POSTGLACIAL DEVELOPMENT OF A MAINE BOG AND PALEOENVIRONMENTAL IMPLICATIONS

Stratigraphic data on gross peat components, plant macrofossils, polle n, ash after ignition, and radiocarbon ages are used to reconstruct th e developmental history of the north unit of Caribou Bog in central Ma ine, which presently consists of a sparsely wooded, ombrotrophic (rais ed), center surrounded by extensive wooded fen. A lake existed from 12 500 to 8500 BP, when terrestrialization led to peatland initiation th roughout the basin within similar to 500 years. Near the center of the present peatland, limnic sedge fen developed to sedge fen at 8000 BP, and to Larix laricina wooded fen at 7000 BP. At 5500 BP the wooded fe n became Sphagnum dominated and sparsely wooded, a condition that has persisted at the peatland center. Only two early transitions are clear ly related to climate forcing. An abrupt shift from silt-clay to organ ic lake sediment similar to 10 400 BP is typical of basins throughout the region. This shift correlates with rapid changes in local and regi onal vegetation, and likely reflects increased biological productivity caused by a rapid warming of climate. Peatland initiation 8500-8000 B P coincides with a drop of water level, probably associated with a rap id shift to drier climate. We estimate that the water level around the peatland was at least 0.4 m above the present level at and before 850 0 BP, dropped at least 1.7 m (min. 1.4 m with correction for peat comp action) in the next 500 years, and rose to the present level around 70 00 BP or later. Major hydroseral changes after 8000 BP are asynchronou s at several coring sites and are not consistently correlated with reg ional paleoclimatic events. These changes were probably induced by aut ogenic hydrological processes associated with peat accumulation.