.