What was the Devonian Period?

The Devonian Period, whose symbol is D , is the fourth of the Paleozoic in the geological age. The Devonian belongs to the Phanerozoic Paleozoic, starting at the isotope age of 416 ± 2.8Ma and ending at 359.2 ± 2.5Ma. In the late Devonian, amphibians appeared.

Devonian in English called Devonian

Devonian period (the age of fish)

Devon comes from Japanese and is a Japanese transliteration of a county name on the southwestern peninsula of England, England (now called

377 million years ago, the earth entered

Devonian Paleogeography

Devonian landform

The basic framework of the Devonian paleogeography is mainly composed of the Gondwana continent, Laurasia continent, and the paleo-Mediterranean and paleo-pacific oceans (see Figure [Early Devonian Ames Paleogeography]). Gondwana ancient land is the most complete and largest ancient land, including more than half of the known continental crust, distributed around the Antarctic region. Consists of Africa, Arabia, Madagascar, South America, India, Australia, New Zealand, Antarctica and possibly Southern Europe, Turkey, Afghanistan, Iran, China's Tibet, etc. The western part of Lloyd's continent is composed of Laurent's ancient land and Baltic's ancient land. The Laurentous Land is dominated by the North American platform, plus Scotland and part of Ireland. The ancient Baltic land mainly includes the Russian platform west of the Urals, Finland, and Scandinavia. The continental sediments of the European and American continents contain similar non-marine and freshwater fish fossils and plant fossils. The eastern part of the United States and Europe is composed of scattered large land blocks or small to micro land groups. Among them, Siberia, Kazakhstan, North China and South China ancient lands are larger.

Devonian

The latter is located near the equator and the northern mid-latitude zone. Siberia is in the high latitude zone. The Devonian covers about 85% of the earth's sea area, and its distribution characteristics include the vast ancient Pacific Ocean that forms the northern hemisphere, the ancient Mediterranean Sea to the north of the Gondwana continental land, and the narrow intercontinental sea between land blocks. And the land surface above the continent. The ocean circulation model proposed by PH Hecker and BJ Wittsk (1979) believes that strong currents develop on the west side of the ocean due to the rotation of the earth and the blocking of the land. Ocean currents in the mid-latitude zone of the northern hemisphere move eastward, and there are two sets of reverse swirls in the subtropical ocean currents in the southern hemisphere, and positive swirls over the Gondwana shelf in high latitudes. Based on paleomagnetic data, the Devonian poles are located approximately in Zimbabwe and Botswana in southern Africa. The paleoclimate inferred from the nature of the sediments indicates that North America may be located in the subtropical zone and the Russian platform is located in the dry climate zone, leading to severe evaporation. Reef-phase evaporites, carbonates, and red beds exist on the Siberian platform. Kazakhstan has thick clastic rocks, red beds, coal beds, and bauxite, and contains evaporites. Their climate is estimated to range from warm to humid . The southern part of the Gondwana supercontinent is mainly developed with thick and single clastic rocks, which only partially contain carbonate rocks, which may represent cold or warm and humid climates. The eastern South America is mainly clastic rocks, lacking carbonate rocks and terrestrial sediments; it is dominated by bivalves and has a low degree of differentiation. There are very few or missing skeletal fossils such as corals, foraminifers, and bryozoites, which all indicate that Frigid climate. Moraine rock, moraine conglomerate, and monsoon mud are deposited in the Banaiba Basin in northeastern Brazil, indicating that there has been glacial activity. The Devonian years and days are different in length from today. According to the determination of the number of growth patterns of various types of fossils (coral, foraminifera, bivalves), the average is 400 days per year, and about 21 to 22 hours per day and night. In the Devonian, the distance between the moon and the earth was about half what it is today, which is consistent with the inferences of geophysicists and astronomers, which is attributed to the weakening of the Earth's rotation speed. Orogenic movement, transgression and retreat, and biological events. The Arcadian movement formed highlands along central and eastern North America, affecting the Lower Middle Devonian folds from Newfoundland to North Abracia, New York. The submicron plate collided with the European and American continents. Elsmere and Antler orogenies occurred in the Franklin and Cordillera belts in the northern and western margins of the Laurentian Land.The movement spread throughout the northwest of the Arctic during the Middle and Late Devonian. The non-known Mauritania orogenic belt extends from Sirra Leone to the Little Atlas Mountains. East Australia suffered a strong Tiberapo orogeny, which caused the unconformity of the Devonian and its underlying strata in different eras to form the Nikamba system. The Ningxia movement in the Qilian Mountains of the ancient China and North Korea occurred in the Middle Devonian and Late Devonian, and it appeared as unconformity contact between two sets of continental strata. Some scholars have inferred that the collision between the Siberian plate and the Kazakh plate occurred in the Late Devonian.

