Editing Death Valley National Park (section)

==Geologic history==
{| class="wikitable"
|-
! Era
! Rock Units/Formations
! Principal Geologic Events
|-
| Cenozoic
| Alluvial fans, stream, and playa deposits, dunes, numerous sedimentary, volcanic, and plutonic units in separate and interconnected basins and igneous fields (includes Artist Drive, Furnace Creek, Funeral, and Nova Formations).
| Major unconformity, continued deposition in modern Death Valley, opening of modern Death Valley, continuing development of present ranges and basins, onset of major extension.
|-
| Mesozoic
| Granitic plutons, Butte Valley
| Thrust faulting and intrusion of plutons related to Sierra Nevada batholith; shallow marine deposition; unconformity.
|-
| Paleozoic
| Resting spring Shale, Tin Mountain Limestone, Lost Burro, [[Hidden Valley Dolomite]], Eureka Quartzite, Nopah, Bonanza King, Carrara, Zabriskie Quartzite, Wood Canyon.
| Development of a long-continuing carbonate bank on a passive continental margin; numerous intervals of emergence, interrupted by deposition of a blanket of sandstone in Middle Ordovician time. Deposition of a wedge of silliciclastic sediment during and immediately following the rifting along a new continental margin.
|-
| Proterozoic
| Crystalline basement, Pahrump, Stirling Quartzite, Johnnie, Ibex, Noonday Dolomite, Kingston Peak, Beck Spring, Crystal Spring.
|  Regional metamorphism, Major unconformity, rapid uplift and erosion, shallow marine deposition, glacio-marine deposition, unconformity. Shallow to deep marine deposition along an incipient continental margin.
|}

[[File:Death Valley basin cross section.png|thumb|upright=1.8|The Death Valley basin is filled with sediment (light yellow) eroded from the surrounding mountains. Black lines show some of the major faults that created the valley.]]
{{main|Geology of the Death Valley area}}
The park has a diverse and complex geologic history. Since its formation, the area that comprises the park has experienced at least four major periods of extensive [[volcanism]], three or four periods of major [[sedimentation]], and several intervals of major [[plate tectonics|tectonic]] deformation where the crust has been reshaped. Two periods of [[glaciation]] (a series of ice ages) have also had effects on the area, although no [[glacier]]s ever existed in the ranges now in the park.<ref>{{Cite web |date=December 18, 2009 |title=USGS Changing Climates and Ancient Lakes |url=https://pubs.usgs.gov/of/2004/1007/climates.html |access-date=November 15, 2023 |website=USGS Western Region Geology and Geophysics Science Center}}</ref>

===Basement and Pahrump Group===
Little is known about the history of the oldest exposed [[rock (geology)|rock]]s in the area due to extensive [[metamorphism]] (alteration of rock by heat and pressure). [[Radiometric dating]] gives an age of 1,700&nbsp;million years for the metamorphism during the [[Proterozoic]].<ref name="Wright1997p611"/> About 1,400&nbsp;million years ago a mass of [[granite]] now in the Panamint Range intruded this complex.<ref name="Wright1997p631">{{harvnb|Wright and Miller|1997|p=631}}</ref> Uplift later exposed these rocks to nearly 500&nbsp;million years of erosion.<ref name="Wright1997p631"/>

The Proterozoic sedimentary [[formation (geology)|formations]] of the [[Geology of the Death Valley area#Pahrump Group|Pahrump Group]] were deposited on these basement rocks. This occurred following uplift and erosion of any earlier sediments from the Proterozoic basement rocks. The Pahrump is composed of arkose [[conglomerate (geology)|conglomerate]] (quartz clasts in a concrete-like matrix) and [[mudstone]] in its lower part, followed by [[Dolomite (rock)|dolomite]] from [[Carbonate rock|carbonate]] banks topped by [[algal mat]]s as [[stromatolite]]s, and finished with basin-filling sediment derived from the above, including possible [[glacial till]] from the hypothesized [[Snowball Earth]] glaciation.<ref>{{harvnb|Wright and Miller|1997|pp=631–632}}</ref> The very youngest rocks in the Pahrump Group are [[basalt]]ic lava flows.

===Rifting and deposition===
[[File:Late Precambrian Noonday Formation.jpg|thumb|left|The Noonday Dolomite was formed as a carbonate shelf after the break-up of [[Rodinia]].]]
A [[rift]] opened and subsequently flooded the region as part of the breakup of the supercontinent [[Rodinia]] in the [[Neoproterozoic]] (by about 755&nbsp;million years ago) and the creation of the [[Pacific Ocean]]. A shoreline similar to the present [[Atlantic Ocean]] margin of the United States lay to the east. An [[algal mat]]-covered carbonate bank was deposited, forming the Noonday Dolomite.<ref name="Wright1997p632">{{harvnb|Wright and Miller|1997|p=632}}</ref> Subsidence of the region occurred as the [[continental crust]] thinned and the newly formed Pacific widened, forming the Ibex Formation. An angular [[unconformity]] (an uneven gap in the geologic record) followed.

A true [[ocean basin]] developed to the west, breaking all the earlier formations along a steep front. A wedge of clastic sediment then began to accumulate at the base of the two underwater precipices, starting the formation of opposing [[continental shelf|continental shelves]].<ref name="Wright1997p634">{{harvnb|Wright and Miller|1997|p=634}}</ref> Three formations developed from sediment that accumulated on the wedge. The region's first known [[fossil]]s of complex life are found in the resulting formations.<ref name="Wright1997p634"/> Notable among these are the [[Ediacaran|Ediacara fauna]] and [[trilobite]]s, the evolution of the latter being part of the [[Cambrian Explosion]] of life.

