Misplaced Pages

#928071

125-605: The orogeny is named for Caledonia , the Latin name for Scotland . The term was first used in 1885 by Austrian geologist Eduard Suess for an episode of mountain building in northern Europe that predated the Devonian period . Geologists like Émile Haug and Hans Stille saw the Caledonian event as one of several episodic phases of mountain building that had occurred during Earth's history . Current understanding has it that

250-588: A NW-dipping one beneath Laurentia. About 430 Ma accretion in the Southern Uplands and Ireland switched from being orthogonal (at a right angle) to a sinistrally (left-lateral) transpressive one as indicated by cleavage transecting folds counterclockwise. Turbidite deposition in the oceanic trench overlapped onto the Lakesman-Leinster terrane. Laurentia-Avalonia convergence and Iapetus Ocean subduction ceased by C. 420 Ma as indicated by

375-823: A collision with a continental fragment. The Shelveian Orogeny occurred particularly in the Shelve area in Shropshire , in eastern Wales and in the English Midlands in the Late Ordovician and was related to the Taconic orogeny . It formed the Shelve Anticline and Rytton Castle Syncline and was the most important tectonic event in the area between the Cambrian and Devonian . Folding

500-417: A few species of the order Proetida . The subsequent end-Devonian extinction , which occurred at around 359 Ma, further impacted the ecosystems and completed the extinction of all calcite sponge reefs and placoderms. Devonian palaeogeography was dominated by the supercontinent Gondwana to the south, the small continent of Siberia to the north, and the medium-sized continent of Laurussia to

625-527: A late Caledonian phase and as having been driven by the closure of the Iapetus Ocean . However, there is also an argument that it would more appropriate to regard it as a proto- Variscan orogeny. This is because this Devonian event postdated the collision of Avalonia with Laurentia by 15–20 million years and was coeval with the early phase of the Variscan orogeny (Eo-Variscan or Ligerian) and because it

750-763: A low-latitude archipelago to the north of Gondwana. They were separated from the southern continent by an oceanic basin: the Paleo-Tethys . Although the western Paleo-Tethys Ocean had existed since the Cambrian, the eastern part only began to rift apart as late as the Silurian. This process accelerated in the Devonian. The eastern branch of the Paleo-Tethys was fully opened when South China and Annamia (a terrane equivalent to most of Indochina ), together as

875-529: A massive extinction event . ( See Late Devonian extinction ). Primitive arthropods co-evolved with this diversified terrestrial vegetation structure. The evolving co-dependence of insects and seed plants that characterized a recognizably modern world had its genesis in the Late Devonian Epoch. The development of soils and plant root systems probably led to changes in the speed and pattern of erosion and sediment deposition. The rapid evolution of

1000-467: A mid- Silurian weakening of deformation in the accretionary wedge. Magma production should be larger in convergent tectonic regimes during subduction and markedly reduced with the change to post-subduction collisional regimes. However, during Iapetus subduction (455–425 Ma) this was low and intrusive rocks were largely absent across all terranes in the concerned area in this period. Most Acadian magmatism occurred post-subduction (425-390 Ma) in

1125-420: A range of evidence, such as plant distribution, points to a Late Devonian warming. The climate would have affected the dominant organisms in reefs ; microbes would have been the main reef-forming organisms in warm periods, with corals and stromatoporoid sponges taking the dominant role in cooler times. The warming at the end of the Devonian may even have contributed to the extinction of the stromatoporoids. At

1250-418: A regional tectonic setting with alternating transpression and transtension phases. High rates of magma generation coincided with a c. 418–404 Ma Early Devonian sinistral transtension phase. This decreased during the 404–394 Ma Acadian transpression. In addition, the Southern Uplands accretionary wedge lacks evidence of the presence of a volcanic arc as usually found near subduction zones. This has led to

1375-585: A stretching lineation perpendicular to the fold hinges. The Southern Belt and the rest of the Central belt underwent sinistral transpression . This reflects a Late Ordovician – Silurian change from an orthogonal to an oblique tectonic plate collision. In the Central Belt the cleavage transects folds in a clockwise sense and is accompanied by a sub-horizontal stretching lineation. In the Southern belt

SECTION 10

#1732775906929

1500-664: A terrestrial ecosystem that contained copious animals opened the way for the first vertebrates to seek terrestrial living. By the end of the Devonian, arthropods were solidly established on the land. The Late Devonian extinction is not a single event, but rather is a series of pulsed extinctions at the Givetian-Frasnian boundary, the Frasnian-Famennian boundary, and the Devonian-Carboniferous boundary. Together, these are considered one of

1625-534: A transition from orthogonal compression to transpression during the later stages of Acadian deformation. This makes the island more similar to the Southern Uplands terrane of Scotland than the Lake District inlier in this respect. In Ireland the Acadian Orogeny affected the four main terranes of the island: Grampian, Midland Valley, Longford-Down and Leinster. Tectonic deformation was mild as

1750-541: A unified continent, detached from the northeastern sector of Gondwana. Nevertheless, they remained close enough to Gondwana that their Devonian fossils were more closely related to Australian species than to north Asian species. Other Asian terranes remained attached to Gondwana, including Sibumasu (western Indochina), Tibet, and the rest of the Cimmerian blocks. While the South China-Annamia continent

1875-602: A volcanically active region during the Devonian, as it continued to assimilate smaller island arcs. The island arcs of the region, such as the Balkhash-West Junggar Arc, exhibited biological endemism as a consequence of their location. Siberia was located just north of the equator as the largest landmass in the Northern Hemisphere. At the beginning of the Devonian, Siberia was inverted (upside down) relative to its modern orientation. Later in

2000-622: A warm temperate climate . In the Late Devonian, by contrast, arid conditions were less prevalent across the world and temperate climates were more common. The Devonian Period is formally broken into Early, Middle and Late subdivisions. The rocks corresponding to those epochs are referred to as belonging to the Lower, Middle and Upper parts of the Devonian System. The Early Devonian lasted from 419.2 to 393.3 Ma. It began with

