Amargosa Chaos
Encyclopedia
The Amargosa Chaos is a series of geological formations located in the Black Mountains
in southern Death Valley
. In the 1930s, geologist Levi F. Noble
studied the faulting and folding in the area, dubbing it the "Amargosa chaos" due to the extreme warping of the rock. Later researchers discovered that the region had experienced substantial tension that pulled large blocks of crust apart.
Modern geologists have documented four major deformational events that faulted and folded the Amargosa Chaos. The first event metamorphosed Death Valley's Precambrian
basement rocks
and occurred around 1,700 million years ago.
The second event began while layered younger Precambrian sediments were being deposited on top of the beveled surface of older metamorphic
basement rocks. This deformational event shifted the crust vertically, creating thinning and thickening of some sedimentary layers
as they were being deposited.
The two events responsible for the chaotic appearance of the Amargosa Chaos did not occur until over half a billion years later, during Mesozoic
or Early Tertiary
time. This third event folded the layered Precambrian and Cambrian
sedimentary rocks.
The fourth and final event occurred quite recently, geologically speaking. This phase of deformation coincided with severe crustal stretching that created the deep valleys and high mountains of this part of the Basin and Range
province. In just a few million years, during Late Miocene
to Pliocene
time, older rocks were intensely faulted and sheared. In some areas all that remains of some thick rock layers are lens-shaped pods of rock bounded on all sides by faults. Other layers have been sliced out of their original sequence altogether.
Black Mountains (California)
The Black Mountains are located in the southeastern part of Inyo County, California, in southeast Death Valley National Park.-Geography:The Black Mountains are essentially a continuation of the Amargosa Range, and lie in a generally north-south direction at the south-southwest end...
in southern Death Valley
Death Valley
Death Valley is a desert valley located in Eastern California. Situated within the Mojave Desert, it features the lowest, driest, and hottest locations in North America. Badwater, a basin located in Death Valley, is the specific location of the lowest elevation in North America at 282 feet below...
. In the 1930s, geologist Levi F. Noble
Levi F. Noble
Levi Fatzinger Noble was an American geologist. He was born in 1882 into a prominent and wealthy family of Auburn, New York. He received his bachelor’s degree in 1904 and his doctorate in 1909, both from Yale University....
studied the faulting and folding in the area, dubbing it the "Amargosa chaos" due to the extreme warping of the rock. Later researchers discovered that the region had experienced substantial tension that pulled large blocks of crust apart.
Modern geologists have documented four major deformational events that faulted and folded the Amargosa Chaos. The first event metamorphosed Death Valley's Precambrian
Precambrian
The Precambrian is the name which describes the large span of time in Earth's history before the current Phanerozoic Eon, and is a Supereon divided into several eons of the geologic time scale...
basement rocks
Basement (geology)
In geology, the terms basement and crystalline basement are used to define the rocks below a sedimentary platform or cover, or more generally any rock below sedimentary rocks or sedimentary basins that are metamorphic or igneous in origin...
and occurred around 1,700 million years ago.
The second event began while layered younger Precambrian sediments were being deposited on top of the beveled surface of older metamorphic
Metamorphic rock
Metamorphic rock is the transformation of an existing rock type, the protolith, in a process called metamorphism, which means "change in form". The protolith is subjected to heat and pressure causing profound physical and/or chemical change...
basement rocks. This deformational event shifted the crust vertically, creating thinning and thickening of some sedimentary layers
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
as they were being deposited.
The two events responsible for the chaotic appearance of the Amargosa Chaos did not occur until over half a billion years later, during Mesozoic
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
or Early Tertiary
Tertiary
The Tertiary is a deprecated term for a geologic period 65 million to 2.6 million years ago. The Tertiary covered the time span between the superseded Secondary period and the Quaternary...
time. This third event folded the layered Precambrian and Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...
sedimentary rocks.
The fourth and final event occurred quite recently, geologically speaking. This phase of deformation coincided with severe crustal stretching that created the deep valleys and high mountains of this part of the Basin and Range
Basin and Range
The Basin and Range Province is a vast physiographic region defined by a unique topographic expression. Basin and Range topography is characterized by abrupt changes in elevation, alternating between narrow faulted mountain chains and flat arid valleys or basins...
province. In just a few million years, during Late Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
to Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
time, older rocks were intensely faulted and sheared. In some areas all that remains of some thick rock layers are lens-shaped pods of rock bounded on all sides by faults. Other layers have been sliced out of their original sequence altogether.
See also
- Geology of the Death Valley areaGeology of the Death Valley areaThe exposed geology of the Death Valley area presents a diverse and complex set of at least 23 formations of sedimentary units, two major gaps in the geologic record called unconformities, and at least one distinct set of related formations geologists call groups...