A search on the Internet reveals few examples of limestone fens. Fox Valley, Ilinois has one called Kildeer nature area. Pennsylvania has one in Cherry Valley of southeast Monroe County. Ireland shows one in Ballyhoura County near Limerick called  Kilcolman.

It is interesting that Lemont with its rich heritage of Irish Quarry workers should share such a natural site.
 
 Notice the limestone bedrock just below the surface and the water seeping up through the bed in the photo on the left.

Wildlife in the fen may include birds such as cardinals, Red-winged blackbirds, yellow finches, and red-tailed hawks. Frogs probably will be found especially at evening and in early morning coyotes may be seen looking for prey and maybe red foxes. Canada geese will be found in nearby lakes and ponds, along with blue herons that like shallow water such as in the I&M canal. Lemont is a great habitat for wildlife now that the natural areas have been opened up along the canal and around the many stone quarries.  

Insects abound, especially if thistle is nearby, which it frequently is. Some insects that can be expected are butterflies, dragonflies, bumblebees, and mosquitoes.

Here is another area called the “Flats” where the water is very shallow on limestone bedrock and east of the water treatment plant.