2125-639: A westward direction. The combined convergence of this microcontinent and the two continents created continental collisions between them, the mentioned orogenic events and the closure of the Iapetus and Tornquist oceans. Continental collisions started in the Mid Silurian and mountain building and ended in the Early Devonian (420–405 Ma). The Grampian orogeny involved collisions between two landmasses of Laurentia and an oceanic island arc in

2250-596: Is a large basement massif. It is part of a magmatic belt which, starting from the Lake District , to the north of this massif, bears record of the subduction of part of the Tornquist Sea beneath Avalonia and its closure. The closure of the Rheic Ocean , which took place soon after, occurred through subduction along the southern margin of this massif. The Trans-European Suture Zone or Tornquist Zone

2375-558: Is a supernatural police drama that takes place in Glasgow, Scotland. Ptolemy's account in his Geography also referred to the Caledonia Silva , an idea still recalled in the modern expression " Caledonian Forest ", although the woods are much reduced in size since Roman times. Some scholars point out that the name "Scotland" is ultimately derived from Scotia , a Latin term first used for Ireland (also called Hibernia by

2500-435: Is an exposed N–S trending thrust zone which marks the western limit of intense Caledonian deformation. The dominant structures are interpreted as having resulted from sinistral transpression , which involved strain partitioning of regional deformation between sinistral strike-slip movements in the east and NW-directed oblique thrusting and folding further to the west. This orogenic event also affected Scotland and

2625-588: Is composed mainly of the Manx Group and the Dalby Group which were deformed in a sinistral transpression zone during the sinistral, oblique closure of the Iapetus Ocean. Folds are transected clockwise by their cleavage , major strike-parallel sinistral faults and ductile shear zones thought to be related to this transpression. All primary folds have the same style and are associated with

SECTION 20

#1732775906929

2750-578: Is good evidence that Rheic oceanic crust experienced intense subduction and metamorphism under Mexico and Central America. The closure of the eastern part of the Rheic Ocean is associated with the assemblage of central and southern Europe. In the early Paleozoic, much of Europe was still attached to Gondwana, including the terranes of Iberia , Armorica (France), Palaeo-Adria (the western Mediterranean area), Bohemia , Franconia , and Saxothuringia . These continental blocks, collectively known as

2875-975: Is indicated by the absence of orogenic structures or high-pressure metamorphic rocks , which are either not present or buried. This event occurred close to the end of the Ordovician , 440 Ma. It docked with the Baltica margins in southern Denmark , the south-western corner of the Baltic Sea and Poland . It came to comprise Silesia in Poland , northern Germany , the Netherlands , Belgium and part of north-eastern France (the Ardennes Mountains). The Anglo-Brabant massif or London-Brabant Massif in central and southern England and in Belgium

3000-430: Is observed in many of those plants. Some of the early land plants such as Drepanophycus likely spread by vegetative growth and spores. The earliest land plants such as Cooksonia consisted of leafless, dichotomous axes with terminal sporangia and were generally very short-statured, and grew hardly more than a few centimetres tall. Fossils of Armoricaphyton chateaupannense , about 400 million years old, represent

3125-597: Is the area of the suture of Baltica and Eastern Avalonia. It runs from a portion of the North Sea close to Denmark , through southern Denmark, a portion of the Baltic Sea between Denmark and Poland (by Germany's Rügen Island), and through Poland. It then follows the eastern margin of the Eastern Carpathian Mountains in western Ukraine . Finally, it runs to the Black Sea . However, in

3250-792: Is the toe end of the Southern Uplands turbidite accretionary wedge onlapping or thrust onto the Avalonia continental margin. The broad deformation style and age of the Manx Group are very similar to the equivalent features of the Skiddaw Group in the Lake District and the Ribband Group in SE Ireland. This group is thought to be their regional equivalent. It underwent two main deformation phases which also affected

3375-675: The Anglo-Scottish border . It consists of a series of faults with no traces of subduction , such as ophiolite remnants or oceanic trench -derived rocks. The Iapetus Suture also extends along the margin of the Baltoscandian platform of the Fennoscandian Peninsula which collided with the eastern margin of Greenland along the eastern margin of Laurentia in the Scandian orogeny. According to some authors,

3500-641: The Antler orogeny , which extended into the Carboniferous. Mountain building could also be found in the far northeastern extent of the continent, as minor tropical island arcs and detached Baltic terranes re-join the continent. Deformed remnants of these mountains can still be found on Ellesmere Island and Svalbard . Many of the Devonian collisions in Laurussia produce both mountain chains and foreland basins , which are frequently fossiliferous. Gondwana

3625-565: The Frasnian , 382.7 to 372.2 Ma, during which the first forests took shape on land. The first tetrapods appeared in the fossil record in the ensuing Famennian subdivision, the beginning and end of which are marked with extinction events. This lasted until the end of the Devonian, 358.9 Ma. The Devonian was a relatively warm period, although significant glaciers may have existed during the Early and Middle Devonian. The temperature gradient from

3750-936: The Great Glen Fault which affected the Moine Supergroup and the Dalradian rocks in Scotland and the Shetland Islands through the Walls Boundary Fault , which is the northeast-ward extension of the Great Glen Fault. As mentioned above, the British Isles were separated and belonged to two different tectonic plates: Laurentia ( Scotland and northern and western Ireland ) and Avalonia ( England and Wales and

3875-483: The Late Carboniferous . The first ammonites , a subclass of cephalopod molluscs , appeared. Trilobites , brachiopods and the great coral reefs were still common during the Devonian. The Late Devonian extinction , which started about 375 Ma, severely affected marine life, killing off most of the reef systems, most of the jawless fish, half of all placoderms, and nearly all trilobites save for

Caledonian orogeny - Misplaced Pages Continue

4000-640: The Lochkovian Stage 419.2 to 410.8 Ma, which was followed by the Pragian from 410.8 to 407.6 Ma and then by the Emsian , which lasted until the Middle Devonian began, 393.3 Ma. During this time, the first ammonoids appeared, descending from bactritoid nautiloids . Ammonoids during this time period were simple and differed little from their nautiloid counterparts. These ammonoids belong to

