Cerro Gordo Formation

Cerro Gordo Formation
Name	Cerro Gordo Formation
Type	Formation
Period	Cambrian
Age	Cambrian
Region	Nevada, United States
Country	United States

Cerro Gordo Formation The Cerro Gordo Formation is a Cambrian stratigraphic unit exposed in eastern Sierra Nevada and adjacent basins of Nevada. It crops out near historical mining districts such as Cerro Gordo, California and influenced early geological mapping by figures associated with the United States Geological Survey and state surveys. The unit preserves fossil assemblages and sedimentary fabrics that tie it to regional transgression events recognized across the Cordilleran region and correlate with Cambrian units in the Great Basin and Basin and Range Province.

Description

The Cerro Gordo Formation forms cliff- and ledge-forming intervals in the Inyo Mountains and parts of eastern Sierra County and western Lander County, Nevada. Stratigraphic thickness varies along strike, reflecting paleotopography first described during mapping campaigns led by surveyors linked to the California Geological Survey and the United States Geological Survey. Exposures around mining localities such as Cerro Gordo, California and camps associated with Silver Peak, Nevada show lateral facies changes that helped clarify regional Cambrian stratigraphy correlated with classic sections in the White-Inyo Mountains and the Death Valley National Park region.

Stratigraphy

The formation lies above older Cambrian and late Neoproterozoic substrates mapped in the Sierra Nevada foothills and is overlain by younger Cambrian and Ordovician units recognized in Nevada by workers affiliated with the Nevada Bureau of Mines and Geology. Correlations have been proposed with the Wood Canyon Formation, Zabriskie Quartzite, and other Cambrian sequences studied by paleontologists and stratigraphers from institutions such as Stanford University and the University of California, Berkeley. Biostratigraphic ties using trilobite zones and chemostratigraphic markers have been compared with type sections described near Eureka and the Pahrump Group exposures.

Lithology and Sedimentology

Lithologies include interbedded quartzite, sandstone, siltstone, and carbonate-rich strata typical of Cambrian shallow-marine shelves documented in the Great Basin. Detrital frameworks and heavy-mineral suites resemble those reported from nearby Cambrian units by researchers at the Smithsonian Institution and the American Museum of Natural History. Sedimentary structures such as planar and trough cross-bedding, ripple marks, and storm-generated conglomeratic horizons tie the unit to depositional styles recorded by field parties from the U.S. Geological Survey and academics from University of Nevada, Reno.

Age and Paleontology

Biostratigraphic age assignments place the Cerro Gordo Formation in the Cambrian, based on trilobite faunas, small shelly fossils, and trace fossils comparable to assemblages described from the Burgess Shale-equivalent intervals and the Elrathia kingii-bearing horizons of the House Range. Paleontological work by teams associated with Harvard University and the California Academy of Sciences recovered trilobites, brachiopods, and archaeocyathan-like structures that support correlation with Middle to Late Cambrian stages recognized in global zonations promulgated by the International Commission on Stratigraphy. Isotopic chemostratigraphy and detrital zircon dating by groups at Caltech and the University of California, Los Angeles have contributed to refining absolute ages.

Depositional Environment

Sedimentological and paleontological evidence indicates deposition in a shallow continental shelf to ramp setting influenced by eustatic sea-level changes during the Cambrian transgression known across the Cordilleran region and the Laurentia paleocontinent. Facies gradients and storm-response deposits are consistent with processes documented in studies from the Great Basin National Park area and analogs in the Sauk Sequence. Provenance signals link sediment delivery to paleo-highlands studied by tectonic reconstructions involving researchers from Massachusetts Institute of Technology and the Geological Society of America.

Economic Resources and Uses

Although not a major ore host compared with nearby Paleozoic mineralized belts investigated by the U.S. Bureau of Mines, the Cerro Gordo Formation's quartzites have served as local building stone and as markers for exploration adjacent to historic silver and lead districts around Cerro Gordo, California and Tonopah, Nevada. Aggregates derived from resistant quartzite beds have been used by municipal projects tied to Inyo County and private enterprises; economic assessments have been performed by the Nevada Bureau of Mines and Geology and consulting firms collaborating with the U.S. Geological Survey.

History of Study and Naming

The unit was recognized and named during late 19th- and early 20th-century geological surveys conducted in association with mining booms and mapping efforts by the United States Geological Survey and state geological surveys. Early fieldwork involved geologists who also worked on regional syntheses alongside figures connected to institutions such as Harvard University and the Smithsonian Institution. Subsequent systematic stratigraphic, paleontological, and geochronological studies have been published by researchers affiliated with Stanford University, the University of Nevada, Reno, and international collaborators attending meetings of the Geological Society of America.

Category:Cambrian geology of Nevada