In order to plan your visit, you can see the actual water level at the Ottawa River Regulation Planning Board. A level of 41.7 meters and less at Gatineau is required to let you see the fossils. Even at this level, the fossils will still be under approximately 15 to 30 centimeters of water. The best time to access and see them is from the middle of the summer to the end of fall, depending on the water levels which vary with the rain. The fossils are usually completely exposed in fall.
Stromatolite fossils are exposed in the fall near the Champlain bridge when the water level of the Ottawa River is low. It's also possible to see them when the water level is higher, but you may have to wet your feet. Most plants and animals will not become fossils. They decay very quickly or get eaten by other critters. If a plant, an animal, or a trace is going to become a fossil, it has to be buried quickly by sediment (like mud). This happens in places like rivers, lakes, and oceans. Over time, many layers of sediment build up and eventually turn to rock. After more time passes, the layers of rock are brought to the surface of the Earth by forces like earthquakes. The overlying layers of rock are eroded exposing the fossils.
Stromatolites represent the most primitive life forms and are neither plants not animals. They are formed by the action of algae that trap sediments and form layers that eventually harden. These organisms thrived in the warm ancient seas of the Ottawa area about 450 million years ago when the North American plate was near the equator. They are solid cauliflower-shaped structures built by cyanobacteria.
To log the cache, you can publish a picture of your GPSr with the fossils as a background at the posted coordinates if you would like (a photo is 100% optional) and please answer the following questions by email:
You will notice cracks through the stromatolites. Which direction do they run in and why do you think they run in that particular direction?
Describe the stromatolites found at this location. What is the approximate diameter of the largest stromatolite and the smallest stromatolite you found on the site?
You'll find the parking at N45 24.677 W75 45.951 and the trailhead at N45 24.699 W75 45.878. You'll have to follow the small trail and jump from a rock to another if there's water (watch out as there's some poison ivy at the beginning of the trail). The level of water can greatly vary between years and it can be hard to predict. Be ready to come back empty handed.