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geological periods and epochs
Значение термина geological periods and epochs в knolik
geological periods and epochs - geological periods and epochs
geological periods and epochs - Main fossil-bearing geological periods and their ages (it must be emphasized that the latter are only approximate) are as follows:
| Era | Period | Million years since beginning of period |
| Cenozoic | Quaternary Tertiary | 1.5 65 |
| Mesozoic | Cretaceous Jurassic Triassic | 135 190 225 |
| Palaeozoic | Permian Carboniferous Devonian Silurian Ordovician Cambrian | 280 345 395 440 500 570 |
The Quaternary period is subdivided into the Recent (or Holocene) epoch (since the last glaciation) and the Pleistocene epoch. The Tertiary period is subdivided into the following epochs (in brackets, millions of years since beginning of epoch): Pliocene (7), Miocene (26), Oligocene (38), Eocene (54), Palaeocene (65). Sometimes the Pleistocene, Pliocene and Miocene are grouped into the Neogene, and the Oligocene, Eocene and Palaeocene into the Palaeogene. The Cambrian and all subsequent periods are known as the Phanerozoic; the pre-Cambrian as the Gryptozoic. The Upper Palaeozoic is Devonian to Permian, the Lower is Cambrian to Silurian, inclusive.
The fossil record begins in Pre-Cambrian times with the discovery of a few organisms resembling bacteria and blue-green algae in deposits dating back more than three billion years. A few green algae have been identified from an upper Pre-Cambrian formation approximately one billion years old. In Cambrian rocks, in addition to algae, a great variety of aquatic invertebrate animals (brachiopods, trilobites, etc.) occur as well as micro-organisms including fungi. There is little doubt that many fragile primitive organisms died without trace. Spores with wall markings like those of various land plants were also present. In Ordovician times fish-like vertebrates (Ostracoderms) made their appearance. Primitive land plants are known from the Silurian period. Colonization of land by plants was an event of enormous importance for animals making it possible for them too, dependent on green plants for food to live there permanently. By die late Devonian, arthropods, including insects, were established on land and the first terrestrial vertebrates, amphibians, had appeared. Club mosses, horsetails and ferns, many of them tree-like, were now abundant. They provided an enormously rich flora in Carboniferous times. Gymno-sperms, mosses and liverworts, algae and fungi were also present. Tremendous accumulations of the remains of Carboniferous plants, partially decayed and subjected to intense pressure by overlying deposits, formed the coal seams of today. The Mesozoic era was the age of the great dinosaurian reptiles, and gymnosperms were the dominant plants. Angiosperms appeared in the Jurassic, became increasingly dominant towards the end of the Cretaceous as the gymnosperms declined, and remained the dominant plant group to the present day. The ascendancy of the mammals also began with the end of the Mesozoic.
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| geobotany | В начало буква "" буквосочетание "" | geophytes |
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