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105-511: The Moab Fault has been the focus of a number of studies, covering a range of topics including fault zone architecture, fault cementation, and fault seal prediction. The Moab Fault was active during a period between the Triassic and early Tertiary , with a break from mid- Jurassic until at least mid- Cretaceous . It is associated with two salt anticlines formed within the Fold and Fault Belt of

210-630: 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

315-626: 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

420-409: A body of water or beneath ice. Unconsolidated surficial materials may also be given a lithology. This is defined by grain size and composition and is often attached to an interpretation of how the unit formed. Surficial lithologies can be given to lacustrine , coastal, fluvial , aeolian , glacial , and recent volcanic deposits, among others. Examples of surficial lithology classifications used by

525-555: 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

630-411: A continually-increasing extent of metamorphism. Metamorphic facies are defined by the pressure-temperature fields in which particular minerals form. Additional metamorphic rock names exist, such as greenschist (metamorphosed basalt and other extrusive igneous rock) or quartzite (metamorphosed quartz sand). In igneous and metamorphic rocks, grain size is a measure of the sizes of the crystals in

735-474: 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

840-408: A hand lens, the visible mineralogy is included as part of the description. In the case of sequences possibly including carbonates , calcite - cemented rocks or those with possible calcite veins, it is normal to test for the presence of calcite (or other forms of calcium carbonate ) using dilute hydrochloric acid and looking for effervescence . The mineralogical composition of a rock is one of

945-810: A lithology is based on the rock type . The three major rock types are igneous , sedimentary , and metamorphic . Igneous rocks are formed directly from magma , which is a mixture of molten rock, dissolved gases, and solid crystals. Sedimentary rock is formed from mineral or organic particles that collect at the Earth's surface and become lithified . Metamorphic rock forms by recrystallization of existing solid rock under conditions of great heat or pressure. Igneous rocks are further broken into three broad categories. Igneous rock composed of broken rock fragments created directly by volcanic processes ( tephra ) are classified as pyroclastic rock . Pyroclastic rocks are further classified by average fragment ( clast ) size and whether

1050-471: 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

1155-461: A particular depositional environment and may provide information on paleocurrent directions. In metamorphic rocks associated with the deeper levels of fault zones , small scale structures such as asymmetric boudins and microfolds are used to determine the sense of displacement across the zone. In igneous rocks, small-scale structures are mostly observed in lavas such as pahoehoe versus ʻAʻā basaltic flows, and pillows showing eruption within

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1260-617: 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

1365-569: A rock describes the relationship between the individual grains or clasts that make up the rock. Sedimentary textures include the degree of sorting , grading , shape and roundness of the clasts. Metamorphic textures include those referring to the timing of growth of large metamorphic minerals relative to a phase of deformation—before deformation porphyroclast —after deformation porphyroblast . Igneous textures include such properties as grain shape, which varies from crystals with ideal crystal shapes ( euhedral ) to irregular crystals (anhedral), whether

1470-508: A rock. Examples of lithologies in the second sense include sandstone , slate , basalt , or limestone . Lithology is the basis of subdividing rock sequences into individual lithostratigraphic units for the purposes of mapping and correlation between areas. In certain applications, such as site investigations , lithology is described using a standard terminology such as in the European geotechnical standard Eurocode 7 . The naming of

1575-636: A sample. The colour of a rock or its component parts is a distinctive characteristic of some rocks and is always recorded, sometimes against standard colour charts, such as that produced by the Rock-Color Chart Committee of the Geological Society of America based on the Munsell color system . The fabric of a rock describes the spatial and geometric configuration of all the elements that make it up. In sedimentary rocks

1680-458: 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

1785-449: 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

1890-585: 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

1995-468: 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 ,

2100-472: Is an asymmetric fold with a wavelength of approximately 1 km, an amplitude of 350 m and a length of over 10 km. The internal geometry of the Moab fault zone is complex in terms of the numbers of slip zones, the partitioning of throw between them and the distribution of fault rocks, all of which vary over the fault surface. One study by Berg and Skar analyzes the arrangement of fractures in damage zones of

