The Exmouth Plateau is an elongate northeast striking extensional passive margin located in the Indian Ocean roughly 3,000 meters offshore from western and northwestern Western Australia .
92-683: The plateau makes up the westernmost structural unit of the Northern Carnarvon Basin , which comprises the Exmouth, Barrow, Dampier, and Beagle Sub-basins, and the Rankin Platform. The Exmouth Plateau was once a part of the northern shore of eastern of Gondwanaland until it broke away during Late Jurassic to Early Cretaceous , leaving behind the oceanic crust of the Argo, Cuvier, and Gascoyne abyssal plains that now surround
184-630: A bolide impact, for which an impact crater containing Manicouagan Reservoir in Quebec , Canada , has been singled out. However, the Manicouagan impact melt has been dated to 214±1 Mya. The date of the Triassic-Jurassic boundary has also been more accurately fixed recently, at 201.4 Mya. Both dates are gaining accuracy by using more accurate forms of radiometric dating, in particular the decay of uranium to lead in zircons formed at time of
276-626: A cosmopolitan distribution . Coelacanths show their highest post- Devonian diversity in the Early Triassic . Ray-finned fishes (actinopterygians) went through a remarkable diversification in the beginning of the Triassic, leading to peak diversity during the Middle Triassic; however, the pattern of this diversification is still not well understood due to a taphonomic megabias . The first stem-group teleosts appeared during
368-555: A chain of mountain ranges stretching from Turkey to Malaysia . Pangaea was fractured by widespread faulting and rift basins during the Triassic—especially late in that period—but had not yet separated. The first nonmarine sediments in the rift that marks the initial break-up of Pangaea, which separated eastern North America from Morocco , are of Late Triassic age; in the United States , these thick sediments comprise
460-474: A few exposures in the west. During the Triassic peneplains are thought to have formed in what is now Norway and southern Sweden. Remnants of this peneplain can be traced as a tilted summit accordance in the Swedish West Coast . In northern Norway Triassic peneplains may have been buried in sediments to be then re-exposed as coastal plains called strandflats . Dating of illite clay from
552-471: A long beak-like snout), and Shringasaurus (a horned herbivore which reached a body length of 3–4 metres (9.8–13.1 ft)). One group of archosauromorphs, the archosauriforms , were distinguished by their active predatory lifestyle, with serrated teeth and upright limb postures. Archosauriforms were diverse in the Triassic, including various terrestrial and semiaquatic predators of all shapes and sizes. The large-headed and robust erythrosuchids were among
644-617: A pseudosuchian. Pseudosuchians were far more ecologically dominant in the Triassic, including large herbivores (such as aetosaurs ), large carnivores (" rauisuchians "), and the first crocodylomorphs (" sphenosuchians "). Aetosaurs were heavily-armored reptiles that were common during the last 30 million years of the Late Triassic until they died out at the Triassic-Jurassic extinction. Most aetosaurs were herbivorous and fed on low-growing plants, but some may have eaten meat. " rauisuchians " (formally known as paracrocodylomorphs ) were
736-458: A short period of time, becoming extinct about 220 million years ago. They were exceptionally abundant in the middle of the Triassic, as the primary large herbivores in many Carnian-age ecosystems. They sheared plants with premaxillary beaks and plates along the upper jaw with multiple rows of teeth. Allokotosaurs were iguana-like reptiles, including Trilophosaurus (a common Late Triassic reptile with three-crowned teeth), Teraterpeton (which had
828-567: A specialized subgroup of cynodonts, appeared during the Triassic and would survive the extinction event, allowing them to radiate during the Jurassic. Amphibians were primarily represented by the temnospondyls , giant aquatic predators that had survived the end-Permian extinction and saw a new burst of diversification in the Triassic, before going extinct by the end; however, early crown-group lissamphibians (including stem-group frogs , salamanders and caecilians ) also became more common during
920-449: A strandflat of Bømlo , southern Norway, have shown that landscape there became weathered in Late Triassic times ( c. 210 million years ago) with the landscape likely also being shaped during that time. Eustatic sea level in the Triassic was consistently low compared to the other geological periods. The beginning of the Triassic was around present sea level, rising to about 10–20 metres (33–66 ft) above present-day sea level during
1012-585: A supercontinent has less shoreline compared to a series of smaller continents, Triassic marine deposits are relatively uncommon on a global scale. A major exception is in Western Europe , where the Triassic was first studied. The northeastern margin of Gondwana was a stable passive margin along the Neo-Tethys Ocean, and marine sediments have been preserved in parts of northern India and Arabia . In North America , marine deposits are limited to
