SMITHERS ROAD TRIP, CONTINUES TO CACHE CREEK!
Our next stop was the Cache Creek Melange! Anyone can check out this amazing geological feature at the side of the road near the southern end of the town.
A melange is a rock unit of breccias that is large enough to map and can have clasts that can be up to 1000 metres! Breccias are a type of rock that are formed from angular gravel and boulder-sized clasts that are cemented together in a matrix. The angular clasts tell us that they have not been transported very far from their source.
The Cache Creek Melange formed along a subduction zone where a deep oceanic trench was formed as the less dense oceanic crust went under the denser continental crust. As this happened, it became unstable and large parts of the sediment would break off and create large underwater landslides which would tumble into the depths! This creates the jumbled and chaotic beds of mudstones, limestones, cherts and silts that you see in the picture below! In the photo you can see how the sediments are slumped and contorted around each other.
A fascinating features of melanges is that you can find microfossils in the sediments of the rock which we can date. When we date the microfossils, it can tell us how each block/clast can come from very different times. Even millions of years apart!
The Cache Creek Melange deposit tells us about the forces that built the province of British Columbia. During the Jurassic Period, 201.3-145.5 million years ago, when many large islands were slamming into the side of the North American continent and the ocean floor between was being pushed up to form the mountains that we see today!