Geology of the Grand Teton area

The geology of the Grand Teton area consists of some of the oldest rocks and one of the youngest mountain ranges in North America. The Teton Range, mostly located in Grand Teton National Park, started to grow some 9 million years ago. An older feature, Jackson Hole, is a basin that sits aside the range.

The 2.5 billion year old metamorphic rocks that make up the east face of the Tetons are marine in origin and include some volcanic deposits. These same rocks are today buried deep inside Jackson Hole. Paleozoic rocks were deposited in warm shallow seas while Mesozoic deposition transitioned back and forth from marine to non-marine sediments with the Cretaceous Seaway periodically covering the area late in that era.

Perhaps 3,000 million years ago in Precambrian time, sand, limey ooze, silt and clay were deposited in a marine trough (accurate dating is not possible, due to subsequent partial recrystallization of the resulting rock). Interbeded between these layers were volcanic deposits, probably from an island arc. These sediments were later lithified into sandstones, limestones, and various shales. These rocks were 5 to 10 miles (8 to 16 km) below the surface when orogenies (mountain-building episodes) around 2,800 to 2,700 million years ago intensely folded and metamorphosed them, creating alternating light and dark banded gneiss and schist. Today these rocks dominate the Teton Range with good examples easily viewable in Death Canyon and other canyons in the Teton Range. The green to black serpentine created was used by Native Americans to make bowls.

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