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Silurian- Devonian Periods


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Silurian -Devonian: Facies, Fauna, Flora, Stratigraphy , Tectonics and Paleoclimate

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Silurian- Devonian Periods

  1. 1. •Duration: about 30 millions years. • Maximunm thickness: 70,000 feet. • The Silurian Period (from the name of an ancient British tribe, the Silures) lies between approximately 439 mya and 409 mya. • The name was given by Marchison 1885 for agroup of formations in Wales in an area inhabited by the Silurian tribe. •During this time, a great deal of volcanic activity was taking place, generating lava flows and ash. •No new major groups of organisms appeared at this time, with old groups flourishing or declining Silurian : Facies Different facies can be found: 1-Black clayey Graptoloitic - shals radiolaria shale (deep water facies) 2- Sandy shales , sandston, Conglomerate(shallow water facies) 3- Volcanic facies. 4-Shelly facies: sandy and calcareous(coastal facies of littoral platform rich in fossils as graptolites.
  2. 2. Significant Events  Life on Land It was during the Silurian that the first life came out of the water and colonized the land. Increased ozone from photosynthetic water plants provided protection from ultraviolet rays, make the terrestrial environment hospitable to those organisms that could prevent desiccation.  First Vascular Plants The first plants with internal vascular channels appeared in the Silurian. Plants were now able to transport food and gases to other parts of their structure, allowing for a significant increase in size.  First Insects The insects arose in the Silurian, probably becoming the first animal forms to venture out of the water.  First Jawed Vertebrates The first fish with jaws appeared during the Silurian, providing a much better predator capability and ultimately giving rise to the vertebrates known today.
  3. 3. Some Typical Siluria Organisms Gastropod Platyceras Eurypterid Echinoderm Jawless fish Silurian Ecosystems Benthic
  4. 4. Silurian Graphics BirkeniaBaragwanathia
  5. 5. Cooksonia Crinoid
  6. 6. EurypteridCrinoid
  7. 7. Early PlantSnail
  8. 8. The Silurian 443 to 417 Million Years Ago • The Silurian (443 to 417 million years ago) was a time when the Earth underwent considerable changes that had important repercussions for the environment and life within it. • The Silurian witnessed a relative stabilization of the earth's general climate, ending the previous pattern of erratic climatic fluctuations. One result of these changes was the melting of large glacial formations. This contributed to a substantial rise in the levels of the major seas . • Coral reefs made their first appearance during this time, and the Silurian was also a remarkable time in the evolution of fishes. • Not only does this time period mark the wide and rapid spread of jawless fish, but also the highly significant appearances of both the first known freshwater fish as well as the first fish with jaws. • It is also at this time that our first good evidence of life on land is preserved, including relatives of spiders and centipedes, and also the earliest fossils of vascular plants.
  9. 9. • Subdivisions of the Silurian: • The chart at left shows the major subdivisions of the Silurian Period. This chart is mapped, to allow you to travel back to the Ordovician or forward to the Devonian. • The Silurian Period is part of the Paleozoic Era. Upper Silurian= Middle Silurian= Lower Silurian= The lower Silurian had a great variation in the nature of these sediments. The fauna are well distinct. Shelly deposits are characterized by the abundance of Brachiopods.The Graptolitic facies on the other hand are defined by Monograptus, Diplograptus, Dictynema, Phyloograptus. In the middle Silurian ; the previously mentioned facies are interstratified and much limestone was formed. This latter is due to the greater spread of waters which took place during the middle of the period. In the late Silurian ; along and nearly complete emergence took place giveng rise to sandy beds with no graptolites.
  10. 10. Silurian: Stratigraphy • The Silurian lasted from about 443 to 417 million years ago. Its stratigraphy is subdivided into four epochs (from oldest to youngest): the Llandovery, the Wenlock, the Ludlow, and the Pridoli. • Each epoch is distinguished from the others by the appearance of new species of graptolites. • Graptolites are a group of extinct colonial, aquatic animals that put in their first appearance in the Cambrian period (543 -490 million years ago) and persisted into the Early Carboniferous (354-290 million years ago). • The beginning of the Silurian (and the Llandovery) is marked by the appearance of Parakidograptus acuminatus, a species of graptolite. • The Llandovery (443-428 million years ago) preserves its fossils in shale, sandstone, and gray mudstone sediment. Its base (beginning) is marked by the appearance of the graptolites Parakidograptus acuminatus and Akidograptus ascensus. • The Llandoverian epoch is subdivided into the Rhuddanian, Aeronian, and Telychian stages.
