Reconstruction of Environmental Conditions in the Eastern Part of Primorsky Krai (Russian Far East) in the Late Holocene

摘要

This paper examines a 115 cm long profile section of lacustrine-swamp sediments from the Langou I Bay (eastern part of Primorsky Krai; 44 degrees 25 ' 10.16 '' N, 135 degrees 54 ' 26.08 '' E). According to the produced age model, the sediments are 3900 years old. A multiproxy study involving geochemical, chironomid, diatom, and palynological analysis indicates that the climatic and environmental conditions on the seacoast in the eastern part of Primorsky Krai developed in many respects synchronously with known climatic phases of the Late Holocene. The period from ca. 4200 to 2600 cal years BP corresponds to the first and second warm stages of the Jomon period and the late Jomon transgression in Japan. The peak of summer temperatures in the vicinity of the Langou I Bay occurred between 2900 and 2600 cal years BP. The cooling that began after 2600 cal years BP was not as severe in the study area as in Japan (cold Jomon and Kofun stages): the reconstructed temperatures were 1 degrees C lower than now; in Japan, they were 2-3 degrees C below the current level. The Medieval Climate Optimum (Nara-Heian-Kamakura stage in Japan) reconstructed for the eastern part of Primorsky Krai in the period from 1250 to 750 cal years BP featured a humid climate with summer temperatures ca. 1.5 degrees C higher than at present. The period between 750 and 250 cal years BP correlates with the Little Ice Age: summer temperatures had dropped to 1.5-2 degrees C below the modern one. In the last 200 years, the lake has been shallowing and has nearly dried out. This period is marked by temperature fluctuations amid the trend of climate warming.