SAINT-HIPPOLYTE AND SAINTE-SOPHIE QUARRIES-Continued
These quarries are located on both sides of the town limit, between Sainte-Sophie and Saint-Hippolyte, in the Low Laurentians. They are located more precisely in the geological Precambrian Grenville province and are more than 544 million years old.
In these quarries, there are sedimentary rocks of plutonic origin that have been distorted by a regional metamorphism which resulted in granite gneiss formations.
Superficial deposits of sand and gravel can also be found. They date back to the last glacial, between 70,000 and 10,000 years ago, during the Quaternary Period.
The term “plutonic rock” (named after Pluto, the god of hell) refers to an intrusive body of igneous rock formed beneath the earth’s surface, within the continental or oceanic crust, following the slow cooling of magma. The term “granitic” refers to the mineralogical composition of the rock that resembles granite’s. Finally, the term “gneiss” refers to the high level of metamorphism that affected an area and distorted pre-existing granite rocks.
These quarries’ sand and gravel come from sub-glacial deposits named Eskers.
These sediments were deposited by streams flowing in sub-glacial tunnels. They come from the erosion of rock produced by the passage of a glacier. The transportation of sediments through water streams promotes the sorting of particles and the natural washing of finer-grained ones (silt and clay).
