A conceptual model of the deglaciation of Atlantic Canada

We present a conceptual model for the deglaciation of Atlantic Canada in which a role is played by ice streams. The ice margin lay close to the edge of the continental shelf at the last glacial maximum. Ice streams occupying shelf troughs comprised: (1) a major ice stream in the Laurentian Channel; (2) secondary streams in the Bay of Fundy/Gulf of Maine, Trinity Trough and Notre Dame Channel; and (3) lesser ice streams elsewhere. Early retreat in the northeast (Notre Dame Bay) and in the southwest (Bay of Fundy/Gulf of Maine) was mainly by calving along embayments. By 18 ka (radiocarbon years) a calving embayment had opened on Emerald Basin (Scotian Shelf). Retreat along channels marooned ice on intervening banks. A major calving episode beginning just before 14 ka removed ice from the Gulf of St. Lawrence, triggering re-advances down secondary troughs. Isolation of a Newfoundland ice cap produced radial drainage via fiords and more extensive flow into the St. George's Bay lowlands on the west coast. By 13 ka most ice was on land, and was ablating by melting rather than calving. Shelf ice caps persisted until 11 ka.