Abstract
Abundant beetle fossil assemblages including eight species of donaciine beetles (Chrysomelidae : Donaciinae) were found from the Holocene alluvial sediments at the Daibu archeological site (Jomon Period to Recent) in Washima-mura, Santo-gun, Niigata Prefecture, Japan.The strata of the site are composed of seven depositional facies : (1) clay ; (2) silt-very fine sand ; (3) massive peaty silt ; (4) laminated peaty silt ; (5) peat ; (6) peaty silt-very fine sand ; (7) sandy peat. The species composition of the donaciine fossils is closely related with these facies. The donaciine fossils are rare in the (1) clay, (2) silt-very fine sand, and (7) peaty sand facies. (3) Massive peaty silt, (4) laminated peaty silt, and (5) peat facies yield abundant remains of Plateumaris sericea and Plateumaris constricticollis. On the other hand, (6) peaty silt-very fine sand facies yields abundant remains of Donacia provosti and Donacia ozensis. The donaciine beetles live in marshy environments and they cat aquatic plants. Compared with habitats of the modern donaciine beetles, I recognized eight donaciine associations, which might correspond with peculiar paleoenvironments.Stratigraphic paleoenvironmental change is presumed in this site based on the donaciine associations, other beetle fossils, plant macrofossils and depositional facies. The lowest A zone (Late to latest Jomon Period : ca. 3, 200-2, 500 yrs BP) was deposited under the influence of streams. The middle B zone (Latest Jomon Period : ca. 2, 500 yrs BP) had still water environments accompanied with floating-leaved plants of Trapa and Nuphar. The uppermost C zone (Latest Jomon to Edo Period : ca. 2, 500-300 yrs BP) was represented by swamp accompanied with hydrophytes of reeds and sedges, and areas of still water accompanied with emergent plants.
