Nadezhda G. Razjigaeva

Deposits of historical and paleotsunamis on the coast of eastern Primorye

Deposits left by tsunamis from earthquakes in the Sea of Japan floor were identified for the first time on the coast of eastern Primorye. Data are presented on the definite coastal zones from Plastun Bay to Peschanaya Bay, Ol’ga Bay, and from Valentin Bay to Proselochnaya Bay. Historical and Late Holocene paleotsunamis, the traces of which were found in the sections, were presumably the larger scale events than known tsunamis of the 20th century. The grain-size composition of the tsunamigenic deposits was analyzed, their similarity with and difference from the other coastal-marine facies were established, and the source areas of the material were determined. The age of the events, the height of the wave runups, and the length of the flood zones on the coastal areas with different geomorphology were determined. The obtained data may serve as the first step for compiling a geological record of tsunamis for the northwestern Sea of Japan.

Chronology of Tsunamis Documented in Sections of the Coastal Lowlands in East Primorye

One of the fields in the study of how catastrophic events are manifested is investigation of sediments produced by historical and paleotsunamis. This infor� mation allows researchers to define the age, scale, and frequency of these events in the past. These studies are especially topical for the coasts of the Russian Far East where chronicles have provided almost no evidence and instrumental observations have been carried out only since the second half of the 20th century (1, 2). The longterm works on studying paleotsunamis have been being carried out in the Kuril-Kamchatka Region (3-5), but there are no data on the sediments of the historical and paleotsunamis for the continental coast of the Sea of Japan until the recent time. The Primorye is located in the rare seismoactive zones of Russia, and although most earthquakes in this region are deep focus ones, some strong shallow earthquakes of 5-7 in magnitude have been reported (6). Large tsu� namis in the region are related to the earthquakes whose epicenters are clustered along the narrow band of the shelf and submarine slope of the island of Japan, stretching to Moneron Island (2). Four large tsunamis were reported here during the 20th century: in 1907, 1940, 1983, and 1993; the effects of the last two events were investigated on the coasts of Primorye immedi� ately after the tsunami struck (1, 7, 8). The effects of these tsunamis on the natural and economic objects located in the coastal zone were also assessed, and the zonation of coasts in terms of tsunami hazard was car�

The Eruptions of Sarychev Peak Volcano, Kurile Arc: Particularities of Activity and Influence on the Environment

More then 68 quaternary volcanic edifices are picked out in the Kurile Islands, among them 36 are active and potentially dangerous. During 45 thousand years not less then 12 large explosive eruptions, connected with the formation of the calderas, have occurred. During these eruptions a great amount of ash emitted and large pumice-pyroclastic covers formed, that caused the climate and landscape changes (Melekestsev et al., 1988).

Middle Pleistocene Warming Phase Based on the Deposits of a Buried Oyster Reef, Southern Lesser Kuril Islands

376 Information about manifestation of a warming phase in geological history is of great interest from the viewpoint of estimating the tendencies of environ� mental evolution under climate changes of recent decades. The Middle Pleistocene climate rhythmicity in the southern Russian Far East has been studied studied fragmentarily. However, the Pleistocene is characterized by a series of remarkable warmings, whose variations, intensity, and time spans need to be investigated. Middle Pleistocene paleoclimatic recon� structions have been made for Primorye, Sakhalin, and Chukotka [1–4]. For the Kuril Islands, the depos� its of this age have been studied poorly and the results obtained are quite ambiguous. This is related to poor preservation of the sedimentary covers in small island territories due to erosion during the subsequent trans� gressions, high dynamicity of the islands, intensive volcanism, and other factors. The main objects of paleoreconstructions are the deposits of coastal swamped lowlands; these deposits are characterized by frequent facies changes and poor preservation. Strati� graphically sound constructions of the Middle Pleis� tocene have been made for the Greater Kuril Islands, where deposits of two transgressions (MIS�11 and MIS�9) [5] were distinguished on Kunashir Island; on Iturup Island, the Middle Pleistocene is represented