Geoscience Alliance Field Trip
Saturday, September 18, 2010
The field trip will focus on the diverse and scenic geology within 10 miles of Black Bear casino. The goal of the trip is to two fold: to introduce participants to the long and diverse geologic history and the spectacular scenery of this part of Minnesota and to provide a venue for casual interaction and spirited discussion. The trip will be 2 and half hours long and we will visit 5 or 6 sites. We will travel by bus.
The trip will begin with a visit to Jay Cooke State Park where down cutting by the St Louis River has exposed the Early Proterozoic Thomson Formation and the Middle Proterozoic Fond du Lac Formation. The Thomson Formation is a flysch sequence, which was subsequently metamorphosed during the Penokean Orogeny (ca 1850 Ma). Outcrop(s) we will visit will display both the sedimentology and metamorphic features of the Thomson Formation.
An angular unconformity and approximately 900 Ma of time separate the Thomson formation and the Fond du Lac Formation. The Fond du Lac Formation is a sedimentary unit deposited in a fluvial environment. The Fond du Lac Formation was deposited in half-graben system that formed late in the history of the Mid Continental Rift system. Outcrop we will visit will display both the sediments and sedimentary structures commonly found in the Fond du Lac Formation.
Another approximately 900 Ma of time separates the Fond du Lac Formation from the overlying glacial deposits. Outcrops visited will display the deposits of both the Superior Lobe of the Laurentide Ice Sheet and Glacial Lake Duluth. The units provide a detailed record of both the history and sedimentary environments of these Late Quaternary features.