Kroenke Silurian and Devonian stratigraphic sections, Czech

The Devonian sediments have two major transgressive-regressive cycles, separated by early and late Devonian regressions, and are found in almost all Devonian development areas. Changes in global sea level rise and fall at the next level are also evident. M. House (1983) summarized the 18 Devonian sea-level rise and fall curves of New York State, and compared them with the corresponding horizons in Belgium, Germany, and the European part of the former Soviet Union. South China also has obvious reflections. JG Johnson et al. (1985) believed that there were at least 14 Devonian transgressive-regressive cycles (referred to as TR cycles) caused by at least 14 global sea-level rises and falls, which are characterized by deepening events followed by shallower sequences.

Devonian archeological site

Global biological events caused by sea-level changes, hypoxic events, and possible celestial collisions occurred repeatedly within the Devonian. Mainly manifested in the sudden extinction of organisms and a large amount of radiation. They are closely related to the special black rock series. At least eight global biological events were identified within the Devonian. Three of them are particularly important: The Pharci-ceras incident or Tafannik incident occurred at the turn of the Devonian in the middle and late days, close to the death of brachiopod scallops and the appearance of bowstone swallows. Period. Six families of brachiopods and 15 families of radiant corals disappeared. Most of the Asteraceae, Agoniatitidae, Pinacitidae, and Anarcestidae have disappeared, and Pharciceratidae, which has an umbilical leaf surge, has disappeared. New Evolution Series. With this incident, etc.

Devonian eroded landforms in Tarim

(Homoctenids) were differentiated, radiation from Palmatelepids (Palmatolepids), and biomass of planktonic mesothelium suddenly increased. The incident coincided with rising seas. The Kellewasser event, representing the biological crisis in the Late Devonian, also known as the Fras-Famian event, the most obvious changes are the sharp decline in biomass, the disappearance of reef-building organisms, and brachiopods More than a dozen families of 3 radiant corals of animals have perished. After this event, there was widespread sea retreat around the world, evaporites spread widely, and glacial deposits occurred in South America. The Hengenberg event occurred near the Devonian-Carboniferous boundary. Poseidon stones, Pha-copida trilobites, scutellosa, and jawless species that prevailed in the Late Devonian era all died. Toothstones have a shallow water protognathodus biophase between palmatelepids and siphonodellids evolution series.

Devonian biological reefs in South China

After the incident, new radiation occurred in the categories of chrysanthemum, dentate, mesial, coral, brachiopod, and vertebrate. The black shales associated with this event are widely distributed in Western Europe, North America and South China. The marine life of China belongs to the world flora, which can be further divided into Junggar-Xing'an, Nantianshan, South China and Tibet-Western Yunnan, and early Devonian vertebrates in China. Most of them are endemic and belong to the independent biological area of South China. . ^[5]

Devonian sedimentary strata

The Devonian sediments are distributed all over the world, and the total amount of sediments is larger than that of other palaeozoic families.

