Title Chronological framework for the deglaciation of the Lake Michigan Lobe of the Laurentide ice sheet from ice-walled lake deposits
Author Curry, B.; Petras, J.
Author Affil Curry, B., University of Illinois at Urbana-Champaign, Illinois State Geological Survey, Champaign
Source JQS. Journal of Quaternary Science, 26(4), p.402-410, . Publisher: John Wiley and Sons for the Quaternary Research Association, Chichester, United Kingdom. ISSN: 0267- 8179
Publication Date May 2011
Notes In English. 32 refs. GeoRef Acc. No: 310650
Index Terms radioactive age determination; carbon isotopes; glacial deposits; isotopes; lacustrine deposits; lake deposits; paleoclimatology; Pleistocene; Quaternary deposits; radioactive isotopes; sediments; United States--Illinois--Kendall County; United States--Illinois--Newark; absolute age; Angiospermae; C-14; carbon; Cenozoic; deglaciation; Dicotyledoneae; glacial environment; glaciolacustrine environment; Illinois; Kendall County Illinois; lacustrine environment; Lake Michigan Lobe; lake sediments; Laurentide ice sheet; lithostratigraphy; Newark Illinois; paleoenvironment; Plantae; Quaternary; Salix; Salix hervacea; Spermatophyta; United States; upper Pleistocene
Abstract A revised chronological framework for the deglaciation of the Lake Michigan lobe of the south-central Laurentide Ice Sheet is presented based on radiocarbon ages of plant macrofossils archived in the sediments of low- relief ice-walled lakes. We analyze the precision and accuracy of 15 AMS 14C ages of plant macrofossils obtained from a single ice- walled lake deposit. The semi-circular basin is about 0.72 km wide and formed of a 4- to 16-m-thick succession of loess and lacustrine sediment inset into till. The assayed material was leaves, buds and stems of Salix herbacea (snowbed willow). The pooled mean of three ages from the basal lag facies was 18 27050 14C a BP (21 810 cal. a BP), an age that approximates the switch from active ice to stagnating conditions. The pooled mean of four ages for the youngest fossil-bearing horizon was 17 77040 14C a BP (21 180 cal. a BP). Material yielding the oldest and youngest ages may be obtained from sediment cores located at any place within the landform. Based on the estimated settling times of overlying barren, rhythmically bedded sand and silt, the lacustrine environment persisted for about 50 more years. At a 67% confidence level, the dated part of the ice-walled lake succession persisted for between 210 and 860 cal. a (modal value: 610 cal. a). The deglacial age of five moraines or morainal complexes formed by the fluctuating margin of the Lake Michigan lobe have been assessed using this method. There is no overlap of time intervals documenting when ice-walled lakes persisted on these landforms. The rapid readvances of the lobe during deglaciation after the last glacial maximum probably occurred at some point between the periods of ice-walled lake sedimentation. Abstract Copyright (2010), John Wiley & Sons, Ltd.
URL http://hdl.handle.net/10.1002/jqs.1466
Publication Type journal article
Record ID 66000023