Reconstruction of late Holocene extreme hydrological events of the Valentin Bay coast, the Sea of Japan
The scale and age of extreme hydrological events that have manifested over the past 2000 years on the coast of the Valentin Bay is established on the basis of stratigraphic study and radiocarbon dating of sections of different facies deposits. The deposits of 4 major historical tsunamis (1993, 1983, 1644 and XII century) and paleo-tsunami, which occurred 1700-1800 cal. yr. BP, were found. Sedimentation zones were mapped. The composition of diatoms in tsunami sands has been studied in detail. It is shown that tsunami waves carried both marine and brackish-water species, as well as most of the freshwater forms redeposited from the coastal lake. The main supply of material was from the depths up to 5 m. The correlation of events with the data obtained on the Japanese Islands was carried out. It has been suggested that the most dangerous for this part of the coast of Eastern Primorye are tsunamis caused by submarine earthquakes with epicenters located near the Okushiri Island. The tsunamis associated with earthquakes with epicenters located near the northwestern Honshu Island, were less pronounced. The data on the irregularity of the frequency of extreme floods over the last millennium has been obtained. It was established that the pluvial phase of the Warm Medieval Period ended in the early to mid-XII century. During the Little Ice Age, the water content of the rivers was insignificant, only two events were identified that correspond to the warm phase of the mid-14th century - early 15th century, comparable to the catastrophic floods of the late 20th - early 21st century. Only two modern floods traces were recorded in the sedimentary cover of the Valentin Bay coast.