On the Claremont College campus, there's several art sculptures. However, one in particular uses geology (and biology). Cretaceous was created in 2014 by Carol Bove and is one of two sculptures on campus that incorporates Petrified Wood into a sculpture.
This EarthCache provides an opportunity to explore the geology, paleobotany, and fossilization processes of petrified wood. Visitors will gain insight into how wood becomes stone, the unique mineralogy of the area, and what these ancient trees tell us about Earth's distant past.
🌲 What is Petrified Wood?
Petrified wood is a type of fossilized plant material where the original organic components of wood have been replaced with minerals, most commonly silica (SiO₂) in the form of quartz, while preserving the tree’s original structure. This fossilization process is called permineralization, which occurs over millions of years.
The wood at Petrified Forest primarily originated from a now-extinct tree related to modern-day conifers, often referred to by its scientific name, Araucarioxylon arizonicum.
⏳ How Did This Happen?
While it is not known where this petrified wood originated from (i.e. where it was sourced), I can make a few assumptions. It is likley Cretaceous in age due to that information being in the title of the installation.
Key Locations for Cretaceous Petrified Wood:
- United States:
- South Dakota: The Hell Creek Formation in the northwestern part of the state contains wood from the end of the Cretaceous; the Early Cretaceous Lakota Sandstone near the Black Hills also contains specimens.
- Alabama: Found in the central part of the state, particularly in Tuscaloosa County, with specimens roughly 90 million years old.
- Oklahoma: Common in the Antlers Formation in the southeastern part of the state.
- Virginia: Located in the northeastern corner of Prince William Forest Park.
- International:
- South America: A major forest exists near the Peru-Ecuador border, featuring trees from roughly 100 million years ago.
- Canada: Axel Heiberg Island in Nunavut holds a large petrified forest, and deposits exist in the badlands of southern Alberta.
- Ukraine: Specimens have been identified in the Cenomanian stage (approx. 100-94 million years ago) deposits in the Donetsk region.
During the Cretaceous (approx. 140-66 million years ago), these region was a lush, tropical floodplain filled with rivers, forests, and diverse wildlife. When trees died, they often fell into rivers and were quickly buried under sediment rich in volcanic ash. This rapid burial protected the logs from decay and provided the necessary minerals for fossilization.
Over time, groundwater carrying dissolved silica infiltrated the buried logs. This silica gradually replaced the organic wood tissues, cell by cell, crystallizing into quartz. Impurities such as iron, manganese, and carbon gave the petrified wood its brilliant reds, yellows, purples, and blacks.
🧪 The Colors of Petrified Wood
The colors in the petrified logs are not just beautiful—they are chemical clues. Here are the most common colorations and their causes:
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🔴 Red/Orange: Iron oxide (hematite)
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⚫ Black: Carbon or manganese oxides
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🟡 Yellow/Brown: Goethite or limonite
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🟣 Purple/Blue: Trace amounts of manganese or hematite
Works Cited
https://www.nps.gov/pefo/learn/nature/petrified-wood.htm
https://www.journals.uchicago.edu/doi/10.1086/629441
https://home.nps.gov/articles/000/permineralization-and-replacement.htm
https://granitegeek.concordmonitor.com/2018/06/12/where-wuold-we-be-105-million-years-ago/
https://en.wikipedia.org/wiki/Permineralization
https://www.geocaching.com/geocache/GC205H5
TO LOG A FIND ON THIS CACHE YOU MUST ANSWER ALL THE QUESTIONS BELOW. YOU CAN CONTACT ME THROUGH MY EMAIL OR THE GEOCACHING MESSAGE CENTER TO SEND YOUR ANSWERS. ANY INCORRECT ANSWERS MAY RESULT IN A CLARIFICATION RESPONSE FROM ME.
1. "Cretaceous in Claremont" on the first line of your email AND list all geocaching names of your party so I can match your answers to them. If you all want to learn something, I would prefer each cacher send me individual emails in the spirt of earthcaching.
2. Take a photo of you (or your signature item if you don't want to show your face) with the petrified wood in the photo. This photo MUST be uploaded to your "found it" log.
3. Tell me the diameter, height, and overall shape of the wood. Is the log rounded or oblong shaped? Why do you think this is the case?
4. Look closely at the texture of the petrified wood. (a) Are growth rings visible? If so, try and estimate the age by counting them. (b) If not, what does this tell you about the tree’s growth environment?
5. (a) Describe the colors you see and (b) based on this, name the two dominate minerals that are present.