This is Mazon Monday post #215. What's your favorite Mazon Creek fossil? Tell us at email:[email protected].
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Despite the morning storm and intermittent rain on the way down, about 20 ESCONI members braved the weather and showed up for a very successful day of collecting Pennsylvanian fossils. Trips to this locality have been very popular, most trips filling up quickly. We did have a few cancellations this time, so get on the waiting list next time. It's worth the 3 hour drive from the Chicago area, with nice fossils found on every trip. There's always a chance for immediate gratification with the plant fossils in the "Red Dog" shale, which is fired grey shale formed when the spoil pile spontaneously combusted at some time in the past.. This trip there were quite a few carbonized plant fossils in the gray shale. If you're the patient type, there are fossil bearing concretions, which can be opened via freeze/thaw or hammering. We always recommend the freeze/thaw method as it tends to be a more gentle way to open a concretion.
To learn more about this locality, check out the ISGS Guidebook from a trip in 2005. Look for "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, put together a nice guide to the fossils of the area in 2021 (See Mazon Monday #86).
Pre-collecting explanation of the site and the rules.
Plenty of happy and familiar faces...
Roger found a huge chunk of coal. The Herrin Coal seems heavier and more solid than the remains we find at Braceville.
He found it in the area with many chunks of shale and coal. Those were productive for finding carbonized plants and concretions.
It was a windy day... especially on top!
Of course, we had to take the required selfie photo. This is of the group discussing the finds of the day. It's always a good time!
Here are some photos of fossils found during the trip... a nice concretion.
Carbonized plants
Calamites.
Aphlebia crispa
A beautiful piece of bark
A concretion in the shale with a fern.
Hope to see you in the fall!
Some of these photos came from Ralph Jewell's excellent report on the Fossil Forum.
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