Click here to skip to the content

Malcolm McLeod, Chris White and Sandra Barr

The geology of southern New Brunswick is complex and has proved difficult to interpret. The Precambrian rocks present a particular challenge and include sedimentary rocks deposited in ancient oceans, fragments of continental crust and lava and ash forged in volcanic islands. The rocks were formed by continental collisions, from volcanic activity erupting into ocean sediments, and the subduction of ocean crust. They have been metamorphosed, subjected to changes in temperature and pressure, and over time the story of their beginnings has become hidden.

View transcript (Adobe Flash Player, 2 minutes 9 seconds, 5.1 MB)

For best viewing of this site, you will need the plugin: Adobe Flash Player

It is relatively simple to determine age relationships between rocks that are well stratified (layered). However, it is difficult to establish the relationships between rocks that have been moved and changed as much as New Brunswick’s Precambrian rocks. Scientists use radiometric dating as the principal source of information about the age of rocks. Radiometric dating has been an important factor in sorting out the sequence of events that created the Precambrian geology in New Brunswick.

Mapping and unraveling the story has been the job of many geologists, including Malcolm McLeod from the New Brunswick Department of Natural Resources, Chris White from the Nova Scotia Geological Survey and Sandra Barr from Acadia University. They have been using these techniques to determine the ages of rocks and reveal their origins. Rocks like the lava (Dacite) of the McBrien Lake Formation (554 ±14 million years old) and the Fairville Granite (548 ± 2 million years old) are pieces of the plate tectonics puzzle.