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#17327719227491104-566: A system of listric normal faults near the eastern region of the Exmouth Plateau. These listric faults were a product from the development of a major low angle detachment fault between a sedimentary base of Permian-Triassic upper crust and the mid-crustal horizon. As a result, brittle deformation and crustal thinning in the upper crust of the eastern Exmouth Plateau occurred, while in the west, the lower crystalline crust and lithosphere experienced shear stress and thinning. The formation of
1196-659: Is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya ), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is the first and shortest period of the Mesozoic Era and the seventh period of the Phanerozoic Eon . Both the start and end of the period are marked by major extinction events . The Triassic Period
1288-682: Is a low-energy, offshore-marine deposit in a period when input of the terrigenous sediments to the offshore was low minimal. Carnarvon Basin The Carnarvon Basin is a geological basin located in the north west of Western Australia which extends from the Dampier Archipelago to the Murchison bioregion, and is the main geological feature that makes up the North West Shelf . The onshore part of
1380-468: Is a recent study of North American faunas. In the Petrified Forest of northeast Arizona there is a unique sequence of late Carnian-early Norian terrestrial sediments. An analysis in 2002 found no significant change in the paleoenvironment. Phytosaurs , the most common fossils there, experienced a change-over only at the genus level, and the number of species remained the same. Some aetosaurs ,
1472-508: Is likely a paraphyletic group rather than a true clade. Tanystropheids were a family of protorosaurs which elevated their neck size to extremes, with the largest genus Tanystropheus having a neck longer than its body. The protorosaur family Sharovipterygidae used their elongated hindlimbs for gliding. Other archosauromorphs, such as rhynchosaurs and allokotosaurs , were mostly stocky-bodied herbivores with specialized jaw structures. Rhynchosaurs, barrel-gutted herbivores, thrived for only
1564-469: Is no evidence of glaciation at or near either pole; in fact, the polar regions were apparently moist and temperate , providing a climate suitable for forests and vertebrates, including reptiles. Pangaea's large size limited the moderating effect of the global ocean; its continental climate was highly seasonal, with very hot summers and cold winters. The strong contrast between the Pangea supercontinent and
1656-605: Is subdivided into three epochs: Early Triassic , Middle Triassic and Late Triassic . The Triassic began in the wake of the Permian–Triassic extinction event , which left the Earth's biosphere impoverished; it was well into the middle of the Triassic before life recovered its former diversity. Three categories of organisms can be distinguished in the Triassic record: survivors from the extinction event, new groups that flourished briefly, and other new groups that went on to dominate
1748-460: Is superimposed by 22 sea level drop events widespread in the geologic record, mostly of minor (less than 25-metre (82 ft)) and medium (25–75-metre (82–246 ft)) magnitudes. A lack of evidence for Triassic continental ice sheets suggest that glacial eustasy is unlikely to be the cause of these changes. The Triassic continental interior climate was generally hot and dry, so that typical deposits are red bed sandstones and evaporites . There
1840-411: Is usually divided into Early , Middle , and Late Triassic Epochs , and the corresponding rocks are referred to as Lower, Middle, or Upper Triassic. The faunal stages from the youngest to oldest are: During the Triassic, almost all the Earth's land mass was concentrated into a single supercontinent , Pangaea ( lit. ' entire land ' ). This supercontinent was more-or-less centered on
1932-578: The Carnian (early part of the Late Triassic), some advanced cynodonts gave rise to the first mammals . During the Triassic, archosaurs displaced therapsids as the largest and most ecologically prolific terrestrial amniotes. This "Triassic Takeover" may have contributed to the evolution of mammals by forcing the surviving therapsids and their mammaliaform successors to live as small, mainly nocturnal insectivores . Nocturnal life may have forced
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#17327719227492024-614: The Jurassic , when the temnospondyls had become very rare. Most of the Reptiliomorpha , stem-amniotes that gave rise to the amniotes, disappeared in the Triassic, but two water-dwelling groups survived: Embolomeri that only survived into the early part of the period, and the Chroniosuchia , which survived until the end of the Triassic. The Permian–Triassic extinction devastated terrestrial life. Biodiversity rebounded as