2205-540: Is impractical, they may be classified chemically using the TAS classification . This is based on the total content of silica and alkali metal oxides and other chemical criteria. Sedimentary rocks are further classified by whether they are siliciclastic or carbonate . Siliciclastic sedimentary rocks are then subcategorized based on their grain size distribution and the relative proportions of quartz, feldspar, and lithic (rock) fragments. Carbonate rocks are classified with

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2310-508: 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

2415-469: 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

2520-615: Is present in the Moab Fault at values >c. 20%, but varies depending on the location of the transect. Triassic The Triassic ( / t r aɪ ˈ æ s ɪ k / try- ASS -ik ; sometimes symbolized 🝈 ) 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

2625-1100: Is separated into six sedimentologically distinct stratigraphic units: the Navajo Sandstone, the Page Sandstone , the Dewey Bridge and Slick Rock members of the Entrada Sandstone, the Moab Tongue, and the Curtis Formation . The stratigraphy of the outcropping fault zone can be divided into three lithological groups: mudstone -dominated, mixed mudstone-sandstone, and sandstone-rich sequences. The mixed mudstone-sandstone sequences include interbedded fluvial and aeolian sandstones and floodplain /lacustrine mudstones and siltstones . Sandstone-rich intervals are primarily aeolian in origin. Distinctive types of veining , calcite cementation and iron oxide reduction exist adjacent to

2730-460: 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

2835-429: Is that of a faulted anticline, modified by a minor component of normal drag adjacent to the fault. The fault is composed of three main components: a poorly exposed southern section, a central section (where the greatest throws are found), and a complex branching northern section that tips out to the northwest. At the north end of the Moab valley, there is a fault transfer zone, where the fault steps east. This zone transfers

2940-477: Is the diameter of the grains and/or clasts that constitute the rock. These are used to determine which rock naming system to use (e.g., a conglomerate , sandstone , or mudstone ). In the case of sandstones and conglomerates, which cover a wide range of grain sizes, a word describing the grain size range is added to the rock name. Examples are " pebble conglomerate" and "fine quartz arenite ". In rocks in which mineral grains are large enough to be identified using

3045-601: 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 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

3150-578: 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

3255-475: The Dunham or Folk classification schemes according to the constituents of the carbonate rock. Metamorphic rock naming can be based on protolith , mineral composition, texture, or metamorphic facies . Naming based on texture and a pelite (e.g., shale , mudrock ) protolith can be used to define slate and phyllite . Texture-based names are schist and gneiss . These textures, from slate to gneiss, define

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3360-614: 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

3465-568: 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

3570-658: 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

3675-474: 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

3780-707: The Paradox Basin in east-central Utah. The Paradox Basin is part of the Colorado Plateau that formed during the Late Paleozoic . Movement on the basement faults began in the Proterozoic and was greatest during mid- Pennsylvanian Rocky Mountain tectonism . The fault was reactivated at ~60 Ma, likely due to reinitiated salt movement during the Laramide orogeny . Following its deposition,

3885-464: The QAPF classification , which is based on the relative content of quartz , alkali feldspar , plagioclase , and feldspathoid . Special classifications exist for igneous rock of unusual compositions, such as ultramafic rock or carbonatites . Where possible, extrusive igneous rocks are also classified by mineral content using the extrusive QAPF classification, but when determining the mineral composition

3990-735: 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

4095-463: 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 the Triassic and survived the extinction event. The earliest known neopterygian fish, including early holosteans and teleosts , appeared near

4200-524: 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

4305-437: 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

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4410-832: 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

4515-472: The Bartlett segment of the Moab Fault. The Bartlett fault consist of a fault core surrounded by damage zones in the footwall and hanging wall. The fault core consists of a variety of fault rocks and entrained bodies of clastic host rocks, which indicate variation in strain intensity and deformation style. Berg and Skar suggest that the most important cause for asymmetric strain distribution is the development of

4620-405: 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

4725-563: 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

4830-402: 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

4935-562: 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

5040-613: 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

5145-432: 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, the first time among vertebrates, becoming the pterosaurs . Therapsids , the dominant vertebrates of the preceding Permian period, saw a brief surge in diversification in

5250-600: 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

5355-486: 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

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5460-618: 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