  11. 11. Life of the Silurian The most distinective of the Silurian-----------------------Tabulate Tetracorsls 1-Reef building Coelenterates: a-Tetracorals : flourished to the end of the Paleozoic represented by Cyathophyllum, Goniophyllum and Zaphrentis b- Heliolitides , Stromatoporoides. c-Tabulata: confined to the Paleozoic) very aboundant e.g. Honey Corals Favosites and chain Corals HalysitesDictyonema, Diplograptus, Phyllograptus and Monograptus 2-Graptolites:. 3-Echinoderms: Echinosphaerites 4-Brachiopods: Spirifer, Orthis, Atrypa 5-Crinoides: flourished in clear water and they were important reef builders 6-Trilobites: Calymene, Phacops,Dalma, Asaphus 7-Mollusca: Cephalopods are abundant Nautiloids e.g. Orthoceras , Cyrtoceras and Trochoceras reach their maximum in the Silurian 8-Eurypterids: ( earliest sea scorpions)this group reached the peak of its development in the Silurian and declined abruptly in the Devonian. 9-Fishes: In the upper Silurian beds , of Sweden and Norway, well preserved fossils of very primitive Jaw –less fishes have been found. 10-Land plants: in 1953, a single type of plant fossil from the late Silurian of Australia was described as a land plant.There is still no evidence of Silurian land plant at the end of the period and this could be considered the start of terrestial life
  12. 12. Silurian Critters : On the left, Dalmanites limuluris, a trilobite from the Silurian of New York. To the right, Grammysia cingulata, a brachiopod from the Upper Ludlow of England.
  13. 13. Early Plants Early Plants : Cooksonia, on the left, has usually been considered the oldest known land plant. Fossils assigned to several species are known from North America, Europe, Asia, and Africa, and from both the Late Silurian and Early Devonian. The lycophyte Baragwanathia, on the right, is structurally more complex than Cooksonia, but Silurian fossils of this plant have been found in Australia, significantly earlier than in the Northern Hemisphere.
  14. 14. Silurian: Tectonics and Paleoclimate • During the Silurian , the Earth witnessed many changes in the way in which landmasses were distributed around the globe. Although there were no major volcanic events, a deglaciation and rise in sea levels occurring at that time produced varying periods of continent coverage and exposure. • The variation of ocean levels occurred along side the process of continental fragmentation and grouping that occurred from the Cambrian to the present . • At that time, the continents were distributed very differently than they are today. The Silurian world consisted of a vast north polar ocean and a south polar supercontinent (Gondwana) with a ring of approximately six continents. • By the Silurian period, a large portion of the Rodinian landmass had become fragmented, and those fragments migrated toward the equatorial region. Most of these fragments were eventually assembled by a series of plate collisions into the super-continents of Laurussia and Laurasia. The modern Philippine islands were most likely inside the Arctic Circle, while Australia and Scandinavia resided in the tropics; South America and Africa were probably over the South Pole.
