Fossil Collecting at Mazon Creek

The Mazon Creek location is world famous for its exquisite preservation of soft body fauna.
The fossils are found inside concretions which are scattered throughout the strip mine overburden which has been dumped in piles across the entire area.
The State of Illinois acquired some of the strip mined land and has opened it as a wildlife preserve but it is open to fossil hunters too.
I have been here a couple of times.

One of the entries to the the northern half of the Mazonia South Unit.

Unopened Concretions

There are some paths throughout the area. Unfortunately, the spoils piles have become almost totally overgrown with dense vegetation.

One of the many small ponds, nearly inaccessible due to the vegetation.

Amazingly, the state has allocated sections of the park to be plowed up to expose the concretions.
At the time we were there, I would estimate that over 5 acres were recently turned over for the fossil hunters.
Finding it required asking one of the employees. The location is not posted.

We found dozens of nodules but I suspect that they are much more dense when the soil is first turned over.
It would not take long for the area to be cleaned out. Lets hope they continue to churn the soil.

Nodule, in hand.

Even so, there are nodules to be found throughout the park.
One method I used to find the concretions is to look underneath the scrub on the spoil piles for bare spots.

With some diligence, fragments of concretions are not too difficult to find. I found this many in about 3 hours or scrambling over hill and dale.
Fortunately, I am not sensitive to poison ivy.

In those three hours, I found nothing that was immediately recognizable as a fossil.
However, the nature of these fossils is such that they may not be recognizable to the untrained eye until after some cleaning.
My strategy is to pick up anything that looks like a concretion and inspect them later.

Only about 40% of the concretions do contain any fossils and most of those are blobs.
Most of what I found was non-fossiliferous or are jellyfish blobs.
However, after cleaning and inspecting them all, I found a few interesting ones.

A shrimp of some sort (35 mm)

A bivalve? (20 mm)

Part of a tiny horseshoe crab? (25 mm)

A decent Jellyfish Blob (35mm)

A nice Jellyfish (4") from the plowed area

A nice fern (4") from the plowed area

The best publication on the Mazon Creek Fauna is a book called Richardson's Guide.

Print this map of the park to locate the area where the soil is churned.

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