Boulder Garden - Earliest Signs of Life
You are standing in the Carpenter Lake Boulder Garden, an exhibit that showcases some of the geological wonders of the Great Lakes region. This eartchache will provide a short lesson on Stromatolites and how these fossils record the earliest known examples of biological life on our planet!
There are a ton of geological exhibits in this section of the park and if you enjoy geology (and since you're reading this Earthcache I will assume that you do), you'll love this area!
Stromatolites
Stromatolites are colonies of single celled organisms known as cyanobacteria. These colonies are the first known organisms to exist on earth and they're the reason earth is so bountiful today. 3.5 billion years ago the earth's atmosphere was comprised predominantly of carbon dioxide and other gasses that are not compatible with most complex biological life as we know it. Cyanobacteria were the driving force in creating our modern atmosphere by converting those gases to oxygen through photosynthesis. These creatures originated in a maritime environment, most likely a warm inland sea.
How do we know these cyanobacteria existed? After all, 3.5 Billion years ago is a long time past! These single celled organisms created colonies on sedimentary stones and left their mark in the form of fossils. These structures are characterized by thin, alternating light and dark circular layers. These alternating layers are largely produced by the trapping of sediment washed up during storms in a sticky secretion that the colony exudes to stick to the stone on some occasions and by limestone precipitation by the blue-green algae on others. Limestone precipitation is thought to cause lighter bands while sediment entrapment is thought to cause darker bands.
An example of ancient stromatolites found in Upstate New York
As the cyanobacteria dies it doesn't drift away, rather the colony keeps growing on top of it. This process, combined with the deposition of limestone precipitate helped to create fossils that preserve the legacy of this long dead colony. Geologists and paleontologists are able to know so much about stromatolites in part because these creatures and colonies still exist - this means that scientists are able to observe the lifecycle of these colonies today in places like Western Australia.
Living Stromatolites in Western Australia
Logging Requirements
Please send your answers to questions 1-2 to the CO via the messaging system or email. You do not have to wait for a response in order to claim your find.
- What does the presence of stromatolites in a rock tell us about how the area where it was found looked several billion years ago? (Hint: where would these fossils have formed?)
- Describe the stromatolites you found at GZ in terms of overall size, and the pattern of their rings. Is one color of ring more common? If so what does this tell you about which process was more predominant in causing the formation you see before you?
- Take a photo of yourself (or a personal object) in front of the park. Do not include the stromatolite in your photo.
Resources
- https://en.wikipedia.org/wiki/Stromatolite
- https://www.britannica.com/science/stromatolite
- https://www.nps.gov/articles/stromatolites-of-capitol-reef-national-park.htm
- https://science.cranbrook.edu/discover/glacial-boulder-project/stromatolites-in-dolomite