Mikulic Leads Field Trip to Examine Silurian Rocks of Northeastern Illinois

ISGS group at Thornton quarry

On July 28th Donald Mikulic led a geological field trip to examine the Silurian rocks of northeastern Illinois as part of the UNESCO IGCP (International Geoscience Program) Project 591 meeting that was held in Cincinnati, Ohio. This trip was used to demonstrate current research results concerning the influence of climatic change on the Silurian rock record.

Twenty-five scientists from a number of countries, including Great Britain, Germany, France, Belgium, the Czech Republic, China, Estonia, and Canada attended this geological field trip. The stops included the large Hanson Material Service quarry at Thornton near Chicago, the Vulcan Materials Company quarry at Kankakee, and outcrops in Kankakee River State Park.

The enormous Thornton Quarry is one of the most important exposures of Silurian rocks in the country. It is the best exposed Silurian reef in the world and, because of its large size, provides critical evidence on how glacial-eustatic sea level changes controlled the development of ancient reefs and impacted the character of sediments deposited on the surrounding sea floor.

The Vulcan Materials Company quarry is important for its unique exposure of the carbonate equivalent of the famous Waldron shale of the Ohio River Valley which marks a globally recognized sea level change boundary.

Exposures in Kankakee River State Park are historically important for the role they have played in regional studies of Silurian rocks and the unique exposures of iron beds which mark the boundary between the Ordovician and Silurian time periods. Globally this boundary marks a well-recognized glacial-eustatic sea level change representing one of the largest extinction events in Earth history.

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