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.
The Emigrant Formation is dominated by shales, with limestone common at the base and top of the formation.[1]
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]
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
|
|
Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.
|
This section details all the fossils from the Cambrian sections of the Emigrant formation.
| Genus
|
Species
|
Notes
|
Images
|
| Hexactinellid spicules[6]
|
|
Sponge skeleton, with six rays.
|
|
This section details all the fossils from the Ordovician unit at the top of the Emigrant Formation.
| Genus
|
Species
|
Notes
|
Images
|
| Inarticulate brachiopods[2]
|
|
Lophotrochozoan brachiopods, poor preservation hinders full identification.
|
|
| Genus
|
Species
|
Notes
|
Images
|
| Branching Trace Fossils[2]
|
|
Branching traces.
|
|
Lua error in mw.title.lua at line 392: bad argument #2 to 'title.new' (unrecognized namespace name 'Portal').
- ^ a b c d e f g Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ a b c d e f g h i j k Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ a b c d e f g h i j k l m n o p Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ a b c d e f g h i j k Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ a b c d e f g Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ a b Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
