North American Glaciation Finally Dated
Paul bristolia at yahoo.com Fri Nov 14 12:12:57 EST 2008
People, who work with Quaternary meteorite impacts should
know that the age and duration of the Illinoian (“glacial”)
Stage has finally been directly determined in its type
region by the Illinois State Geological Survey. As a part
of research associated with geological mapping in north-central Illinois, they recovered cores that sampled the the full
thickness of Illinoian glacial tills (Glasford Formation)
and outwash (Pearl formation) lying within an ancient buried
valley of the Mississippi River. Using optically stimulated
luminescence (OSL) dating, they were able to date Illinoian
glacial outwash overlying and interbedded with Illinoian
glacial tills. Using OSL dating, they also dated glacial
outwash underlying the oldest Illinoian glacial till, the
Kellerville Till Member, comprising the glacial sediments
that define the Illinoian Stage.
The Illinois State Geological Survey found was that the
glacial sediments, which comprised the Illinois glacial lobe,
all accumulated over a period of time between 130,000 to
200,000 years ago. Because these sediments define the
Illinoian Stage, it is approximately equivalent in time to
Marine Isotope Stage (MIS) 6 instead of Marine Isotope
stages 6, 7, and 8 together, a period of time from 130,000
to 300,000 BP, as previously hypothesized. Based upon
this research, the geologists at the Illinois State Geological
Survey now infer that the Yarmouth Geosol (paleosol), which
underlies Illinoian glacial sediments that buried it, was
created by weathering of older glacial deposits from about
191,000 to 424,000 years ago during a period of geologic
time equivalent to Marine Isotope stages 7, 8, 9, 10, and
11.
An article, abstract, and powerpoint presentation about the
OSL dating of the Illinoian Stage are:
(1.) McKay, E.D., 2007, Six Rivers, Five Glaciers, and an Outburst
Flood: the Considerable Legacy of the Illinois River. Proceedings
of the 2007 Governor's Conference on the Management of the
Illinois River System: Our continuing Commitment, 11th Biennial
Conference, Oct. 2-4, 2007, 11 p.
http://ilrdss.sws.uiuc.edu/govconf2007/session2a/DonMcKay.pdf(2.) McKay, E.D., and R.C. Berg, 2008, Optical ages spanning
two glacial-interglacial cycles from deposits of the ancient
Mississippi River, north-central Illinois. Geological Society of
America Abstracts with Programs, Vol. 40, No. 5, p. 78
Abstract at:
http://gsa.confex.com/gsa/2008NC/finalprogram/abstract_137641.htm(3.) Powerpoint presentation at:
http://gsa.confex.com/gsa/viewHandout.cgi?uploadid=295In addition, it has been about a quarter of a century since
North American geomorphologists and Quaternary geologists
abandoned the climatic and chronological framework used by
early geomorphologists and Quaternary geologists to subdivide
glacial and nonglacial deposits within north-central United States
into four glacial and interglacial stages. About a quarter of a
century ago, the accumulation of stratigraphic and chronological
data discredited the Yarmouthian (interglacial), Kansan (glacial),
Aftonian (interglacial), and Nebraskan (glacial) stages as being
scientifically meaningless as either climatic, stratigraphic, or
chronostratigraphic subdivisions of the Pleistocene. As a result,
the use of these stages to classify north American Quaternary was
abandoned and they were all merged into the Pre-illinoian Stage.
For further reading about why the Nebraskan, Aftonian, Kansan,
and Yamouthian stages were abandoned by North American
geomorphologists and Quaternary geologists as antiquated and
meaningless nomenclature, a person can read:
Aber, J.S., 1991, Glaciations of Kansas. Boreas. vol. 20, no. 4,
pp. 297-314.
Boellstorff, J., 1978, Chronology of some Late Cenozoic deposits
from the central United States and the Ice Ages. Transactions of
the Nebraska Academy of Science. vol 6, pp. 35–49.
Hallberg, G.R., 1986, Pre-Wisconsin glacial stratigraphy of the
Central Plains region in Iowa, Nebraska, Kansas, and Missouri,
Quaternary Science Reviews. vol. 5, pp. 11-15.
Richmond, G.M. and D.S. Fullerton, 1986, Summation of Quaternary
glaciations in the United States of America. Quaternary Science
Reviews. vol. 5, pp. 183-196.
Roy, M., P.U. Clark, R.W. Barendregt, J.R., Glasmann, and R.J.
Enkin, 2004, Glacial stratigraphy and paleomagnetism of late
Cenozoic deposits of the north-central United States, Geological
Society of America Bulletin. vol. 116, no. 1-2; pp. 30-41;
DOI: 10.1130/B25325.1
The PDF file for Roy et al. (2004) can be found at:
http://geo.oregonstate.edu/people/faculty/publications/clarkp/Royetal-GSAB-2004.pdf
Stiff, B. J., and A.K. Hansel, 2004, Quaternary glaciations in Illinois. in Ehlers, J., and P.L. Gibbard, eds., pp. 71-82, Quaternary Glaciations: Extent and Chronology 2: Part II North America, Elsevier, Amsterdam. ISBN 0-444-51462-7
A nice summary of the relationships between the North American,
English, and European Pleistocene stratigraphic nomenclature can
be found in “Global correlation tables for the Quaternary” at;
http://www.quaternary.stratigraphy.org.uk/correlation/chart.htmland McMillan, A.A., 2005, A provisional Quaternary and Neogene
lithostratigraphic framework Great Britain, Netherland Journal of
Geosciences. vol. 84, n0. 2, pp, 87-107.
It can be found at:
http://www.njgonline.nl/publish/articles/000245/article.pdfhttp://nora.nerc.ac.uk/680/I have written more about the North American Quaternary stages
for Wikipedia at:
1. Illinoian Stage
http://en.wikipedia.org/wiki/Illinoian_Stage2. Pre-Illinoian Stage
http://en.wikipedia.org/wiki/Pre-Illinoian_Stageand 3. Kansan glaciation
http://en.wikipedia.org/wiki/Kansan_glaciationThese pages have references and links to PDF files that
a person can freely download.
Yours,
Paul H.
