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Minnesota Geology

Field Trip, Summer 2000 and Other MN DNR Workshops

Arlyn DeBruyckere with Dr. Tim Kroeger and Dr. John Annexstad
Bemidji State University
All of the pages and photos are copyright © 2000-2004 by Arlyn DeBruyckere.
Educational use is freely granted, for any other use contact Arlyn DeBruyckere

A basic review of MN Geology page

A review of Geologic Time in MN

Basic Geologic History in MN

The core of the field trip began about 7 am on June 23.  Dr. Annexstad began with a story of how Lake Bemidji was used to test C130 cargo aircraft with skis to determine if they would work for landing on Antarctica.
     Much of the trip between Bemidji and Grand Rapids was in a drainage way for the Wadena Lobe of the of the Wisconsinan glaciation period.  The remnants of the glaciation are the outwash sediments that form the topsoil, rivers and lakes of the region that are visible on the map.  So much water was released by the melting glacier that specific  channels were not established for some time forming  many valleys and braided streams in addition to the main channel that became the Mississippi River.  Today roadways are often built in or along these channels.  Some of the lakes that were left are called Oxbow Lakes as the drainage channel changed course and left behind a bend in the river that became a lake.   Click here to see more detail of glacial features.

   Further south and west is the Itasca Moraine (near Itasca State Park) that is material left over from the St. Louis Sublobe.   The vast majority of the surface of Minnesota contains only remnants of glaciers as the glacial sediments are up to 150 m (450 feet) thick. Only a few small areas have bedrock at or near the surface.
(1)  The many bogs and lakes in the area are evidence of the relative youth of the system in comparison to the well defined drainage areas of southern Iowa and Kansas where there are very few lakes.

    This cross section bedrock map of Minnesota is a good resource to have handy throughout this virtual field trip. Looking at the small maps of the state (black) one should see a white line going from the north to the south with a slight angle to the east. As one lookes at the larger maps the bedrock indicated follows this line with the left side being the northern most part and the right the southern most part.

    The swamp or bog areas can be identified from the road by the lack of significant tree vegetation.  Where the ground is saturated with the water the vegetation is poor because of the lack of minerals in the soil.  Many areas have 40 to 50 feet of peat that has been deposited in the last 5000 years.  Peat is the precursor to coal and it is estimated that five to six feet of peat to get one foot of coal.  Wyoming  has some coal beds that are over 100 feet thick.

    By the time we get to the city of Deer River we are beginning to see outwash sediments from the St. Louis Sublobe which is still part of the Wisconsinan glacial period but occurred much later than the Wadena Lobe. We are in an area that has characteristic ground moraines or cover moraines that occur underneath stagnant ice.  The stones and rocks are well rounded and are mixed with silt and clay.

    At our first stop which is near the town of Taconite, we will see evidence of the mixture of material of the Wadena lobe that came from the north and the St. Louis Sublobe that came from the northeast.  This is near the edge of the glacial lake Upham and glacial lake Aitkin.  From Grand Rapids to Taconite we will cross gently rolling terrain that is the end moraines of the St. Louis Sublobes.  The material left by the glacier contains all kinds of unsorted sediment that is both rounded and angular.  Grand Rapids is also on the western edge of the Mesabi Iron Range that is defined by the Animikie Basin.

Page 2, a glacial esker

Page 4, Hill-Annex Mine

Page 6, Hull-Rust Mine

Page 6e, The Giant's Ridge & Laurentian Divide

Page 6f, Ely Greenstone & Pillow Lava

Page 6g, Corsica Mine and Stromatolites

Page 6h, Hoyt Lakes LTV Mine Reclaimation

Page 6i, LTV Mine Pit

Page 6j, Pokegama Quartzite - Shore of the Animike Basin

Page 6k, Wetlegs area - Duluth Complex, gabbro rocks

Page 7, Duluth Harbor

Page 7a, Lake Superior North Shore

Page 8, The Mouth of the Lester River

Page 9, Thomson Dam & Jay Cooke State Park

Page 10, Lake Agassiz

Page 11, St. Cloud Granite

Page 12, River Warren

Page 13, Mankato Limestone

Page 14, River Warren and the Mississippi

Page 15a, Minneapolis area gravel & limestone

Page 16, Interstate Park - The St. Croix River

Page 17, Morton Gneiss

Page 18, Alexander Ramsey Park, Redwood Falls

Page 19, Pipestone National Monument

Page 21, Jasper - Sioux Quartzite

Page 22 - Driftless Area & Karst Topography

Page 26 - Mystery Cave & Forestville State Park

Page 30 - Overpass Quarry in Houston County

Page 31 - Biesanz Stone Company

Page 33 - Mississippi River Valley at Winona

Page 90 - Badlands & Devil's Tower

Page 91 - Glaciated Mountain

Page 92 - Black Canyon of the Gunnison

1.  Ojakangas, Richard W. & Matsch, Charles L.; Minnesota's Geology, 1982, p18