CGRG Bibliography of Canadian Geomorphology
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Author : Barendregt, R.W.; and Duk-Rodkin, A.
Date : 2003.
Title : Chronology and extent of Pleistocene glaciers and ice sheets in western North America: a magnetostratigraphic assessment.
Publication : Geoscience Horizons. 2003 Geological Society of America Annual Meeting & Exposition. November 2-5, 2003. Washington State Convention & Trade Center, Seattle, Washington.
Issue :
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Abstract
Studies of Oxygen 18 isotope and calcium carbonate content in cores from the deep ocean, and the presence of ice-rafted debris in cores taken from continental margins have long suggested that earth's past climate has experienced cold periods, some of which produced extensive glaciation on land. While oceanographers have provided evidence for well over 100 such cold periods in the past 3.0 million years, many of which clearly point to periods of ice sheet development, the terrestrial record initially suggested only relatively few glaciations. With appropriate sampling and analytical techniques polarity data can be obtained from glacial tills as well as from altered sediments such as paleosols, and these can be assigned to the Chrons and subchrons of the global Geomagnetic Polarity Timescale. Combined with tephrochronology, palynology, and other proxy records of paleoclimate, magnetostratigraphy has proven to be a valuable tool in modeling the timing and extent of ice sheet development in the Late Cenozoic. It has been in particular, the contribution of magnetostratigraphy which has provided timelines for glacial and interglacial events of the past 3.0 million years, and assigned sediments to the 3 Chrons and 4 subchrons of this period. In 1998 Barendregt and Irving reconstructed the distribution and extent of ice sheets in western North America based on available paleomagnetic data. Their map showed marked differences between the Matuyama and Brunhes Chrons. Recent work completed in northern Canada and Alaska has yielded magnetochron and subchron ages of tills, intertill beds, and preglacial sediments and has provided considerable refinement of ice sheet dimensions and timing of glaciations in Northwestern North America. In the absence of absolute dating tools, magnetostratigraphy affords a valuable means of assigning terrestrial ice age deposits to the geological timescale, and most importantly, allows a correlation to the more complete marine record. The distribution and timing of past ice sheets will undoubtedly become better defined with future magnetostratigraphic work.
Bibliography of Canadian Geomorphology