4125-651: The Maeatae and the Caledonians (Latin: Caledonii ). Other ancient authors, however, used the adjective "Caledonian" more generally to describe anything pertaining to inland or northern Britain. The name is probably derived from a word in Common Brittonic . According to Zimmer (2006), Caledonia is derived from the tribal name Caledones (or Calīdones ), which he etymologises as " 'possessing hard feet', alluding to standfastness or endurance", from

4250-674: The Maritime Provinces of Canada has been applied to the early Devonian deformation phase in the British Caledonides by analogy with the one that occurred in what is now North America . Late Caledonian orogeny is another term used in reference to this phase. This phase involved a soft docking or soft collision rather an orogen -causing hard continental collision like the Eastern Avalonia docking with Baltica. This orogenic event has been interpreted as

4375-642: The Proto-Celtic roots * kal- 'hard' and * φēdo- 'foot'. Similarly, journalist Alistair Moffat suggests the name is related to the Welsh word caled 'hard', which could refer to the rocky land or the hardiness of the people. The name of the Caledonians may be found in toponymy , such as Dùn Chailleann , the Scottish Gaelic name of the town of Dunkeld , meaning 'fort of

4500-521: The Rodinia supercontinent . The majority of its bulk consisted of the landmass of Gondwana . Near the end of the Neoproterozoic, during the breakup of this supercontinent, Laurentia and Baltica rifted from the western ( Amazonian craton ) and northern (African) margins of Gondwana respectively. Laurentia first drifted westward away from Gondwana and then migrated northward. This led to

4625-639: The Roman Empire's occupation of Scotland , the area they called Caledonia was physically separated from the rest of the island by the Antonine Wall . The Romans several times invaded and occupied it, but unlike the rest of the island, it remained outside the administration of Roman Britain . Latin historians , including Tacitus and Cassius Dio , referred to the territory north of the River Forth as "Caledonia", and described it as inhabited by

4750-450: The Scandinavian Caledonides . The first phase that is often included in the Caledonian orogeny is the Finnmarkian Orogeny, which was an early deformation event in Arctic (northern) Norway which preceded the Scandian phase (see below) in this area. Its onset has been dated at c. 500 Ma (Late Cambrian ). It continued to c. 460 Ma and was reactivated in the Scandian phase at ~425–415 Ma. According to van Roermund and Brueckner (2004), there

4875-410: The Sudetes Mountains and the Eastern Carpathians, it evolved through the Variscan and the Alpine orogenies, rather than the Caledonian one. The Scandian phase involved a collision between eastern Greenland on the eastern margin of Laurentia and the margin of the Baltoscandian platform of the Fennoscandian peninsula of Baltica. It involved the Scandinavian Caledonides in what is now Norway and

5000-423: The cladoxylopsids and progymnosperm Archaeopteris . These tracheophytes were able to grow to large size on dry land because they had evolved the ability to biosynthesize lignin , which gave them physical rigidity and improved the effectiveness of their vascular system while giving them resistance to pathogens and herbivores. In Eifelian age, cladoxylopsid trees formed the first forests in Earth history. By

5125-466: The opening of the Iapetus Ocean between Laurentia, Baltica and Gondwana. Its initial opening phase was between the adjacent Laurentia and Baltica (to the West and East respectively) and caused the two to breakup c. 615 Ma or 590 Ma. Then the part between Laurentia and Gondwana (to the east), opened c. 550 Ma. Further spreading of the Iapetus Ocean also caused Laurentia and Baltica to move away from each other. Baltica drifted northward, too. This involved

Caledonian orogeny - Misplaced Pages Continue

5250-452: The " Big Five " mass extinctions in Earth's history. The Devonian extinction crisis primarily affected the marine community, and selectively affected shallow warm-water organisms rather than cool-water organisms. The most important group to be affected by this extinction event were the reef-builders of the great Devonian reef systems. Amongst the severely affected marine groups were the brachiopods, trilobites, ammonites, and acritarchs , and

5375-433: The Armorican Terrane Assemblage, split away from Gondwana in the Silurian and drifted towards Laurussia through the Devonian. Their collision with Laurussia leads to the beginning of the Variscan Orogeny , a major mountain-building event which would escalate further in the Late Paleozoic. Franconia and Saxothuringia collided with Laurussia near the end of the Early Devonian, pinching out the easternmost Rheic Ocean. The rest of

5500-414: The Armorican terranes followed, and by the end of the Devonian they were fully connected with Laurussia. This sequence of rifting and collision events led to the successive creation and destruction of several small seaways, including the Rheno-Hercynian, Saxo-Thuringian, and Galicia-Moldanubian oceans. Their sediments were eventually compressed and completely buried as Gondwana fully collided with Laurussia in

5625-418: The Caledonian continental collisions involved another microcontinent, Armorica (southern Portugal , most of the north of France and parts of southern Germany and the Czech Republic ), even smaller than Avalonia. This microcontinent probably did not form one consistent unit, but was instead a series of fragments, of which the current Armorican and Bohemian Massifs are the most important. The ocean between

5750-402: The Caledonian orogeny encompasses a number of tectonic phases that can laterally be diachronous , meaning that different parts of the mountain range formed at different times. The name "Caledonian" can therefore not be used for an absolute period of geological time, it applies only to a series of tectonically related events. In the Neoproterozoic most of the Earth's landmasses were united in

5875-414: The Caledonii', and possibly in that of the mountain Sìdh Chailleann , the 'fairy hill of the Caledonians'. According to Historia Brittonum , the site of the seventh battle of the legendary King Arthur was a forest in what is now Scotland, called Coit Celidon in early Welsh. The name seems to relate to that of a large central Brythonic tribe, the Caledonii , one amongst several in

6000-511: The Carboniferous. Sea levels in the Devonian were generally high. Marine faunas continued to be dominated by conodonts, bryozoans , diverse and abundant brachiopods , the enigmatic hederellids , microconchids , and corals . Lily-like crinoids (animals, their resemblance to flowers notwithstanding) were abundant, and trilobites were still fairly common. Bivalves became commonplace in deep water and outer shelf environments. The first ammonites also appeared during or slightly before

