Orthocerida is an order of extinct nautiloid cephalopods also known as the Michelinocerda that lived from the Early Ordovician () possibly to the Late Triassic ().

The Cambrian is the first geological period of the Paleozoic Era, lasting from million years ago ( mya ) ; it is succeeded by the Ordovician.

The Cambrian period follows the Ediacaran and is followed by the Ordovician period.

Bioimmuration is known in the fossil record from the Ordovician to the Recent.

The larger part of the island is formed from highly faulted and folded sedimentary rocks of Ordovician age.

The Chazy Reef is an extensive Ordovician carbonate rock formation which extends from Tennessee to Quebec and Newfoundland.

It is the longest of the Phanerozoic eras, and is subdivided into six geologic periods ( from oldest to youngest ): the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian.

The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443. 7 ± 1. 5 million years ago ( mya ), to the beginning of the Devonian Period, about 416. 0 ± 2. 8 mya.

However, only one species is known from each of the Ordovician and Silurian periods, with a few more known from the Carboniferous ( Mazon Creek ).

It is not clear when the transition to a terrestrial existence was made, but it is considered plausible that it took place between the Ordovician and late Silurian — approximately — via the intertidal zone.

He is best known for pioneering faunal analysis of Silurian beds by means of index fossils, especially graptolites, and his proposal ( eventually adopted ) that the beds between the Cambrian beds of north Wales and the Silurian beds of South Wales should be assigned to a new geological period: the Ordovician.

Submerged in the river in the lower valley, hidden from view, is the Queenston Formation ( Upper Ordovician ), which is composed of shales and fine sandstones.

The connection between grazer and stromatolite abundance is well documented in the younger Ordovician evolutionary radiation ; stromatolite abundance also increased after the end-Ordovician and end-Permian extinctions decimated marine animals, falling back to earlier levels as marine animals recovered.

The Delamerian Fold Belt is mainly composed of Neoproterozoic-Cambrian rocks and was deformed in the Late Cambrian Delamerian Orogeny whereas the Lachlan Fold Belt contains mainly Cambrian-Devonian rocks with the main deformations occurring in the late Ordovician to early Carboniferous interval.

In paleontology, Ampyx is a genus of asaphid trilobite from the Middle Ordovician.

The upper part of the mountain mesa consists of Ordovician quartzitic sandstone, commonly referred to as Table Mountain Sandstone ( TMS ), which is highly resistant to erosion and forms characteristic steep grey crags.

This valley floor is part of the Ordovician Martinsburg Formation ( shale and slate ) which make up most of the valley — and the Jacksonburg Formation ( mostly limestone ).

The bedrock is mostly ( 92. 3 %) Ordovician in age, with 7 % being Cambrian and the remainder Pre-Cambrian.

Downpatrick is characterised by the rolling drumlins that are a feature of the Lecale area and a legacy of glaciation during the Pleistocene, the Down drumlins themselves are underlaid by Ordovician and Silurian shales and grits.

Branchville is on the Ordovician Martinsburg Formation.

Most of Frankford Township is on the Ordovician Martinsburg Formation.

The Ordovician geologic period was first described by Charles Lapworth in 1879 based on rocks located in the original lands of the Ordovices.

* Earth. ox. ac. uk-For more extensive geologic information see Ordovician paleogeography and the evolution of the Iapetus ocean.

Category: Ordovician geologic formations

In fact, the Hirnantian ( also known as the End Ordovician and the Ordovician-Silurian ) mass extinction event represents the second largest such event in geologic history.

For example, the beginning of the Tremadocian Stage of the Ordovician Period is marked by the first appearance ( FAD ) of the conodont Iapetognathus fluctivagus in the geologic record.

Despite the long recognition of its distinction from younger Ordovician rocks and older Precambrian rocks, it was not until 1994 that this time period was internationally ratified.

Life continued to flourish during the Ordovician as it did in the Cambrian, although the end of the period was marked by a significant mass extinction.

The Ordovician and Silurian periods were warm greenhouse periods, with the highest sea levels of the Paleozoic ( 200 m above today's ); the warm climate was interrupted only by a ~ 30 Ma cool period, the Early Palaeozoic Icehouse, culminating in the Hirnantian glaciation.

A. Öpik named a new genus of orthide brachiopod from the Ordovician period of earth history Sampo.

Evidence for the existence of sharks dates from the Ordovician period, over 450 – 420 million years ago, before land vertebrates existed and before many plants had colonized the continents.

Although corals first appeared in the Cambrian period, some, fossils are extremely rare until the Ordovician period, 100 million years later, when rugose and tabulate corals became widespread.

They originated as marine animals, possibly in the Cambrian period, but the first confirmed chelicerate fossils, eurypterids, date from in the Late Ordovician period.

Charles Lapworth ( 20 September 1842 – 13 March 1920 ) was an English geologist who pioneered faunal analysis using index fossils and identified the Ordovician period.

The earliest echinoid fossils date to the upper part of the Ordovician period ( circa 450 MYA ), and the taxon has survived to the present as a successful and diverse group of organisms.

The features of the Ridge and Valley province were created approximately 300-400 million years ago during the Ordovician period and Appalachian orogeny — a period of tremendous pressure and rock thrusting that caused the creation of the Appalachian Mountains.

They developed in the Late Cambrian period and became a significant group of sea predators during the Ordovician period.

Most other shell forming organisms appear during the Cambrian period, with the Bryozoans being the only calcifying phylum to appear later, in the Ordovician.

That period postdates the Cambrian and Ordovician periods, whose names are also derived from ancient Wales.

By the Ordovician period the gastropods were a varied group present in a range of aquatic habitats.

The Gnathostomata first appeared in the Ordovician period and became common in the Devonian period.