Fiona MacDonald

Peggy's Cove region is ideal for estimating paleo ice margin retreat due to the high density of large (>2m) quartz bearing boulders in the area, for estimating glacial erosion rates, and is strategically situated near the coast so glacial chronology will help provide a link between marine and terrestrial chronologies. Seven boulders and four bedrock surfaces were sampled for exposure dating, and a surficial geology map with ice flow direction was determined for the area. The hypothesis (H) and question (Q) asked were; (H) The boulders on bedrock ridges near Peggy's Cove represent an ice marginal retreat between 17 to 15.9"0.3 kyr; and (Q) What is the effectiveness of glacial erosion on the Halifax Pluton during the Wisconsinan glaciation? Exposure dating using 10Be, a cosmogenic nuclide was used to estimate the exposure age of the boulders, and a comparison of the concentrations of 10Be in the boulders and bedrock surfaces lead to a simple glacial erosion model. The results of exposure dating showed a remarkable agreement between the terrestrial cosmogenic nuclide (TCN) exposure ages of the boulders, and calibrated marine and terrestrial 14C dates. The weighted mean age of 6 boulders (excluding one outlier) indicates an ice marginal retreat at 16.4 + 2.8 ka. Snow cover and erosion have probably had less than a 1% effect, and we assume continuous exposure since initial deglaciation. The ages imply that the ice was gone before the Younger Dryas, and ice flow readings indicate an ice flow direction of southwestern and southeastern, which is consistent with recent literature for the area. The glacial erosion on the streamlined ridges ranges from 0 to 2.6 m or 0 to 4.5 cm/kyr.

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Pages: 123
Supervisor: John Gosse