In my research, I have had the pleasure of focusing many projects in the area located on the border between Minnesota and Ontario near the general region of Rainy Lake. This area is part of the Superior Province, the world’s largest contiguous Archean granite-greenstone terrane. The tectonic history of this area (one version of it) began approximately 2.7 billion years ago when a series of volcanic island arcs collided into one another creating a classic Archean granite-greenstone terrane. Between two of these island arc subprovinces, the Wawa and the Wabigoon, lie the Quetico metasediments that were probably deformed during the collision.
At this boundary between the Quetico and Wabigoon subprovinces, the rocks have undergone a prolonged history of deformation. The rocks at the boundary have undergone ductile deformation as evidenced by their prominent foliation and lineation mineral fabrics. Two major shear zones, the Seine River- Rainy Lake and the Quetico, localize deformation.
Hop on the bus to any of the stops below:
Seine River Conglomerates: ***The World’s Prettiest Rocks: Check these out first!***
The Seine River conglomerates are the featured attraction of the field area. They formed approximately 2.7 billion years ago along the boundary between the Quetico and Wabigoon subprovinces. They were beautifully deformed.
All of these pictures are taken on subhorizontal surface. Wouldn’t you like to see a 3D view of the conglomerates so you can see that they are flattened?
By looking at the conglomerates from all sides, we can see that they have been extremely flattened into pancake-like shapes. These photos show conglomerate clasts that are cut in 3, approximately perpendicular, sections. In these pictures, the blue dots are 5 cm across, and the masking tape line is oriented along the strike of the surface (horizontal).
The Ottertail Pluton
The Ottertail Pluton is part of the Algoman Suite of plutons, the youngest rocks in the area (approximately 2685 Ma).
Even though the Seine River conglomerates are the star attraction of the field area, many other beautiful and interesting rocks are also great field trip stops.
Scenic Waterways in Borderland
When you finally take your eyes off the rocks, there is plenty of other scenery in Borderland. You can enjoy all the water: lakes, rivers, swamps- thanks to our friends the glaciers.