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]
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]
^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
^ abPruss, 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.
^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.
