Ottawa Gatineau Geoheritage

The Ottawa-Gatineau Geoheritage Project promotes greater public knowledge and appreciation of the geology and related landscapes in and around Canada's National Capital Region

20. Petrie Island

Modern shoreline processes and the geology of imported blocks


Petrie Island

North end of Trim Rd., Ottawa, Ont.

Petrie Island beach.

Photo by A. Tweedle

Petrie Island is a sand island, composed of stratified sand and silt deposited by the Ottawa River and locally contains boggy areas with deposits of organic material (peat). The impact of erosion and deposition can be observed along the shoreline.

Cobbles and boulders of Precambrian and Paleozoic rock can be found in places and represent glacially transported material from the north, ultimately left as a lag deposit when the finer-grained glacial sediments were washed away by the river. A variety of igneous and metamorphic rock types can be seen among the Precambrian samples.

Also on the site are blocks of Ordovician sedimentary rock (mainly limestone and dolostone with some black shale layers) that were hauled in to reduce shoreline erosion. Numerous primary features can be seen in these rocks, including mudcracks in black shale layers, ripple marks and trace fossil burrows.

Visit the Friends of Petrie Island clubhouse to learn more.