Structure of Late Pleistocene and Holocene Sediments in the Petrozavodsk Bay, Lake Onego (NW Russia)

Dmitry Subetto,Mikhail Aleshin,Vera Strakhovenko,Natalia Shalaeva,Andrei Loktev,Mikhail Tokarev,Alexandra Kiskina,Alexandr Rybalko,Maksim Potakhin,Dmitry Korost,Pavel Belyaev,Nathalie Dubois,Natalia Belkina,Yuriy Kublitskiy,Natalia Kostromina,Vladislav Kuznetzov,Alexander Orlov

doi:10.3390/min10110964

Abstract

Here, we present new results from seismic, geological, and geochemical studies conducted in 2015–2019 in the Petrozavodsk Bay of Lake Onego, NW Russia. The aims of these investigations were to (i) to characterize the structure of Quaternary deposits and (ii) provide new evidence of modern geodynamic movements and gas-seepage in Holocene sediments. The structure of the recovered deposits was composed of lacustrine mud, silt and sands from the Holocene, limno-glacial clays (varved clays) from the Late Glacial–Interglacial Transition, and glacial deposits (till) from the Late Pleistocene. The thickness of these deposits varied in different parts of the bay. Many pockmarks created by gases escaping and reaching sediment-water interface were observed in these deposits. Such pockmarks can play a significant role in the geochemical and biological processes in the bottom sediment surface, and gases that escape might modify the physicochemical characteristics of the environment.

Highlights

Geological explorations of Lake Onego have been conducted since the 1960s, but research was carried out only with short gravity corers [1].The sediment cores obtained in these studies were no Minerals 2020, 10, 964; doi:10.3390/min10110964 www.mdpi.com/journal/mineralsMinerals 2020, 10, 964 longer than 1–1.5 m, only reaching the Upper and Middle Holocene
Quaternary deposits around the lake basin, including sediment cores from small lakes located near Lake
Demidov [5,6] used these data and the findings of Finnish researchers to present the first model of the development of Lake Onego in the Late Pleistocene and Holocene [2], which has been used until now in different variations

Summary

Introduction

Geological explorations of Lake Onego have been conducted since the 1960s, but research was carried out only with short gravity corers [1].The sediment cores obtained in these studies were no Minerals 2020, 10, 964; doi:10.3390/min10110964 www.mdpi.com/journal/mineralsMinerals 2020, 10, 964 longer than 1–1.5 m, only reaching the Upper and Middle Holocene. At the end of the last century did Finnish scientists and Karelian Research Center experts conduct geochronological and lithostratigraphic studies [2]. These studies have determined the lake basin formation about. Demidov [5,6] used these data and the findings of Finnish researchers to present the first model of the development of Lake Onego in the Late Pleistocene and Holocene [2], which has been used until now in different variations. The stratigraphy of Lake Onego’ sediments and the main stages of paleogeographic development of the lake basin during the Late Pleistocene–Holocene has become significantly more precise [4,7,8]. Specific data on the structure of the bottom sediments in Lake Onego are currently not available

Methods

Results

Conclusion