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]
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Color key
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Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.
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Arthropoda
| Genus
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Species
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Notes
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Images
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| Houcaris (?)
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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]
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| Ursulinacaris[8]
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A Hurdiid radiodont.
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| Bristolia[1]
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An olenellid trilobite.
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| Olenellus
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An olenellid trilobite. Fossil specimens from the Pyramid Shale Member have been found preserving the first evidence of chitin in trilobites.[9]
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Lophotrochozoa
| Genus
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Species
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Notes
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Images
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| Microcornus[4]
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Lophotrochozoan hyolith.
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| Parkula[4]
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Lophotrochozoan hyolith.
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| Hyolithellus (?)[4]
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Lophotrochozoan hyolith.
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Chancelloriidae
Porifera (Sponges)
| Genus
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Species
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Notes
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Images
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| Archaeocyathus[5]
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Archaeocyathide sponge.
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Ichnogenera
Undescribed
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Species
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Notes
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Images
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| Disc-shaped fossils[11]
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Disc-shaped organisms, resemble either porpitids or eldonids, especially to Discophyllum.
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See also
References
- ^ a b c d e f g h i Stewart, J. H. "Upper Precambrian and Lower Cambrian Strata, in the Southern Great Basin California and Nevada" (PDF). U.S. Geological Survery. Geological Survey Professional.
- ^ 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
- ^ 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
- ^ a b c d e f 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. Bibcode:2017JPal...91..883W. doi:10.1017/jpa.2017.8. ISSN 0022-3360. JSTOR 48572351.
- ^ a b 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. Bibcode:2024Palai..39..210P. doi:10.2110/palo.2024.005.
- ^ 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. Bibcode:2021PalZ...95..209W. doi:10.1007/s12542-020-00545-4.
- ^ McCall, Christian R.A. (September 2023). "A large pelagic lobopodian from the Cambrian Pioche Shale of Nevada". Journal of Paleontology. 97 (5): 1009–1024. Bibcode:2023JPal...97.1009M. doi:10.1017/jpa.2023.63.
- ^ Pates, Stephen; Daley, Allison C.; Butterfield, Nicholas J. (December 2019). "First report of paired ventral endites in a hurdiid radiodont". Zoological Letters. 5 (1) 18. doi:10.1186/s40851-019-0132-4. PMC 6560863. PMID 31210962.
- ^ 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.
- ^ Sundberg, Frederick A. (1983). "Skolithos linearis Haldeman from the Carrara Formation (Cambrian) of California". Journal of Paleontology. 57 (1): 145–149. ISSN 0022-3360. JSTOR 1304617.
- ^ 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 e3312. Bibcode:2017PeerJ...5e3312L. doi:10.7717/peerj.3312. PMC 5463991. PMID 28603667.