Emigrant Formation

Not to be confused with the Emigrant Springs Formation, a different formation of a similar age.

Emigrant Formation
Stratigraphic range: Cambrian–Early Ordovician PreꞒ Ꞓ O S D C P T J K Pg N
Type	Formation
Sub-units	See: Members
Underlies	Palmetto Formation
Overlies	Mule Spring Limestone
Lithology
Primary	Shale
Other	Mudstone, Limestone, Chert, Sandstone
Location
Region	Nevada
Country	United States
Type section
Named for	Emigrant Pass

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. ^[1]

Members

The formation contains three members, which are as follows, in ascending age:

• Limestone & Siltstone Member: This member is the thinnest of the three, only getting up to 150 m (490 ft) 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. ^[1]
• Shale Member: This member can get up to 250 m (820 ft) thick in some areas, and is, as the name suggests, entirely dominated by shale, which may be faulted and repeated in many places. ^[1]
• Limestone & Chert Member: This member is the thickest of the three, getting up to 300 m (980 ft) thick in some areas, and contains a mixture of ribbon limestone, inter-bedded shales, as well as mega-breccia. ^[1]

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. ^[2]

Paleobiota

The biota of the Emigrant Formation is mainly composed of trilobites like Olenellus and Bathyuriscus , ^[3] as well as some small shelly fauna in the form of Pelagiella and Microcornus . ^[4] 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. ^[2]

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.

Cambrian

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

Arthropoda

Arthropoda
Genus	Species	Notes	Images
Amecephalus [3]	Amecephalus (?) sp. A. arrojosensis	Ptychoparid trilobite.
Mexicella [3]	M. robusta	Ptychoparid trilobite.
Paraantagmus [3]	P. latus	Ptychoparid trilobite.
Onchocephalites [3]	Onchocephalites sp. O. claytonensis O. runcinatus	Ptychoparid trilobite.
Tonopahella [3]	T. goldfieldensis	Ptychoparid trilobite.
Syspacephalus [3] [5]	S. variosus S. laticeps S. mccollumorum	Ptychoparid trilobite.
Achlysopsis [5]	A. brighamensis A. liokata	Ptychoparid trilobite.
Eokochaspis [3]	E. nodosa E. delamarensis (?) E. piochensis (?) E. longspina (?)	Ptychoparid trilobite.
Chancia [5]	C. maladensis	Ptychoparid trilobite.
Kistocare [5]	Kistocare sp.	Ptychoparid trilobite.
Elrathia [5]	E. marginalis	Ptychoparid trilobite.
Alokistocare [5]	A. paranotatum	Ptychoparid trilobite.
Meteoraspis [5]	Meteoraspis sp.	Ptychoparid trilobite.
Coosella [5]	Coosella sp.	Ptychoparid trilobite.
Coosia [5]	Coosia sp.	Ptychoparid trilobite.
Crepicephalus [5]	Crepicephalus sp.	Ptychoparid trilobite.
Tricrepicephalusalus [5]	Tricrepicephalus sp.	Ptychoparid trilobite.
Cedaria [5]	Cedaria sp. 1 Cedaria sp. 2 C. selwyni C. brevifrons	Ptychoparid trilobite.
Utia (?) [5]	U. curio (?)	Ptychoparid trilobite.
Kochaspid (?) [3]	Kochaspid (?) sp.	Ptychoparid trilobite.
Ptychoparioid [3] [5]	Ptychoparioid sp. A Ptychoparioid sp. B	Ptychoparid trilobites.
Oryctocephalus [3] [5]	Oryctocephalus sp. A O. americanus O. minor O. orientalus O. indicus O. maior O. reynoldsi	Corynexochid trilobite.
Euarthricocephalus [5]	E. nevadensis E. (?) wheelera	Corynexochid trilobite.
Ovatoryctocara [3] [5]	O. sinensis Oryctocephalus (?) sp.	Corynexochid trilobite.
Glossopleura [5]	G. walcotti	Corynexochid trilobite.
Zacanthoides [5]	Zacanthoides sp. Z. longipgus Z. divergens	Corynexochid trilobite.
Thoracocare [5]	T. minuta	Corynexochid trilobite.
Parkaspis [5]	P. drumensis	Corynexochid trilobite.
Kootenia (?) [5]	Kootenia (?) sp.	Corynexochid trilobite.
Pseudagnostus [1] [5]	P. josepha P. brighamensis P. bonnerensis	Agnostid trilobite.
Pagetia [5]	P. aspinosa P. rugosa P. claytonensis P. fossula	Agnostid trilobite.
Agnostoid [5]	Agnostoid sp. 1 Agnostoid sp. 2	Agnostid trilobite.
Bathyuriscus [3] [5]	Bathyuriscus sp. B. terranovensis	Biceratopsid trilobite. Previously described as Wenkchemnia walcotti and W. sulcata.
Bolbolenellus [3]	B. brevispinus	Biceratopsid trilobite.
Olenellus [3] [5]	Olenellus sp. O. puertoblancoensis (?)	Olenellid trilobite.
Wujiajiania [1]	W. sutherlandi	Olenellid trilobite.
Oryctocara [5]	Oryctocara sp.	Oryctocarid trilobite.
Oryctocarella [5]	Oryctocarella sp.	Oryctocarid trilobite.
Labiostria [1]	L. westropi	Aphelaspid trilobite.
Crassifimbra [3]	C. walcotti	Trilobite, family unknown.
Quasimodaspis [2]	O. brentsae	Tremaglaspidid artiopod.

