TY - JOUR

T1 - Paleohydrological changes in the eastern Baltic Sea during the Middle/Late Pleistocene transition and the Last Interglacial

AU - Ruchkin, MV

AU - Sheetov, MV

AU - Taldenkova, EE

AU - Pushina, ZV

AU - Dudanova, VI

AU - Ovsepyan, YS

AU - Konstantinov, EA

AU - Nosevich, ES

AU - Mustafin, MA

N1 - Times Cited in Web of Science Core Collection: 2 Total Times Cited: 2 Cited Reference Count: 148

PY - 2025

Y1 - 2025

N2 - The Mga Sea existed from the latest Middle Pleistocene to the latest Last Interglacial (LIG) within the Gulf of Finland, Lake Ladoga, Lake Onega basins and the connecting straits. Paleohydrological changes in the Mga Sea evolution are traced with a multiproxy approach using X-ray fluorescence, carbon and nitrogen (CN), grain size, X-ray diffraction (XRD) analyses, along with microfossil data (diatoms and benthic foraminifers) for Mikulino (Eemian) and Upper Moscow (Upper Saalian) marine sediments in the Sverdlov Factory section of the Neva Lowland (St. Petersburg region, Russia). In addition, varve chronology is applied to the Upper Moscow glaciomarine/glaciolacustrine deposits as time constraints on paleogeographic changes in the Mga basin during the Middle/Late Pleistocene transition. The results indicate that saline waters entered the glacial lake in the periphery of the Scandinavian Ice Sheet at least 1100 years before the onset of the Mikulino Interglacial. During the period between similar to 1050 and 550 years before the LIG, the basin was freshened and became again connected with the ocean afterwards. In the early LIG, the Mga Sea experienced brackish conditions with predominantly oxygenated near-bottom waters indicated by an impoverished benthic foraminiferal assemblage with Elphidium clavatum as dominant species, as well as by geochemical and lithological proxies. Diatom and geochemical data reveal a steep rise in water salinity and depth in the middle of the Quercus regional pollen assemblage zone (RPAZ M-4). The highstand phase lasted until regression began in the Carpinus-Picea zone (RPAZ M6-7). The increase in water salinity and depth led to the spread of marine molluscs at the base of RPAZ M-5, though limited to a few species due to the onset of hypoxia in near-bottom waters. Fully anoxic conditions were established at the end of RPAZ M-5 and persisted till the end of the Mikulino Interglacial, with a brief oxygenation excursion in the first half of the Pinus zone (RPAZ M-8). At the end of RPAZ M-8 or at the beginning of the Early Valdai (Early Weichselian), the Mga basin became freshwater. The Mga Sea shared much similarity with the Late Glacial/Holocene Baltic Sea in evolution patterns.

AB - The Mga Sea existed from the latest Middle Pleistocene to the latest Last Interglacial (LIG) within the Gulf of Finland, Lake Ladoga, Lake Onega basins and the connecting straits. Paleohydrological changes in the Mga Sea evolution are traced with a multiproxy approach using X-ray fluorescence, carbon and nitrogen (CN), grain size, X-ray diffraction (XRD) analyses, along with microfossil data (diatoms and benthic foraminifers) for Mikulino (Eemian) and Upper Moscow (Upper Saalian) marine sediments in the Sverdlov Factory section of the Neva Lowland (St. Petersburg region, Russia). In addition, varve chronology is applied to the Upper Moscow glaciomarine/glaciolacustrine deposits as time constraints on paleogeographic changes in the Mga basin during the Middle/Late Pleistocene transition. The results indicate that saline waters entered the glacial lake in the periphery of the Scandinavian Ice Sheet at least 1100 years before the onset of the Mikulino Interglacial. During the period between similar to 1050 and 550 years before the LIG, the basin was freshened and became again connected with the ocean afterwards. In the early LIG, the Mga Sea experienced brackish conditions with predominantly oxygenated near-bottom waters indicated by an impoverished benthic foraminiferal assemblage with Elphidium clavatum as dominant species, as well as by geochemical and lithological proxies. Diatom and geochemical data reveal a steep rise in water salinity and depth in the middle of the Quercus regional pollen assemblage zone (RPAZ M-4). The highstand phase lasted until regression began in the Carpinus-Picea zone (RPAZ M6-7). The increase in water salinity and depth led to the spread of marine molluscs at the base of RPAZ M-5, though limited to a few species due to the onset of hypoxia in near-bottom waters. Fully anoxic conditions were established at the end of RPAZ M-5 and persisted till the end of the Mikulino Interglacial, with a brief oxygenation excursion in the first half of the Pinus zone (RPAZ M-8). At the end of RPAZ M-8 or at the beginning of the Early Valdai (Early Weichselian), the Mga basin became freshwater. The Mga Sea shared much similarity with the Late Glacial/Holocene Baltic Sea in evolution patterns.

KW - Middle/Late Pleistocene transition

KW - MIS 5e

KW - Eemian

KW - Baltic Sea

KW - Diatoms

KW - Benthic foraminifers

KW - Geochemical proxies

KW - Grain size analysis

KW - Varve chronology

KW - DEGLACIATION CHRONOLOGY

KW - POLLEN STRATIGRAPHY

KW - SEDIMENT CORE

KW - LEVEL CHANGES

KW - LAKE ONEGA

KW - YOLDIA SEA

KW - CLAY VARVE

KW - ICE-SHEET

KW - MARINE

KW - BROMINE

U2 - 10.1016/j.quascirev.2025.109244

DO - 10.1016/j.quascirev.2025.109244

M3 - статья

VL - 360

JO - Quaternary Science Reviews

JF - Quaternary Science Reviews

SN - 0277-3791

ER -