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

Author:
  • B. Brandon Curry
  • Michael E. Konen
  • Timothy H. Larson
  • Catherine H. Yansa
  • Keith C. Hackley
  • Helena Alexanderson
  • Thomas V. Lowell
Publishing year: 2010
Language: English
Pages: 82-90
Publication/Series: Quaternary Research
Volume: 74
Issue: 1
Document type: Journal article
Publisher: Academic Press

Abstract english

The "type" DeKalb mounds of northeastern Illinois, USA (42.0 degrees N, -88.7 degrees 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 degrees W, 41.5028 degrees N). The youngest age, 16,250 cal yr BP, is associated with a mound on the Deerfield Moraine (-87.9102 degrees W, 42.4260 degrees 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. (C) 2010 University of Washington. Published by Elsevier Inc. All rights reserved.

Keywords

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

Other

Published
  • ISSN: 0033-5894
Helena Alexandersson
E-mail: helena [dot] alexanderson [at] geol [dot] lu [dot] se

Professor

Quaternary Sciences

+46 46 222 44 83

435

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Aeolian sand project

Project members
Members of the aeolian sand project: Martin Bernhardson, Sara Florén, Edyta Kalińska-Nartiša and Helena Alexanderson.

Read more about the project here.