Earth:Carrara Formation

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Carrara Formation
Stratigraphic range: Lower Cambrian–Middle Cambrian
[1]
Fossils from the Pyramid Shale member, Carrara Formation
TypeFormation
Sub-unitsSee: Members
OverliesZabriskie Quartzite
Thickness0–2,000 feet (0–610 m)[1]
Lithology
PrimarySiltstone
OtherShale, Limestone, Quartzite, Sandstone
Location
RegionCalifornia and Nevada
CountryUnited States

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

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. Fossil specimens from the Pyramid Shale Member have been found preserving the first evidence of chitin in trilobites.[9]

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][10]
  • S. linearis
 Burrows.

Undescribed

Genus Species Notes Images
Disc-shaped fossils[11]
  • "Carrara specimens"
 Disc-shaped organisms, resemble either porpitids or eldonids, especially to Discophyllum.


See also

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

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Stewart, J. H.. "Upper Precambrian and Lower Cambrian Strata, in the Southern Great Basin California and Nevada". Geological Survey Professional. https://pubs.usgs.gov/pp/0620/report.pdf. 
  2. ↑ Palmer and Halley 1979, Physical Stratigraphy and Trilobite Biostratigraphy of the Carrara Formation (Lower and Middle Cambrian)in the Southern Great Basin. USGS Prof. Pap. 1047
  3. ↑ Lieberman et al. 2017, Disc-shaped fossils resembling porpitids or eldonids from the early Cambrian (Series 2: Stage 4) of western USA. PeerJ 5:e3312
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 Wotte, Thomas; Sundberg, Frederick A. (2017). "Small shelly fossils from the Montezuman–Delamaran of the Great Basin in Nevada and California". Journal of Paleontology 91 (5): 883–901. doi:10.1017/jpa.2017.8. ISSN 0022-3360. Bibcode: 2017JPal...91..883W. https://www.jstor.org/stable/48572351. 
  5. ↑ 5.0 5.1 Pruss, Sara B.; Karbowski, Grace; Zhuravlev, Andrey Yu; Webster, Mark; Smith, Emily F. (30 June 2024). "DEAD CLADE WALKING: THE PERSISTENCE OF ARCHAEOCYATHUS IN THE AFTERMATH OF EARLY CAMBRIAN REEF EXTINCTION IN THE WESTERN UNITED STATES". PALAIOS 39 (6): 210–224. doi:10.2110/palo.2024.005. Bibcode: 2024Palai..39..210P. 
  6. ↑ Wu, Yu; Fu, Dongjing; Ma, Jiaxin; Lin, Weiliang; Sun, Ao; Zhang, Xingliang (June 2021). "Houcaris gen. nov. from the early Cambrian (Stage 3) Chengjiang Lagerstätte expanded the palaeogeographical distribution of tamisiocaridids (Panarthropoda: Radiodonta)". PalZ 95 (2): 209–221. doi:10.1007/s12542-020-00545-4. Bibcode: 2021PalZ...95..209W. 
  7. ↑ McCall, Christian R.A. (September 2023). "A large pelagic lobopodian from the Cambrian Pioche Shale of Nevada". Journal of Paleontology 97 (5): 1009–1024. doi:10.1017/jpa.2023.63. Bibcode: 2023JPal...97.1009M. 
  8. ↑ Pates, Stephen; Daley, Allison C.; Butterfield, Nicholas J. (December 2019). "First report of paired ventral endites in a hurdiid radiodont". Zoological Letters 5 (1). doi:10.1186/s40851-019-0132-4. PMID 31210962. 
  9. ↑ Bailey, Elizabeth; Tsurkan, Mikhail; Nowacki, Krzysztof; Jesionowski, Teofil; Ehrlich, Hermann (1 December 2025). "EVIDENCE FOR SURVIVING CHITIN IN CAMBRIAN TRILOBITES FROM THE CARRARA FORMATION, WESTERN NORTH AMERICA". Palaios 40 (12): 379–387. doi:10.2110/palo.2024.025. 
  10. ↑ Sundberg, Frederick A. (1983). "Skolithos linearis Haldeman from the Carrara Formation (Cambrian) of California". Journal of Paleontology 57 (1): 145–149. ISSN 0022-3360. https://www.jstor.org/stable/1304617. 
  11. ↑ Lieberman, Bruce S.; Kurkewicz, Richard; Shinogle, Heather; Kimmig, Julien; MacGabhann, Breandán Anraoi (6 June 2017). "Disc-shaped fossils resembling porpitids or eldonids from the early Cambrian (Series 2: Stage 4) of western USA". PeerJ 5. doi:10.7717/peerj.3312. PMID 28603667. Bibcode: 2017PeerJ...5e3312L. 



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