2116-568: The Lake Lugano region of northern Italy and southern Switzerland , was in Middle Triassic times a lagoon behind reefs with an anoxic bottom layer, so there were no scavengers and little turbulence to disturb fossilization, a situation that can be compared to the better-known Jurassic Solnhofen Limestone lagerstätte . The remains of fish and various marine reptiles (including the common pachypleurosaur Neusticosaurus , and
2208-509: The Mesozoic Era. Reptiles , especially archosaurs , were the chief terrestrial vertebrates during this time. A specialized group of archosaurs, called dinosaurs , first appeared in the Late Triassic but did not become dominant until the succeeding Jurassic Period. Archosaurs that became dominant in this period were primarily pseudosuchians , relatives and ancestors of modern crocodilians , while some archosaurs specialized in flight,
2300-658: The Newark Supergroup . Rift basins are also common in South America, Europe, and Africa. Terrestrial environments are particularly well-represented in the South Africa, Russia, central Europe, and the southwest United States. Terrestrial Triassic biostratigraphy is mostly based on terrestrial and freshwater tetrapods, as well as conchostracans ("clam shrimps"), a type of fast-breeding crustacean which lived in lakes and hypersaline environments. Because
2392-474: The Olenekian and Anisian of Gondwana . Both kannemeyeriiform dicynodonts and gomphodont cynodonts remained important herbivores during much of the period. Therocephalians included both large predators ( Moschorhinus ) and herbivorous forms ( bauriids ) until their extinction midway through the period. Ecteniniid cynodonts played a role as large-sized, cursorial predators in the Late Triassic. During
2484-681: The Valanginian unconformity. The Winning Group consists of Muderong Shale, Windalia Radiolarite, and Gearle Siltstone. The Muderong Shale is actually considered a siltstone and was deposited in a low energy, offshore-marine environment. The deposition of these sediments makes a good seal for gas buildups in the Exmouth Plateau and the surrounding sub-basins of the Northern Carnvon Basin. The Windalia Radiolarite are primarily carbonate marine deposits commonly containing poorly preserved radiolarians and forminiferas. The Gearle Siltstone
2576-735: The surviving species repopulated empty terrain, but these were short-lived. Diverse communities with complex food-web structures took 30 million years to reestablish. Archosauromorph reptiles, which had already appeared and diversified to an extent in the Permian Period, exploded in diversity as an adaptive radiation in response to the Permian-Triassic mass extinction. By the Early Triassic, several major archosauromorph groups had appeared. Long-necked, lizard-like early archosauromorphs were known as protorosaurs , which
2668-468: The thecodonts ) disappeared, as did most of the large labyrinthodont amphibians, groups of small reptiles, and most synapsids. Some of the early, primitive dinosaurs also became extinct, but more adaptive ones survived to evolve into the Jurassic. Surviving plants that went on to dominate the Mesozoic world included modern conifers and cycadeoids. The cause of the Late Triassic extinction is uncertain. It
2760-437: The traversodont cynodonts—were much reduced in the northern half of Pangaea ( Laurasia ). These extinctions within the Triassic and at its end allowed the dinosaurs to expand into many niches that had become unoccupied. Dinosaurs became increasingly dominant, abundant and diverse, and remained that way for the next 150 million years. The true "Age of Dinosaurs" is during the following Jurassic and Cretaceous periods, rather than
2852-832: The Anisian to Ladinian of the Tethysian domain, and from the Carnian and Rhaetian of a larger area that includes also the Boreal domain (e.g., Svalbard Islands), the North American continent, the South China block and Argentina . The best-studied of such episodes of humid climate, and probably the most intense and widespread, was the Carnian Pluvial Event . The Early Triassic was the hottest portion of
Exmouth Plateau - Misplaced Pages Continue
2944-933: The Carnarvon Basin covers about 115,000 km and the offshore part covers approximately 535,000 km with water depths up to 3,500 metres. It is separated into two major areas - the Northern Carnarvon Basin, and the Southern Carnarvon Basin. The Northern Carnarvon Basin includes the Exmouth Plateau , Wombat Plateau (on the northern part of the Exmouth Plateau), Investigator Sub-basin, Rankin Platform, Exmouth Sub-basin, Barrow Sub-basin, Dampier Sub-basin, Beagle Sub-basin, Enderby Terrace, Peedamullah Shelf and
3036-405: The Carnian and include early sauropodomorphs and theropods. Most Triassic dinosaurs were small predators and only a few were common, such as Coelophysis , which was 1 to 2 metres (3.3 to 6.6 ft) long. Triassic sauropodomorphs primarily inhabited cooler regions of the world. The large predator Smok was most likely also an archosaur, but it is uncertain if it was a primitive dinosaur or
