Mount Simon Sandstone facts for kids
The Mount Simon Sandstone is a very old rock layer found deep underground in parts of the central United States. It's a type of sandstone, which is a rock made from tiny grains of sand cemented together over millions of years. This rock layer is special because it's the very first (or "basal") layer of a larger group of rocks called the Potsdam Sandstone.
Quick facts for kids Mount Simon SandstoneStratigraphic range: Upper Cambrian ? |
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|---|---|
| Type | Geological formation |
| Unit of | Potsdam Sandstone |
| Underlies | Eau Claire Formation and Rome Formation |
| Overlies | Hinckley Sandstone and Middle Run Formation |
| Thickness | up to 2,000 feet (610 m) |
| Lithology | |
| Primary | Coarse sandstones |
| Other | Occasional fine dark grey or maroon shales |
| Location | |
| Extent | Illinois, Indiana, Kentucky, Michigan, Minnesota, Ohio, and Wisconsin, |
| Type section | |
| Named for | Mount Simon escarpment in Eau Claire County, Wisconsin |
| Named by | E. O. Ulrich |
| Thickness at type section | 235 feet |
Contents
What is the Mount Simon Sandstone?
The Mount Simon Sandstone is a thick layer of rock that formed a very long time ago. It's mainly made of coarse, rough sand grains. Sometimes, you can also find thin layers of dark grey or reddish-brown shale within it. Shale is a type of rock made from hardened mud.
How it Formed
This sandstone formed in a "nearshore environment." Imagine a very ancient beach or a shallow sea where sand was deposited. Over millions of years, this sand was buried under more layers of sediment. The pressure and natural cements then turned the loose sand into solid rock.
The Mount Simon Sandstone sits directly on top of much older rocks from the Precambrian era. This contact is called an unconformity, which means there's a gap in the rock record, like a missing chapter in Earth's history book.
Where is it Found?
You can find the Mount Simon Sandstone deep underground in several states across the United States. These include Illinois, Indiana, Kentucky, Michigan, Minnesota, Ohio, and Wisconsin. It can be incredibly thick, reaching up to 2,000 feet (about 610 meters) in some places!
Above the Mount Simon Sandstone, you'll usually find another rock layer called the Eau Claire Formation. In some areas, younger rocks from the Ordovician period might sit directly on top.
Naming the Mount Simon Sandstone
This rock formation was named after the Mount Simon escarpment. An escarpment is a long, steep slope or cliff. This particular one is located in Eau Claire County, Wisconsin. The geologist E. O. Ulrich was the person who officially named this sandstone formation.
Age of the Rock
Scientists believe the Mount Simon Sandstone formed during the Cambrian Period, specifically in the Upper Cambrian. This means it's incredibly old, dating back hundreds of millions of years! While its exact age is still being studied, it's known to be one of the oldest sedimentary rock layers in this region.
In the St. Francois Mountains of Missouri, there's a similar rock layer called the La Motte Sandstone formation. It's considered to be the same age and type of rock as the Mount Simon Sandstone.