5565-536: The Moab Fault. Solum et al. describe the occurrence of clay-rich fault along four fault zones: R191, Corral Canyon, Courthouse Canyon, and the Bartlett Wash exposure. While fault rocks along the R191 location and Bartlett Wash are enriched in clays relative to protolith , those at Corral Canyon and Courthouse Canyon show little difference in composition relative to protolith, suggesting that fault rock formation at

5670-462: The Moab fault zone were described. These exposures provide excellent data on lateral variation and structure features within the fault zone. The most studied transects include the Moab Canyon, R191 Canyon, Corral Canyon , Courthouse Mine, Bartlett Wash, and Waterfall Canyon . The Moab Fault is a sharply defined brittle shear zone (1–10 m wide). The overall geometry of the southern fault segment

5775-487: The Moab fault, moving into the porous sandstone units where they interacted with oxygenated meteoric water. Chan et al. use Ar-Ar dating to define the age of this fluid movement. They determine a mineralization age of c. 25-20 Ma, which coincides with episodic uplift of the Colorado Plateau or with La Sal Mountains volcanism . The Moab Fault is characterized by patterns of iron oxide reduction that also suggest

5880-450: 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

5985-475: 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

6090-408: 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

6195-476: 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 the Jurassic. The Triassic

6300-609: 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

6405-428: 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 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

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6510-417: The Triassic. Lithology The lithology of a rock unit is a description of its physical characteristics visible at outcrop , in hand or core samples , or with low magnification microscopy. Physical characteristics include colour, texture, grain size , and composition. Lithology may refer to either a detailed description of these characteristics, or a summary of the gross physical character of

6615-839: 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

6720-415: 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 the north and Gondwana to the south. The global climate during

6825-455: 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

6930-412: 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 the equator and extended between the poles, though it did drift northwards as

7035-506: 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,

7140-473: The displacement along the fault from one segment to another. Within this zone there is very dense faulting. Along the southern segment, footwall bed dips define a structural high symmetrically disposed about the point of maximum throw. A prominent hanging wall feature of the southern segment is the Moab Anticline, with a crestal collapse graben accommodated by an array of normal faults. The Moab Anticline

7245-428: 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

7350-405: 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

7455-640: 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

7560-475: The extensive presence of shaley gouge even at low stratigraphic levels suggest that the Moab Fault was a conduit for fluid flow while supporting significant across-fault pressure differences. Clay smear is among the family of structures that detect fluid flow in sedimentary basins. Clay smear processes are applied to instances of cross-fault flow when porous and permeable rocks, specifically sandstones and shales, are cut by normal faults. According to Foxford et al.,

7665-480: 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

7770-418: The fault acted as a conduit for mineralizing fluids. It is suggested that red sandstones adjacent to the Moab Fault were bleached by reducing fluids. Iron oxide reduction is concentrated within high permeability , well-connected sandstones and spatially associated with cemented veins – indicating that the reduction event coincided with vein formation, and thus with the final stages of faulting. Permeability along

7875-431: The fault may have been promoted by the highly anisotropic shaley gouge fabrics or by fault zone fractures. After analyzing geochemical data of carbonate cements and iron-oxide reduced sandstones from the Moab Anticline, Garden et al. suggest that following fault movement, the fault zone was the locus of vertical migration of over-pressured hydrocarbon and aqueous, carbonate-saturated fluids. These observations, combined with

7980-523: The fault, especially in Jurassic Navajo and Entrada sandstones. Calcite, barite , ankerite , and pyrite cemented veins are found in immediate proximity of the fault. The presence and amount of clays in fault rocks is a useful indicator in determining: The presence of clays in fault rock influences both the mechanical and hydrologic properties of clay-bearing faults. Field mapping shows that layers of clay gouge and shale smear are common along

8085-440: The fragments are mostly individual mineral crystals , particles of volcanic glass , or rock fragments. Further classifications, such as by chemical composition , may also be applied. Igneous rocks that have visible mineral grains ( phaneritic rocks) are classified as intrusive , while those that are glassy or very fine-grained ( aphanitic ) are classified as extrusive rock . Intrusive igneous rocks are usually classified using

