Farmington Canyon Complex
Age: Late Archean to Early Proterozoic
The rocks of the Precambrian Farmington Canyon Metamorphic Complex are among the oldest rocks in Utah. They have been dated to about 2.5 billion years old, putting them at the boundary of the Late Archean Eon and the Early Proterozoic Eon. It is referred to as a “metamorphic complex” because it isn’t a single type of rock, but a group of several types of rocks.
Analysis of the chemistry and mineralogy of the rock of the complex suggest that their protolith consisted of sedimentary material washed off of the continent and deposited directly upon the basaltic sea floor. During the Late Archean Eon, subduction and continental accretion caused the rocks to become folded and metamorphosed. This would have produced a folded mountain belt, perhaps similar to the Ural Mountains, that ran approximately east-West across North-central Utah. Today, these metamorphic rocks can be found along the Wasatch Front between Ogden and Bountiful, Utah. The Farmington Canyon Complex can also be found on Antelope Island, in the Great Salt Lake. The photos were taken of cobbles and boulders which were used to armor the causeway on which the road to the island crosses the lake. Notice that they are not only folded but the original sedimentary rock has recrystallized into bands of lighter and darker minerals. Such banded metamorphic rocks are known as “gneiss”
The photos below are of folded gneiss of the Farmington Canyon Complex.
Analysis of the chemistry and mineralogy of the rock of the complex suggest that their protolith consisted of sedimentary material washed off of the continent and deposited directly upon the basaltic sea floor. During the Late Archean Eon, subduction and continental accretion caused the rocks to become folded and metamorphosed. This would have produced a folded mountain belt, perhaps similar to the Ural Mountains, that ran approximately east-West across North-central Utah. Today, these metamorphic rocks can be found along the Wasatch Front between Ogden and Bountiful, Utah. The Farmington Canyon Complex can also be found on Antelope Island, in the Great Salt Lake. The photos were taken of cobbles and boulders which were used to armor the causeway on which the road to the island crosses the lake. Notice that they are not only folded but the original sedimentary rock has recrystallized into bands of lighter and darker minerals. Such banded metamorphic rocks are known as “gneiss”
The photos below are of folded gneiss of the Farmington Canyon Complex.
