User:Abyssal/Portal:Ordovician

Portal topics: Activities; Culture; Geography; Health; History; Mathematics; Nature; People; Philosophy; Religion; Society; Technology; Random portal

The Ordovician Portal

Introduction

The Ordovician (/ɔːrdəˈvɪʃi.ən, -doʊ-, -ˈvɪʃən/ or-də-VISH-ee-ən, -⁠doh-, -⁠VISH-ən) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period 485.4 Ma (million years ago) to the start of the Silurian Period 443.8 Ma.

The Ordovician, named after the Welsh tribe of the Ordovices, was defined by Charles Lapworth in 1879 to resolve a dispute between followers of Adam Sedgwick and Roderick Murchison, who were placing the same rock beds in North Wales in the Cambrian and Silurian systems, respectively. Lapworth recognized that the fossil fauna in the disputed strata were different from those of either the Cambrian or the Silurian systems, and placed them in a system of their own. The Ordovician received international approval in 1960 (forty years after Lapworth's death), when it was adopted as an official period of the Paleozoic Era by the International Geological Congress.

Life continued to flourish during the Ordovician as it did in the earlier Cambrian Period, although the end of the period was marked by the Ordovician–Silurian extinction events. Invertebrates, namely molluscs and arthropods, dominated the oceans, with members of the latter group probably starting their establishment on land during this time, becoming fully established by the Devonian. The first land plants are known from this period. The Great Ordovician Biodiversification Event considerably increased the diversity of life. Fish, the world's first true vertebrates, continued to evolve, and those with jaws may have first appeared late in the period. About 100 times as many meteorites struck the Earth per year during the Ordovician compared with today. (Full article...)

Show new selections below (purge)

edit

Selected article on the Ordovician world and its legacies

A fungus (/ˈfʌŋɡəs/; plural: fungi) is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants and animals. One major difference is that fungal cells have cell walls that contain chitin, unlike the cell walls of plants and some protists, which contain cellulose. These and other differences show that the fungi form a single group of related organisms, named the Eumycota. The discipline of biology devoted to the study of fungi is known as mycology. Genetic studies have shown that fungi are more closely related to animals than to plants.

Abundant worldwide, most fungi are inconspicuous because of the small size of their structures, and their cryptic lifestyles in soil, on dead matter, and as symbionts of plants, animals, or other fungi. They may become noticeable when fruiting, either as mushrooms or molds. Fungi perform an essential role in the decomposition of organic matter and have fundamental roles in nutrient cycling and exchange. However, little is known of the true biodiversity of Kingdom Fungi, which has been estimated at 1.5 million to 5 million species. Phylogenetic studies published in the last decade have helped reshape the classification of Kingdom Fungi, which is divided into one subkingdom, seven phyla, and ten subphyla. A group of all the fungi present in a particular area or geographic region is known as mycobiota. (see more...)

More articles...

edit

Selected article on the Ordovician in human science, culture and economics

Oil shale geology is a branch of geologic sciences which studies the formation and composition of oil shales–fine-grained sedimentary rocks containing significant amounts of kerogen, and belonging to the group of sapropel fuels. Oil shale formation takes place in a number of depositional settings and has considerable compositional variation. Oil shales can be classified by their composition (carbonate minerals such as calcite or detrital minerals such as quartz and clays) or by their depositional environment (large lakes, shallow marine, and lagoon/small lake settings). Much of the organic matter in oil shale is of algal origin, but may also include remains of vascular land plants. Three major type of organic matter (macerals) in oil shale are telalginite, lamalginite, and bituminite. Some oil-shale deposits also contain metals which include vanadium, zinc, copper, uranium.

Most oil shale deposits were formed during Middle Cambrian, Early and Middle Ordovician, Late Devonian, Late Jurassic, and Paleogene times through burial by sedimentary loading on top of the algal swamp deposits, resulting in conversion of the organic matter to kerogen by diagenetic processes. The largest deposits are found in the remains of large lakes such as the deposits of the Green River Formation of Wyoming and Utah, USA. Oil-shale deposits formed in the shallow seas of continental shelves generally are much thinner than large lake basin deposits. (see more...)

More articles...

edit

Selected image

Fossil Mountain, Utah; Ordovician shales and limestones.
Photo credit: Wilson44691

More pictures...

edit

Did you know?

... that the extinct trilobite Bumastus (artist's rendition pictured) was named after its resemblance to large grapes?
... that the fossil bivalve Emiliodonta shared its name with a coccolithophore for about a decade?
... that the Ordovician age bivalve Villicumia has overlapping teeth seen in few other bivalves?
... that fossils of the extinct bivalve family Praenuculidae have been found on every continent except Antarctica?
...that ostracoderms are the earliest known vertebrate animals?