3128-563: The Early Triassic, forming small patches of reefs of modest extent compared to the great reef systems of Devonian or modern times. At the end of the Carnian, a reef crisis occurred in South China. Serpulids appeared in the Middle Triassic. Microconchids were abundant. The shelled cephalopods called ammonites recovered, diversifying from a single line that survived the Permian extinction. Bivalves began to rapidly diversify during
3220-402: The Early Triassic, while others (e.g. capitosaurs ) remained successful throughout the whole period, or only came to prominence in the Late Triassic (e.g. Plagiosaurus , metoposaurs ). The first Lissamphibians (modern amphibians) appear in the Triassic, with the progenitors of the first frogs already present by the Early Triassic. However, the group as a whole did not become common until
3312-562: The Early and Middle Triassic. Sea level rise accelerated in the Ladinian, culminating with a sea level up to 50 metres (164 ft) above present-day levels during the Carnian. Sea level began to decline in the Norian, reaching a low of 50 metres (164 ft) below present sea level during the mid-Rhaetian. Low global sea levels persisted into the earliest Jurassic. The long-term sea level trend
3404-688: The Gascoyne Platform, Southern Carnarvon Basin with an estimated age of 100-300 Ma. 24°48′24″S 115°13′29″E / 24.80667°S 115.22472°E / -24.80667; 115.22472 This article about a location in Western Australia is a stub . You can help Misplaced Pages by expanding it . This article about a specific Australian geological feature is a stub . You can help Misplaced Pages by expanding it . Triassic The Triassic ( / t r aɪ ˈ æ s ɪ k / try- ASS -ik ; sometimes symbolized 🝈 )
3496-403: The Jurassic. The Triassic was named in 1834 by Friedrich August von Alberti , after a succession of three distinct rock layers (Greek triás meaning 'triad') that are widespread in southern Germany : the lower Buntsandstein (colourful sandstone ) , the middle Muschelkalk (shell-bearing limestone ) and the upper Keuper (coloured clay ). On the geologic time scale , the Triassic
3588-613: The Jurassic. There were many types of marine reptiles. These included the Sauropterygia , which featured pachypleurosaurus and nothosaurs (both common during the Middle Triassic, especially in the Tethys region), placodonts , the earliest known herbivorous marine reptile Atopodentatus , and the first plesiosaurs . The first of the lizardlike Thalattosauria ( askeptosaurs ) and the highly successful ichthyopterygians , which appeared in Early Triassic seas, soon diversified. By
3680-609: The Lambert Shelf. The main sub-basins for petroleum exploration in the basin have been Dampier, Exmouth and Barrow. The Southern basin consists of the Gascoyne, Merlinleigh, Bidgemia and Byro Sub-basins and Bernier Platform and is flanked to the east by the Archaean Pilbara Block. The Gnargoo structure , which has remarkable similarities to Woodleigh crater , is a proposed 75 km impact crater on
3772-600: The Latest Olenekian Cooling (LOC), from 248 to 247 Ma, temperatures cooled by about 6 °C. The Middle Triassic was cooler than the Early Triassic, with temperatures falling over most of the Anisian, with the exception of a warming spike in the latter portion of the stage. From 242 to 233 Ma, the Ladinian-Carnian Cooling (LCC) ensued. At the beginning of the Carnian, global temperatures continued to be relatively cool. The eruption of
Exmouth Plateau - Misplaced Pages Continue
3864-486: The Middle Triassic, becoming highly abundant in the oceans. Aquatic insects rapidly diversified during the Middle Triassic, with this time interval representing a crucial diversification for Holometabola , the clade containing the majority of modern insect species. In the wake of the Permian-Triassic mass extinction event , the fish fauna was remarkably uniform, with many families and genera exhibiting
3956-618: The Middle Triassic, some ichthyopterygians were achieving very large body masses. Among other reptiles, the earliest turtles , like Proganochelys and Proterochersis , appeared during the Norian Age (Stage) of the Late Triassic Period. The Lepidosauromorpha , specifically the Sphenodontia , are first found in the fossil record of the earlier Carnian Age, though the earliest lepidosauromorphs likely occurred in
4048-781: The Mungaroo laid down only for a short period of time between the beginning of the Rhaetian to the Early Hettangian . Due to the thickness of fluvial deltaic deposits from the Mungaroo Formation, the transgressional sequence of the Brigadier Formation is correlated with the subsidence of sub-basins across region during the Middle and Late Triassic . The distribution of sediment packages throughout
4140-682: The Northern Carnarvon Basin and Exmouth Plateau varies with location during the Jurassic. By the Pliensbachian , the general beginning structure of the Northern Carnarvon Basin was formed, creating the Exmouth, Barrow, and Dampier sub-basins along the proximal end of the northwestern Australian margin. Rapid subsidence of the Northern Carnarvon sub-basins ensued the deposition of the Dingo Claystones. These Claystones are thick marine shale deposits separated into two sequence,
