Palynology of a 250-m core from Lake Biwa: a 430,000-year record of glacial-interglacial vegetation change in Japan

Lake Biwa is situated in western Honshu, and is the largest and oldest fres hwater lake in Japan. During 1982-1983, a long core was drilled to a bottom depth of 1422 m in order to investigate the palaeolimnological record, whi ch contains 911 m of various sedimentary units overlying Palaeozoic-Mesozoi c basements. A 249.5-m core of the uppermost bed (T Bed) was palynologicall y examined at intervals of ca. 2 m. The investigated part of the core cover s approximately the last 430,000 years of the mid-Upper Pleistocene and Hol ocene, and five glacial-interglacial cycles can be recognized. Ten major ve getational zones could be recognized from the bottom to the surface. The zo nes bearing even numbers, BW-10, 8, 6, 4 and 2, matched glacial periods in which pollen of subarctic taxa (Pinaceae, Betula) and cool-temperate taxa ( Fagus, Lepidobalanus) was dominant. In the glacial periods, high pollen val ues for temperate conifers such as Cryptomeria, Cupressaceae and Sciadopity s indicate interstadial periods. Zones bearing odd numbers, BW-9, 7, 5, 3 a nd 1, matched interglacial periods with high pollen values for the warm-tem perate taxon Cyclobalanopsis, or showed the characteristic appearance of La gerstroemia, and temperate coniferous taxa (Cryptomeria, Cupressaceae). The re were two vegetational types in the interglacial periods. One was the typ e indicated by BW-9 and 1 zones, when warm-temperate evergreen broad-leaved trees such as Cyclobalanopsis and Castanopsis showed high pollen values, a nd the warm-temperate deciduous broad-leaved tree Lagerstroemia was lacking . The climate of these interglacial periods seems to have been cold and dry in winter, and warm and wet in summer. The other was the vegetational type recorded in BW-7, 5 and 3 zones, where Lagerstroemia showed low pollen val ues, and the warm-temperate evergreen broad-leaved trees mentioned above we re poorly represented. The climate seems to have been mild and wet in winte r, and cool and wet in summer. The dominant pollen values far cool-temperat e deciduous broad-leaved taxa such as Fagus and Lepidobalanus are very impo rtant indicators of the initiation of both glacial and interglacial periods in western Japan. (C) 1999 Elsevier Science B.V. All rights reserved.