This is Throwback Thursday #87. In these, we look back into the past at ESCONI specifically and Earth Science in general. If you have any contributions, (science, pictures, stories, etc ...), please sent them to [email protected]. Thanks!
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Field & Street was a column in the Chicago Reader from at least 1984 until April 2004. For most of its existence, it was written by Jerry Sullivan and ran bi-weekly. The Reader has an archive of many of the columns on their website. In case you haven't heard of the Chicago Reader, it's a free Chicago weekly newspaper that has been published since 1971. They bill themselves as "Chicago's alternative nonprofit newsroom". The Chicago Reader is the paper that published the "The Vanishing Mother Lode of Mazon Creek" in 2004.
Jerry Sullivan (1938-2000) was a career naturalist and journalist, who besides writing the "Field & Street" column, served as the associate director for land management with the Forest Preserve District of Cook County until his untimely death in 2000. The University of Chicago Press has a book that contains a collection of his columns. It's an interesting read.
A selection of savvy observations on urban ecology from one of the Midwest’s foremost authorities on the subject, Hunting for Frogs on Elston collects the best of naturalist Jerry Sullivan’s weekly Field & Street columns, originally published in the Chicago Reader. Engaging, opinionated, inspiring, and occasionally irreverent, Hunting for Frogs on Elston pays tribute to Chicago’s natural history while celebrating one of its greatest champions.
Published in association with the Chicago Wilderness coalition, Hunting for Frogs on Elston comprehensively chronicles Chicagoland’s unique urban ecology, from its indigenous prairie and oft-delayed seasons to its urban coyotes and passenger pigeons. In witty, informed prose, Sullivan evokes his adventures netting dog-faced butterflies, hunting rattlesnakes, and watching fireflies mate. Inspired by regional flora and fauna, Sullivan ventures throughout the metropolis and its environs in search of sludge worms, gyrfalcons, and wild onions. In reporting his findings to otherwise oblivious urbanites, Sullivan endeavors to make “alienated, atomized, postmodern people feel at home, connected to something beyond ourselves.“
In the sprawling Chicagoland region, where an urban ecosystem teeming with remarkable life evolves between skyscrapers and train tracks, no writer chronicled the delicate balance of nature and industry more vividly than Jerry Sullivan. An homage to the urban ecology Sullivan loved so dearly, Hunting for Frogs on Elston is his fitting legacy as well as a lasting gift to the urban naturalist in us all.
What brings me to this post is a particular column he wrote for the May 30th, 1991 edition of the Reader. In the article, he documents a field trip he took to Pit 11 with the Field Museum. I remember the Field Museum trips. I never took one to Pit 11, but did manage to visit the Elmer Larson Quarry near DeKalb, IL. on a few occasions to collect Silurian fossils. Dave Dolak guided many of these trips. I think there was even a bus trip to southern Indiana to visit the famous Route 1 road cut.
Often, the Field Museum would take a bus to an area called ESCONI Hill, which unfortunately is pretty overgrown now. Back in the day, it probably looked something like this.
Ralph Jewell on the Fossil Forum
Unfortunately, it was raining on the day of his trip. Oh, for a chance to collect the bare slopes of the Pit 11 he describes!
What I needed was a mentor. Starting my first-ever fossil hunt, I was wandering without coherent aim, staring at the muddy ground with a hopeless expression. Wanting this to be easy, certain that it would be very hard, I felt like a man looking behind the bureau for his car keys when he knows perfectly well he left them locked in the car. If you want to find fossils, I thought, attach yourself to somebody who knows how to look for them. There must be a technique, a knack, a secret that separates the adept from the ignorant.
Did I mention that it was raining? Very hard, in fact. When it rains, the bare earth on the steep slopes of piles of strip-mine spoils gets very slippery. But the bare slopes are where the action is, because there is nothing green and leafy to block your view of the fossils.
The bare slopes were striated with parallel gullies running almost straight up and down. The rain continued to fall, and the gullies became rushing streams. The waters were gray, colored by the sand and clay suspended in them. The eroded beds of these tiny, precipitous streams were where the most rocks would be exposed, and the fossils were all inside rocks.
There is a summary of the history of the area and of fossil collecting the spoil piles.
We were digging in mounds of strip-mine debris because these heaps of earth and rock are part of Mazon Creek, one of the premier fossil beds in the world. Three hundred million years ago, in the Pennsylvanian Era, the area around the towns of Braidwood, Morris, Coal City, and Essex was the edge of a river delta. The river drained lands to the north and east, and it met the sea around Braidwood. Coal formed in the coastal swamps of that delta. Silt in the ancient river flowed over the delta and out to sea. The deepening silt buried the bodies of plants and animals, buried them so soon after death that even the outlines of the soft parts of their bodies are now visible. Since the Pennsylvanian Era, the geology of northeastern Illinois has been peaceful enough to leave the delicate fossils undisturbed.
