ПАЛЕОСЕЙСМОГЕННЫЕ ТЕКТОНИЧЕСКИЕ РВЫ – УНИКАЛЬНЫЕ АРХИВЫ ИСТОРИИ БЕЛОГО МОРЯ В ГОЛОЦЕНЕ

Abstract

Various sedimentary archives at the Karelian coast of the White Sea (Kindo Peninsula, White Sea Biological Station area) as the paleoseismic fault trenches filling, marine terraces sections and buried shell lenses have been studied. The results were obtained by applying the paleoseismological approach in course of detailed field studies with the identification of characteristic morphological, structural and dynamic features of ancient earthquakes. The lithostratigraphic study of depositional sequence was verified by radiocarbon, diatom, plant macrofossil analysis of peat and the degree of its decomposition and loss-of-ignition analyzes. It was established that the earthquake that generated the seismic fault trench system occurred in the Late Glacial or Early Holocene with the formation of a seismic underwater fracture, and the trench “opened” because of the subsequent lifting of the bottom, erosion and removal of fragmented rocks in the wave-breaking zone shortly before filling it with Holocene sediments. Sediments that filled the paleoseismic trench accumulated over the period from 9 ka BP to the present, with a break for passage through the coastal zone. They demonstrate a successive change from marine sedimentary environment (gray silt with Hiatella arctica shells, dated back to 9 ka BP) to coastal-marine (sand with clasts), then again to an isolated, gradually desalinated lagoon-type sea gulf (mica silt dated back to 3 ka BP), and ultimately – swamp overgrown with spruce forest (woody peat dated back to 2 ka BP). The structure of the upper part of the section could be caused by a) a weak rise in sea level in the Late Holocene, or b) a weak lowering of the block of the earth’s crust with a seismic trench located on it. New data were obtained on specific features of subfossil malacofauna taphocoenosis formation in the Kandalaksha Bay of the White Sea and on the changes of sedimentation environment under the conditions of rising coast. The traces of strong seismicity in the Late Galcial epoch and postglacial time were discovered. Therefore, a comprehensive approach to the study of seismogenic forms combined with a full range of age-related markers of various paleogeographic events proved to be very productive.