ОТРАЖЕНИЕ ПАЛЕОСЕЙСМИЧЕСКИХ СОБЫТИЙ В ПОЗДНЕПЛЕЙСТОЦЕН-ГОЛОЦЕНОВЫХ ОТЛОЖЕНИЯХ ТЕРРАС ОЗЕРА ИМАНДРА (КОЛЬСКИЙ РЕГИОН)

Abstract

Soft-sediment deformation structures have been indentified in glaciolacustrine deposits of the terrace complexes of the Lake Imandra (Kola Region, NE of the Fennoscandian Shield). According to the paleoseismological criteria, we found that these deformation structures were induced by strong earthquakes. These earthquakes led to the occurrence of secondary deformations of various morphology and sizes in the sandy-sandy sediments, forming a single complex consisting of intensely deformed and destructed deposits and associated clastic dikes and cracks. Among the plastic deformations, the phenomena of liquefaction, boudinage structures, flame structures, irregular convolute stratifications, diapir-like structures and synsedimentary folds are developed. Among brittle deformations, cracks and micro-fractures and dykes, predominate. The spatial and stratigraphic distributions of soft-sediment deformation structures were used to infer about the activation of faults during the Late Glacial and Postglacial period of the sub-latitudinal and north-western strike directions that limit the different-scale blocks of the earth’s crust. According to radiocarbon analysis data and paleogeographic reconstructions, the formation of soft-sediment deformations took place at the end of the Young Dryas – the beginning of the Preboreal period between 12900–11500 cal yr BP, and later, in the Preboreal period – beginning of the Boreal period between 11500– 9900 cal yr BP. It was this period that was accompanied by increased seismic activity not only in the Kola region, but also in the whole of Fennoscandia.