Palynostratigraphy and Th/U ages of upper Pleistocene interglacial and interstadial deposits on Cape Breton Island, eastern Canada

On Cape Breton Island (Nova Scotia), near the margin of the Wisconsinan ice sheet, karst depressions in Mississippian gypsum-bearing rocks contain interglacial and interstadial organic-rich deposits. Three palynostratigraphic units have been observed and tentatively dated by Th/U measurements on embedded fossil wood. The first, dated at ca. 125 ka, may be assigned to the oceanic /sup 18/O substage 5e; thermophilous forests (Quercus, Ostrya, pinus strobus) developed in response to a climate warmer than the present. The second unit, rich in Abies balsamea pollen and dated at ca. 87 ka, may relate to the /sup 18/O substage 5a; it reflects a cool and wet climate not unlike that of today. The third unit probably spans part of the mid-Wisconsinan (/sup 18/O stage 3); it shows alternating boreal forest-tundra forest assemblages indicative of climatic oscillations during a generally cold interval.