Structural and lithological comparison of convolutions in lacustrine complexes (Q_3-4) of the Baltic Shield, Northern Yakutia, Tien Shan

E.S. Gorbatov¹, S.F. Kolesnikov², A.M. Korzhenkov¹, H.A. Vardanyan¹

¹ Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia

² Moscow State University of Geodesy and Cartography (MIIGAiK), Moscow, Russia

Corresponding author: E.S. Gorbatov, e-mail: e.s.gor@mail.ru

Abstract. In order to clarify the genesis of liquefaction folds (convolutions) developed at lithological boundaries in lacustrine sediments, a comparison of these structures was carried out in the three considered regions. Folds in each region differ in morphology, composition of sediments, vertical gradient of their density and viscosity upon deformation. It is proposed to use the ratio of the widths of syn- and anticlinal folds in the convolution horizon (K_S) to analyze the latter, in which K_S > 1 corresponds to the normal viscosity gradient, and K_S < 1 – to its inversion. Convolutions of the Baltic Shield and Yakutia from K_S ≥ 1 are noted in the most liquefied sediments with unstable density stratification (sands-on-silts), which indicates the possibility of their spontaneous formation during lithogenesis. Folds with K_S ≈ 1 are widespread in Yakutia, which indicates their cryogenic genesis. Convolutions in the Tien Shan were formed with a stable stratification of sediments in terms of density (silts-on-sands), and low-fluidized coarse-grained sediments with viscosity inversion were also involved in deformation. These signs indicate the seismic initiation of liquefaction processes. The results obtained substantiate the lithogenic genesis of convolutions in the lacustrine complexes of the Baltic Shield, cryogenic and lithogenic in Yakutia and seismogenic in the Tien Shan. It is proposed to determine the scatter of the K_S value in the diagrams for diagnosing the genesis of convolutions. For lithogenic structures, this parameter is shifted to the region with K_S > 1, and for seismites, it is relatively symmetric with respect to K_S = 1.

Keywords: lacustrine sediments, convolutions, soft-sediment deformation structures, seismites, cryoturbations, convective instability, vertical gradients of density and viscosity of sediments, genetic diagrams, Baltic Shield, Northern Yakutia, Tien Shan

About the authors:

GORBATOV Evgenii Sergeevich – Schmidt Institute of Physics of the Earth, Russian Academy of Sciences. Russia, 123242, Moscow, Bolshaya Gruzinskaya st., 10-1. E-mail: e.s.gor@mail.ru

KOLESNIKOV Sergey Fedorovich – Moscow State University of Geodesy and Cartography (MIIGAiK). Russia, 105064, Moscow, Gorokhovsky per., 4. E-mail: sfkol@yandex.ru

KORZHENKOV Andrey Mikhailovich – Schmidt Institute of Physics of the Earth, Russian Academy of Sciences. Russia, 123242, Moscow, Bolshaya Gruzinskaya st., 10-1. E-mail: korzhenkov@ifz.ru

VARDANYAN Hasmik Ashotovna – Schmidt Institute of Physics of the Earth, Russian Academy of Sciences. Russia, 123242, Moscow, Bolshaya Gruzinskaya st., 10-1. E-mail: asmikvar@yandex.ru

Cite this article as: Gorbatov E.S., Kolesnikov S.F., Korzhenkov A.M., Vardanyan H.A. Structural and lithological comparison of convolutions in lacustrine complexes (Q_3-4) of the Baltic Shield, Northern Yakutia, Tien Shan, Voprosy Inzhenernoi Seismologii (Problems of Engineering Seismology). 2021. V. 48, No. 3. P. 41–59. [in Russian]. https://doi.org/10.21455/VIS2021.3-2

English translation of the article will be published in Seismic Instruments, ISSN: 0747-9239 (Print) 1934-7871 (Online), https://link.springer.com/journal/11990