This is Mazon Monday post #304.  What’s your favorite Mazon Creek fossil?  Tell us at  email:esconi.info@gmail.com.

---

In May 1970, the Field Museum opened an exhibit about Mazon Creek. It was called “Illinois by the sea: a coal age environment” and ran from May 25th until September 25th. It was a successful exhibit that featured Field Museum fossils and contributions from ESCONI members. Many familiar names were among the contributors.

There was an announcement in the ESCONI newsletter in September 1970.

DON’T MISS THIS FIELD MUSEUM EXHIBIT!–via Terry Wolfe

Inaugurated May 25th to become the newest exhibit at the Field Museum, this exhibit will remain until only October 25. The exhibit is entitled, “Illinois By the Sea: A Coal Age Environment”. The exhibit represents 16 years of research by Museum staff scientists. Both the Morris-Braidwood area and the Mecca, Ind. area (near Terre Haute) are represented nothing more during Pennsylvanian time nearly 300,000,000 years ago. Most striking is evidence of animal behavior (in this case sharks) under the stress of over-population crowding. The crowding was caused by the recession of the seas from Illinois-Indiana leaving pools with marine creatures in them which slowly disappeared. Many examples of fossils are shown including sharks, sea cucumbers, jelly fishes, worms, tullymonsters, and various flora. If you also look at the names of the contributors of the fossils specimens, you will notice the names of several of our fellow club members.

And, the Field Museum had an article with photos in their June 1970 bulletin.

Illinois by the sea:
a coal age environment

The story of life in this area 300 million years ago is graphically displayed in a new exhibit, Illinois By the Sea: A Coal Age Environment, which will be shown through October 25 in Hall 9.

Studies by Museum scientists of the Mazon Creek, Illinois, and Mecca, Indiana, vicinities yielded a wealth of fossil material.

Based on 16 years of ongoing research by the Museum’s department of geology, the exhibit demonstrates how, during the Pennsylvanian period, these sites bordered the inland sea that occupied most of Illinois. In the Mecca area, the sea inundated the coal forest and during the dry seasons of the following years, the water level was lowered periodically. Animal life became concentrated and trapped in shallow pools. The crowding in some of these pools was extremely severe. The behavior of the sharks is dramatically documented by the fossil remains.

The evidence discovered in the shale are intact pieces of skeletons, and whole skeletons with clearly marked injuries. This led scientists to believe that the creatures ate each other, and that some animals were disgorged in various stages of digestion. In some cases, the sharks could not swallow the prey whole, and they bit off pieces of their victims and let the rest sink to the bottom. Black mud accumulated rapidly, preserving the remains from complete bacterial destruction. The mud firmed up rapidly and, with time, became shale. It is through this shale that the secrets of Mecca were discovered.

Mazon Creek represents the second project presented in the exhibit. About 300 species of animal fossils were discovered, all encased in hard ironstone concretions. The latter preserved many soft-bodied animals in Pit 11 of the Mazon Creek area. Scientists were able to study such animals as bristle worms, Tully monsters, jelly fish, sea cucumbers and the only known fossil lamprey from these concretions.