Emigrant Formation
Emigrant Formation is a geologic formation in Nevada that spans the Cambrian to early Ordovician periods. It preserves fossils from both time periods. The rocks are mainly shale, with limestone at the base and top, and also include mudstone, chert, and sandstone.
The formation has three layers from oldest to youngest. The base includes limestone and chert. Above it lies a lower Ordovician unit called the Platy Limestone Unit, which is mostly fine-grained, flat-lying limestone with pale-red siltstone interbeds. The very top is not well preserved and sits against the Palmetto Formation along a fault; its exact age is uncertain but may be early Ordovician, possibly representing a transitional bed between Emigrant and Palmetto.
Fossils in the Emigrant Formation include Cambrian trilobites such as Olenellus and Bathyuriscus, and small shelly fossils like Pelagiella and Microcornus. At the top, a sparse lower Ordovician fossil assemblage is found, including the chelicerate Esmeraldacaris and graptolites.
In short, the Emigrant Formation records a Cambrian-to-early-Ordovician ecosystem in western Nevada, with shale-dominated rocks and distinct limestone layers at the bottom and top.
This page was last edited on 3 February 2026, at 18:13 (CET).