Diatoms in the Holocene sediments of the Tersky Сoast of the White Sea in connection with the history of its development in the postglacial time

Abstract

This paper demonstrates the results of diatom analysis of the Holocene sediments from the southeastern part of the Tersky Coast of the White Sea. The main subject of the study is the diatom assemblages’ concentration and composition, as well as the ratio of the main diatom ecological groups in sediments. The study sites were located on the Tersky Coast from the village Chavanga to the right coast of the Varzuga River, at heights from 17 to 52 m. Our reconstruction of the Tersky Coast of the White Sea development is based on diatom study of Holocene sediments from three cores. Age was determined according to radiocarbon dating. In this work, the author determines the features of environmental development, starting from the first half of the early Holocene, clarified the age of the main transgressive stages - Folas, Tapes, Trivia and the absolute heights of their marine sediments. According to the changes in concentration and composition  of the main ecological groups of diatoms, the author records the significant trends in the water temperature changes in coastal reservoirs and hydrobiological conditions in the Holocene, such as short-term decrease in the temperatures of the end of Boreal and the first half of Atlantic time, the Holocene hydrobiological optimum, and changes in temperatures of the Subboreal and Subatlantic time.