4232-590: The Permian extension that occurred just prior to the late Triassic extension event across the northwestern margin of Australia. Lying atop unconformable unit of Paleozoic sediments, the Locker Shale is composed of marine sediments deposited in a transgressional environment during the Late Permian extension. These marine sediments were deposited at the base of the Late Triassic and continued up until
4324-450: The Permian extinction, Archaeplastida (red and green algae) had been the major marine phytoplanktons since about 659–645 million years ago, when they replaced marine planktonic cyanobacteria , which first appeared about 800 million years ago, as the dominant phytoplankton in the oceans. In the Triassic, secondary endosymbiotic algae became the most important plankton. In marine environments , new modern types of corals appeared in
4416-475: The Permian. The Procolophonidae , the last surviving parareptiles , were an important group of small lizard-like herbivores. The drepanosaurs were a clade of unusual, chameleon-like arboreal reptiles with birdlike heads and specialised claws. Three therapsid groups survived into the Triassic: dicynodonts , therocephalians , and cynodonts . The cynodont Cynognathus was a characteristic top predator in
4508-408: The Triassic (teleosts are by far the most diverse group of fish today). Predatory actinopterygians such as saurichthyids and birgeriids , some of which grew over 1.2 m (3.9 ft) in length, appeared in the Early Triassic and became widespread and successful during the period as a whole. Lakes and rivers were populated by lungfish (Dipnoi), such as Ceratodus , which are mainly known from
4600-497: The Triassic and survived the extinction event. The earliest known neopterygian fish, including early holosteans and teleosts , appeared near the beginning of the Triassic, and quickly diversified to become among the dominant groups of fish in both freshwater and marine habitats. The vast supercontinent of Pangaea dominated the globe during the Triassic, but in the latest Triassic ( Rhaetian ) and Early Jurassic it began to gradually rift into two separate landmasses: Laurasia to
4692-609: The Triassic, enlarging the Neo-Tethys Ocean which formed in their wake. At the same time, they forced the Paleo-Tethys Ocean to shrink as it was being subducted under Asia. By the end of the Triassic, the Paleo-Tethys Ocean occupied a small area and the Cimmerian terranes began to collide with southern Asia. This collision, known as the Cimmerian Orogeny , continued into the Jurassic and Cretaceous to produce
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#17327719227494784-505: The Upper and Lower Dingo Claystones. The Lower Dingo sequence cannot be found in the Exmouth Plateau, because deposition During the Early to Middle Jurassic was restricted to sediments filling in the empty troughs of the Northern Carnarvon sub-basins. As deposition continued through the Middle and Late Jurassic , the troughs of sub-basins filled allowing more of the Dingo sediment overflow into
4876-839: The Wrangellia Large Igneous Province around 234 Ma caused abrupt global warming, terminating the cooling trend of the LCC. This warming was responsible for the Carnian Pluvial Event and resulted in an episode of widespread global humidity. The CPE ushered in the Mid-Carnian Warm Interval (MCWI), which lasted from 234 to 227 Ma. At the Carnian-Norian boundary occurred a positive δ C excursion believed to signify an increase in organic carbon burial. From 227 to 217 Ma, there
4968-401: The bizarre long-necked archosauromorph Tanystropheus ), along with some terrestrial forms like Ticinosuchus and Macrocnemus , have been recovered from this locality. All these fossils date from the Anisian and Ladinian ages (about 242 Ma ago). The Triassic Period ended with a mass extinction, which was particularly severe in the oceans; the conodonts disappeared, as did all
5060-419: The central and southern margins of the Exmouth Plateau now known as the Gascoyne and Cuvier Abyssal Plains. As Australia continued to diverge away from the Antarctic land mass, it migrated in a northeastern direction and rotated counterclockwise to it present location, leaving the Exmouth Plateau along the continent's western margin. In the begin of the late Triassic , high volumes of sediments accumulate off of
5152-421: The continental break up at the southern margin of the Exmouth Plateau. This followed seafloor spreading at the Gascoyne and Cuvier Abyssal Plains and erosion at the surface of the Exmouth, Dampier and Barrow sub-basins and an unconformity at the top of the early to middle Valanginian . By the middle to late Valanginian and through the Cretaceous major transgression occurred with deposit of the Winning Group atop
5244-447: The dental plates, abundant in the fossils record. Hybodonts , a group of shark-like cartilaginous fish , were dominant in both freshwater and marine environments throughout the Triassic. Last survivors of the mainly Palaeozoic Eugeneodontida are known from the Early Triassic. Temnospondyl amphibians were among those groups that survived the Permian–Triassic extinction. Once abundant in both terrestrial and aquatic environments,
