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Saint John Geology


Dr. Sandra Barr, Department of Earth and Environmental Science, Acadia University, Nova Scotia

The fascinating thing about the geology of the Saint John area is how many different kinds of rocks there are juxtaposed against one another. Rocks with very, very different histories and ages and origins. And some examples sitting here, there’s some marbles. We don’t really know for sure the ages of deposition for these carbonate rocks but some people think it is as much as a billion years ago. It may have been as young as 600 million years ago. Still very old, but a lot less than a billion. The marble comes in a lot of different colours - grey, white – just related to small variations in their chemical compositions.

Other really fascinating rocks associated with those marbles, there’s a lot of igneous rocks formed underground as magmas cooled very slowly and these rocks formed in what we called volcanic arcs, underneath volcanic arcs. Places like Japan or the Andes Mountains in the modern world. And we don’t know where these rocks were when they were forming, but more than likely it was against areas that are now part of Columbia in South America. In addition to these rocks we are looking at here there are other belts of rocks that were probably closer to Africa or maybe even Baltica at various times in the history of the area.