Westfield State College PHYS 0106 (Spring, 2001) Earth History Timeline
Proterozoic Eon: Mesoproterozoic Era

Timeline Links Phanerozoic Neoproterozoic Mesoproterozoic Paleoproterozoic Archean Other Links Historical Geology Page Physical Geology Page Mike's Home Page

Grenville Orogeny Writer/Researcher: Jessica Millot Editor: Lynn Sniatkowski Web Page Builder: Jessica Millot An orogeny is an episode of mountain building. The Grenville Orogeny occurred a little over one billion years ago during the Precambrian in the eastern part of present day Canada. The area is now known as the Grenville provinvce, as Canada is divided into geographic subdivisions, also known as structural provinces. The northern boundary of this province is known as the "Grenville front." The Canadian provinces have been through the following four major organic episodes, from oldest to most recent: Kenorian, Hudsonian, Elsonian, and Grenville. The occurence of a new organic episode usually covers up most of the evidence from the previous one. This is not always entirely the case, as at the border of the Grenville province there are traces of previous orogenies still present, although masked. The Grenville orogeny occured when a mountain range was formed, due to the collisions of small continents. These collisions were responsible for the completion of the supercontinent Rodinia. Over the next almost four hundred million years no action took place between the colliding plates. Therefore, the mountain range eroded and lowered itself in height, as the collision cooled down. This eventually resulted in flat land once again. Steps of the Grenville Orogeny from the Hartwick College Geology Department Website During the time of the orogeny the Iapetus Ocean bordered the eastern side of North America. A new continental margin was formed at this time. This boundary is where the Appalachian Mountains began their formation. Today, the area is recognized for its "crystalline limestone and other metamorphosed sediments of the well-sorted types" unlike the remainder of the Canadian provinces. These exposed rocks have been recrystalized as a result of the orogenic episodes in Canada. The Adirondack Mountains of upstate New York contain rocks from the Grenville orogeny that have not been deformed as much as they have around here in Western Massachusetts. Grenville gneiss is present in the Bershires in the forms of metamorphosed and sedimentary rocks. REFERENCES - Dunbar, Carol O. and Karl M. Waage. Historical Geology: Third Edition. New York: John Wiley and Sons, Inc., 1969. - Rankama, Kalervo, Ed. The Precambrian: Volume 2. New York: Interscience Publishers, 1965. - Skehan, James W. Roadside Geology of Massachusetts. Montana: Mountain Press Publishing Company, 2001. - Stanley, Steven M. Earth and Life Through Time. New York: W.H. Freeman and Company, 1986.