Petaloid organs preserved in an arctic plant macrofossil assemblage from full-glacial sediments in southeastern Minnesota

A small suite of plant macrofossils indicates that southeastern Minnesota s upported subarctic to arctic vegetation 18,700 yr B.P. Fossil tepals of Pol ygonum viviparum are exceptionally web preserved; they occur with more frag mentary remains of Dryas integrifolia, Vaccinium uliginosum var. alpinum, a nd probable species of arctic Salix, S. cf. herbacea, and S. cf. arctica. T he pollen spectrum from this site is dominated by Picea, Pinus, and Cyperac eae, which are typical of midwestern full-glacial sequences. Tundra-like co nditions with permafrost were present in southeastern Minnesota during full -glacial time. Local environments 18;700 yr B.P. reconstructed from both ph ysical and paleobotanical evidence include wind-swept ridge tops with thin loess, outcrops of dolostone and sandstone on valley walls, colluvial slope s, sandy to gravelly floodplains, shallow ftoodplain pools, wet meadows, an d peaty turfs, all in a treeless or nearly treeless environment. (C) 1999 U niversity of Washington.