6125-451: The Dalby Group: a) a pervasive slaty cleavage associated with gently to moderately plunging folds which also affected many of the minor igneous intrusions , b) a gently dipping crenulation cleavage associated with small folds verging towards the bedding dip direction. There are several ductile shear zones which run subparallel to the Manx Group northeast-oriented boundary faults which indicate predominantly sinistral shear and possibly

6250-420: The Devonian Period. The newly evolved forests drew carbon out of the atmosphere, which were then buried into sediments. This may be reflected by a Mid-Devonian cooling of around 5 °C (9 °F). The Late Devonian warmed to levels equivalent to the Early Devonian; while there is no corresponding increase in CO 2 concentrations, continental weathering increases (as predicted by warmer temperatures); further,

6375-408: The Devonian seas. The first abundant genus of cartilaginous fish, Cladoselache , appeared in the oceans during the Devonian Period. The great diversity of fish around at the time has led to the Devonian being given the name "The Age of Fishes" in popular culture. The Devonian saw significant expansion in the diversity of nektonic marine life driven by the abundance of planktonic microorganisms in

SECTION 50

#1732775906929

6500-597: The Devonian to often be dubbed the Age of Fishes . The armored placoderms began dominating almost every known aquatic environment. In the oceans, cartilaginous fishes such as primitive sharks became more numerous than in the Silurian and Late Ordovician . Tetrapodomorphs , which include the ancestors of all four- limbed vertebrates (i.e. tetrapods ), began diverging from freshwater lobe-finned fish as their more robust and muscled pectoral and pelvic fins gradually evolved into forelimbs and hindlimbs , though they were not fully established for life on land until

6625-434: The Devonian, as free- sporing land plants ( pteridophytes ) began to spread across dry land , forming extensive coal forests which covered the continents. By the middle of the Devonian, several groups of vascular plants had evolved leaves and true roots , and by the end of the period the first seed -bearing plants ( pteridospermatophytes ) appeared. This rapid evolution and colonization process, which had begun during

6750-451: The Early Devonian and the existence of fossils such as Protichnites suggest that amphibious arthropods may have appeared as early as the Cambrian ). By far the largest land organism at the beginning of this period was the enigmatic Prototaxites , which was possibly the fruiting body of an enormous fungus, rolled liverwort mat, or another organism of uncertain affinities that stood more than 8 metres (26 ft) tall, and towered over

6875-420: The Early and Middle Devonian, the west coast of Laurussia was a passive margin with broad coastal waters, deep silty embayments, river deltas and estuaries, found today in Idaho and Nevada . In the Late Devonian, an approaching volcanic island arc reached the steep slope of the continental shelf and began to uplift deep water deposits. This minor collision sparked the start of a mountain-building episode called

7000-405: The Hercynian orogeny. Caledonia Caledonia ( / ˌ k æ l ɪ ˈ d oʊ n i ə / ; Latin : Calēdonia [kaleːˈdonia] ) was the Latin name used by the Roman Empire to refer to the part of Scotland that lies north of the River Forth , which includes most of the land area of Scotland . Today, it is used as a romantic or poetic name for all of Scotland. During

7125-408: The Iapetus Ocean orthogonally (at a right angle ). Its drift included an up to 55° counterclockwise rotation with respect to the subduction zone to its north, mainly in the 470–450 Ma timeframe. It moved significantly faster than Baltica but slowed down to a rate comparable to that of the latter in the Late Ordovician when it got close to it. The main phases of the Caledonian orogeny resulted from

7250-427: The Iapetus Ocean outboard the main margin of the Laurentia tectonic plate (the future North America). There two Laurentian landmasses were Scotland and northern and western Ireland . The other parts of the British Isles ( England and Wales and the rest of Ireland) were part of the Avalonia microcontinent. Two parts of Avalonia have been distinguished, a western and an eastern one. The term Western Avalonia refers to

7375-428: The Lakesman terrane and north Wales . Transpression resulted in regionally clockwise transecting sinistral transpressive cleavages which were superimposed on pre-existing structures. Folding northwest of the Iapetus Suture is weak and this northward weakening of deformation may indicate that it is linked with Rheic Ocean subduction rather than Iapetus Ocean closure. The Lake District in north-western England

7500-446: The Late Devonian the tectonic situation had relaxed and much of South America was covered by shallow seas. These south polar seas hosted a distinctive brachiopod fauna, the Malvinokaffric Realm, which extended eastward to marginal areas now equivalent to South Africa and Antarctica. Malvinokaffric faunas even managed to approach the South Pole via a tongue of Panthalassa which extended into the Paraná Basin . The northern rim of Gondwana

7625-453: The Late Devonian. The Altai-Sayan region was shaken by volcanism in the Early and Middle Devonian, while Late Devonian magmatism was magnified further to produce the Vilyuy Traps , flood basalts which may have contributed to the Late Devonian Mass Extinction. The last major round of volcanism, the Yakutsk Large Igneous Province, continued into the Carboniferous to produce extensive kimberlite deposits. Similar volcanic activity also affected

SECTION 60

#1732775906929

7750-455: The NE into a marine basin which bridged the Avalonia and Laurentia margins. The tectonic contact between the two groups has been correlated either with the Windermere Supergroup (Lake District) turbidites or the Riccarton Group, ( Southern Uplands terrane ).The former hypothesis implies that the Dalby Group was originally deposited on the Manx Group and was subsequently faulted into its present day relationship. The latter one implies that it

7875-413: The Ordovician; these continents were by then further north. It also involved the consumption of both the Iapetus Ocean and the Tornquist Ocean along its northern margin. Avalonia's motion was related to slab pull created by the subduction of the Iapetus Ocean beneath the margin of Laurentia to its northwest and possibly also by ridge push created by the spreading of the Rheic Ocean. It migrated across