To paleontologists, the Mazon Creek fossil beds take in about 70 square miles in Will, Grundy, and Kankakee counties. The name comes from the fact that the first fossils were discovered in small bedrock outcrops along Mazon Creek (or Mazon River on contemporary maps). There weren’t many such outcrops. Most of the bedrock is buried under a deep layer of glacial debris, so it wasn’t until coal mining began around Mazon Creek that the richness of the fossil life came to be appreciated.
Coal miners sank shafts through the glacial stuff and then through a layer of soft, dark rock called the Francis Creek shale. This late Pennsylvanian shale lies directly over the coal beds, so when the first mines were dug at Braidwood, Illinois, in 1855 and in nearby Coal City in 1858, the miners pulled large piles of shale up to the surface and heaped them around the pitheads.
Local fossil collectors combed through the heaps of rock and dirt and then passed their findings along to the professional paleontologists, who published as quickly as possible. The first academic paper on Mazon Creek fossils appeared in 1864. Since then all sorts of distinguished scientists, including Edward Drinker Cope, one of the founding lunatic geniuses of paleontology in America, have published hundreds of papers on the Mazon Creek fossils. To date, about 325 species of animals and perhaps 350 species of plants have been found in Mazon Creek sites.
They have been found inside concretions, rocks that formed around the fresh dead bodies of 300 million years ago. The concretions are made of siderite, a combination of iron and carbonates that produces a reddish brown rock with a rather gritty texture. Concretions are usually flattened disks or ovals with rounded edges. They may be an inch long, or they may be a foot long.
Jerry does a good job describing the science as it was known in 1991. Although, he missed it on the name of the Tully Monster. This was just a few years after the Tully Monster was named the State Fossil of Illinois. The gregarium in Tullimonstrum gregarium actually means common.
The discoveries are extraordinary. Jellyfish are rarely found in the fossil record. In Mazon Creek there are not only two species but also hundreds of specimens of each. Mazon Creek also gave us the world’s oldest isopod fossil. Isopods are small crustaceans that are still with us today. The world’s oldest squid came from there, and the only known fossil lamprey. Other soft animals that are beautifully preserved include worms, sea cucumbers, and larval fish.
The most famous of Mazon Creek’s fossils is the Tully monster, a wormlike creature of, as they say in the journals, uncertain affinities. The first fossil of Tullimonstrum gregarium was pulled from Pit 11 about 30 years ago by Francis J. Tully, a local man who was into fossil collecting as a hobby. He took his find to Dr. Eugene Richardson at the Field Museum, and Richardson published a description in 1966, naming the fossil in honor of its discoverer.
A Tully monster could be as much as 14 inches long. It has a flattened tail and a long proboscis carrying teethlike projections. It has been shoehorned into various phyla since its discovery. Lately it is being proposed as an ancestor to the vertebrates, and it will probably be proposed as a lot of other things in the future. For the moment, it may be officially placed among the Problematica.
The second word in the Tully monster’s scientific name is revealing. The Tully monster is gregarious. It likes to hang out with the other monsters. We can believe this because hundreds of fossils of this unique creature have been found in Pit 11. There were whole schools of monsters in these waters in the Pennsylvanian Era, and parts of many of them were preserved in the amazing Francis Creek shale.
He did collect some concretions. I wonder what became of them... did they open up via freeze/thaw or did they succumb to the hammer to reveal their secrets?
I certainly have a fine collection of concretions from my collecting trip. However, I don’t know for certain that they have fossils in them. You can stand a concretion on edge and bang it with a hammer. If it is ready to split, it will split along the plane of weakness created by the fossil. So you bang a couple of times, but if it shows no signs of splitting you stop hammering. Further beating will just crush the whole rock.
To open the strong rocks–like all of those I collected–you need cycles of freezing and thawing, of water seeping into cracks in the rock and freezing. The sudden expansion widens the crack. After the next thaw water seeps into the wider crack and then freezes and expands again.
This is God’s way of breaking rocks, but he doesn’t have any deadlines. I am trying to speed up the process. I tossed my collected rocks in a bowl of water and froze them. Once they were solid, I took them out and thawed them. And then froze them again. Someday I will find out if I have a sea worm, a fern leaf, or a species of shrimp utterly new to science. It has been known to take two years to pop a rock even with accelerated freezing and thawing. In paleontology, you have to be patient.
All in all, it's a great article! Check it out if you get a chance!
