The Floian is the second stage of the Ordovician Period. It succeeds the Tremadocian with which it forms the Lower Ordovician series. It precedes the Dapingian Stage of the Middle Ordovician. The Floian extended from 477.7 to 470 million years ago. The lower boundary is defined as the first appearance of the graptolite species Tetragraptus approximatus.
The Dapingian is the third stage of the Ordovician period and the first stage of the Middle Ordovician series. It is preceded by the Floian and succeeded by the Darriwilian. The base of the Dapingian is defined as the first appearance of the conodont species Baltoniodus triangularis which happened about 470 million years ago. The Dapingian lasted for about 2.7 million years until about 467.3 million years ago.
Lonchodomas is a genus of trilobites, that lived during the Ordovician. It was eyeless, like all raphiophorids, and had a long straight sword-like frontal spine, that gradually transforms into the relatively long glabella. Both the glabellar spine and the backward directed genal spines are subquadrate in section. Lonchodomas has five thorax segments and the pleural area of the pygidium has two narrow furrows. Lonchodomas occurred in what are today Argentina, Canada (Newfoundland), Estonia, Latvia, Norway, Sweden, the Russian Federation and the United States.
The Traverse Group is a geologic group in Michigan, Indiana and Ohio comprising middle Devonian limestones with calcareous shale components. Its marine fossils notably include Michigan's state stone, the Petoskey stone, among other corals and records of ancient marine life. A range of trilobites has also been found in the Traverse Group.
The Powell Formation or Powell Dolomite is a geologic formation in northern Arkansas, southeast Missouri and Virginia. It contains gastropod, cephalopod, and trilobite fossils dating back to the Ordovician Period.
The Bowen Formation is an Ordovician-age geological formation in the Appalachian region of the eastern United States. It occupies a thin stratigraphic range between the Wardell and Witten formations in some areas of southwest Virginia and northeast Tennessee. It is particularly well-exposed in Tazewell County, Virginia. Unlike its encompassing strata, the Bowen Formation is mostly calcareous sandstone and mudrock rather than limestone. The thicker upper part of the formation is composed of layered red mudrock which is replete with mudcracks. The thinner lower part, which is not always preserved, is a coarser unit of dark grey stratified sandstone which weathers to a rusty-brown color. Fossils are rare, restricted to stromatolites and Tetradium fibratum.
The Whitesburg Formation is a dark limestone with interbedded shales geologic formation in Tennessee and Virginia. It preserves fossils dating back to the Ordovician period.
The Collier Shale is a geologic formation in the Ouachita Mountains of Arkansas and Oklahoma. Dating from the Late Cambrian to Early Ordovician periods, the Collier Shale is the oldest stratigraphic unit exposed in Arkansas. First described in 1892, this unit was not named until 1909 by Albert Homer Purdue in his study of the Ouachita Mountains of Arkansas. Purdue assigned the type locality to the headwaters of Collier Creek in Montgomery County, Arkansas, but did not designate a stratotype. As of 2017, a reference section for this unit has yet to be designated.
The Manitou Limestone is a geologic formation in Colorado. It preserves fossils dating back to the Ordovician period.
The Ely Limestone is a geologic formation in Nevada and Utah. It preserves fossils dating back to the Carboniferous period.
The Pogonip Group is an Ordovician period geologic group located in southern Nevada and in Utah.
The Mule Spring Limestone is a geologic formation in the Saline Range of eastern California and Split Mountain and Goldfield Hills of Nevada.
The Joana Limestone is a limestone geologic formation in White Pine County and Nye County Nevada.
The Coils Creek Limestone is a geologic formation in Nevada. It preserves fossils dating back to the Devonian period.
The Wood Canyon Formation is a geologic formation in the northern Mojave Desert of Inyo County, California and Nye County and Clark County, Nevada.
The Windfall Formation is a geologic formation in northeastern and southern Nevada.
The Hanson Creek Formation is a geologic formation in Nevada. It preserves fossils dating back to the Dapingian-Katian stages of the Ordovician period.
The Copenhagen Formation is a geologic formation in Nevada.
The Cobourg Formation is a geologic formation in Ontario. It preserves fossils dating back to the Ordovician period. Technically the formation extends into New York State with Canadian section called Lindsay Formation. The formation was named by Raymond (1921). The Cobourg formation was estimated to have a total thickness of about 70 m.
The Rabbitkettle Formation is a geologic formation in the Yukon, comprising thin bedded silty and occasionally siliciclastic limestones deposited in deep waters. It preserves fossils dating back to the Ordovician period.