  15. 15. • There was no major volcanic activity during the Silurian; however, • The period is marked by major orogenic (mountain-building) events in eastern North America and in northwestern Europe, resulting in the formation of the mountain chains • there. This was called the Caledonian Orogeny. • In other areas, large igneous rock formations of the Middle Silurian arose, such as those in Central Europe, as well as light sedimentation throughout the Baltic region. While not characterized by dramatic tectonic activity, the Silurian world experienced gradual continental changes that would be the basis for greater global consequences in the future, such as those that created terrestrial ecosystems. • The Silurian oceans are also of particular interest for activity between the regions known as Laurentia Baltica and Avalonia. The ocean basins between these areas substantially closed together, continuing a geologic trend that had begun much earlier. The new marine habitats produced by these profound changes in the Silurian seas provided the framework for significant biological events in the evolution of life Coral reefs, for example, made their first appearances in the fossil record during this time
  16. 16. Silurian • During the middle and late Paleozoic, about a third of the Rodinian mass was torn apart and moved to equatorial regions. • Most of these blocks were assembled by a series of plate collisions into the super continents of Laurussia [the Old Red continent] by the Devonian and Laurasia by the Pennsylvanian. • Meanwhile the remains of Rodinia, Gondwana, rotated clockwise and moved northward to collide with Laurasia -- the result was the super continent Pangaea [all land]. Pangaea was shaped like a huge "pack man", mouth agape and facing eastward across the equator. The large,open mouth was the Tethys Ocean. Baltica and the attached micro continent Avalonia begin colliding with North America in scissors fashion [north to south] to form the Caledonian- Acadian orogeny.  Silurian Localities: 1- In Europe the silurian facies border the following areas: • The Baltic shield zone • The Northern European Geosyncline • The Middle European zones (Armerican, Bohemia) • The Mediterranean zones, including the following: A-Montagne Noire B- Carnic Alps C- Sardinia D- Morocco 2- In Egypt: Silurian deposits occur : • Um Bogma-Abu Durba---Central Sinai • Western Desert (Southern part)golf kebeir plateau • Eastern Desert( Qena Valley-El-Dakhala)
  17. 17.  Climate • Generally warm, mild especially in the middle of the period. Both lithology and biology offer evidences, since L.S. are widely spread and corals are well developed. Arid climate prevailed locally.  Orogeny • At the end of the Periods, the rising of the Caledonian mountains took place. This chain north-eastward across the British Isles and Scandinavia . Very little igneous activity in the British area.  Paleogeography • The distribution of Oceans and continents is not much more different from that during the Ordovician except that some parts of the land are floaded by sea water such as North Russia, West China and Brazil.
  18. 18. All fossils in the Silurian Atrypa reticularis © 2004 Pentamerus © 2003
  19. 19. Orthoceras © 2003 Eurypterus remipes © 2005
  20. 20. Favosites © 2004 Halysites © 2001
  21. 21. Halysites © 2003 Eucalyptocrinit es
  22. 22. Platyceras © 1998 Arctinurus boltoni © 2005
  23. 23. Diacalymene clavicula © 1998 Gravicalymene © 2001
  24. 24. Monograptus priodon © 2004 Syringopora © 2004
  25. 25. Artinurus boltoni © 2006 Dalmanites limulurus © 2001
  26. 26. •Duration: 50 millions years . •Maximum thickness : 62,000 feet. •The Devonian Period (after Devon, England) began about 417 million years ago and ended about 354 million years ago. • During this time, Europe and North America were still drifting together, and the northern Appalachians were being formed. North America was mostly tropical or subtropical, and numerous shallow, saltwater seas surrounded the coasts. •During this period, much of Europe was submerged by the transgressive sea from the beginning still near its end . By the close of the periods, emergence was gradual and finally complete.
  27. 27. Two distinct facies could be distinguished :- • Marine (Typical Devonian) Facies: These are formed of continuous sheets of great extension covering large parts of earth crust. They are composed of the normal succession of marine deposits of a transgressing sea. They contain Trilobites, Molluscs, Brachiopods and Corals • Lacustrine ( Old Red Sandsone) Facies: These are formed of vast thickness of fossilifeous sands and muds, that accumulated from the rugged mountains being aggraded by streams. They are mostly cofined to the British Isles, North and Western Europe and North America. They were laid down in basins were denudation was extremely active. • These sediments are characterized by their bright colour althought red is the dominant one. • Oxidation products of Fe and Mg ions stained also the sandstones, siltstones and shales . • This Oxidation is due to good aeration of the soil during dry seasons. The dominant fossils of the old red are fresh – water fished and Eurypterids. Plant fossils are locally abundant. Devonian: Facies
  28. 28. Significant Events  Sharks and Bony Fish The first sharks and bony fishes appeared in the Devonian, which is frequently called the "Age of Fishes."  Rise of Amphibians It was during the Devonian that the first colonization of the land by vertebrates occurred. Amphibians like Ichthyostega, while predominantly aquatic, had the physical capabilities necessary for life on land.  Plant Diversification The first land plants appeared in the Silurian, but it was in the Devonian that many new forms first appeared. The lycopods, bryophytes, sphenophytes, and pteridophytes all appeared in the Devonian. Among these were the first seed plants, those that could reproduce in the absence of water.
