Carrara Formation

The Carrara Formation is a geologic formation in California and Nevada. It preserves fossils dating back to the Cambrian period.^[2][3][1]

Carrara Formation
Stratigraphic range: Lower Cambrian–Middle Cambrian PreꞒ Ꞓ O S D C P T J K Pg N [1]
Fossils from the Pyramid Shale member, Carrara Formation
Type	Formation
Sub-units	See: Members
Overlies	Zabriskie Quartzite
Thickness	0–2,000 feet (0–610 m)[1]
Lithology
Primary	Siltstone
Other	Shale, Limestone, Quartzite, Sandstone
Location
Region	California and Nevada
Country	United States

Geology

The Carrara Formation is primarily composed of olive-gray and greenish-gray siltstones and shales, as well as medium-gray limestone in the lower half of the formation, with medium-gray to yellowish-brown silty limestone and limy limestone in the upper half of the formation.^[1] The lower half also contains quartzite rocks, similar to that seen in the underlying Zabriskie Quartzite. In other areas of the lower half, there are olive-gray, greenish-gray or dusky-yellow siltstones and sandy siltstones, along with small amounts of sandstone and limestone. The upper half also contains fine to medium-grained quartzites, white in colour, forming a distinctive band.^[1] In other areas of the formation, it instead consists of inter-stratified siltstones, shales and very fine to medium-grained quartzite.^[1]

Members

The Carrara Formation contains in total nice Members, which are as follows, in ascending age:^[4]

• Eagle Mountain Shale Member
• Thimble Limestone Member
• Echo Shale Member
• Gold Ace Limestone Member
• Pyramid Shale Member
• Red Pass Limestone Member
• Pahrump Hills Shale Member
• Jangle Limestone Member
• Desert Range Limestone Member

Paleobiota

The Carrara Formation contains an abundance of arthropods, like the spiny Bristolia, as well as ichnotaxon like Skolithos, a type of burrow trace fossil.^[1] It also contains some examples of Archaeocyatha, a clade of sponges that went extinct during this time.^[5]

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Arthropoda

Genus	Species	Notes	Images
Houcaris (?)	H?. magnabasis	Radiodont arthropod. Previously described as Anomalocaris magnabasis in 2019, but was reassigned to Houcaris in 2021,[6] although this assignment is now up in the air with subsequent analysis suggesting H. magnabasis may not form a monophyletic clade with other species of Houcaris.[7]
Ursulinacaris[8]	H. grallae	A Hurdiid radiodont.
Bristolia[1]	B. bristolensis	An olenellid trilobite.
Olenellus	O. clarki O. terminatus	An olenellid trilobite.

Lophotrochozoa

Genus	Species	Notes	Images
Microcornus[4]	Microcornus sp.	Lophotrochozoan hyolith.
Parkula[4]	Parkula sp.	Lophotrochozoan hyolith.
Hyolithellus (?)[4]	Hyolithellus (?) sp.	Lophotrochozoan hyolith.

Chancelloriidae

Genus	Species	Notes	Images
Allonia[4]	Allonia sp.	Chancelloriid.
Chancelloria[4]	Chancelloria sp.	Chancelloriid.

Porifera (Sponges)

Genus	Species	Notes	Images
Archaeocyathus[5]	Archaeocyathus sp.	Archaeocyathide sponge.

Ichnogenera

Genus	Species	Notes	Images
Skolithos[1][9]	S. linearis	Burrows.

Undescribed

Genus	Species	Notes	Images
Disc-shaped fossils[10]	"Carrara specimens"	Disc-shaped organisms, resemble either porpitids or eldonids, especially to Discophyllum.

See also

• Earth sciences portal
• United States portal
• Paleontology portal

• List of fossiliferous stratigraphic units in Nevada
• Paleontology in Nevada
• Paleontology in California