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An afternoon walk through the Sag Quarries yielded a few cool fossils. The Sag Quarries are in Lemont near the intersection of Archer Road and Rt. 83. They have been abandoned and flooded for decades and are now part of the Cook County Forest Preserve District.
When walking along the shore you're walking along the edge of the old limestone quarry, so one must be careful not to fall into the deep water. Limestone is everywhere and with a little luck, you can spot fossils that are 450 million years old! The limestone in this area began to form beneath the warm, shallow sea that covered this area over 400 million years ago. Some of the creatures that lived in the sea at this time were shellfish including the Endocerid, a long conical shellfish that could reach lengths of 10 meters or more. The one preserved above was about 18 to 24 inches in length.
It died and sank to the bottom where it was covered up by sediment including sand and tiny particles of calcium from other shells. Over millions of years the sediment compacted and formed the limestone we see today.
The Sag Quarries were in operation in the early 1800's, and during the time of the construction of the I&M Canal. The limestone from these quarries was used to build the Chicago Watertower, Holy Name Cathedral, St. James of the Sag Church (monk's castle) and numerous local buildings.