Mississippi River Valley: The River Warren, the largest of Minnesota’s glacial rivers, was five miles across in some places. Waters from Glacial Lake Agassiz, Glacial Lake Grantsburg, and Glacial Lake Duluth formed the deep valley of the Mississippi River Valley when large quantities of glacial lake melt waters rushed through the area. Sorin’s Bluff and Barn Bluff were islands in the great glacial river. The present day Mississippi River is comparatively tiny as it meanders through the large valley carved by the mighty glacial water flows. Although the enormous glacial River Warren is no more, material from the Minnesota River Valley continues to be deposited in the Mississippi and Lake Pepin.
Red Wing was once at the bottom of a sea whose waters carried organic material and life forms that profoundly changed over time to create Red Wing’s geology. Most of southeastern Minnesota sediment consists of four major layers:
Pure quartz sandstone
Sandstone with abundant
Glauconite, mudstone, shale
Carbonates, mainly dolostone with some limestone
These layers were constructed by changing sea levels when waters flooded Minnesota.
Barn Bluff & Sorin's Bluff
Barn Bluff and Sorin’s Bluff survived as islands in the large glacial water river because their hard overlying Oneota Dolomite prevented their erosion. Red Wing’s geology is exposed at the 150 foot fault by Highway 61.