What are fossilized remains of terrestrial vegetation?
Short Answer: Petrified wood.
The petrifaction process forms, when wood becomes buried in water-saturated sediment or volcanic ash. The presence of water reduces the availability of oxygen which inhibits decomposition by bacteria and fungi. Mineral-laden water flowing through the sediments may lead to per-mineralization, which occurs when minerals fill the interiors of cells and other empty spaces. During replacement, the trees cells act as a template for mineralization. Petrified wood is usually associated with trees that were buried in fine grained sediments of deltas, floodplains or volcanic lahars (destructive mudflow on the slope of a volcano).
Some specimens of petrified wood are so well preserved, that people do not even realize they are fossils until they pick them up and learn they are significantly heavier, giving proof of their fossilized status.
Why is Petrified Wood so Colourful?
Elements such as manganese (not to be confused with magnesium), iron and copper in the water/mud during the petrification process give petrified wood a variety of colours. Pure quartz crystals are colourless, but when contaminants are added to the process the crystals take on a unique colour.
Following is a list of contaminating elements and related colour hues:
- carbon– black
- chromium - green/blue
- Cobalt - green/blue
- Copper - green/blue
- Iron oxides - red, brown, and yellow
- Manganese - pink/orange
- Manganese oxides - blackish/yellow
- Silicon dioxide - clear/white/grey
Where can I find Petrified Wood?
Petrified wood is not rare. It is found in volcanic deposits and sedimentary rocks around the world.
In Canada, it can be found:
- in the badlands of southern Alberta, where it is the provincial stone.
- Axel Heiberg Island in Nunavut has a large petrified forest.
- Along the North Saskatchewan river, around Edmonton.
- Blanche Brook, in Stephenville, Newfoundland, has 305-million-year-old examples.
Rockhounds love petrified wood for it's colourfulness, which means there are a lot of small pieces out there. Larger pieces are much more rare, away from the source, and are often found in private, public or university rock collections such as this Petrified Wood piece here at Guelph University.
Sources: https://geology.com/stories/13/petrified-wood/
https://en.wikipedia.org/wiki/Petrified_wood
To claim a find on this EarthCache, send the answers to the following questions to the CO:
1) Locate the pieces of Petrified wood near GZ, the cache description will help you do this, as there are a number of other rock samples here. How do you know you found the petrified wood samples?
2. How many samples are you able to locate?
2) Trees have annual rings. When you count them you are able to determine the age of a tree. Take a look at the sample here, count the rings when you can, estimate when you can’t to determine how old this tree was when it died.
3) This is a colourful sample of petrified wood. Using the table below, create a list of elements contained in this wood sample, based on colours hues of this petrified wood sample. Also identify what percentage of the sample contains these minerals, and where these minerals are found on the sample. Information on the cache page will be helpful to complete this.
