The three sections, Don Valley Brickyard, Scarborough Bluffs and Bomanville Bluffs on north-shore of Lake Ontario, are the longest and thickest Quaternary terrestrial sediments in northeastern North America and a relatively complete record of the evolution of the Laurentide Ice Sheet since late Pleistocene. Reconstruction of the evolution has to be depended on the accurate absolute dates of the key units from these reference sections. The established stratigraphic chronology framework has been based mainly on limited ~(14)C and luminescence (TL and IRSL using multiple-mineral technique) ages, diamictons interpreted as till representing ice advance that was controlled by climate change, and comparison with marine oxygen isotope stages. However, there is great uncertainty because well-preserved organic materials were difficult to find in glacial sediments and ~(14)C dating range is limited to the last 50 ka. The thermoluminescence ages reported in the 1980s and 1990s are conflicting. Feldspar infrared stimulated luminescence ages reported recently focused on a sublayer of Bowanville Bluffs section only and with no ages for other units. Thus, the stratigraphic chronology of these classic sections remains unclear. Quartz optical stimulated luminescence, that has advantages over ~(14)C, feldspar TL and feldspar IRSL dating by directly defining the timing of deposition and quartz is more rapidly bleached than feldspar, has been widely applied to a wide range of Quaternary sediments as a result of rapid technical developments. Here a review of the Late Pleistocene chronology is tried to provide for the Laurentide Ice Sheet in the Great Lakes of North America, and also two quartz OSL ages for a key unit stratigraphy. The two ages were dated using SAR-SGC protocol (using large aliquot) on two samples from Glaciofluvial Sand unit of Bowmanville Bluffs section. The results are (41.63.8) ka and (48.14.4) ka, indicating it deposited in MIS 3. Further OSL dating using small aliquot or single grain are required to refine the chronology.
1.中国科学院寒区旱区环境与工程研究所, 冰冻圈科学国家重点实验室 2.生物地质与环境地质国家重点实验室, 兰州, 甘肃 730000, 中国 3.中国地质大学(武汉), 生物地质与环境地质国家重点实验室 4.冰冻圈科学国家重点实验室, 武汉, 湖北 430074, 中国 5.Department of Environmental, Earth and Ocean Sciences, University of Massachusetts at Boston, Boston, 730000, USA