Abstract
The vegetation and environment in the middle Pleistocene in and around Hata, Takashima City, Shiga Prefecture, central Japan were reconstructed based on a plant macrofossil assemblage from the Hata Formation, Kobiwako Group. This assemblage composed mainly of fossil fruits and seeds included 20 genera and 17 families of 23 deciduous broad-leaf tree taxa, and 18 genera and 16 families of 27 herbaceous taxa. Conifers and evergreen broad-leaf trees were absent, and Alnus japonica, the most dominant taxon, amounted to 36.7 % of the total. Other major components were Styrax sp., Rubus, Mosla dianthera, and Carex including sections Carex and Praecoces. Cyclocarya, the only extinct taxon from Japan among the total 50 taxa, occurred from the uppermost horizon in the Kobiwako Group so far reported. The sedimentary facies of the peaty silt including the fossil assemblage was without any ripples or lamina and indicated sedimentation of a relatively autochthonous assemblage in a stagnant water in the backmarsh of a river. Thus, aquatic vegetation of Trapa and wetland forests of Alnus must have occupied the backmarsh, surrounded by mesic deciduous broad-leaved forests.
