Animal dung turning to stone

November, 2008
by Ray Hill

Many times when I have gone to elementary schools, giving classes on rocks and fossils, I have had kids ask how animal dung, or poop, turns into stone. Called COPROLITE. Here I want to explain this geologic wonder in terms that the layman can understand.

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Here in Georgia we still have a large amount of farm land. Georgia is a very large producer of beef, cotton, tobacco, peaches, pecans, soy beans, and dairy products. Out in rural Georgia where I grew up we saw large pastures with herds of both beef and dairy cattle. Some of these cattle/dairy farms had pastures with many hundreds of acres with hundreds of cows. If you have ever seen a cattle pasture, you know what I'm speaking of.

Now, if you've ever just stopped and watched the cattle in these pastures, you noticed that the cattle do two things all day, and that is eat grass and poop. Due to the cattle getting very little nourishment from eating grass and hay, they must consume a huge quantity every day. Eating this large volume every day causes the cattle to discharge an equal amount of waste. When you see a pasture with cattle, you also see hundreds of piles of poop, what we call cow patties, from the cows. There're everywhere!!

Now think back a few million years. Instead of seeing large herds of cows, you'd see large herds of herbivore type dinosaurs like the duck-billed, Hadrosaur dinosaurs. These dinosaurs are known to have grown to as much as 40 feet in length. That's big. Now imagine how much plant matter one of these animals would consume in a days time. And, how much poop, or waste they would discharge in a days time.

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Wow! Corythosaurus and trackway

Now, just imagine that there is this large valley with hundreds of these huge plant-eating animals roaming about, doing their thing, eating and pooping. Now imagine that far off somewhere a volcano erupts, spewing many tons of volcanic ash into the air, that travels for hundreds of miles. The volcanic ash with its very fine particles drifts about with the prevailing winds. Tons of material. Now stay with me here..... imagine that this volcanic ash starts raining down in the area where these peaceful plant eaters are. And, over a period of days, this volcanic ash covers the valley where the dinosaurs are grazing. It piles up ten, fifteen, twenty feet thick, completely covering the valley.

Now forget the dinos for a minute, we're talking poop here. These hundreds, maybe even thousands, of piles of dinosaur dung are completely covered with the fine-grained volcanic ash. They are buried so completely that now they can not deteriorate or rot away. Dung beetles can't cart them off. The rains can't wash them away. The piles just lay there, buried in this thick layer of volcanic ash.

Beginning almost immediately from the time the piles of dinosaur dung are covered up with the volcanic ash, the minerals in the surrounding soil and ash began to permeate, or penetrate into, the piles of dung. And, over a very long period of time the minerals in the piles of dung are completely replaced with the minerals from the soil and ash. The new minerals, usually silica, is deposited in the dung, displacing the minerals that were there. The original shape and structure of the pile of dung is maintained. And over a long period of time the replaced minerals harden into stone, taking the shape of the pile of dung. This process is known as petrification.
See: A mineral displacement process.
See: Petrified wood.

In many areas in Oregon, Washington, Utah, North Dakota and South Dakota, there are large amounts of fossilized dinosaur coprolite, or dung, being found today. It is my guess that, the event that caused such huge amounts of fossilized coprolite to be found in these areas today is an event happening, a long time ago, in these areas as I described above. After many thousands of years, the soil that once covered the piles of dinosaur dung, has weathered away and now leaves the fossilized material lying on the ground. This is exactly the process that produced the petrified forest in northern Arizona.
See: Petrified Forest.

Ray Hill
Great South Gems & Minerals, Inc.
www.greatsouth.net
888-933-GEMS

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