The DeKalb mounds of northeastern Illinois as archives of deglacial history and postglacial environments

B. Brandon Curry, Michael E. Konen, Timothy H. Larson, Catherine H. Yansa, Keith C. Hackley, Helena Alexanderson, Thomas V. Lowell

Research output: Contribution to journalArticle

Abstract

The "type" DeKalb mounds of northeastern Illinois, USA (42.0°N, -88.7°W), are formed of basal sand and gravel overlain by rhythmically bedded fines, and weathered sand and gravel. Generally from 2 to 7. m thick, the fines include abundant fossils of ostracodes and uncommon leaves and stems of tundra plants. Rare chironomid head capsules, pillclam shells, and aquatic plant macrofossils also have been observed.Radiocarbon ages on the tundra plant fossils from the "type" region range from 20,420 to 18,560. cal. yr BP. Comparison of radiocarbon ages of terrestrial plants from type area ice-walled lake plains and adjacent kettle basins indicate that the topographic inversion to ice-free conditions occurred from 18,560 and 16,650. cal yr BP. Outside the "type" area, the oldest reliable age of tundra plant fossils in DeKalb mound sediment is 21,680. cal yr BP; the mound occurs on the northern arm of the Ransom Moraine (-88.5436°W, 41.5028°N). The youngest age, 16,250. cal yr BP, is associated with a mound on the Deerfield Moraine (-87.9102°W, 42.4260°N) located about 9. km east of Lake Michigan. The chronology of individual successions indicates the lakes persisted on the periglacial landscape for about 300 to 1500 yr.

Original languageEnglish (US)
Pages (from-to)82-90
Number of pages9
JournalQuaternary Research
Volume74
Issue number1
DOIs
StatePublished - Jul 1 2010

Keywords

  • Deglaciation
  • Ice-walled lake
  • Ostracode
  • Pingo
  • Plant macrofossil

ASJC Scopus subject areas

  • Arts and Humanities (miscellaneous)
  • Earth-Surface Processes
  • Earth and Planetary Sciences(all)

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