Menu Close

Where are accreted terranes located How were they formed?

Where are accreted terranes located How were they formed?

eastern Pacific Ocean
All four terranes are separated by major unconformities and faults and were intruded by plutons of Late Jurassic and Early Cretaceous age. These terranes were formed in the eastern Pacific Ocean, far from their present position, and were transported on lithospheric plates to be accreted on the edge of the continent.

Where does accretion take place?

Accretion, in geology, is a process by which material is added to a tectonic plate at a subduction zone, frequently on the edge of existing continental landmasses. The added material may be sediment, volcanic arcs, seamounts, oceanic crust or other igneous features.

How does a terrane become part of a continent?

When a terrane, especially a large terrane, accretes at a subduction zone, a piece of oceanic lithosphere can be wedged up onto the edge of the continent as part of the accretion process.

How does accreted terranes form?

Accreted terranes are the blocks of continental fragments and oceanic islands that have collided with a continent and are now permanently attached. Where plates converged, thicker crust formed at island arcs as magma poured out on the surface as lava flows, and was added to the base of the crust as igneous intrusions.

How do accreted terranes form?

Where does accretion begin?

Instead of just sitting still in space, the bits of gas and dust will eventually start colliding with each other. Some of the dust will stick to other bits of dust and form larger chunks of matter. This sticking together is the beginning of the process of accretion.

How are terranes formed?

In geology, a terrane (in full, a tectonostratigraphic terrane) is a crust fragment formed on a tectonic plate (or broken off from it) and accreted or “sutured” to crust lying on another plate. A sedimentary deposit that buries the contact of the terrane with adjacent rock is called an overlap formation.

How are accreted terranes formed?

What are the different names for accreted terranes?

Accreted terranes may be called exotic terranes, suspect terranes, or tectonostratigraphic terranes. The terms all mean the same thing.

Where does terrane accretion take place on a transform plate?

Because terranes come from a distant location they are often referred to as exotic terranes. Terrane accretion is most common at convergent plate boundaries, but it may be possible for a terrane to be brought from an exotic location along a transform plate boundary.

What causes a continent to become an accreted terrane?

It is also possible for a new divergent plate boundaryto develop that rifts a continent apart. Part of the continent can then drift away on a moving plate to become an accreted terraneon another continent.

Where are the accreted terranes located in Alaska?

The park lands in the northern part of the state lie in the Brooks Range, composed of terranes added to the continent during collision with a continental fragment about 100 million years ago. NPS Sites in Alaska. NP = National Park; NM = National Monument; NPres = National Preserve.