5336-415: The distal margins of Exmouth Plateau. In the Late Jurassic , Gondwanaland begins to break apart creating Western Gondwana, which was composed of the South American and African continental land masses, and Eastern Gondwana. The Eastern Gondwanian continent was composed of Madagascar, Greater India, Antarctica, and Australia. During this period of time Australia shared its southern margin with Antarctica and
5428-416: The distal margins of the region. This depositional sequence characterizes the Upper Dingo Claystones, which are found as thick proximal sequences in the Northern Carnarvon sub-basins and thinner distal sequences in the Exmouth Plateau. During the late Tithonian to early Valanginian there were major changes in depositional patterns, specifically associated with the Barrow Group. At this period of time there
5520-423: The distal portions of the Northern Carnarvon Basin furthest offshore. One of the primary gas source for the Exmouth Plateau and Northern Carnarvon Basin, the Mungaroo Formation contains thick successions of siltstone , sandstone , and coal . The Mungaroo Formation is capped by thin transgressive sequence of shallow marine claystone and limestone called the Brigadier Formation. This is a much thinner formation than
5612-428: The dominant carnivores in the early Triassic. Phytosaurs were a particularly common group which prospered during the Late Triassic. These long-snouted and semiaquatic predators resemble living crocodiles and probably had a similar lifestyle, hunting for fish and small reptiles around the water's edge. However, this resemblance is only superficial and is a prime-case of convergent evolution. True archosaurs appeared in
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#17327719227495704-405: The early Triassic, splitting into two branches: Avemetatarsalia (the ancestors to birds) and Pseudosuchia (the ancestors to crocodilians). Avemetatarsalians were a minor component of their ecosystems, but eventually produced the earliest pterosaurs and dinosaurs in the Late Triassic. Early long-tailed pterosaurs appeared in the Norian and quickly spread worldwide. Triassic dinosaurs evolved in
5796-432: The end of Anisian age when it transitioned in the Mungaroo Formation. The Mungaroo Formation is an intricate fluvial environment of meandering and braided stream deposits laid down in the Ladinian (~241 Mya) to Norian ages (~209 Mya) during the pre-rift active margin of the Northwestern Australian Shelf. It is one of the thickest formations in the region and becomes progressively thicker (approximately 3,000 m thick) in
5888-401: The entire Phanerozoic, seeing as it occurred during and immediately after the discharge of titanic volumes of greenhouse gases from the Siberian Traps. The Early Triassic began with the Permian-Triassic Thermal Maximum (PTTM) and was followed by the brief Dienerian Cooling (DC) from 251 to 249 Ma, which was in turn followed by the Latest Smithian Thermal Maximum (LSTT) around 249 to 248 Ma. During
5980-467: The equator and extended between the poles, though it did drift northwards as the period progressed. Southern Pangea, also known as Gondwana , was made up by closely-appressed cratons corresponding to modern South America , Africa , Madagascar , India , Antarctica , and Australia . North Pangea, also known as Laurussia or Laurasia , corresponds to modern-day North America and the fragmented predecessors of Eurasia . The western edge of Pangea lay at
6072-415: The extinct family Cheirolepidiaceae , which first appeared in the Late Triassic, and would be prominent throughout most of the rest of the Mesozoic. No known coal deposits date from the start of the Triassic Period. This is known as the Early Triassic "coal gap" and can be seen as part of the Permian–Triassic extinction event . Possible explanations for the coal gap include sharp drops in sea level at
6164-414: The fault system closer to the coast caused the initial development of the Exmouth, Barrow, and Dampier sub-basins of the Northern Carnarvon Basin. Carbonate marine sediment, primarily marls, continued to be deposited at this time on the central and western portions of the plateau. Closer to the shoreline siliciclastic mud and silt were deposited from marine and deltaic environments. As extension continued in
6256-406: The first time among vertebrates, becoming the pterosaurs . Therapsids , the dominant vertebrates of the preceding Permian period, saw a brief surge in diversification in the Triassic, with dicynodonts and cynodonts quickly becoming dominant, but they declined throughout the period with the majority becoming extinct by the end. However, the first stem-group mammals ( mammaliamorphs ), themselves
6348-408: The global ocean triggered intense cross-equatorial monsoons , sometimes referred to as the Pangean megamonsoons . The Triassic may have mostly been a dry period, but evidence exists that it was punctuated by several episodes of increased rainfall in tropical and subtropical latitudes of the Tethys Sea and its surrounding land. Sediments and fossils suggestive of a more humid climate are known from