  29. 29. CladoselacheDevonian Sea Devonian Graphics
  30. 30. Dinichthys Dinichthys
  31. 31. CrinoidCrinoid
  32. 32. TrimerusZaphrentis
  33. 33. PhacopsHexagonaria
  34. 34. DolatocrinusCorals and Crinoids
  35. 35. The Devonian 354 to 417 Million Years Ago
  36. 36. • The Rhynie Chert in Scotland is a Devonian age deposit containing fossils of both Zosterophyllophytes and Trimerophytes, the two major lines of vascular plants. This indicates that prior to the start of the Devonian, the first major radiations of the plants had already happened. The oldest known vascular plants in the Northern Hemisphere are Devonian • The vegetation of the early Devonian consisted primarily of small plants, the tallest being only a meter tall. By the end of the Devonian, ferns, horsetails and seed plants had also appeared, producing the first trees and the first forests. Archaeopteris, shown below left, is one of these first trees. • Also during the Devonian, two major animal groups colonized the land. The first tetrapods, or land-living vertebrates, appeared during the Devonian, as did the first terrestrial arthropods, including wingless insects and the earliest arachnids. In the oceans, brachiopods flourished, like the beautifully pyritized brachiopod Paraspirifer bownockeri from Ohio, pictured above and to the right. Crinoids and other echinoderms, tabulate and rugose corals, and ammonites were also common. Many new kinds of fish appeared. • During the Devonian, there were three major continental masses: North America and Europe sat together near the equator, much of their current land underneath seas. To the north lay a portion of modern Siberia. A composite continent of South America, Africa, Antarctica, India, and Australia dominated the southern hemisphere.
  37. 37. Subdivisions of the Devonian: The chart at left shows the major subdivisions of the Devonian Period. This image is mapped to take you back to the Silurian, or forward in time to the Carboniferous Period. The Devonian Period is part of the Paleozoic Era. Subdivisions of the Devonian: •Upper Devonian: red slates overlying massive L.S. with Rhynchonella •Middle Devonian: mostly slates , rare grits, important volcanic tuffs, calcareous bands with abundant Calceola •Lower Devonian: mostly slates and grits, volcanic rocks not of great extent. Spirifer abundant
  38. 38. Life of the Devonian The most distinective of the Devoian-----------------------Tetracorsls and Fishes Flora: Vascular land plants include the Psilophytales and the Lycopod-like form Baragwanathia (australia) Sigillaria, Calamites, Lepidodendron, flowering plants Fauna: Coelentrates: Corals play an important role as reef buildes, all are tetracorals e.g. Calceola sandalina, Stromatoporoids are abundant Graptolites are rare in the lower part become Extinct before the end of the Devonian Period . only dendroid forms e.g. Dictyonema still present. Echinoderms: Echinoides, cystoids and blastoids play only minor role. Crinoids are very abundant and their remain build up the crinoidal L.s. Brachiopods: Productus, Spirifer, Atrypa, Orthis , Stringocephalus, and Rhynchonella are abundant Mollusca: Pelecypods and Gastropods are of no interes Nautiloids more highly developed represented by: Cyrtoceras, Phramoceras and Gyroceras. Cephalopods: Calymena sedgwickii Crustaceans: represented by Phacops and Dalmanites Eurypterids were also flourishing during the Devonian. Fish: Represented by selacians , ganoids and placodems. Ganoid fishes: Osteolepis Armoured fishes: Cephalaspis, Pterichtys Amphibians: small amphibians were recorded from upper Devonian rocks. Insects: May fly. N.B. 1-Graptolites were entirely absent. 2- in the Lacustrine deposites , remains of Eurypterids were recorded.
