Lateglacial and Holocene environmental history of the central Kola region, northwestern Russia revealed by a sediment succession from Lake Imandra

Matthias Lenz,Vasili Kolka,Grigory Fedorov,Larisa Frolova,Anna Cherezova,Niyaz Nigmatullin,Larisa Savelieva,Marlene M Baumer,Natalia Kostromina,Benrd Wagner,Raphael Gromig,Martin Melles,Matthias Moros

doi:10.1111/bor.12465

Abstract

Bolshaya Imandra, the northern sub‐basin of Lake Imandra, was investigated by a hydro‐acoustic survey followed by sediment coring down to the acoustic basement. The sediment record was analysed by a combined physical, biogeochemical, sedimentological, granulometrical and micropalaeontological approach to reconstruct the regional climatic and environmental history. Chronological control was obtained by 14C dating, 137Cs, and Hg markers as well as pollen stratigraphy and revealed that the sediment succession offers the first continuous record spanning the Lateglacial and Holocene for this lake. Following the deglaciation prior to c. 13 200 cal. a BP, the lake's sub‐basin initially was occupied by a glacifluvial river system, before a proglacial lake with glaciolacustrine sedimentation established. Rather mild climate, a sparse vegetation cover and successive retreat of the Scandinavian Ice Sheet (SIS) from the lake catchment characterized the Bølling/Allerød interstadial, lasting until 12 710 cal. a BP. During the subsequent Younger Dryas chronozone, until 11 550 cal. a BP, climate cooling led to a decrease in vegetation cover and a re‐advance of the SIS. The SIS disappeared from the catchment at the Holocene transition, but small glaciers persisted in the mountains at the eastern lake shore. During the Early Holocene, until 8400 cal. a BP, sedimentation changed from glaciolacustrine to lacustrine and rising temperatures caused the spread of thermophilous vegetation. The Middle Holocene, until 3700 cal. a BP, comprises the regional Holocene Thermal Maximum (8000–4600 cal. a BP) with relatively stable temperatures, denser vegetation cover and absence of mountain glaciers. Reoccurrence of mountain glaciers during the Late Holocene, until 30 cal. a BP, presumably results from a slight cooling and increased humidity. Since c. 30 cal. a BP Lake Imandra has been strongly influenced by human impact, originating in industrial and mining activities. Our results are in overall agreement with vegetation and climate reconstructions in the Kola region.

Highlights

Bolshaya Imandra, the northern sub-basin of Lake Imandra, was investigated by a hydro-acoustic survey followed by sediment coring down to the acoustic basement
The basement is overlain by a subparallel sediment unit of 2.0–2.5 m thickness that is acoustically stratified in more flat areas andwidely transparent in steeper areas
The hydro-acoustic data show the existence of large channels, which can be attributed to meltwater channels that formed large glacifluvial systems during the initial deglaciation of the area prior to 13 200 cal. a BP

Summary

Introduction

Bolshaya Imandra, the northern sub-basin of Lake Imandra, was investigated by a hydro-acoustic survey followed by sediment coring down to the acoustic basement. A sparse vegetation cover and successive retreat of the Scandinavian Ice Sheet (SIS) from the lake catchment characterized the Bølling/Allerød interstadial, lasting until 12 710 cal. A BP, climate cooling led to a decrease in vegetation cover and a re-advance of the SIS. The SIS disappeared from the catchment at the Holocene transition, but small glaciers persisted in the mountains at the eastern lake shore. A BP, comprises the regional Holocene Thermal Maximum Our results are in overall agreement with vegetation and climate reconstructions in the Kola region. During the Last Glacial Maximum (LGM), the Kola region was entirely covered by the Scandinavian Ice Sheet (SIS) (Svendsen et al 2004; Hughes et al 2016; Stroeven et al 2016; Patton et al 2017). Boreas published by John Wiley & Sons Ltd on behalf of The Boreas Collegium

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Conclusion