6440-420: The impact. So, the evidence suggests the Manicouagan impact preceded the end of the Triassic by approximately 10±2 Ma. It could not therefore be the immediate cause of the observed mass extinction. The number of Late Triassic extinctions is disputed. Some studies suggest that there are at least two periods of extinction towards the end of the Triassic, separated by 12 to 17 million years. But arguing against this
6532-401: The keystone predators of most Triassic terrestrial ecosystems. Over 25 species have been found, including giant quadrupedal hunters, sleek bipedal omnivores, and lumbering beasts with deep sails on their backs. They probably occupied the large-predator niche later filled by theropods. "Rauisuchians" were ancestral to small, lightly-built crocodylomorphs, the only pseudosuchians which survived into
6624-545: The mammaliaforms to develop fur and a higher metabolic rate . Two Early Triassic lagerstätten (high-quality fossil beds), the Dienerian aged Guiyang biota and the earliest Spathian aged Paris biota stand out due to their exceptional preservation and diversity . They represent the earliest lagerstätten of the Mesozoic era and provide insight into the biotic recovery from the Permian-Triassic mass extinction event. The Monte San Giorgio lagerstätte, now in
6716-573: The margin of an enormous ocean, Panthalassa ( lit. ' entire sea ' ), which roughly corresponds to the modern Pacific Ocean . Practically all deep-ocean crust present during the Triassic has been recycled through the subduction of oceanic plates, so very little is known about the open ocean from this time period. Most information on Panthalassan geology and marine life is derived from island arcs and rare seafloor sediments accreted onto surrounding land masses, such as present-day Japan and western North America. The eastern edge of Pangea
6808-453: The marine reptiles except ichthyosaurs and plesiosaurs . Invertebrates like brachiopods and molluscs (such as gastropods ) were severely affected. In the oceans, 22% of marine families and possibly about half of marine genera went missing. Though the end-Triassic extinction event was not equally devastating in all terrestrial ecosystems, several important clades of crurotarsans (large archosaurian reptiles previously grouped together as
6900-465: The mid to late Jurassic, multiple pull-apart basins and oblique right-lateral strike-slip faulting in the eastern margin of the Exmouth Plateau continued to dominate. The simple shear stress of the Exmouth detachment fault between the base of the upper crust, and the lower crust had been reduced in the east plateau. This reduction in simple shear was in part caused by the deformation that developed series negative flower structures and half-graben systems in
6992-430: The next most common tetrapods, and early dinosaurs, passed through unchanged. However, both phytosaurs and aetosaurs were among the groups of archosaur reptiles completely wiped out by the end-Triassic extinction event. It seems likely then that there was some sort of end-Carnian extinction, when several herbivorous archosauromorph groups died out, while the large herbivorous therapsids —the kannemeyeriid dicynodonts and
7084-512: The north and Gondwana to the south. The global climate during the Triassic was mostly hot and dry, with deserts spanning much of Pangaea's interior. However, the climate shifted and became more humid as Pangaea began to drift apart. The end of the period was marked by yet another major mass extinction, the Triassic–Jurassic extinction event , that wiped out many groups, including most pseudosuchians, and allowed dinosaurs to assume dominance in
7176-402: The order Isoetales (which contains living quillworts ), rose to prominence due to the environmental instability following the Permian-Triassic extinction, with one particularly notable example being the genus Pleuromeia , which grew in columnar like fashion, sometimes reaching a height of 2 metres (6.6 ft). The relevance of lycophytes declined from the Middle Triassic onwards, following
7268-486: The overall structural morphology of the Exmouth Plateau had taken shape, aside from the post-breakup subsidence that occurred afterward from the Late Cretaceous to present day. Activity at the eastern Exmouth Plateau's detachment system had likely ceased which is reason for the completion of the plateau's morphology. The Locker Shale and Mungaroo formation are associated with the syn-rift and post-rift sequences of
7360-487: The return of more stable environmental conditions. While having first appeared during the Permian, the extinct seed plant group Bennettitales first became a prominent element in global floras during the Late Triassic, a position they would hold for much of the Mesozoic. In the Southern Hemisphere landmasses of Gondwana, the tree Dicroidium , an extinct " seed fern " belong to the order Corystospermales
7452-543: The shoreline of western Australia to the northern extend of the Exmouth Plateau by the Mungaroo Deltas. The Carnian (237-228 Ma) to Norian (228-209 Ma) aged fluviodeltaic sediments deposited were siliciclastic claystones and sandstones, and detritus which would late make up the coals found in Mungaroo Formation. As extensional rifting between Greater Indian and the Australian continued, magmatic intrusion along
