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Ordovician


Definition:

The Ordovician describes a geological epoch that began about 485 million years ago and lasted about 42 million years. This era is now divided by scientists into three sections, namely the lower, middle and upper Ordovician, and clearly defined by the first appearance of a species with tooth-like calcium structures in the mouth, the extinct conodonts today. The name of this epoch was coined by the British scientist Charles Lapworth and is derived from the Ordovician. This Celtic tribe settled today's Wales until its conquest by the ancient Romans. Charles Lepworth, by naming the Ordovician, continued the tradition of his colleague, Adam Sedgwick, and achieved a precise definition of that phase, which is located between Cambrian and Silurian. Although Lepworth introduced the name Ordovician in 1879, it lasted until 1960, when it was officially recognized internationally. The three sections of the Ordovician are today divided into several levels, the general structure of which differs significantly from that of the British.

Climate:

After the gradual warming of the entire earth in the Cambrian, the Ordovician was again marked by a climate of strong contrasts. The initially mild to warm, even near the equatorial weather was gradually replaced during the Ordovician by larger icing, which focused mainly on the southern hemisphere. According to researchers, this was due in particular to plants growing on land, which deprived the soil of various minerals such as calcium, magnesium, iron and phosphorus and thus led to a decrease in the carbon content in the earth's atmosphere. The resulting global cooling by several degrees brought near the end of Ordoviziums a mass extinction, through which many species disappeared again.

Geology:

In Ordovician, a large part of today's Central Europe split off from the Gondwana continent and became a micro-continent surrounded by oceans. In the upper Ordovician he finally collided with Baltica, the original Northern Europe and Laurentia, the primordial North America. The collisions caused strong volcanic activity and subsequently the formation of high mountain ranges. The Ordovician is characterized by a high sea level and the existence of several relatively shallow epicontinental seas, which led to large deposits of carbonate on the land masses of the northern hemisphere. In the oceans, reefs were increasingly formed in the Ordovician, formed by sponges and cyanobacteria.

Flora and Fauna (plants and animals):

After the Cambrian explosion, which produced a great biodiversity in the previous epoch (Cambrian), many of these early animals were already extinct again at the beginning of the Ordovician. The following section of the geological history is, as already mentioned, above all because of the appearance of the so-called Conodonts important. These already had pine-like structures in the head region and included more than three thousand species known today. In the Ordovician also the mossy animals and armfeeters as well as the cephalopods developed rapidly, which could reach lengths of up to ten meters. In addition, mussels as well as the peculiarly shaped carpoidea and other echinoderms such as sea urchins, sea cucumbers and starfish now appear for the first time. In the middle Ordovician, corals and stromatopores, which are temporarily also equipped with calcareous skeletons, become more and more important as reef formers. The marine green algae, which already inhabited the seabed in the Cambrian period, continued to expand during this period, adopting regional forms that differ greatly from one another.
Indications of the already mentioned land plants, whose growth in the Ordovician brought about great climatic changes, were discovered by scientists in fossils of spores originating from mosses and fungi.