Palaeo-Ice Sheet Reconstruction of the Former Newfoundland Ice Sheet, using the Glacial Landform Record and Cosmogenic Exposure Dating

The Newfoundland Ice Sheet (NIS), which formed part of the North American Ice Sheet Complex, was situated on the margins of the northeast Atlantic Ocean during MIS 2-4. Although all were confluent at the last glacial maximum, the NIS is known to have supported independent ice centres with advances from the Laurentide Ice Sheet being restricted to Newfoundland’s northwestern margin. Given its distinctive position, it is likely the evolution of the NIS through the last glacial cycle was influenced by a number of external and internal drivers including configuration changes in the Laurentide Ice Sheet, ice stream initiation and shutdown, shifts in oceanic and atmospheric circulation patterns and fluctuating sea levels. As such, Newfoundland is a key location for investigating ice sheet response to a number of internal and external forcing mechanisms during glacial cycles. An established technique for reconstructing former ice sheet behaviour is the mapping and spatial analysis of glacial landforms. This provides a valuable record of former ice sheet extent and behaviour through time as well as ice sheet retreat during deglaciation. Here we present new mapping based on our interpretation of SPOT satellite imagery and digital elevation models across Newfoundland and swath bathymetry from several locations offshore. Our new database consisting of ~150,000 individually mapped subglacial bedforms, which includes drumlins, crag and tails, glacially moulded bedrock lineations and ribbed moraines, significantly increases the known landform record in this region. The new database shows Newfoundland has a complex palimpsest landscape that records multiple ice cap events across the island. We report our attempt at unravelling this record using a glacial inversion approach and flowset analysis, which separates ice flow patterns into snapshots of ice sheet behaviour through time. This approach can be used to help establish relationships between ice cap behaviour and a range of forcing mechanisms. Initial analysis indicates the NIS was dynamic and susceptible to configuration changes throughout the last glacial cycle, including ice divide migration, regional configuration changes, ice stream activity and enhanced ice flow caused by marine drawdown. To enable greater radiometric control of the deglacial behaviour of the NIS, we report forty new cosmogenic exposure ages (10Be and 36Cl) from several sites around southeast Newfoundland. We aim to combine these new exposure ages with existing available cosmogenic records across Newfoundland to provide a temporally constrained reconstruction and deglaciation sequence to this ice sheet reconstruction.