8000-423: The Pontesford-Linley fault system and folding in pre-Ashgill strata, uplift of the adjacent Towi Anticline and igneous activity. The main orogenic events or phases of the Caledonian orogenic cycle were related to the final closure of the Iapetus Ocean. They were, in sequential order, the Grampian phase, the docking of Eastern Avalonia with Baltica, the Scandian phase and the Acadian phase. The latter involved: A)

8125-418: The Romans) and later for Scotland, the Scoti peoples having originated in Ireland and resettled in Scotland. Another, post-conquest, Roman name for the island of Great Britain was Albion , which is cognate with the Scottish Gaelic name for Scotland: Alba . There is an emerging trend to use the term Caledonia to describe New Caledonia in English, which reflects the usage in French of Calédonie (where

8250-460: The SE and east) ... and each tectonic event throughout this 200 million years can be considered as an orogenic phase." This includes tectonic events which were smaller, localised and predated the more well-known main phases of this orogeny. In this definition, the Taconic and Acadian orogenies in what today is North America are included in the phases of the Caledonian orogeny. Some early phases of deformation and metamorphism are recognised in

8375-416: The Silurian and Devonian, it decreased across the span of the Devonian, particularly during the Pragian, and that the overall diversity of nektonic taxa did not increase significantly during the Devonian compared to during other geologic periods, and was in fact higher during the intervals spanning from the Wenlock to the Lochkovian and from the Carboniferous to the Permian. The study's authors instead attribute

8500-404: The Silurian, is known as the Silurian-Devonian Terrestrial Revolution . The earliest land animals , predominantly arthropods such as myriapods , arachnids and hexapods , also became well-established early in this period, after beginning their colonization of land at least from the Ordovician period. Fishes , especially jawed fish , reached substantial diversity during this time, leading

8625-411: The Swedish areas by its border. It occurred from the Wenlock Epoch of the Silurian to the Mid Devonian (430–380 Ma). Gee et al. (2013) and Ladenberger et al. (2012) propose a revised onset dating set at 440 Ma, however, there is no consensus about this. The Scandian orogenic event also led to the formation of mountains of Queen Louise Land (or Dronning Louise Land) in north-eastern Greenland . It

8750-451: The Tinure Fault is the surface expression of the Iapetus Suture zone. The Iapetus Suture is the lineament where the Caledonian collision closed the Iapetus Ocean. In Ireland it runs from the estuary of the River Shannon on the Atlantic coast to Clogherhead on the Irish Sea . It crosses this sea and is exposed in the Niarbyl Fault in the southern part of the northern coast of the Isle of Man . In Britain it runs roughly parallel to

8875-463: The accretion of the Armorican terranes with the southern margin of Laurussia in the Carboniferous Variscan orogeny (about 340 million years ago). The Rhenohercynian basin , a back-arc basin , formed at the southern margin of Euramerica just after the Caledonian orogeny. According to these authors, a small rim from Euramerica rifted off when this basin formed. The basin closed when these Caledonian deformed terranes were accreted again to Laurussia during

9000-570: The area and perhaps the dominant tribe, which would explain the binomial Caledonia/Caledonii. The modern use of "Caledonia" in English and Scots is either as a historical description of northern Britain during the Roman era or as a romantic or poetic name for Scotland as a whole. The name has been widely used by organisations and commercial entities. Notable examples include Glasgow Caledonian University , ferry operator Caledonian MacBrayne , and

9125-661: The beginning of the Mississippian subperiod of the Carboniferous. In 19th-century texts the Devonian has been called the "Old Red Age", after the red and brown terrestrial deposits known in the United Kingdom as the Old Red Sandstone in which early fossil discoveries were found. Another common term is "Age of the Fishes", referring to the evolution of several major groups of fish that took place during

9250-466: The collision was strongly oblique with sinistral transpression and without substantial crustal thickening . Devonian to Carboniferous rocks rest unconformably on Cambrian to Silurian folded and cleaved rocks. There were igneous intrusions with plutons and batholiths . The terrane has three relief belts. The northern belt and the northernmost part of the Central Belt underwent pure shear deformation with an axial planar cleavage and

9375-598: The combined continental mass of Laurentia, Baltica and Avalonia (called Euramerica, Laurussia or Old Red Continent ) and Armorica is called the Rheic Ocean . The paleogeographic position of the Armorica crustal fragments between the Ordovician and Carboniferous is highly disputed though. There are indications that the Bohemian Massif started moving northward from the Ordovician onward, but many authors place

9500-684: The continent (such as Greenland and Ellesmere Island ) established tropical conditions, most of the continent was located within the natural dry zone along the Tropic of Capricorn , which (as nowadays) is a result of the convergence of two great air-masses, the Hadley cell and the Ferrel cell . In these near-deserts, the Old Red Sandstone sedimentary beds formed, made red by the oxidised iron ( hematite ) characteristic of drought conditions. The abundance of red sandstone on continental land also lends Laurussia

9625-548: The continents Laurentia (modern day North America) and Baltica (modern day northern and eastern Europe). The tectonic effects of this collision continued into the Devonian, producing a string of mountain ranges along the southeastern coast of the continent. In present-day eastern North America, the Acadian Orogeny continued to raise the Appalachian Mountains . Further east, the collision also extended

9750-465: The convergence of Baltica, Laurentia and Avalonia which led to the closure of the Iapetus Ocean. McKerrow et al. (2000) give a definition of the Caledonian orogeny which includes "all the Cambrian , Ordovician , Silurian and Devonian tectonic events associated with the development and closure of those parts of the Iapetus Ocean which were situated between Laurentia (to the NW) and Baltica and Avalonia (to

9875-565: The docking of England and Wales (which were part of eastern Avalonia) with eastern and southern Ireland with Scotland and the rest of Ireland (which were part of Laurentia). B) the amalgamation of terranes of Western Avalonia with the eastern margin of the main landmass of Laurentia (see Acadian orogeny article for this orogeny). During the final part of its northwestward migration, Avalonia converged with Baltica and Laurentia to its northeast and northwest respectively. After its amalgamation with Eastern Avalonia, Baltica converged with Laurentia in

