CGRG Bibliography of Canadian Geomorphology
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Author : Eyles, N.; and Schwarcz, H. P.
Date : 1991
Title : Stable isotope record of the glacial cycle from lacustrine ostracodes.
Publication : Geology
Issue : 19(3):
Page(s) : 257-260
Abstract
The stable isotopic (delta-O-18, delta-C-13) composition of freshwater microcrustaceans (ostracodes) is presented for a long (100 m) sequence of late Pleistocene glaciolacustrine sediments at Toronto, Canada. This section may span a substantial part of the last (Wisconsin) glacial cycle from the close of the last (Sangamon) interglacial (oxygen isotope stage 5) to the glacial maximum after 25 ka (O-isotope stage 2). A well-defined secular trend in both delta-O-18 and delta-C-13 for two benthic ostracode species Candona subtriangulata and Candona caudata contained in these early and middle Wisconsin sediments records the increasing contribution of glacial meltwater to the basin; isotopically lightest ostracodes (delta-O-18 = 17 parts- per-thousand) are toward the top of the glaciolacustrine stratigraphy immediately below the erosive base of a late Wisconsin till. In the last stages of the lake, delta-O-18 of the lake water ranged between -17 parts-per-thousand and -21 parts-per-thousand, implying that the lake consisted of between 35% and 55% glacial meltwater. Consistent differences in isotope values for the two ostracode species suggest an isotopically stratified lake and confirm modern ecological data that the two species have different depth preferences. This study provides important information regarding the isotopic composition of meltwaters from the Laurentide ice sheet and may ultimately help constrain the relation between ice volume over the North American continent and delta-O-18 of sea water. This study confirms other glacial geologic data from midcontinent North America which indicate that the maximum regional extent of the Laurentide ice sheet was attained after 25 ka within oxygen isotope stage 2.
Bibliography of Canadian Geomorphology