In axial shift vernacular Lake Winnipeg is a "back-exit lake". Due to an axis shift south roughly 10050 years ago, a lake, which I call Proto-Lake Winnipeg, backed up the Red River valley from Manitoba's Cross Lake sill until the two-outlet Lake Traverse-Cross Lake stage reached the 1100 foot contour in the Lake Traverse area. Initial drainage through the Big Stone Moraine into the Minnesota River valley was, however, via the Fish Creek channel northwest of Ortonville. At this point the upper Mississippi River system captured a large part of the Arctic watershed and funnelled water to the sea, which, at this time, reached up the valley to Keokuk, Iowa. When the shift halted rapid down-cutting of the Lake Traverse sill had dropped the lake roughly 70 feet. A subsequent shift north caused the water to back down the Red River valley behind the Lake Traverse sill and reconnect with the Cross Lake sill to form the second but lower Proto-Lake Winnipeg about 9600 BP. Another shift south (9150 BP) created the third Proto-Lake Winnipeg level shown here and whose outlet sill was at the 975-foot level in the Lake Traverse-Mud Lake area.
The shoreline profiles for these levels are shown in the following figure.
This satellite image (CCRS photo), which centres on the Winisk Lake area of northern Ontario, shows the distinct boundary between the Shield and the Hudson Bay Lowlands (NTS Map 43E). The various terrain patterns on this photo are readily seen by anyone flying in to the community of Webequie on Winisk Lake. The earth science literature ascribes the landscape depicted here as having been produced by the erosive power of continental glaciation. I accepted this for many years but am no longer convinced this is correct. I now believe the pattern displays the impact of water and floating ice in response to shifts of the Earth's axis. A number of such shifts are displayed on the photo. Note the abrupt change in direction in the upper left corner of the photo, which is centred around latitude 53 deg. 45 min. and longitude 87 deg 30 min.
One of the gaps in the watershed divide that was a strait in both the 10500 BP and the 9600 BP shifts was in the Mann Lake area in the White Otter River portion of the Pic River headwaters. The submersions of this sill filled the Pic River valley with extensive amounts of silt and silt. Neither water level filled the Superior basin as they did not reach Sault Ste. Marie. The accompanying figure shows the 10500 BP level terminating in Whitefish Bay at roughly 140 feet below the present lake level. The emerged sill between Nadoway Point and Gros Cap west of Sault Ste. Marie became the new watershed divide, which blocked water flow from the Lake Superior basin into the Huron/Michigan basin during both shifts. With the Superior basin water supply shut off the Huron/Michigan basin evolved into a system of small interconnected lakes (e.g., Lakes Hough and Stanley) and rivers that drained into a body of water that terminated at the eastern extremity of today’s Lake Huron (i.e., in the French River valley). In fact, these small lakes in the Huron basin flowed into a different arm of the same 10500 water body located on the other side of the Nadoway-Gros Cap sill. The arm or embayment was the Gulf of St. Lawrence, which was connected to the Hudson Bay portion by straits in the Kirkland Lake and Rouyn-Noranda area and whose water passed over the North Bay sill. This situation allowed forests to become established on the south side of the Superior basin floor and on the Michigan and Huron basin floors.