10000-469: The early Devonian Period around 400  Ma. Bactritoids make their first appearance in the Early Devonian as well; their radiation, along with that of ammonoids, has been attributed by some authors to increased environmental stress resulting from decreasing oxygen levels in the deeper parts of the water column. Among vertebrates, jawless armored fish ( ostracoderms ) declined in diversity, while

10125-669: The east. Major tectonic events include the closure of the Rheic Ocean , the separation of South China from Gondwana, and the resulting expansion of the Paleo-Tethys Ocean . The Devonian experienced several major mountain-building events as Laurussia and Gondwana approached; these include the Acadian Orogeny in North America and the beginning of the Variscan Orogeny in Europe. These early collisions preceded

10250-569: The end of the Devonian, the first seed-forming plants had appeared. This rapid appearance of many plant groups and growth forms has been referred to as the Devonian Explosion or the Silurian-Devonian Terrestrial Revolution. The 'greening' of the continents acted as a carbon sink , and atmospheric concentrations of carbon dioxide may have dropped. This may have cooled the climate and led to

10375-516: The end of the preceding Silurian period at 419.2 million years ago ( Ma ), to the beginning of the succeeding Carboniferous period at 358.9 Ma. It is the fourth period of both the Paleozoic and the Phanerozoic. It is named after Devon , South West England , where rocks from this period were first studied. The first significant evolutionary radiation of life on land occurred during

10500-412: The equator to the poles was not as large as it is today. The weather was also very arid, mostly along the equator where it was the driest. Reconstruction of tropical sea surface temperature from conodont apatite implies an average value of 30 °C (86 °F) in the Early Devonian. Early Devonian mean annual surface temperatures were approximately 16 °C. CO 2 levels dropped steeply throughout

10625-588: The formation of the single supercontinent Pangaea in the Late Paleozoic. The period is named after Devon , a county in southwestern England, where a controversial argument in the 1830s over the age and structure of the rocks found throughout the county was resolved by adding the Devonian Period to the geological timescale. The Great Devonian Controversy was a lengthy debate between Roderick Murchison , Adam Sedgwick and Henry De la Beche over

10750-492: The free water column as well as high ecological competition in benthic habitats, which were extremely saturated; this diversification has been labeled the Devonian Nekton Revolution by many researchers. However, other researchers have questioned whether this revolution existed at all; a 2018 study found that although the proportion of biodiversity constituted by nekton increased across the boundary between

10875-521: The full name is La Nouvelle-Calédonie). The New Caledonian trade and investment department promotes inward investment with the slogan "Choose Caledonia". Devonian The Devonian ( / d ə ˈ v oʊ n i . ən , d ɛ -/ də- VOH -nee-ən, deh- ) is a geologic period and system of the Paleozoic era during the Phanerozoic eon , spanning 60.3 million years from

11000-497: The hypotheses that arc rocks were eroded and thus have not been preserved, that the arc was displaced by lateral movement along strike-slip faults or that this is due to flat–slab subduction , which reduces magmatism rates. Nelison et al. (2009) propose an Iapetus Ocean subducting slab breakoff model to account for the intrusive rocks in the Grampian terrane being emplaced post-subduction. However, Miles at al. (2016) note that

11125-744: The increased overall diversity of nekton in the Devonian to a broader, gradual trend of nektonic diversification across the entire Palaeozoic. A now-dry barrier reef, located in present-day Kimberley Basin of northwest Australia , once extended 350 km (220 mi), fringing a Devonian continent. Reefs are generally built by various carbonate -secreting organisms that can erect wave-resistant structures near sea level. Although modern reefs are constructed mainly by corals and calcareous algae , Devonian reefs were either microbial reefs built up mostly by autotrophic cyanobacteria or coral-stromatoporoid reefs built up by coral-like stromatoporoids and tabulate and rugose corals . Microbial reefs dominated under

11250-425: The increasing competition, predation, and diversity of jawed fishes . The shallow, warm, oxygen-depleted waters of Devonian inland lakes, surrounded by primitive plants, provided the environment necessary for certain early fish to develop such essential characteristics as well developed lungs and the ability to crawl out of the water and onto the land for short periods of time. Finally, the Late Devonian started with

11375-641: The intrusive rocks in the Trans-Suture Suite and in all the terranes in the region are similar in age and geochemistry. Thus, they argue that the common mechanism for the whole region involved an Iapetus Ocean slab which did not just break off. It also peeled back below the Iapetus Suture for c. 100 km to the SE below Avalonia. Thus they invoke a model of slab drop-off caused by lithospheric mantle delamination . The Lakesman terrane covers

11500-403: The jawed fish (gnathostomes) simultaneously increased in both the sea and fresh water . Armored placoderms were numerous during the early ages of the Devonian Period and became extinct in the Late Devonian, perhaps because of competition for food against the other fish species. Early cartilaginous ( Chondrichthyes ) and bony fishes ( Osteichthyes ) also become diverse and played a large role within

11625-481: The land lay under shallow seas, where tropical reef organisms lived. The enormous "world ocean", Panthalassa , occupied much of the Northern Hemisphere as well as wide swathes east of Gondwana and west of Laurussia. Other minor oceans were the Paleo-Tethys Ocean and Rheic Ocean . By the early Devonian, the continent Laurussia (also known as Euramerica ) was fully formed through the collision of

11750-575: The low, carpet-like vegetation during the early part of the Devonian. Also, the first possible fossils of insects appeared around 416  Ma, in the Early Devonian. Evidence for the earliest tetrapods takes the form of trace fossils in shallow lagoon environments within a marine carbonate platform/shelf during the Middle Devonian, although these traces have been questioned and an interpretation as fish feeding traces ( Piscichnus ) has been advanced. Many Early Devonian plants did not have true roots or leaves like extant plants, although vascular tissue

11875-562: The name "the Old Red Continent". For much of the Devonian, the majority of western Laurussia (North America) was covered by subtropical inland seas which hosted a diverse ecosystem of reefs and marine life. Devonian marine deposits are particularly prevalent in the midwestern and northeastern United States. Devonian reefs also extended along the southeast edge of Laurussia, a coastline now corresponding to southern England , Belgium , and other mid-latitude areas of Europe. In