The sandy mudflats gave way about 550 million years ago to a carbonate platform (similar to the one around the present-day [[Bahama]]s), which lasted for the next 300 million years of [[Paleozoic]] time (refer to the middle of the [[:image:Geologic events in Death Valley.png|timescale image]]). Death Valley's position was then within ten or twenty degrees of the Paleozoic [[equator]]. Thick beds of carbonate-rich sediments were periodically interrupted by periods of emergence. Although details of geography varied during this immense interval of time, a north-northeastern coastline trend generally ran from [[Arizona]] up through [[Utah]]. The resulting eight formations and one group are {{convert|20000|ft|km|0}} thick and underlay much of the Cottonwood, Funeral, Grapevine, and Panamint ranges.<ref name="Wright1997p634"/>

===Compression and uplift===
[[File:Lake Manly system.gif|thumb|The [[Lake Manly]] lake system as it might have looked during its last maximum extent 22,000 years ago<ref name="Kiver1999p281">{{harvnb|Kiver|1999|p=281}}</ref> (USGS image)]]
In the early-to-mid- [[Mesozoic]] the western edge of the North American continent was pushed against the oceanic plate under the Pacific Ocean, creating a [[subduction]] zone.<ref name="Wright1997p634"/> A subduction zone is a type of contact between different crustal plates where heavier crust slides below lighter crust. Erupting volcanoes and uplifting mountains were created as a result, and the coastline was pushed to the west. The [[Sierran Arc]] started to form to the northwest from heat and pressure generated from subduction, and compressive forces caused [[thrust fault]]s to develop.<ref>{{Cite journal |last=Barth |first=A.P. |date=August 1, 2011 |title=Birth of the Sierra Nevada magmatic arc: Early Mesozoic plutonism and volcanism in the east-central Sierra Nevada of California |url=https://pubs.geoscienceworld.org/gsa/geosphere/article/7/4/877/132472/Birth-of-the-Sierra-Nevada-magmatic-arc-Early |journal=Geological Society of America |volume=7 (4) |issue=2011 |pages=877–897 |via=Geoscience World}}</ref>

A long period of uplift and erosion was concurrent with and followed the above events, creating a major unconformity, which is a large gap in the geologic record. Sediments worn off the Death Valley region were carried both east and west by wind and water.<ref name="Wright1997p635"/> No Jurassic- to [[Eocene]]-aged sedimentary formations exist in the area, except for some possibly Jurassic-age [[volcanic rock]]s (see the top of the [[:image:Geologic events in Death Valley.png|timescale image]]).<ref name="Wright1997p635">{{harvnb|Wright and Miller|1997|p=635}}</ref>

===Stretching and lakes===
[[File:Amargosa.jpg|thumb|left|During very wet periods, the [[Amargosa River]] can flow at the surface, as it did in February 2005.]]
[[Basin and Range Province|Basin and Range]]-associated stretching of large parts of crust below southwestern United States and northwestern Mexico started around 16 million years ago and the region is still spreading.<ref name="Wright1997p611"/> This stretching began to affect the Death and Panamint valleys area by 3&nbsp;million years ago.<ref name="Kiver1999p278">{{harvnb|Kiver|1999|p=278}}</ref> Before this, rocks now in the Panamint Range were on top of rocks that would become the Black Mountains and the Cottonwood Mountains. Lateral and vertical transport of these blocks was accomplished by movement on normal [[fault (geology)|fault]]s. Right-lateral movement along strike-slip faults that run parallel to and at the base of the ranges also helped to develop the area.<ref name="Wright1997p616"/> Torsional forces, probably associated with northwesterly movement of the [[Pacific plate]] along the [[San Andreas Fault]] (west of the region), is responsible for the lateral movement.<ref name="Kiver1999p278"/>

Igneous activity associated with this stretching occurred from 12&nbsp;million to 4&nbsp;million years ago.<ref name="Wright1997p616">{{harvnb|Wright and Miller|1997|p=616}}</ref> Sedimentation is concentrated in valleys (basins) from material eroded from adjacent ranges. The amount of sediment deposited has roughly kept up with this subsidence, resulting in the retention of more or less the same valley floor elevation over time.<ref>{{Cite web |date=January 9, 2022 |title=Death Valley Geology |url=https://www.nps.gov/deva/learn/nature/geology.htm |access-date=November 15, 2023 |publisher=National Park Service}}</ref>

[[Pleistocene]] ice ages started 2 million years ago, and melt from alpine [[glacier]]s on the nearby Sierra Nevada Mountains fed a series of lakes that filled Death and [[Lake Panamint|Panamint valleys]] and surrounding basins (see the top of the [[:image:Geologic events in Death Valley.png|timescale image]]). The lake that filled Death Valley was the last of a chain of lakes fed by the [[Amargosa River|Amargosa]] and [[Mojave River]]s, and possibly also the [[Owens River]]. The large lake that covered much of Death Valley's floor, which geologists call [[Lake Manly]], started to dry up 10,500&nbsp;years ago.<ref name="Sharp1997p41">{{harvnb|Sharp|1997|p=41}}</ref> [[Salt pan (geology)|Salt pans]] and [[Dry lake|playas]] were created as ice age glaciers retreated, thus drastically reducing the lakes' water source. Only faint shorelines are left.