Of the sedimentary rocks, most fossils occur in shale, limestone and sandstone. Earth contains three types of rocks: metamorphic, igneous and sedimentary. With rare exceptions, metamorphic and igneous rocks undergo too much heat and pressure to preserve fossils. So most fossils are found in sedimentary rocks, where gentler pressure and lower temperature allows preservation of past life-forms.
Fossils become a part of sedimentary rocks when sediments such as mud, sand, shells and pebbles cover plant and animal organisms and preserve their characteristics through time. Mud forms when larger rocks erode into tiny, usually microscopic, particles.
These particles settle in the calm waters of lakes, swamps and the ocean, covering creatures that live there. Mud and clay combine with minerals and other particles over time to harden into shale.
The hard parts of the creatures covered with mud undergo preservation as fossils when consolidated with other materials inside the shale. Shale splits easily into layers to reveal any fossils inside. Fossils inside shale often include brachiopods, fossilized plants, algae, crustaceans and arthropods trapped in the hardened mud.
The very small mud and clay particles allow small details of organisms to be preserved, like the rare fossils of soft-bodied organisms found in the Burgess Shale.
Limestone forms when calcite from the water crystallizes or when fragments from coral and shells cement together. Limestone often contains fossils of shelled sea creatures. Entire reef formations and communities of organisms are found preserved in limestone. The types of fossils found in limestone include:. Most limestone forms in shallow tropical or subtropical seas. In some cases, fossils make up the entire structure of limestone. If you are a science geek then the prospect of digging up your own fossils has, at some point, probably excited you.
The thrill and excitement of finding, seeing and touching something that hasn't been seen for 50 million years is an incredible feeling. While there are many different ways to find fossils, you can search in streams and oceans for shark teeth and bones, you can dig in the badlands for dinosaur bones, you can search the world for fossils.
But if you're like me, then extra time is not a resource you can come upon easily so here's how I fuel my fossil hunting desires! Southwest Wyoming is home to an area known as fossil lake. Fossil lake has the richest deposit of freshwater fossils in the world! These fossils are found in the local limestone and are as easy to get to as walking up to a rock and picking it up. In and around Kemmerer Wyoming you can find a number of fossil quarries that, for a fee, will allow you to hunt fossils all day long.
Some will even take you on night digs to help uncover pristine, museum quality fossils for the so called 18 inch layer more on that later. I personally recommend Rick Hebdon at Warfield Fossils. If you have a chance to experience the VIP night dig you won't regret it!
Now that you have access to the limestone, what do you do with it. Because the fossils are hidden in the layers of limestone, you need a way to separate the layers to expose them. That's what this instructable is all about!! The first thing you need to find fossils in Limestone is Limestone, but not just any Limestone. Obviously it's easy to get if you live within a days drive but for most of us, that's not the case. More on that at the end A rock hammer is ideal, between oz is fine.
The best is a dual beveled thin chisel to gently separate the thin layers of limestone without cracking them. The best chisels are specifically made for this purpose and can be found at www. You can use a regular chisel found at the hardware store but you need to be careful because they are much thicker. Not required but trust me, you will want some. Limestone is heavy with sharp edges and hammers hurt.
When chiseling anything, pieces fly off and eventually and inevitably hit your eye. Splitting limestone for fossils is fun and rewarding. Seeing something that hasn't been seen in 50 million years is quite a thrill! Kids and adults alike love splitting Limestone and finding fossils. Its a true learning experience and it inspires kids to pursue interests other than xbox and playstation although there's nothing wrong with either. It's nice to get your hands dirty and experience the world around you!
Now that you have your limestone, hammer, chisel and appropriate safety attire, it's time to start splitting. The process of splitting the stone is actually very easy but doing it right can be a challenge. But why limestone and not any other rocks? Limestone is a sedimentary rock formed by deposition of material minerals, calcium carbonate, etc..
As fish, birds, mammals, bugs, etc die, they fall to the bottom and are covered again by more sediment. Over time, the critters that are trapped can end up as fossils. All that being said, you can easily see the different layers of limestone when you look at it from the side.
In this case, only swimming or drifting organisms that die and fall into the mud have a chance to become fossilized. Although this does happen, it is a very rare occurrence. Some sandstones contain fossils as well. Most sandstones do not contain fossils, for various reasons. Water currents in the environment might have been too strong for animals to survive. Also, sands are very porous, so water seeping through the sand might have dissolved the shells away long before the sand was buried and changed into sandstone.
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