12000-625: The naming of the period. Murchison and Sedgwick won the debate and named it the Devonian System. While the rock beds that define the start and end of the Devonian Period are well identified, the exact dates are uncertain. According to the International Commission on Stratigraphy , the Devonian extends from the end of the Silurian 419.2 Ma, to the beginning of the Carboniferous 358.9 Ma – in North America , at

12125-411: The nearby microcontinent of Amuria (now Manchuria , Mongolia and their vicinities). Though certainly close to Siberia in the Devonian, the precise location of Amuria is uncertain due to contradictory paleomagnetic data. The Rheic Ocean, which separated Laurussia from Gondwana, was wide at the start of the Devonian, having formed after the drift of Avalonia away from Gondwana. It steadily shrunk as

12250-747: The north of England down to the Wensleydale in North Yorkshire and crosses the Irish Sea passing by the Island of Anglesey off Wales . Its continuation in eastern Ireland is the Leinster terrane. The combined terrane is termed Leinster-Lakesman terrane. It lies on the southern margin of the Iapetus Suture . It includes the Lake District and the Isle of Man . The Acadian Orogeny affected

12375-447: The northern margin of Gondwana ( Amazonia and northwest Africa) close to the original position of Baltica which had been to its north. Its rifting involved the opening and spreading of the Rheic Ocean to its south, which separated it from Gondwana. This rifting and opening were coeval with and may be related to subduction onset in the Iapetus Ocean. The drift of Avalonia was towards the positions where Baltica and Laurentia had been in

12500-791: The now-defunct British Caledonian airline and Caledonian Railway . The Caledonian Sleeper is an overnight train service from London to Scottish destinations. The Inverness Caledonian Thistle F.C. is a professional football club. In music, " Caledonia " is a popular Scottish patriotic song and folk ballad written by Dougie MacLean in 1977 and published in 1979 on an album of the same name; it has since been covered by various other artists, most notably Frankie Miller and Van Morrison . An original rock piece titled Caledonia appeared on Robin Trower's fourth album, "Long Misty Days", where coincidentally Frankie Miller cowrote another track on that album. The web series Caledonia and associated novel

12625-401: The oldest known plants with woody tissue. By the Middle Devonian, shrub-like forests of primitive plants existed: lycophytes , horsetails , ferns , and progymnosperms evolved. Most of these plants had true roots and leaves, and many were quite tall. The earliest-known trees appeared in the Middle Devonian. These included a lineage of lycopods and another arborescent, woody vascular plant,

12750-693: The opening of the Tornquist Ocean which separated it from the northern margin of Gondwana to the south. The onset of Baltica rifting and the Tornquist Ocean opening are difficult to date due to insufficient palaeomagnetic data but must have occurred in similar times as those of Laurentia and the Iapetus Ocean. Either in the Late Precambrian or Early Ordovician , the Avalonia microcontinent started to drift northwestward from

12875-703: The order Agoniatitida , which in later epochs evolved to new ammonoid orders, for example Goniatitida and Clymeniida . This class of cephalopod molluscs would dominate the marine fauna until the beginning of the Mesozoic Era. The Middle Devonian comprised two subdivisions: first the Eifelian , which then gave way to the Givetian 387.7 Ma. During this time the jawless agnathan fishes began to decline in diversity in freshwater and marine environments partly due to drastic environmental changes and partly due to

13000-676: The outer Hebrides , causing thrusting in the Northern Highlands which culminated in the development of the Moine Thrust Belt , Ben Hope Thrust and Naver- Sgurr Beag Thrust (435–420 Ma) and led to igneous intrusion in Galloway and the Southern Uplands (c. 400 Ma) in Scotland and the enlargement of the Lake District batholith in northern England . All this spanned the Iapetus Suture zone (see below). It also caused northeast trending strike-slip faults, such as

13125-403: The period continued, as the two major continents approached near the equator in the early stages of the assembly of Pangaea . The closure of the Rheic Ocean began in the Devonian and continued into the Carboniferous. As the ocean narrowed, endemic marine faunas of Gondwana and Laurussia combined into a single tropical fauna. The history of the western Rheic Ocean is a subject of debate, but there

13250-472: The period it moved northwards and began to twist clockwise, though it was not near its modern location. Siberia approached the eastern edge of Laurussia as the Devonian progressed, but it was still separated by a seaway, the Ural Ocean . Although Siberia's margins were generally tectonically stable and ecologically productive, rifting and deep mantle plumes impacted the continent with flood basalts during

13375-529: The period. Older literature on the Anglo-Welsh basin divides it into the Downtonian, Dittonian, Breconian, and Farlovian stages, the latter three of which are placed in the Devonian. The Devonian has also erroneously been characterised as a "greenhouse age", due to sampling bias : most of the early Devonian-age discoveries came from the strata of western Europe and eastern North America , which at

13500-624: The rest of Ireland). The Early Devonian Acadian event in this area saw the amalgamation of these landmasses to form the British Isles as they are now. This occurred through NW-dipping subduction of Avalonian oceanic crust beneath the southern margins of the Laurentian landmasses. Since the 1980s the term Acadian , which referred to the Late Silurian to Early Devonian orogeny in the Northern Appalachians , and

13625-557: The rise of the Caledonian Mountains of Great Britain and Scandinavia . As the Caledonian Orogeny wound down in the later part of the period, orogenic collapse facilitated a cluster of granite intrusions in Scotland. Most of Laurussia was located south of the equator, but in the Devonian it moved northwards and began to rotate counterclockwise towards its modern position. While the most northern parts of

13750-527: The same regional cleavage suggesting that they are roughly coeval. There is ductile deformation in some localities and a broad shear zone in the Langness Peninsula which deform the primary cleavage and are thought to have formed during or soon after the main deformation phase. The Dalby Group was overthrust onto the Manx Group, probably in the early Devonian. During the final stage of the Iapetus Ocean closure its turbidites were deposited from

