Geology of The Death Valley Area - Change To Active Margin and Uplift

Change To Active Margin and Uplift

The western edge of the North American continent was later pushed against the oceanic plate under the adjacent ocean. An area of great compression called a subduction zone was formed in the early-to-mid Mesozoic, which replaced the quiet, sea-covered continental margin with erupting volcanoes and uplifting mountains. A chain of volcanoes pushed through the continental crust parallel to the deep trench, fed by magma rising from the subducting oceanic plate as it entered the Earth's hot interior. Thousands of feet (hundreds of meters) of lavas erupted, pushing the ocean over 200 miles (320 km) to the west.

Compressive forces built up along the entire length of the broad continental shelf. The Sierran Arc, also called the Cordilleran Mesozoic magmatic arc, started to form from heat and pressure generated from the subduction. Compressive forces caused thrust faults to develop and granitic blobs of magma called plutons to rise in the Death Valley region and beyond, most notably creating the Sierra Nevada Batholith to the west. Thrust faulting was so severe that the continental shelf was shortened and some parts of older formations were moved on top of younger rock units.

The plutons in the park are Jurassic and Cretaceous aged and are located toward the park's western margin where they can be seen from unimproved roads. One of these relatively small granitic plutons was emplaced 67–87 Ma and spawned one of the more profitable precious metal deposits in the Death Valley area, giving rise to the town and mines of Skidoo. In the Death Valley area these solidified blobs of magma are located under much of the Owlshead Mountains and are found in the western end of the Panamint Mountains. Thrusted areas can be seen at Schwaub Peak in the southern part of the Funeral Mountains.

A long period of uplift and erosion was concurrent with and followed the above events, creating a major unconformity. Sediments worn off the Death Valley region were shed both east and west and carried by wind and water; the eastern sediments ended up in Colorado and are now famous for their dinosaur fossils. No Jurassic to Eocene sedimentary formations exist in the area except for some possibly Jurassic-age volcanic rock around Butte Valley. Large parts of previously deposited formations were removed; probably by streams that washed the sediment into the Cretaceous Seaway that longitudinally divided North America to the east.