Summary of Devonian Division in Major World Regions

Sedimentary strata are generally divided into old red sandstone facies, Rhine facies, and marine facies, which represent the continental environment, the near-shore and far-shore marine environments, respectively. Different basin deposition models are different. Lithofacies represented by the German-Belgian Basin. The Early Devonian was mostly nearshore and foreshore clastic facies. The Middle and Late Devonian developed continental clastic facies, platform carbonate facies, and basin mud. Lithofacies and underwater uplift carbonate facies. South China is similar to Western Europe, with the difference that in the middle and late Devonian platforms, the planktonic siliceous-muddy, carbonate deposits were widely distributed, forming a paleo-geographical pattern with interlaced platforms and basins. The opposite is true in eastern North America, where the Early and Middle Devonian were distributed in shallower carbonates, while the Late Devonian were all in the deeper black shale and delta facies Kaskier intersected and deposited. The island-type volcanic clastic deposits dominate the Junggar-Xing'an fold belt and the Australia-New Zealand trough area. The special rock types belonging to the Devonian include: old red sandstones distributed along the old red ancient land; reef limestones developed in Canada, Ural, Belgium, and South China; black shales widely distributed in North American platforms; South China Manganese-bearing siliceous rocks and bilithic shales in the early Early Devonian.

Due to the stratigraphic structure of Devonshire in the named area, the sequence is unclear, and the metamorphism is local. Therefore, the traditional Devonian classification standards in the Rhine and Ardennes regions are traditionally divided into three systems and seven stages. Due to the influence of the Caledonian movement, Devonian systems were not integrated with Silurian systems in many areas. The Czech Bohemia region has an integrated section of the Silurian- Devonian boundary line. The bottom of the Devonian system is marked by the appearance of a monolithic monolith (Monograptusuniformisuniformis). Devonian stratigraphic section (the dotted line indicates the location of the stratum boundary)]). The 20th layer of the Klenk section near Prague was identified as the Silurian- Devonian boundary layer profile and point. The Devonian-Carboniferous boundary is defined as the first appearance of the Siphonodellasulcata. The global boundary layer profile and points are established in La Serre in the south of France. The division of Devonian in the main regions of the world is shown in the table [World Master

Devonian sequence-lithofacies paleogeography

Summary of Devonian Divisions in Different Areas].

The Devonian in China is mainly distributed in the Tianshan, Xing'an Mountains, Junggar, and Inner Mongolia grasslands in the north, and is mainly dominated by trough-type volcanic debris. Most of the Sino-Korean and Tarim blocks are denuded areas, and only local red clastic sediments are developed. The Devonian in South China is the most developed, with a variety of deposition types, mainly platform-type shallow sea and coastal sediments. The carbonate platform occupies most of it, with crisscross basin cuts in between. Along the southern margin of the ancient continental margin of the Yangtze River, a wide range of near-shore clastic-carbonate deposits developed. The sediments in the southwestern region are relatively complicated, with volcanic rocks and partial metamorphism. The Qinling-Longmen mountainous area is similar to the South China area. Except for the Ningxia Movement in the Qilian Mountains, no orogenic movement has been found in the Devonian. The land-making movement in the middle Devonian period was very significant, sweeping the entire South China area.

Devonian minerals

The Devonian period has important economic value. About 50% of the world's Paleozoic and Devonian occur in Devonian. among them,

Devonian

Russia's Ural-Volga region and Alberta region of Canada account for about 75% of the reserves, they are generally related to the development of reef limestone and black shale oil-bearing parent rocks. Potassium salts related to evaporite are distributed in Saskatchewan and other places in Canada. The Ural Middle Devonian is abundant. Many late Devonian black shales are related to phosphate and uranium ore. The Devonian minerals in southern China are extremely rich: the sedimentary types are distributed along the Devonian paleo coastline, especially the late Devonian Ningxiang-type hematite, which is of economic significance; manganese and phosphate deposits are mostly closely related to basin facies siliceous deposition; Lead, zinc, tin, and other non-ferrous metals are related to reef facies or post-reef facies limestone; widely distributed and quartz sandstones are common building and glass raw materials; the Devonian volcanic rock series in northern Xinjiang is a layer of gold and copper. The geomorphology formed by the weathering and erosion of Devonian rocks constitutes many famous tourist attractions in the world. Such as karsts in South China and the Czech Republic and Slovakia Moravia, the landscape of North Rhine, the coastal erosion of the southwestern United Kingdom and Scotland, the Brest harbour in France and so on.