Северо-западные берега Онежского полуострова Белого моря в голоцене: условия развития, динамика, хронология

Abstract

According to detailed geomorphological studies, radiocarbon dating and Stolbovoe Lake sediments and terrace sedimentary cover diatom analysis three different stages of coastal zone development in the northwest of the Onega Peninsula had been identified and dated. The abrasion coastlines at elevations of 18.5–30 m were formed earlier ~9.5–8.5 cal kyr BP, during the Late Glacial transgression and the glacio-isostatic regression of the Early Holocene. A well-defined predominantly abrasion coastline at elevations of 14–18.5 m was formed ~8.2–5.8 cal kyr BP during the mid-Holocene Tapes transgression with insignificant fluctuations of the sea level with hydrodynamic activity greater than present. A short-term episode (~6.0–5.8 cal kyr BP) of the relative sea level rise on the shore of the Dvina Bay has been identified, probably associated with storm surges. Abrasion-accumulative coastlines at elevations up to 14–15 m were formed after ~5.8 cal kyr BP in the conditions close to modern. At all stages of development, the shores were dynamically young. The leading role of the postglacial uplift in the extension of the coast contour, and of the structure of the glacial relief–in the morpho- and lithodynamics of the coastal zone is shown. During the Tapes transgression, the rates of uplift of adjacent morphostructural blocks differed (~0.5 and 2.1–2.2 mm/year); then the uplift became uniform (~2.8–2.9 mm/year). The structure of the coastal forms indicates the constant prevailing directions of the waves and sediment transport, starting from the middle Holocene.