8190-521: 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

8295-406: The hanging wall syncline and the resulting asymmetric stress pattern expected to exist during fault propagation. The sedimentation of the Moab area was primarily influenced by marine or lacustrine incursions into the margins of major Jurassic ergs. This area consists of a heterogeneous series of dominantly clastic sedimentary rocks. The basal Navajo Sandstone to top Entrada Sandstone interval

8400-420: 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

8505-401: 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

8610-650: The latter locations is governed by mechanical as opposed to authigenic processes. Many studies have documented multiple episodes of fluid flow along the Moab Fault since its formation in the Permo - Triassic . In one study, Eichhubl et al. use the distribution of calcite cement as an indicator of paleofluid migration. They infer that fault-parallel fluid flow was focused along fault segments overprinted by joints and sheared joints. These conclusions support Chan et al.’s hydrogeologic model, which proposes that hydrocarbon and basin brines from Pennsylvanian source rocks migrated along

8715-454: The main visible fabric is normally bedding , and the scale and degree of development of the bedding is normally recorded as part of the description. Metamorphic rocks (apart from those created by contact metamorphism ), are characterised by well-developed planar and linear fabrics. Igneous rocks may also have fabrics as a result of flow or the settling out of particular mineral phases during crystallisation, forming cumulates . The texture of

8820-487: The major ways in which it is classified. Igneous rocks are classified by their mineral content whenever practical, using the QAPF classification or special ultramafic or carbonatite classifications. Likewise metamorphic facies, which show the degree to which a rock has been exposed to heat and pressure and are therefore important in classifying metamorphic rocks, are determined by observing the mineral phases that are present in

8925-545: 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

9030-453: 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

9135-458: 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

9240-399: The most important feature of the Moab Fault zone from the standpoint of seal potential assessment is the nearly constant presence of at least one shaley gouge layer. The shale gouge ratio is one way to describe the amount of clay smear in a fault zone, and is simply defined as the percentage of shale/clay in the slipped interval. Shale gouge ratio, when applied to sand-shale sequences, indicates

9345-430: 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

9450-402: 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

9555-504: 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 the margin of an enormous ocean, Panthalassa ( lit.   ' entire sea ' ), which roughly corresponds to

9660-422: The proportion of phyllosilicate material expected to be incorporated into the fault rock. Thus it provides a measure of the seal capacity, as a shale layer in a fault zone may provide an effective seal to across-fault flow. Previous studies show that a shale gouge ratio of ~20% defines the boundary between sealing and non-sealing faults, with faults sealing at shale gouge ratios above this ‘cut-off’ value. Shale gouge

9765-487: 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

9870-401: The rock shows highly nonuniform crystal sizes (is porphyritic ), or whether grains are aligned (which is described as trachytic texture). Rocks often contain small-scale structures (smaller than the scale of an individual outcrop). In sedimentary rocks this may include sole markings , ripple marks , mudcracks and cross-bedding . These are recorded as they are generally characteristic of

9975-478: The rock. In igneous rock, this is used to determine the rate at which the material cooled: large crystals typically indicate intrusive igneous rock, while small crystals indicate that the rock was extrusive. Metamorphism of rock composed of mostly a single mineral, such as quartzite or marble , may increase grain size ( grain growth ), while metamorphism of sheared rock may decrease grain size (syntectonic recrystallization ). In clastic sedimentary rocks, grain size

10080-481: The salt was deformed to form a series of salt anticlines that were ultimately buried by 1–2 km of Jurassic to Tertiary sediments. The architecture of the Moab fault zone is highly variable, and has been studied by several authors. The first systematic study was conducted by Foxford et al. in 1998, which classified architectural elements into slip band zones, shaley gouge zones and sandstone cataclastics and breccias . Thirty-seven transect exposures within

10185-676: 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

10290-595: 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

10395-577: 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

10500-615: 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

10605-673: 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

10710-505: 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

10815-484: 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

10920-451: 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 is usually divided into Early , Middle , and Late Triassic Epochs , and

11025-528: 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 the Mesozoic Era. Reptiles , especially archosaurs , were the chief terrestrial vertebrates during this time. A specialized group of archosaurs, called dinosaurs , first appeared in

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