Nevadaplano
The Nevadaplano was a high plateau that is proposed to have covered parts of southwestern North America during the late Mesozoic and early Cenozoic, located in the present-day US states of Idaho, Nevada, Utah and possibly others.
Tectonic extension gave rise to the Basin and Range province and separated the Sierra Nevada-Great Valley block from the Nevadaplano, forming today's landscape.
The existence of the Nevadaplano was proposed in 2004 by DeCelles[1][2] and named after the Altiplano high plateau of South America.
[4] Unlike the present-day Andean Altiplano and Tibetan plateau, the Nevadaplano was dismembered during the Cenozoic and thus its structure and evolution are poorly understood.
[1] Its growth began either in the Cretaceous or the Jurassic, when significant tectonic shortening took place[8] behind the Sevier orogen.
Similar to the present-day Altiplano in South America, the combination of an arid climate, tectonic contraction, weak erosion[1] and the accumulation of volcanic rocks both in and below the crust helped raise the Nevadaplano[9] during the Cretaceous, when flat subduction was taking place.
[17] The plateau overrode the heat source of the East Pacific Rise about 28 million years ago.
The heat flow from the Yellowstone hotspot and the addition of magmas into the crust are mechanisms that could have caused the collapse process.
Presently, relic surfaces around the Middle Fork Feather River valley[24] and the high elevations of the northern Basin and Range may be considered remnants of the Nevadaplano.
[28] Isotope analysis indicates that the Nevadaplano stood at high elevations,[1] probably higher than[29] or comparable to the then-Sierra Nevada.
The elevation of the Nevadaplano exceeded 3 kilometres (1.9 mi),[18] but the exact value is controversial,[12] as is whether it was flat or featured rugged topography.
[38] Some normal faulting took place within the Nevadaplano, along with the exposure of core complexes, and generated isolated basins.
[54] Remnants of the Laramide uplands, the Chusca erg[55] or the Sevier fold-and-thrust belt were located east of the Nevadaplano.
[73] Evidence suggests that lakes and alluvial fans existed on the Nevadaplano,[31] the Sheep Pass Formation constitutes the remnants of such landforms.
[74] Fossils of anurans, birds, bivalves, crustaceans, frogs, lizards, mammals, molluscs, ostracods and snakes have been found there,[75] as well as evidence of algae, charophytes, plants[76] and microbial mats.