7544-676: The terminus of the Triassic, there was an extreme warming event referred to as the End-Triassic Thermal Event (ETTE), which was responsible for the Triassic-Jurassic mass extinction. Bubbles of carbon dioxide in basaltic rocks dating back to the end of the Triassic indicate that volcanic activity from the Central Atlantic Magmatic Province helped trigger climate change in the ETTE. During the Early Triassic, lycophytes , particularly those of
7636-595: The terrestrial species had mostly died out during the extinction event. The Triassic survivors were aquatic or semi-aquatic, and were represented by Tupilakosaurus , Thabanchuia , Branchiosauridae and Micropholis , all of which died out in Early Triassic, and the successful Stereospondyli , with survivors into the Cretaceous Period. The largest Triassic stereospondyls, such as Mastodonsaurus , were up to 4 to 6 metres (13 to 20 ft) in length. Some lineages (e.g. trematosaurs ) flourished briefly in
7728-641: The time of the Permo-Triassic boundary; acid rain from the Siberian Traps eruptions or from an impact event that overwhelmed acidic swamps; climate shift to a greenhouse climate that was too hot and dry for peat accumulation; evolution of fungi or herbivores that were more destructive of wetlands; the extinction of all plants adapted to peat swamps, with a hiatus of several million years before new plant species evolved that were adapted to peat swamps; or soil anoxia as oxygen levels plummeted. Before
7820-432: The west plateau. By this time, the lithospheric thinning that had been initiated during the early Jurassic was now considerably thinner. At this period, a magmatic intrusion between the lower crystalline crest and the lithosphere been introduce, underplating this region. In Early Cretaceous , pure shear deformation at the ocean-continental boundary completed the final continental breakup and sea-floor spreading. By this time
7912-622: The western margin (now the Exmouth Plateau) with Greater India. The formation of the Exmouth's northern margin, the Argo Abyssal Plain, was not initiated until 155 million years ago when Australia broke apart from a continental fragment of the Burma Plate that's present location is argued to be subsumed under Asia. It wasn't until 20 million years later that the Greater Indian land mass broke from western Australia, forming
8004-462: The westernmost section of the Exmouth Plateau caused further rifting to the outer margins. By the end of the Late Triassic (209-201 Ma) tectonic activity had relatively slowed down and less deltaic sediments were deposited compared to the Carnian and Norian . More marine sedimentary deposit such as carbonates are found during this time period. During the early Jurassic, extension at the west Australian margin initiated simple shear mechanics creating
8096-615: Was a dominant element in forest habitats across the region during the Middle-Late Triassic. During the Late Triassic, the Ginkgoales (which today are represented by only a single species, Ginkgo biloba ) underwent considerable diversification. Conifers were abundant during the Triassic, and included the Voltziales (which contains various lineages, probably including those ancestral to modern conifers), as well as
8188-673: Was a relatively cool period known as the Early Norian Cool Interval (ENCI), after which occurred the Mid-Norian Warm Interval (MNWI) from 217 to 209 Ma. The MNWI was briefly interrupted around 214 Ma by a cooling possibly related to the Manicouagan impact . Around 212 Ma, a 10 Myr eccentricity maximum caused a paludification of Pangaea and a reduction in the size of arid climatic zones. The Rhaetian Cool Interval (RCI) lasted from 209 to 201 Ma. At
8280-505: Was accompanied by huge volcanic eruptions that occurred as the supercontinent Pangaea began to break apart about 202 to 191 million years ago (40Ar/39Ar dates), forming the Central Atlantic Magmatic Province (CAMP), one of the largest known inland volcanic events since the planet had first cooled and stabilized. Other possible but less likely causes for the extinction events include global cooling or even
8372-484: Was encroached upon by a pair of extensive oceanic basins: The Neo-Tethys (or simply Tethys) and Paleo-Tethys Oceans . These extended from China to Iberia, hosting abundant marine life along their shallow tropical peripheries. They were divided from each other by a long string of microcontinents known as the Cimmerian terranes . Cimmerian crust had detached from Gondwana in the early Permian and drifted northwards during
8464-636: Was large uplift of the Cape Range Fracture Zone that provided sediments from the Barrow Delta prograde northward past Barrow Island and across the Exmouth Plateau. The sediments of the Barrow Group are composed of interbedded shale and fluvial-deltiac sands that were extensively deposited into Exmouth and Barrow sub-basins. Eventually, deposition of the Barrow Delta's sediment ceased during the early or middle Valanginian due to
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