THE ROLE OF LATE-GLACIAL ICE STREAMING IN THE DEGLACIATION OF JAMES BAY

The role of late glacial ice streaming in the deglaciation of James Ba y. During the last 1000 to 1500 years preceding Tyrrell Sea transgress ion at about 8 ka, large quantities of ice disappeared from the Labrad or Sector of the Laurentide Ice Sheet in the Hudson Bay basin. The ons et of this period of rapid deglaciation coincides with the formation o f southwestward flowing ice streams, the existence of which has been d emonstrated in northwestern Ontario. New ice-flow and glacial transpor t data in the Abitibi and James Bay regions indicate that the early do minant SW flow from the Labrador Sector was gradually deflected to the SSE, as far south as southern Abitibi due to the thinning of the ice sheet and the northward progression of Lake Barlow-Ojibway. This major shift in ice-flow direction which took place sometime after 9.5 ka, m arks the beginning of accelerated ice flow in the James Bay corridor w hich led to the formation of an ice stream followed by surges, and the intensive production of icebergs in northern Abitibi shortly before t he drainage of Lake Ojibway into Tyrrell Sea at about 8 ka. The James Bay ice stream flowed to the SSE and cut across an earlier southwestwa rd ice flow indicated by striations and the orientation of landforms o n both sides of James Bay. Its formation preceded the Cochrane surges (8.3 ka) by a few hundred years at the most. Deglaciation of the north ern half of James Bay was rapid, possibly catastrophic, following a sh ort-lived Lake Ojibway transgression in southeastern Hudson Bay. The n ew ice-flow and glacial transport data presented here led to the quest ionning of measurements and interpretation regarding ice-flow chronolo gy reported by previous investigators to explain the deglaciation of J ames Bay.