THE CONTRIBUTION OF LUMINESCENCE DATING TO THE CHRONOLOGY OF THE LATE QUATERNARY DEVELOPMENT OF THE ST. LAWRENCE RIVER DRAINAGE SYSTEM

Major developments have been achieved in the application of luminescence dating methods to sediments in the last 10 years. Among those that might have a definite impact on the chronology in the Late Quaternary are (1) the possibility to evaluate ages from single mineral grains; this allows for the detection of those grains that have been properly bleached before deposition and hence the assessment of the true age of the sediment being dated, (2) the development of a single aliquot dating technique based on regeneration and correction for sensitivity changes, termed SAR, that decreases analytical uncertainties to ca. 3–5 %, a definite improvment over the earlier commonly reported 5-10%, and (3) the emergence of laboratory corrections for the occurrence of anomalous fading in feldspar minerals, these being particularly reliable for sediments of the last 50 ka. These new techniques are being applied to a suite of Late Quaternary sediments from Southern Québec. The samples being selected are mostly beach and eolian sediments, presumed to best represent the sequence of deglaciation and inception of surface drainage in the St. Lawrence River basin. Lateglacial ice-marginal lakes from the Appalachian area, marine Champlain Sea beaches, Lake Lampsilis and transitional proto-St.Lawrence deltas and overlying dunes, and Late Holocene sediments from Lake St.Pierre are being analyzed. The long-term objective of this investigation is to develop a calendar time scale for the Late Quaternary event-stratigraphy framework of Southern Québec that could be extended to adjoining areas of New England and Eastern Canada.