GLACIAL GEOLOGY OF PEGGY'S COVE REGION

Precisely documenting glacier ice volume, geometry, and the timing and rate of ice marginal retreat in Atlantic Canada is important for the reconstruction of past climate changes, and understanding lithospheric responses to sudden glacier loading and unloading. Paleo-ice cover in the Peggy’s Cove region streamlined the granodioritic bedrock into stoss-lee ridges and deposited large granodioritic boulders. The ice is thought to have persisted until 11.0 kyr (non-calibrated ¹⁴C) (Stea & Mott, 1998), or 13.1 to 12.8 kyr calibrated ¹⁴C. Cosmogenic ¹⁰Be and ²⁶Al produced in situ in quartz will be used to determine the deglacial history and net glacial erosion thickness in the Peggy’s Cove region. Seven ideal granodioritic boulders are sampled. The boulders have very large diameters (> 2m), have horizontal (2p) surfaces, experienced no vegetation cover, have little probability of snow cover, have not rolled since deposition, and exhibit weak indications of weathering. Four bedrock samples with similar exposure attributes are taken adjacent to four sampled boulders. The concentrations of cosmogenic nuclides in quartz provide a means of estimating the duration of exposure since deglaciation to within 1 kyr (total uncertainty, 1s). Combined with a glacial geology map compiled at 1:20,000, the results will help determine the timing and rate of ice marginal retreat, sea level involvement, and paleoclimate influences. The total thickness of bedrock removed from the streamlined ridges will be calculated by reducing the data from the accelerator and comparing the ¹⁰Be and ²⁶Al concentrations of the boulders and adjacent bedrock surfaces. An advantage of the study area is that the exposure ages will help tie the terrestrial record of glaciation to the offshore glaciation record for the region.