Lake Chippewa and Stanley formed as the North Bay outlet in Canada was exposed (as the ice withdrew from it).  This very low, isostatically-depressed outlet allowed the waters of Glacial Lake Algonquin to drain rapidly out to the east, lowering the water levels in the Lake Michigan-Huron basin over 300 feet.   The "plug was pulled" about 10,000 years BP.

ice-bdy-9-5k.GIF (108754 bytes)

dg-45.GIF (119992 bytes)

We know a lot about the Marquette readvance because it buried a forest bed at Gribben Lake.  These trees have been dated with radiocarbon methods and have been shown to be about 10,000 years old.  In 1999, another buried forest bed was discovered several miles to the east of Gribben Lake.  Michigan Tech researchers unearthed the trees, many of which were standing in place.  Here's part of that story:
About 10,000 years ago, as Ice Age glaciers thawed in what is now Michigan, a forest of spruce trees sprouted and flourished. Then, quickly, the forest died.  Preserved in rising water and sand, the ancient trees are giving scientists a remarkable look at the last time the world’s climate warmed rapidly and may offer compelling lessons for the present, when most experts believe the Earth is warming again.   Preliminary analysis of the tree rings suggests, for example, that sudden changes in climate may not always be detectable in advance.
    Scientists at Michigan Technological University learned of the discovery, at a nearby site where sand was being mined, by accident.  According to Theodore Bornhorst, of the university’s Department of Geological Engineering and Science, a professor overheard workers
talking about uncovering some buried trees. Scientists and students rushed to the site to find the tops of the trees sticking out of the sand pit, and the race was on to recover at least some of the trees before they were destroyed. Earthen dikes were built to keep water from flooding
the excavation as researchers carefully removed the sand. What they found was astonishing: five acres of ancient forest, still standing and nearly perfectly preserved, down to the moss on the limbs of the trees.
    “It looks very much like a forest you would find today near Hudson Bay,” says Professor Kurt Pregitzer of the university’s Forestry Department. Fossilized vegetation from the same era has been found in the region before, but a standing forest and a complete ecological system gives scientists a unique opportunity to see just what was happening with the climate when nature dropped the curtain on the forest.
The trees began to grow as soon as the glacier retreated north past the site, and the glacier was probably no more than five or 10 miles away
when the most mature trees reached their tallest height of 30 feet.  But a sudden shift toward warmer temperatures accelerated melting of the
glacier, flooding the area with water.  The standing water probably killed the trees, some of which were about 145 years old, but the silt preserved the needles and cones lying on the forest floor. If the process had ended there, the trees would have rotted, according to Bornhorst, but then a curious thing happened.  The climate apparently changed again, probably even greater warming, sending more water into the forest. The water carried along fine sand ground up by the retreating glacier, which quickly buried the trees. But not so quickly as to knock the trees down. “It had to have been a very rapid but gentle burial,” Bornhorst says, because even tiny “limblets” of new growth survived the process.
As students and professors worked side by side to keep the water out of the pit, researchers with chain saws collected 140 cross-sections of
the trees. But in a few days the dikes began to give way, and water was allowed to reflood the area, reburying the trees. Miners returned to excavate the sand, a process that destroyed what remained of the ancient forest. “It’s gone now,” Pregitzer says.
Here are some images from this site.
guys&trees.jpg (116834 bytes)

paleologger.jpg (127349 bytes)

While the Great Lakes' levels were low, you now know that forests grew on the dry, exposed lake beds.  Here's an excerpt from a study about a shipwreck diving expedition that came upon such a "drowned" forest in Lake Superior.  Recall that Lake Superior had a low phase similar to the one that occurred in Lakes Michigan-Huron.  However, the low phase in Lake Superior (named the Houghton low phase) was shorter lived.

The Forest From 6,000 BC

When Captain Peter Lindquist discovered a prehistoric forest almost 200 feet under Lake Superior, he was amazed.  Capt. Lindquist became excited when his depth finder showed what appeared to be masts standing up off the bottom in 180 feet of water. Gearing up with double tanks, he and his partner started down on their very deep dive with high expectations of dropping onto a shipwreck standing intact on the bottom. Instead of masts, however, they found themselves among several tall trees standing upright on the lake bottom! "Upright on the lake floor, the
trees were one to two feet in diameter and perhaps 15 to 20 feet high, with branches intact. Sitting on the bottom, it was like looking up through maples" Though he never left the dive line, Captain Lindquist saw at least five trees at the site (see image below).

log1.gif (52711 bytes)

    Another mysterious tree was found amid the wreckage of the wooden freighter HERMAN H. HETTLER in Munising's East Channel. Suspecting that the tree was extremely old, Captain Pete Lindquist sent samples of the wood for carbon dating. The laboratory results showed an age of 7,910 years plus or minus l00 years, but provided no clue as to why a nearly 8,000 year old tree would be found amid the remains of a 1926 shipwreck.
    Where did these trees come from ?
    It is probable that thousands of years ago when the lake level was lower, the trees actually grew where they now stand. A parallel might be drawn with the Gribben Forest, a stand of 10,000 year old spruce trees uncovered during the excavation of a tailings basin for the Tilden Mine in Marquette County. Some of the Gribben trees were still standing where they had grown and had been buried by sand and silt washed out from a melting glacier at the end of the last Ice Age. During the Ice Age, the Great Lakes, as well as the oceans, were believed to have been much lower than present levels due to the tremendous amount of water frozen in the glaciers that covered much of the continents. The trees might have grown on the southern shores of a smaller, shallower Lake Superior and drowned when the lake level rose with the melting of the glaciers.

dg-47.GIF (117098 bytes)

This material has been compiled for educational use only, and may not be reproduced without permission.  One copy may be printed for personal use.  Please contact Randall Schaetzl ( for more information or permissions.