Emigrant Formation

The Emigrant Formation is a Cambrian to Ordovician geologic formation in Nevada. It preserves fossils dating back to the Cambrian period, as well as the Ordovician period.

Geology The Emigrant Formation is dominated by shales, with limestone common at the base and top of the formation. It is overlain by the Palmetto Formation, whilst it is underlain by the limestone dominated Mule Spring Limestone in the Outer Shelf of Nevada, and the siltstone and shale dominated Carrara Formation in the Middle Shelf of Nevada.

Members The formation contains three members, which are as follows, in ascending stratigraphic order (lowest to highest):

Limestone & Siltstone Member: This member is the thinnest of the three, only getting up to thick in some areas, and is dominated by lime mudstone. At the base of the member, it is entirely composed of shale, which gives way to calcareous sandstone, and then the common lime mudstones above that. Within these lime mudstones, there are occasional layers of more shale and chert. Shale Member: This member can get up to thick in some areas, and is, as the name suggests, entirely dominated by shale, which may be faulted and repeated in many places. Limestone & Chert Member: This member is the thickest of the three, getting up to thick in some areas, and contains a mixture of ribbon limestone, inter-bedded shales, as well as mega-breccia.

The Emigrant Formation also contains lower Ordovician aged rocks above the Limestone & Chert Member, informally known as the "Platy Limestone Unit". This unit is primarily composed of fine-grained, platy limestone, which are inter-bedded with pale-red siltstone. The very top of the unit is not preserved, and contacts the overlying Palmetto Formation at a fault, and the unit itself is also difficult to age, although a lower Ordovician age is suggested, though more evidence will be needed to pinpoint the exact age of the unit. It has also been noted that this unit may represent a transitional bed between the Emigrant and Palmetto Formations.

Paleobiota The biota of the Emigrant Formation is mainly composed of trilobites like Olenellus and Bathyuriscus, as well as some small shelly fauna in the form of Pelagiella and Microcornus. It also contains a sparse collection of fossils from a lower Ordovician unit right at the top of the formation, containing the chelicerate Esmeraldacaris, as well as some graptolite fauna.

Cambrian This section details all the fossils from the Cambrian sections of the Emigrant formation.

