Reconstructing the last Newfoundland Ice Sheet (Part 1): Glacial geomorphology and ice-flow geometries

The former Newfoundland Ice Sheet occupied a sensitive position on the eastern margin of the Laurentide Ice Sheet and northwest Atlantic during the last glaciation, where it was exposed to interactions between regional ice-sheet configuration, ocean circulation, atmospheric forcing and sea-level change. Yet despite its importance, the internal flow geometry, divide migration and relative sequence of ice-flow reorganisation of the Newfoundland Ice Sheet remain poorly constrained. This limits its use as a palaeo-analogue for understanding the behaviour of smaller, marine-influenced ice sheets. Here we use glacial inversion and geomorphological mapping to reconstruct the ice-flow geometry and relative flow history of the Newfoundland Ice Sheet from an island-wide and inner-shelf landform record. The mapped dataset comprises ~162,000 landforms, including glacial lineations, ribbed moraines, eskers and moraines, integrated with ~11,300 bedrock striae measurements. Flowset analysis reduces this record to 190 distinct ice-flow configurations derived from glacial lineations, ribbed moraines and striae. Glacial lineation flowsets provide the primary glaciodynamic framework, while striae and ribbed moraine flowsets provide complementary constraints on flow direction, flow pathway and relative chronology. The resulting framework reveals a strongly multi-temporal ice-sheet bed, repeated reorganisation of ice-flow geometry, migration of dispersal centres, and contrasting basal conditions between northern and southern Newfoundland. These results show that the Newfoundland Ice Sheet was not characterised by simple radial flow from static dispersal centres, but by repeated reconfiguration of flow pathways, ice-divide positions and basal thermal regime through the last glacial cycle. Together with ice-marginal, offshore stratigraphic and chronological evidence, this flowset framework establishes the empirical basis for the reconstruction of ice-sheet growth, maximum configuration, retreat pattern and final decay presented in the companion Part 2 paper (McHenry and Dunlop, submitted).