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Roger Weller, geology instructor

wellerr@cochise.edu

Petrified Wood
by Demetra Moore
Physical Geology
SWpring 2012                  

Petrified Wood
 

                Today in this paper we will be talking to you about how petrified wood is made and where it comes from. How odd petrified wood can be, what makes petrified wood change color and where it is usually found.  What is made with petrified wood, and how you can tell petrified wood apart from other things?
 

What Is petrified wood, the word, to petrify, literally means, "turn to stone."  Petrified wood, then, is wood that has turned to stone. The early Cretaceous Lakota Sandstone deposits, which are found on the outside edge of the Black Hills, probably contain the oldest petrified wood specimens in the state. These fossils formed between 120 and 130 million years ago. Species in these deposits include bald or white cypress, several species of palm, and several species of cycadeoids. Here are some pictures of the process of how petrified wood is made.
 

The process of petrified wood starts out  as when a stump or a log is lying on the floor or has fallen to the ground and is left there with water trapping the tree’s original plant structure  and if the oxygen in the tree is cleared out with the water materials then the tree gets hollow and starts to petrify as seen in these lovely descriptions below.

 
When a tree falls to the ground in some rare cases it will be covered up in mud before it has a chance to decay.



If the tree is covered up quickly enough it will retain its same shape while under the mud  
If we zoom in and look at the tree cells very closely we will see that they start to become hollow
as the cells deteriorate or break down.  If we could only look at a tree this close we would see
that the cells that make the tree brown would be made of cellulose.  
When the tree Decays cells turn Hollow and are full of calcite and silicon and water.




 

When they water evaporates it leaves behind minerals that fill up the cells and now the tree is full of rock.

 
Thus forming petrified trees

 Oxygen, which causes oxidation or rotting of all types of materials, would have to have been kept away from the dead plant material to prevent it from decaying before it was preserved. Killing plant materials were they are deprived of oxygen by being buried by water sediments covering the plants.  Most Fossil wood is found in ancient rivers and flood plains environments.

Minerals, including silica dissolved from volcanic ash, absorbed into the porous wood over hundreds and thousands of years crystallized within the cellular structure, replacing the organic material as it broke down over time. Sometimes crushing or decay left cracks in the logs. Here large jewel-like crystals of clear quartz, purple amethyst, yellow citrine, and smoky quartz formed.

 When the tree reacts the water, three things may happen.

·         1. The log may disintegrate and not be fossilized.

·         2. The log may be reduced by compression to a coal or it may become petrified. If petrification takes place.

·        3.  Minerals from the water are deposited in fluid fills the openings in the wood.

My Petrified Wood

Side

Bottom

     This is called permineralization and it preserves the tissues in the wood, in other situations minerals may also replace the woody tissues of the log, this process is called replacement. The mineral replacement process is very slow, probably taking millions of years.

Some studies say that what is in Petrified wood are and I quote. “The mineral content of petrified wood is easily identified using a mass spectrometer or X-ray diffraction technology. Silica, in the form of silicon dioxide (SiO2), commonly known as quartz, is the most common replacement mineral. Often traces of other minerals give petrified wood its unique color and characteristics. Iron oxide will cause reds, browns, yellows and earth tones. Copper and chrome oxide create greens, silicates of aluminum produce whites, and manganese dioxide makes black.” It sounds accurate.
 

Where is Petrified Fossil wood found?
 

Most Petrified Fossil wood is mostly found in Hell Creek in Northwest South Dakota, where supposedly the last of the dinosaurs where living at the time, until they all died. Petrified wood from Paleocene Epoch deposits can be found on the prairies of western South Dakota, especially in the mid-northwest tier of counties and in the Badlands. These Paleocene are younger fossils  and they  are found in the Cretaceous deposits. These types of Petrified wood began to form 65 million years ago. The younger fossils include conifer species, such as  metasequoia, sequoia, hemlock, yew, and pine. Only seven species of tree have been identified through petrified wood, over 200 species of plants have currently been identified from other Triassic fossils, such as leaves, pollen, and spores.

Why Does South Dakota Have Such Different Fossil Species?

            Plate Tectonics make the land appear solid and stable in reality the parts are massive plates that are moving very slowly.. During the early Cretaceous ,  Here is a brief definition on Cretaceous,  the period of the Mesozoic Era, from 140 million to 65 million years ago, characterized by the greatest development and subsequent extinction of dinosaurs and the advent of flowering plants and modern insects. The entire North American continent was located much farther south thus  was a few degrees to the south of our present latitude and was much closer to sea level. . Apparently, during the Cretaceous Period, they experienced higher average temperatures and greater precipitation than occur here today. Over the great expanse of geologic time, the North American plate acted as a huge barge, carrying the fallen trees that were buried under sediments.
 

 
     Each piece is like a giant crystal, often sparkling in the sunlight as if covered by glitter.
    The rainbow of colors is produced by impurities in the quartz, such as iron, carbon, and manganese.
 

What is made from petrified wood?
 

Well now that you know at least a little bit of what makes Petrified wood and where it comes from, now we will look at what Petrified wood can be used for.



There is a lot of things Petrified wood can be used for and these are some of it. Some are just decoration.
 

Jewelry is one of the most common thing to make Petrified wood into, like this skull snake ring. See Above.
 

Other things are Like this skull head , it shows the different colors in Petrified wood. See Above

  

Even this sink is made up from Petrified wood. See Above

 

Finally, these tables where made from Petrified wood.

In conclusion, petrified fossil wood is one of the things that I myself have always been curious about because I never knew anything about them.  All I remember was that these two petrified woods were given to me when I was a child and I never knew what they really were. I hope that you have learned a great deal about petrified fossil wood in this paper and I hope you will take it to heart and tell your friends what you know about them. If you want to find out where more sites are for what Petrified wood is for see www.skullis.com.