  39. 39. Life of the Devonian  1-Change in the Devonian Seas • The Devonian seas were dominated by brachiopods, such as the spiriferids, and by tabulate and rugose corals, which built large bioherms, or reefs, in shallow waters. Encrusting red algae also contributed to reef building. In the Lower Devonian, ammonoids appeared, leaving us large limestone deposits from their shells. Bivalves, crinoid and blastoid echinoderms, graptolites, and trilobites were all present, though most groups of trilobites disappeared by the close of the Devonian. • The Devonian is also notable for the rapid diversification in fish. • Benthic armored fish are common by the Early Devonian. These early fish are collectively called ostracoderms", and include a number of different groups. • By the Mid-Devonian placoderms, the first jawed fish, appear. Many of these grew to large sizes and were fearsome predators. • Of the greatest interest to us is the rise of the first sarcopterygiians, or the lobe-finned fish, which eventually produced the first tetrapods just before the end of the Devonian.  2-Change in the Devonian Landscape • By the Devonian Period, life was well underway in its colonization of the land. Before this time, there is no organic accumulation in the soils, causing these soil deposits to be a reddish color. This is indicative of the underdeveloped landscape, probably colonized only by bacterial and algal mats.
  40. 40. • By the start of the Devonian, however, early terrestrial vegetation had begun to spread. These plants did not have roots or leaves like the plants most common today, and many had no vascular tissue at all. • They probably spread largely by vegetative growth, and did not grow much more than a few centimeters tall. • These plants included the now extinct zosterophylls and trimerophytes. The early fauna living among these plants were primarily arthropods: mites, trigonotarbids, wingless insects, and myriapods, though these early faunas are not well known. • By the Late Devonian, lycophytes, sphenophytes, ferns, and progymnosperms had evolved. • Most of these plants have true roots and leaves, and many are rather tall plants. • The progymnosperm Archaeopteris, whose leaves are shown at right, was a large tree with true wood. In fact it is the oldest such tree known, and produced some of the world's first forests. • By the end of the Devonian, the first seed plants had appeared. This rapid appearance of so many plant groups and growth forms has been called the "Devonian Explosion". Along with this diversification in terrestrial vegetation structure, came a diversification of the arthropods.
  41. 41. Devonian: Localities•Devonian localities on this server: (see map above) Hunsrück Shale, Germany Rhynie Chert - This Early Devonian fossil bed in Scotland includes some of the most famous fossil plants ever found, as well as fossil fungi and arthropods. It is the oldest terrestrial ecosystem found so well preserved. •Distribution of the Devonian 1-Region of the Old Red Sandstone: this is found in the Scandnivia and in the Baltic countries in the form of continental and lagoonal facies. 2- Region of the Ardennes : it is characterized by the presence of shaly- sandy facies. 3-The Mediterranean Region: this is characterized by the presence of deep water facies . 4- Eastern Europe: There is a passage from continental facies in the Russian plarform to geosynclinal type in the Ural Mountains.
  42. 42.  In Egypt: Devonian deposits occur : • Um Bogma-Abu Durba---Central Sinai • Western Desert (Southern part) golf kebeir plateau • Eastern Desert( Qena Valley-El-Dakhala)  Devonian: Orogeny • Culmination of folding and evolution in Scotland, Lake District and Wales. Then local sinking in fresh water basins with periods of renewed uplift in Scotland. • About the Middle Devnian, the Acadian revolution • Started , uplift of sediments accompanied by igneous activity which continued still the end of the period. Volcancity was prominent through the whole period.  Devonian: Climate • Could possibly be hot, coloration was due to high Temperature. Seasnal aridity was recorded in differents of the world Devonian: Localities
  43. 43. Paleogeography of the Devonian •The rising up of the Caledonian chain took place after the silurian and its effect is restricted to Scotland, Ireland and Norway. At the same time, a great tract of land appeared in N. Western Europe that played an important part during the subsequent Paleozoic history.
