AGE AND DEVELOPMENTAL HISTORY OF IOWA FENS

C.A. Thompson and E.A. Bettis III


Iowa Department of Natural Resources, Geological Survey Bureau, 109 Trowbridge Hall, Iowa City, IA 52242-1319
Journal of the Iowa Academy of Science (in press)

ABSTRACT


Iowa fens are small, minerotrophic peatlands maintained by shallow groundwater. Eighteen fen sites located across northern Iowa were mapped and radiocarbon dated to assess the timing of initial peat accumulation. The radiocarbon ages span the Holocene, ranging from 1,240 to 10,900 B.P., however most fens postdate 5,000 B.P. The dominance of late-Holocene ages suggests that Holocene climatic change may have strongly influenced the record of peat accumulation. During the mid-Holocene Iowa was warmer and drier than at present, and peat was degraded or accumulated slowly in fens. The range of ages also implies that the commencement and subsequent rate of peat accumulation depends on local variations in landscape development and resultant hydrology.