A GEOLOGICAL SITE
The cave
Eventhough its popular name is “cave”, its geological features are more of an abrupt rock face that eroded away.
Time did its continuous work so that now the rocks tell our story. They formed 500 million years ago when the early Appalachians were born. These rocks are sediments deposited in basins along the western margin of the Iapetus Ocean. It shows a sequence called the Rivière Ouelle Formation. The basal sequence is composed of calcareous sandstone, topped by red stilties and argillites alternately which colour is due to the presence of ferrous ores and an oxidizing environment. The fine alternation between red and brown-grey layers is the result of variation in the current flow carrying the sediments. The sandstone beds were caused by more important mass movements on the slope of the basin. About 400 million years ago, the Iapetus Ocean closed and the old North-American and European continents collided causing these rocks to break along the faults. The folded structure shows the tremendous forces that once created a mountain range much higher than the present Appalachians. Then, these mountains were rounded off and carved by the slow process of weathering, water and glacial erosion.
The particles of rock are carried downstream by rivers and accumulate again in the seabed. They might form other rocks under large layers of sediments. The cycle will lasts until the energy from continental drift will come to a halt.
