Posts Tagged ‘limestone’

Cause For Celebration!

Fossil hunting offers a wide variety of possibilities.

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Trilobites shed their armor six to eight times during their life. This translates into finding their sheds (which are never common). Trilobite fossils are found in limestone, shale and dolomite in Illinois. Most of mine are from limestone.

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The oldest ones in Illinois come from Cambrian age rocks 500 million years old. Trilobites went extinct 250 million years ago.

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 Over years and years of fossil hunting, I found several partial trilobite fossils.  I never expected the possibility of finding a whole one.

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Then there, one sunny afternoon, on the the shale of a small outcrop, near the top of a hill, by a lake, lay this 7/8 inch trilobite.

My “whoop” echoed through the hills!

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Keith, my son, went to a Sierra Club seminar on Paleozoic monsters recently. Joseph Drevian, from USGS, gave the program. He found a partial trilobite from the same outcrop where I found my whole one. Keith sent him a picture of the one I found.

My trilobite is from the Grove Church member of the Kincaid limestone, part of Elviran Stage Chester series of the Missisippi system. It is a proetid trilobite  named Paladin sp.

Boy, that’s a mouthful.

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I searched and searched until I found pictures of the shale outcropping where I found the trilobite.

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That’s my mother fossil hunting on the slope.

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This last picture shows the whole shale area. Horses later moved their trail to down through the shale. Then a major flood in 2008 completely changed the landscape, and I haven’t been back since.

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Lower World Exposed

Twelve inches on rain fell in in one day in Harrisburg, Illinois on May 6, 2008. Needless to say, the area had major flooding. We live on a hill just outside town and had no damage.

The same storm system produced flooding strong enough to expose the “lower world” near a lake where I used to hike.

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The height of my best friend offers scale to the changed landscape. The following pictures were taken on an earlier trip when I discovered the flood results.

The lake  is to the left behind the hill.  A creek was dammed up to form it.

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Rocks aren’t debris, even though this looked like a debris field

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The water also left interesting-shaped mounds of sand over the landscape. Their size and shapes varied considerably.

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Notice the height of the sand, soil and rocks that had traveled a considerable distance.

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Walking took a lot of concentration … and energy.

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I sure had to wonder how such a variety of rocks were shaped and ended up underground. It had to take eons.

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These stones were limestone, if I remember right.

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There’s a lot of exposed sandstone in the surrounding hills.

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The round stone looked like it belonged in a grist mill.

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I wondered what wildlife might have been hiding back in the tunnels/cavities, waiting for me to leave.

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The road to the lake used to be straight ahead and tad left.

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It would’ve been handy to have a geologist along for the hike … but that would’ve been a distraction. It was just me and Buffy, alone to explore.

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My truck stopped way back  here.

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Here I followed the narrow remains of the road into Millstone Lake.

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The levee is near the upper left corner of this picture.

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The water rose high enough in the lake to go over a low area between here and the levee.

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The area was grown up by the end of the year, and didn’t have anywhere near the character by then.

I wasn’t upset with the changes resulting from the storm. Instead, I stayed excited, going from one discovery to the next, as I explored the “lower world.”

The forces of nature always fascinate me.

Horseshoe Upheaval

Southern Illinois definitley has an unique feature, known as the Horseshoe Upheaval.

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The rocks are about 350 million years old and were once some 3,500 feet below the surface. The tremendous power of the earth forced them upward. These upturned rocks are silca-rich limestone and chert of the Fort Payne Formation.

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The Fort Payne layer is the deep rust-colored layer in the above illustration. A line marks the location of the upheaval. The narrow wedge is sandwiched on both sides by younger rocks. This suggests the fault system went through two episodes of movement in opposite directions. First the rocks south of the fault zone were uplifted, bringing the Fort Payne rock to the surface. Then the southern block dropped back down. A wedge of the Fort Payne rock was sheared off and jammed in place within the fault zone.

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I left my truck in the picture for size comparison.

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Notice how the layered chert is turned almost vertical

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Walking isn’t the easiest at this site.

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Calcite veining occurs in a lot of the rock.

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Mosses, lichens and a few plants grow in the upheaval.

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Buffy and I climbed up the slope and

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into the bowl-like top of the upheaval. Obviously, the area is better seen before the trees leaf out.

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This shows limestone.

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We didn’t circle the whole top area. Walking wasn’t the easiest.

The Horseshow Upheaval is part of the Saline County Fish and Wildlife Area.

A Rare Shale Glade

There are limestone glades, sandstone glades and even shale glades.

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This one is a shale glade.

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You can tell by the shale on the surface. Glades are determined by the amount of rock at the surface.

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Patches of mosses and lichens grow on the glade,

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and not on the surrounding hills.

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Now comes the exciting part: This glade is the only one of its kind in North America! There is shale on other glades, but it isn’t the same age as the shale on this one.

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Glades the age of this one are so rare that they’re considered a globally endangered plant community!