Russian scientists have reconstructed the history of the formation of the Solovetsky Archipelago over the past ten thousand years. The study showed how the territory changed from the departure of the glacier to the appearance of warm sea pools, where the water temperature was higher than the modern one.
About 8-7 thousand years ago, in the shallow strait between the Solovetsky Islands on the site of the modern Anzer Salma, there were special hydrological conditions that contributed to the massive development of marine mollusks, and the water temperature was 1-2 °C higher than today. This conclusion was reached by researchers from St. Petersburg State University, the Geological Institute of the Kola Scientific Center of the Russian Academy of Sciences, Lomonosov Moscow State University, the Institute of Geography of the Russian Academy of Sciences, the A.P. Karpinsky All-Russian Scientific Research Geological Institute, the A.I. Herzen Russian State Pedagogical University, the Split Scientific Company, VNIIOCEANGEOLOGY and P.P. Shirshov Institute of Oceanology of the Russian Academy of Sciences.
The White Sea is located on the periphery of the Baltic Shield and represents the inner shelf basin of the Arctic Ocean. Its geological history is closely connected with the cycles of glaciations and interglacials of the Quaternary period. The last glaciation on the Russian territory of the Eastern European Plain is called the Valdai glaciation. The cold snap began about 115-100 thousand years ago and was accompanied by the gradual formation of glaciers in the Scandinavian Mountains. About 22-17 thousand years ago, the glacier reached its maximum.
At that time, the entire territory of the White Sea, as well as the entire Kola Peninsula, were buried under a continuous ice sheet. The most active movement of the glacier took place in the basin of the White Sea: the ice moved in a single stream, which near its edge split into so-called blades and tongues. It was between such blades, Dvinskaya and Onega, that the territory of the Solovetsky Islands turned out to be.
Interpretation of digital relief models, georadar surveys, seismoacoustic profiling of the seabed, sampling of sediment cores and examination of geological sections on land, as well as radiocarbon, palynological and diatom analyses allowed scientists to reconstruct events that occurred on the territory of the archipelago after the retreat of the glacier, namely— the transgression of the Late Glacial White Sea. This transgression, associated with global sea level rise, led to the flooding of coastal areas. A cold desalinated reservoir formed in the straits between the islands, where precipitation from the glacial-marine reservoir accumulated.
Scientists have recorded traces of the former shore of this reservoir at altitudes of 21-25 meters above modern sea level on Bolshoy Solovetsky Island and on Anzer Island. According to the authors, it was a body of water much larger than the modern White Sea and much colder, filled with numerous icebergs and floating ice. Numerous cold and muddy streams of meltwater from the melting glacier flowed into it from the west. As a result, the basin was significantly desalinated compared to the Ocean. Only by the middle of the Holocene, in conditions of climatic optimum, the basin acquired the features of a modern marine system.
The authors also managed to confirm the hypothesis of the existence of a local and relatively "warm" marine reservoir in the Solovetsky Archipelago in the Boreal and Atlantic periods of the Holocene. This conclusion was the result of a comprehensive comparison of terrestrial and marine geological data.
Scientists have established that in the Boreal period (about 8 thousand years ago), a special hydrological regime was formed in the Anzer Salma. The core taken in the inter—island Strait revealed a horizon rich in shells of marine mollusks - Chlamys islandica, Astarte borealis and Hyatella arctica. Palynological and lithological data suggest that the water temperature here was 1-2 °C higher than the current one. Such conditions contributed to the "flourishing" of the molluscan fauna, which peaked in the Atlantic period of the Holocene (about 7 thousand years ago).
Similar "shell horizons" are known in other areas of the White Sea, but it was in the Solovetsky Strait that they turned out to be especially powerful and well-preserved. According to the researchers, this indicates locally favorable conditions, probably due to shallow water, limited circulation and protection from waves.
The research was supported by a grant from the Russian Science Foundation.
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