13875-464: The south of the suture) which were at the Laurentia and Avalonia margins respectively. The emplacement of the plutons occurred after the subduction of the Iapetus Ocean ended. The Southern Uplands terrane is thought to be an accretionary wedge . Deep marine sedimentation here in response to subduction begun 455 Ma and marked the switch from an initial SE-dipping Iapetus subduction under Avalonia to

14000-628: The terminus of the Devonian, Earth rapidly cooled into an icehouse , marking the beginning of the Late Paleozoic icehouse . The Devonian world involved many continents and ocean basins of various sizes. The largest continent, Gondwana , was located entirely within the Southern Hemisphere . It corresponds to modern day South America , Africa , Australia , Antarctica , and India , as well as minor components of North America and Asia . The second-largest continent, Laurussia,

14125-535: The time straddled the Equator as part of the supercontinent of Euramerica where fossil signatures of widespread reefs indicate tropical climates that were warm and moderately humid. In fact the climate in the Devonian differed greatly during its epochs and between geographic regions. For example, during the Early Devonian, arid conditions were prevalent through much of the world including Siberia, Australia, North America, and China, but Africa and South America had

14250-521: The warmer conditions of the early and late Devonian, while coral-stromatoporoid reefs dominated during the cooler middle Devonian. By the Devonian Period, life was well underway in its colonization of the land. The moss forests and bacterial and algal mats of the Silurian were joined early in the period by primitive rooted plants that created the first stable soils and harbored arthropods like mites , scorpions , trigonotarbids and myriapods (although arthropods appeared on land much earlier than in

14375-808: The westernmost part of the microcontinent which amalgamated the east coast of the main part of the Laurentia tectonic plate (what is now North America) to the west in the area of the northern Appalachians and the Maritimes . Eastern Avalonia refers to a) the part which amalgamated with Baltica , b) England a Wales and eastern and south-eastern Ireland which amalgamated with Scotland and the north and west of Ireland (which were part of Laurentia). The easternmost part of Eastern Avalonia amalgamated with Baltica through an oblique soft docking governed by dextral strike-slip convergence and shear , rather than through an orogen-causing hard continental collision . This

14500-555: The world saw the disappearance of an estimated 96% of vertebrates like conodonts and bony fishes , and all of the ostracoderms and placoderms. Land plants as well as freshwater species, such as our tetrapod ancestors, were relatively unaffected by the Late Devonian extinction event (there is a counterargument that the Devonian extinctions nearly wiped out the tetrapods ). The reasons for the Late Devonian extinctions are still unknown, and all explanations remain speculative. Canadian paleontologist Digby McLaren suggested in 1969 that

14625-713: Was a distinct orogenic event which was separate and slightly younger than that of the Finnmarkian one, which they dated at 455 Ma. They named it the Jämtlandian Orogeny . It involved the Seve Nappe Complex of the Swedish Caledonides in central Sweden , which is interpreted as the stretched outermost edge of Baltica. Contrary to the previous opinion that it had been subducted beneath an oceanic island arc , they propose that it involved

14750-626: Was accompanied by late stage igneous intrusions . The event caused a major unconformity in Shropshire with considerable erosion before the deposition of sediments in the Llandovery Epoch of the Silurian (444–443 Ma). There was no break in sediments in the area until the end of the Early Devonian , which was caused by the Acadian Orogeny in the British Isles . It was associated with dextral (right-lateral) strike-slip movement in

14875-545: Was at the north-western margin of the English part of Eastern Avalonia which converged and collided with Scotland and was thus involved in the Acadian phase. Generally, Acadian deformation metamorphosed mudrocks throughout various geologic formations of the district into slates by creating slaty cleavages . The Early Palaeozoic rocks in the Isle of Man in the Irish Sea crop out close to or probably on Iapetus suture . The island lies immediately to its SE. The island

15000-680: Was by far the largest continent on the planet. It was completely south of the equator, although the northeastern sector (now Australia) did reach tropical latitudes. The southwestern sector (now South America) was located to the far south, with Brazil situated near the South Pole . The northwestern edge of Gondwana was an active margin for much of the Devonian, and saw the accretion of many smaller land masses and island arcs. These include Chilenia , Cuyania , and Chaitenia , which now form much of Chile and Patagonia . These collisions were associated with volcanic activity and plutons , but by

15125-442: Was mostly a passive margin, hosting extensive marine deposits in areas such as northwest Africa and Tibet . The eastern margin, though warmer than the west, was equally active. Numerous mountain building events and granite and kimberlite intrusions affected areas equivalent to modern day eastern Australia , Tasmania , and Antarctica. Several island microcontinents (which would later coalesce into modern day Asia) stretched over

15250-438: Was northwest of Gondwana, and corresponds to much of modern-day North America and Europe . Various smaller continents, microcontinents , and terranes were present east of Laurussia and north of Gondwana, corresponding to parts of Europe and Asia. The Devonian Period was a time of great tectonic activity, as the major continents of Laurussia and Gondwana drew closer together. Sea levels were high worldwide, and much of

15375-521: Was not related to the Iapetus Ocean. It also has been argued that, although the Acadian orogeny in the British Isles involved the Iapetus Ocean closure, its driving force was actually a push from the south caused by the northward subduction of the Rheic Ocean which lied to the south of Avalonia and separated it from Gondwana . The closure of this ocean involved the (early) Eo-Variscan collision of Gondwana-related terranes in which Eastern Avalonia

15500-463: Was peripherally involved. Subduction of the Iapetus Ocean occurred beneath the Midland Valley terrane of Scotland. There is a Trans-Suture Suite of intrusive plutons which straddle both sides of the trace of the Iapetus Suture in the Southern Uplands terrane of Scotland (to the north of the suture) and the Lakesman-Leinster terrane of northern England and eastern Ireland (to

15625-577: Was the newest addition to the Asian microcontinents, it was not the first. North China and the Tarim Block (now northwesternmost China) were located westward and continued to drift northwards, powering over older oceanic crust in the process. Further west was a small ocean (the Turkestan Ocean), followed by the larger microcontinents of Kazakhstania , Siberia , and Amuria . Kazakhstania was

#928071