  44. 44. Devonian: Tectonics and Paleoclimate • Significant changes in the world's geography took place during the Devonian. During this period, the world's land was collected into two supercontinents, Gondwana and Euramerica. These vast landmasses lay relatively near each other in a single hemisphere, while a vast ocean covered the rest of the globe. • These supercontinents were surrounded on all sides by subduction zones. With the development of the subduction zone between Gondwana and Euramerica, a major collision was set in motion that would bring the two together to form the single world- continent Pangea in the Permian. • In addition to global patterns of change, many important regional activities also occurred. The continents of North America and Europe collided, resulting in massive granite intrusions and the raising of the Appalachian Mountains of eastern North America. Vigorous erosion of these newly uplifted mountains yielded great volumes of sediment, which were deposited in vast lowlands and shallow seas nearby. • Extensive reef building, producing some of the world's largest reef complexes, proceeded as stromatoporoids and corals appeared in increasing numbers. These were built in the equatorial seas between the continents. Large areas of shallow sea in North America, central Asia, and Australia became basins in which great quantities of rock salt, gypsum, and other minerals precipitated. • Near the end of the Devonian, a mass extinction event occurred. • Glaciation and the lowering of the global sea level may have triggered this crisis, since the evidence suggests warm water marine species were most affected. • Meteorite impacts have also been blamed for the mass extinction, or changes in atmospheric carbon dioxide. It is even conceivable that it was the evolution and spread of forests and the first plants with complex root systems that may have altered the global climate. Whatever the cause, it was about this time that the first vertebrates moved onto the land.
  45. 45. The Devonian Mass Extinction • Species Affected • The Devonian mass extinction occurred during the latter part of the Devonian at the Frasnian - Famennian boundary. • The crisis primarily affected the marine community, having little impact on the terrestrial flora. This same extinction pattern has been recognized in most mass extinctions throughout earth history. • The most important group to be affected by this extinction event were the major reef- builders including the stromatoporoids, and the rugose and tabulate corals • This late Devonian crisis affected these organisms so severely that reef-building was relatively uncommon until the evolution of the scleractinian (modern corals in the Mesozoic era. Among other marine invertebrates, seventy percent of the taxa did not survive into the Carboniferous. • Fast Facts •Devonian period ranged from 417-354 million years ago. •A major intra-Devonian extinction occurred at the Frasnian-Famennian boundary •Geological Setting •Following the Ordovician mass extinction rediversification of surviving groups occurred throughout the Silurian and Devonian. In addition, the Devonian saw the first appearance of sharks, bony fish, and ammonoids During the Devonian the world's oceans were dominated by reef-builders such as the stromatoporoids, and corals and some of the world's largest reef complexes were built. Terrestrial newcomers in the Devonian included amphibians, insects, and the first true land plants, giving rise to the first forests. •Amongst the severely affected groups were the brachiopods trilobites conodonts and acritarchs as well as all jawless fish, and placoderms
  46. 46. Speculated Causes of the Devonian Extinction  Glaciation • Evidence supporting the Devonian mass extinction suggests that warm water marine species were the most severely affected in this extinction event. • This evidence has lead many paleontologists to attribute the Devonian extinction to an episode of global cooling, similar to the event which is thought to have cause the late Ordovician mass extinction. • According to this theory,the extinction of the Devonian was triggered by another glaciation event on Gondwana, as evidenced by glacial deposits of this age in northern Brazil. Similarly to the late Ordovician crisis, agents such as global cooling and widespread lowering of sea-level may have triggered the late Devonian crisis.  Meteorite Impact • Meteorite impacts at the Frasnian-Famennian boundary have also been suggested as possible agents for the Devonian mass extinction. Currently, the data surrounding a possible extra-terrestrial impact remains inconclusive, and the mechanisms which produced the Devonian mass extinction are still under debate
  47. 47. All fossils in the Devonian Grammysia © 2003 Cornellites © 2005
  48. 48. Brachiopoda © 2003 Atrypa © 2003
  49. 49. Cupularostrum saxatilis © 2005 Cymtostrophia © 2004
  50. 50. Mucrospirifer © 2004 Pseudoatrypa © 2005
  51. 51. Pseudoatrypa devonia © 2005 Tenticospirifer cyrtina © 2005
  52. 52. Tylothyris © 2003 Cystodictya © 2003
  53. 53. Favosites turbinatus © 2006 Hexagonaria © 2004
  54. 54. Siphonophrentis © 2004 Tabulata © 2001
  55. 55. Basidechenella © 2001 Ceratonurus sp © 2005
  56. 56. Cordania falcata © 2002 Dicranurus hamatus elegantus © 2005
  57. 57. Cordania falcata © 2002 Dicranurus hamatus elegantus © 2005
  58. 58. Greenops © 2001 Phacops rana © 2001
  59. 59. Phacops rana milleri © 2002 Reedops deckeri © 2005