Relative dating of the pennsylvanian period


These rocks were originally deposited as sediment, which was compressed into sedimentary rocks and then altered by heat and pressure into a metamorphic rock called gneiss.The metamorphism occurred about 1 billion years ago during a mountain-building event, or orogeny, in eastern North America called the Grenville Orogeny.Gold was deposited from mineral-rich hot waters moving through cracks in the volcanic rocks on the sea floor.This gold has been mined in the Dahlonega area since its discovery in 1828.These metamorphic rocks, called the Grenville gneisses, form the "basement" upon which the younger rocks of the Appalachian mountain system have been deposited.630 and 700 million years ago, the rifting (or splitting apart of the continent) began, which led to the opening of the Iapetus Ocean (or proto‚ÄďAtlantic Ocean) along the eastern margin of North America.As the sea flooded over the eastern edge of North America during the Paleozoic, a thick (5 to 10 kilometers or more) sequence of shallow marine sediments was deposited.

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A volcanic island arc and possibly a small continent collided with North America in the Middle to Late Ordovician period, resulting in the formation of a large mountain range to the east.The geologic history of Georgia is not completely known or fully understood, and many significant questions remain.The state can be subdivided into five regions or provinces based on characteristic landforms, types and ages of rocks, and geologic structures.Numerous animals, including corals, brachiopods, snails, nautiloid cephalopods, crinoids, trilobites, and bryozoans, inhabited the shallow sea.During the Ordovician period (488 to 444 million years ago), the Iapetus Ocean began to close as a drifting continental tectonic plate neared eastern North America.This mountain-building event is called the Taconic Orogeny.

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