Arthropoda

Arthropoda GenusSpeciesNotesImagesAmecephalus Amecephalus (?) sp. A. arrojosensisPtychoparid trilobite.Mexicella M. robustaPtychoparid trilobite.Paraantagmus P. latusPtychoparid trilobite.Onchocephalites Onchocephalites sp. O. claytonensis O. runcinatusPtychoparid trilobite.Tonopahella T. goldfieldensisPtychoparid trilobite.Syspacephalus S. variosus S. laticeps S. mccollumorumPtychoparid trilobite.Achlysopsis A. brighamensis A. liokataPtychoparid trilobite.Eokochaspis E. nodosa E. delamarensis (?) E. piochensis (?) E. longspina (?)Ptychoparid trilobite.Chancia C. maladensisPtychoparid trilobite.Kistocare Kistocare sp.Ptychoparid trilobite.Elrathia E. marginalisPtychoparid trilobite.Alokistocare A. paranotatumPtychoparid trilobite.Meteoraspis Meteoraspis sp.Ptychoparid trilobite.Coosella Coosella sp.Ptychoparid trilobite.Coosia Coosia sp.Ptychoparid trilobite.Crepicephalus Crepicephalus sp.Ptychoparid trilobite.Tricrepicephalusalus Tricrepicephalus sp.Ptychoparid trilobite.Cedaria Cedaria sp. 1 Cedaria sp. 2 C. selwyni C. brevifronsPtychoparid trilobite.Utia (?) U. curio (?)Ptychoparid trilobite.Kochaspid (?) Kochaspid (?) sp.Ptychoparid trilobite.Ptychoparioid Ptychoparioid sp. A Ptychoparioid sp. BPtychoparid trilobites.Oryctocephalus Oryctocephalus sp. A O. americanus O. minor O. orientalus O. indicus O. maior O. reynoldsiCorynexochid trilobite.Euarthricocephalus E. nevadensis E. (?) wheeleraCorynexochid trilobite.Ovatoryctocara O. sinensis Oryctocephalus (?) sp.Corynexochid trilobite.Glossopleura G. walcottiCorynexochid trilobite.Zacanthoides Zacanthoides sp. Z. longipgus Z. divergensCorynexochid trilobite.Thoracocare T. minutaCorynexochid trilobite.Parkaspis P. drumensisCorynexochid trilobite.Kootenia (?) Kootenia (?) sp.Corynexochid trilobite.Pseudagnostus P. josepha P. brighamensis P. bonnerensisAgnostid trilobite.Pagetia P. aspinosa P. rugosa P. claytonensis P. fossulaAgnostid trilobite.Agnostoid Agnostoid sp. 1 Agnostoid sp. 2Agnostid trilobite.Bathyuriscus Bathyuriscus sp. B. terranovensisBiceratopsid trilobite. Previously described as Wenkchemnia walcotti and W. sulcata.Bolbolenellus B. brevispinusBiceratopsid trilobite.Olenellus Olenellus sp. O. puertoblancoensis (?)Olenellid trilobite.Wujiajiania W. sutherlandiOlenellid trilobite.Oryctocara Oryctocara sp.Oryctocarid trilobite.Oryctocarella Oryctocarella sp.Oryctocarid trilobite.Labiostria L. westropiAphelaspid trilobite.Crassifimbra C. walcottiTrilobite, family unknown.Quasimodaspis O. brentsaeTremaglaspidid artiopod.

Lophotrochozoa

GenusSpeciesNotesImagesMicrocornus Microcornus sp.Lophotrochozoan hyolith.Parkula P. esmeraldinaLophotrochozoan hyolith.Haplophrentis H. carinatusLophotrochozoan hyolith.Hyolithellus (?) Hyolithellus (?) sp.Lophotrochozoan hyolith. May possibly be an annelid.Hyolithides ???Undetermined lophotrochozoan hyoliths, are either preserved as molds, or are too poorly preserved for identification.Anabarella A. chelataHelcionellid mollusc.Pelagiella P. subangulataPelagiellid mollusc.Costipelagiella C. nevadensePelagiellid mollusc.

Chancelloriidae

GenusSpeciesNotesImagesAllonia Allonia sp.Chancelloriid.Chancelloria Chancelloria sp.Chancelloriid.

Echinodermata

GenusSpeciesNotesImagesEchinoderm Ossicles ???Calcareous element that makes up the endoskeleton of echinoderms.

Porifera (Sponges)

GenusSpeciesNotesImagesHexactinellid spicules ???Sponge skeleton, with six rays.

Flora

GenusSpeciesNotesImagesArchaeooides A. granulatusMicroalgae. Girvanella Girvanella sp.Cyanobacteria structures.

Ordovician This section details all the fossils from the Ordovician unit at the top of the Emigrant Formation.

Arthropoda

Arthropoda GenusSpeciesNotesImagesEsmeraldacaris E. richardsonaeMollisonid chelicerate.Caryocaris Caryocaris sp.Caryocarid arthropod.

Lophotrochozoa

GenusSpeciesNotesImagesInarticulate brachiopods ???Lophotrochozoan brachiopods, poor preservation hinders full identification.

Hemichordata

GenusSpeciesNotesImages Dictyonema Dictyonema sp.Dendroid graptolite. Clonograptus Clonograptus sp.Graptolites.

Porifera (Sponges)

GenusSpeciesNotesImagesHexactinellid spicules ???Sponge skeleton.Tetractinellid spicules ???Sponge skeleton.

Ichnogenera

GenusSpeciesNotesImagesBranching Trace Fossils???Branching traces.

Emigrant Formation

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