Lophotrochozoa

Genus	Species	Notes	Images
Microcornus [4]	Microcornus sp.	Lophotrochozoan hyolith.
Parkula [6] [4]	P. esmeraldina	Lophotrochozoan hyolith.
Haplophrentis [7]	H. carinatus	Lophotrochozoan hyolith.
Hyolithellus (?) [4]	Hyolithellus (?) sp.	Lophotrochozoan hyolith. May possibly be an annelid. [8]
Hyolithides [7]	???	Undetermined lophotrochozoan hyoliths, are either preserved as molds, or are too poorly preserved for identification.
Anabarella [6] [4]	A. chelata	Helcionellid mollusc.
Pelagiella [4]	P. subangulata	Pelagiellid mollusc.
Costipelagiella [6] [4]	C. nevadense	Pelagiellid mollusc.

Chancelloriidae

Genus	Species	Notes	Images
Allonia [4]	Allonia sp.	Chancelloriid.
Chancelloria [6] [4]	Chancelloria sp.	Chancelloriid.

Echinodermata

Genus	Species	Notes	Images
Echinoderm Ossicles [6] [4]	???	Calcareous element that makes up the endoskeleton of echinoderms.

Porifera (Sponges)

Genus	Species	Notes	Images
Hexactinellid spicules [6]	???	Sponge skeleton, with six rays.

Flora

Genus	Species	Notes	Images
Archaeooides [4]	A. granulatus	Microalgae.
Girvanella [6]	Girvanella sp.	Cyanobacteria structures.

Ordovician

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

Arthropoda

Arthropoda
Genus	Species	Notes	Images
Esmeraldacaris [2]	E. richardsonae	Mollisonid chelicerate.
Caryocaris [2]	Caryocaris sp.	Caryocarid arthropod.

Lophotrochozoa

Genus	Species	Notes	Images
Inarticulate brachiopods [2]	???	Lophotrochozoan brachiopods, poor preservation hinders full identification.

Hemichordata

Genus	Species	Notes	Images
Dictyonema [2]	Dictyonema sp.	Dendroid graptolite.
Clonograptus [2]	Clonograptus sp.	Graptolites.

Porifera (Sponges)

Genus	Species	Notes	Images
Hexactinellid spicules [2]	???	Sponge skeleton.
Tetractinellid spicules [2]	???	Sponge skeleton.

Ichnogenera

Genus	Species	Notes	Images
Branching Trace Fossils [2]	???	Branching traces.

See also

• Earth sciences portal
• United States portal
• Paleontology portal

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

References

1. Sundberg, Frederick A.; Kurkewicz, Richard; Rooks, Dustin L. (July 2007). "WUJIAJIANIA SUTHERLANDI FAUNA (ELVINIA BIOZONE, PAIBIAN STAGE, FURONGIAN SERIES—"UPPER" CAMBRIAN) FROM THE EMIGRANT FORMATION, NEVADA". Journal of Paleontology. 81 (4): 794–796. doi:10.1666/pleo0022-3360(2007)081[0794:WSFEBP]2.0.CO;2.
2. Waggoner, Ben (2003). "Non-Trilobite Arthropods from the Silver Peak Range, Nevada". Journal of Paleontology. 77 (4): 706–720. ISSN   0022-3360.
3. Sundberg, Frederick A.; McCollum, Linda B. (September 2003). "Early and Mid Cambrian trilobites from the outer‐shelf deposits of Nevada and California, USA". Palaeontology. 46 (5): 945–986. doi:10.1111/1475-4983.00328.
4. 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. ISSN   0022-3360.
5. Sundberg, Frederick A. (May 2018). "Trilobite biostratigraphy of the Cambrian 5 and Drumian stages, Series 3 (Laurentian Delamaran, Topazan, and Marjuman stages, Lincolnian Series) of the lower Emigrant Formation at Clayton Ridge, Esmeralda County, Nevada". Journal of Paleontology. 92 (S76): 1–44. doi:10.1017/jpa.2017.130.
6. Skovsted, Christian B (1 April 2006). "Small shelly fossils from the basal Emigrant Formation (Cambrian, uppermost Dyeran Stage) of Split Mountain, Nevada". Canadian Journal of Earth Sciences. 43 (4): 487–496. doi:10.1139/e05-119.
7. Sun, Haijing; Babcock, Loren E.; Peng, Jin; Kastigar, Jessica M. (2 January 2017). "Systematics and palaeobiology of some Cambrian hyoliths from Guizhou, China, and Nevada, USA". Alcheringa: An Australasian Journal of Palaeontology. 41 (1): 79–100. doi:10.1080/03115518.2016.1184426.
8. Skovsted, Christian B.; Peel, John S. (January 2011). "Hyolithellus in life position from the Lower Cambrian of North Greenland". Journal of Paleontology. 85 (1): 37–47. doi:10.1666/10-065.1.

• Various Contributors to the Paleobiology Database. "Fossilworks: Gateway to the Paleobiology Database". Archived from the original on 25 March 2022. Retrieved 8 July 2014.