Geology of Percé

A site of geological interest

The territory proposed by the Geopark of Percé is very interesting from a geological point of view because it gathers different geological periods and different phenomena. There are rocks of sedimentary origin that were formed, for the most part, hundreds of millions of years ago.

The Percé Rock is undoubtedly the emblematic site of the Geopark. World famous, he helped to make the village of Percé famous. Each year, 400 000 visitors come to see and photograph it. Bonaventure Island, home to the world's most accessible gannet colony, is also iconic, while annually 100 000 visitors take the boat to visit.

In addition to these two emblematic sites, many geological riches are available to the public in Percé. It is possible to see rocks that reflect different stages of the formation of the Canadian Shield and the Gaspé Peninsula. Five distinct geologic periods are visible in the Geopark: Cambrian (542-489 Ma), Ordovician (489-443 Ma), Silurian (443-418 Ma), Devonian (418-359 Ma) and Carboniferous ( 359-299 Ma).

It is thus possible to observe a whole context of faults that have displaced the rocks and brought into contact rock formations of very distant ages. It is also possible to see the effects of erosion on the rock (especially on the Rocher-Percé), to discover from the top of Mount Sainte-Anne the particular geomorphology of the heart of Percé or to see the remains of the geological history of the region (fossils, ice marks, etc.).

The region of Percé is at the heart of a large orogenic chain, called Appalachian Orogen, which covers the Atlantic side of the North American continent (Figure 9). This orogenic chain was formed in several successive phases of folds, fractures and uprisings, between the end of the Precambrian (towards 600 Ma) and the end of the Paleozoic (towards 250 Ma), that is to say on a period of nearly 350 million years.

Since its formation, and apart from the magmatic and tectonic events related to the opening of the Atlantic in Jurassic and Cretaceous, the Quebec segment of this chain has been subjected to the erosive action of elements whose recent activity ( a few tens of thousands of years ago) shaped the landscape that we are currently seeing.

To reconstruct the geological history of the Percé region, the geologist has ancient rock archives that tell him about the nature of
rocks, paleogeography of depositional environments, tectonics and age of rocks (consolidated or loose). The geomorphologist uses recent landforms and sediments that reflect the activity of the erosion agents that shaped the current relief.

The territory of the Percé Geopark is particularly rich in rock archives (rocks and fossils) and in various forms of terrain that testify
from its past and recent past. In many sites, the rocks are well exposed so that we can decipher and illustrate this geological history.

Regional geology

The Percé region is part of the Appalachian geological province of Quebec, which extends south of the St. Lawrence from the US border to the Magdalen Islands. The Appalachians of Quebec are limited to the North by a set of faults, called the Logan Fault. Between the Laurentian Shield (or Canadian Shield) and the Logan Fault lies the St. Lawrence Platform, a sequence of Paleozoic sedimentary rocks, therefore of the same period as the Appalachians, but relatively undeformed.

SOURCES: UQAR, Geopark of Percé