This is Mazon Monday post #86. What's your favorite Mazon Creek fossil? Tell us at email:[email protected].
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In 2021, ESCONI had a couple field trips to collect fossils from a spoil pile of an old shaft coal mine near Danville, IL. All proved successful with many interesting specimens collected. Have a look at the following links for information about these field trips.
Here are a few pictures from the June 22nd trip.
Found by Joe Vitosky, this fossil is a Calamostachys cone.
Found by Marie Angkuw, this fossil is an Alethopteris.
Found by Sue Dibblee, these fossils are various forms of fern.
Found by Diane Bedrosian, this fossil is a form of Lepidodendron bark with leaf scars.
Found by Rob Russell, this fossil appears to be a seed.
The spoil pile dates to around the turn of the 20th century. The Dering Coal Company opened the mine in 1904. It was in operation from 1904 until 1946 by various companies, including the Peabody Coal Company which operated the mine from 1916 until 1944. This shale pile is Pennsylvanian in age about 305 million years old, which is about 2.5 million years younger than Mazon Creek's Colchester Coal No. 2. The pile is composed mostly of the Energy shale, which is just above the Herrin No. 6 coal. It contains compressions of plants, and contains concretions. The pile spontaneously combusted at some point, turning some of the gray shale into "Red Dog" shale. More information on this site can be found in the ISGS Guidebook http://library.isgs.illinois.edu/Pubs/pdfs/ftgb/ftgb2005A-kickapoo.pdf under "Stop 6".
The gob pile, an abandoned mine dump, is the accumulation of waste products from an underground mine (fig. 12). The piles are known variously as gob piles, slate dumps, boney piles, and culm banks. The gob pile stands about 150 feet above the general land surface. Excellent plant fossils have been collected from the gob pile at this mine. A second large gob pile, located southeast of this stop on the east side of the road, has been reclaimed.
The Dering Coal Company opened the No. 4 Mine here in 1904 to mine the Herrin Coal, which was reported to range from 4.5 to 10.0 feet thick and averaged 5.75 feet at a depth of 208 feet. Four feet of Danville Coal was reported to occur 100 feet from the surface. The mine shaft was located about 300 feet west of the road at the end of the gob pile. The Dering Coal Company operated the No. 4 Mine from 1904 to 1909, followed by the Brazil Block Coal Company, Brazil No. 4 mine, from 1909 to 1911. The Dering Coal Company once again operated the mine between 1911 and 1916, followed by the Peabody Coal Company, which changed the mine name to the Peabody No. 24 Mine and operated it from 1916 to 1944. The last owner was the Chicago Harrisburg Coal Company, which operated the mine from 1944 to 1946. The mine had a cumulative production of 18,054,349 tons.
The gob pile was created by dumping unwanted rocks that were removed from the mine. The early mining methods were labor intensive. Coal miners dug several inches of underclay by hand from under the coal seam so they could break the coal down and out from what is called the working face. In addition, along their haulage ways, they dug out rock above the coal to make a high tunnel so that mules pulling the mine cars could walk through. Rock that fell and sagged into the haulage ways had to be removed to keep them open. The waste rock that could not be stowed in the underground openings left after the coal was mined was brought to the surface and dumped on the pile.
The composition of the waste rock in the gob pile is from both the underclay, which is a soft gray shale, the rock the miners called “soapstone,” and the Energy Shale, the gray shale above the Herrin Coal that formed the roof of the mine and was dug down to heighten the haulage ways. Exposed to weather, the shale softened, and finally turned to mud.
These gob piles contain iron pyrite, sometimes called “fool’s gold” because of its yellow metallic luster. Pyrite is iron sulfide, which is stable buried beneath the earth surface. When exposed to water and oxygen, however, pyrite oxidizes and produces sulfuric acid, iron oxides, and hydroxides. The iron oxides and hydroxides, which are similar to common rust, tint these gob piles red. Sulfuric acid, however, pollutes both the water and the soil around the mines.
In addition, some gob piles have been known to spontaneously combust and burn for many years after the old mines were abandoned. This combustion is initiated by the oxidation of the pyrite and the absorption of oxygen. Air leaks through the pile to the coal and shale material and supplies the needed oxygen for combustion. Conditions do not allow heat to dissipate, and temperature rises, which ignites the coal and shale materials. The cooked shale makes hard brick-like chips that clink underfoot. This red deposit is nicknamed “red dog” by miners. Does the red shale remind you of the red bricks that were manufactured in the Danville area?
Less common are the plates of “blistered” black shale. The miners called this rock “slate,” perhaps because it is hard and splits into smooth sheets. The black shale generally lies on top of the gray shale above the Herrin Coal. Sometimes, however, the black shale is close enough to the coal to be taken down when heightening the haulage ways. Strewn over the slopes are dark gray and brown ironstone nodules—heavy for their size— which were formed in the gray shale above the coal. Of course, there are a few pieces of coal on the pile.
Jack Witty, author of three ESCONI Mazon Creek books, attended the field trips. During the trips, he spent time identifying specimens and taking pictures. Many more pictures were sent in by ESCONI members to Andrew Young. These additional photos were used to help compile the following fossil guides. The guides provided below should be useful tools for identification as there isn't much information available on the plant species of the Herrin Coal deposits.
| Group | Description | Files |
| Lycopsida | Ancestors of the club mosses. These fossils include parts of both arborscent (tree-like) and more herbaceous plants. The largest arborescent forms could grow to more than 40 meters (130 ft.) in height. | |
| Sphenopsida | Ancestors of the horsetails. The sphenophytes include both arborescent (tree-like) and more scrambling (climbing) or shrub-by forms. These plants are characterized by whorls of leaves and hollow stems with a node-inter-node organization. | |
| Filicopsida | Ferns. Most resemble modern tree ferns and produced sporangia (spore cases) with spores (reproductive cells) of a single type on the lower sides of the leaves. Like modern ferns they had pinnately divided leaves which grew from furled fronds called fiddleheads. | |
| Pteridosperms | Seed Ferns. Pteridosperm foliage appears similar to true ferns. Pteridosperms were arborescent or herbaceous. Unlike ferns, they had seeds and pollen organs. They inhabited a wide range of environments and were a diverse group of plants during this time. Seed ferns are now extinct. |
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| Cordaitales | Ancestral Conifers. Arborescent or scrambling shrub-like plants, with large strap-like leaves distributed at the branch tips and along their length. Like modern conifers, they produced separate male and female cone-like structures. All are now extinct. |
