The Campito Formation is a geologic formation in the Last Chance Range, California, and Esmeralda County, Nevada. It preserves fossils dating back to the Cambrian period.
The Campito Formation is mainly composed of very fine to fine-grained quartzite, with small amounts of siltstone, getting up to 3,500 ft (1,100 m) thick.[3]
Members
The formation is split into two distinct members, which are as follows, in ascending age:
Andrews Mountain Member: It is the thickest of the two members, getting up to 2,800 ft (850 m) thick. It is composed of olive-gray or greenish-gray very fine to fine grained silty quartziticsandstone or quartzite and interbedded layers of dark-greenish-gray siltstones, which weather to a greenish-black or just black. The quartzite layers are composed of sub-angular very fine to fine grains of quartz, feldspar and other metallic minerals, all set within a muscovite, chlorite, and biotite.[3]
Montenegro Member: It is the thinnest of the two members, only getting up to 1,000 ft (300 m) thick. It is composed of dark-greenish-gray and greenish-gray siltstone composed of a mixture of quartz, muscovite, and chlorite. The siltstone is evenly laminated to thin-bedded. There are also commonly occurring archeocyathid-bearing limestone beds in the upper sections of the member.[3]
Paleobiota
The Campito Formation contains a number of fossils, most of which are found within the Montenegro Member. They range from archeocyathid sponges like Ethmophyllum, to arthropod trilobites like Nevadia,[3] and a wealth of ichnogenera, from burrows like Skolithos, to resting traces like Rusophycus.[4]
↑ 5.05.15.25.3Stewart, H. J. (2007). "Fallotaspidoid trilobite assemblage (Lower Cambrian) from the Esmeralda Basin (western Nevada, U.S.A.): The oldest trilobites from Laurentia". Alcheringa: An Australasian Journal of Palaeontology31: 123–140. doi:10.1080/03115510701586897.
↑ 8.08.1Signor, Philip W.; Mcmenamin, Mark A. S. (March 1988). "The Early Cambrian worm tube Onuphionella from California and Nevada". Journal of Paleontology62 (2): 233–240. doi:10.1017/S0022336000029863.
↑ 9.09.19.29.39.49.59.69.79.8Stewart Hollingsworth, J. (May 2005). "The earliest occurrence of trilobites and brachiopods in the Cambrian of Laurentia". Palaeogeography, Palaeoclimatology, Palaeoecology220 (1-2): 153–165. doi:10.1016/j.palaeo.2004.08.008.
↑Skovsted, Christian B.; Balthasar, Uwe; Vinther, Jakob; Sperling, Erik A. (May 2021). "Small shelly fossils and carbon isotopes from the early Cambrian (Stages 3–4) Mural Formation of western Laurentia". Papers in Palaeontology7 (2): 951–983. doi:10.1002/spp2.1313.