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 ==