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162-529: The scientific consensus is that the main cause of the extinction was the flood basalt volcanic eruptions that created the Siberian Traps , which released sulfur dioxide and carbon dioxide , resulting in euxinia (oxygen-starved, sulfurous oceans), elevating global temperatures, and acidifying the oceans . The level of atmospheric carbon dioxide rose from around 400 ppm to 2,500 ppm with approximately 3,900 to 12,000 gigatonnes of carbon being added to

324-571: A and b . Their chloroplasts are surrounded by four and three membranes, respectively, and were probably retained from ingested green algae. Chlorarachniophytes , which belong to the phylum Cercozoa , contain a small nucleomorph , which is a relict of the algae's nucleus . Euglenids , which belong to the phylum Euglenozoa , live primarily in fresh water and have chloroplasts with only three membranes. The endosymbiotic green algae may have been acquired through myzocytosis rather than phagocytosis . (Another group with green algae endosymbionts

486-408: A and c , and phycobilins. The shape can vary; they may be of discoid, plate-like, reticulate, cup-shaped, spiral, or ribbon shaped. They have one or more pyrenoids to preserve protein and starch. The latter chlorophyll type is not known from any prokaryotes or primary chloroplasts, but genetic similarities with red algae suggest a relationship there. In the first three of these groups ( Chromista ),

648-617: A brief period of domination in the early Spathian, probably related to a transient oxygenation of deep waters. Neospathodid conodonts survived the crisis but underwent proteromorphosis. In the PTME's aftermath, disaster taxa of benthic foraminifera filled many of their vacant niches. The recovery of benthic foraminifera was very slow and frequently interrupted until the Spathian. In the Tethys, foraminiferal communities remained low in diversity into

810-628: A ceiling limiting the maximum ecological complexity of marine ecosystems until the Spathian. Recovery biotas appear to have been ecologically uneven and unstable into the Anisian , making them vulnerable to environmental stresses. Whereas most marine communities were fully recovered by the Middle Triassic, global marine diversity reached pre-extinction values no earlier than the Middle Jurassic, approximately 75 million years after

972-454: A cubic km per day per km of fissure length ) and the relatively low viscosity of basaltic lava. However, the lateral extent of individual flood basalt flows is astonishing even for so fluid a lava in such quantities. It is likely that the lava spreads by a process of inflation in which the lava moves beneath a solid insulating crust, which keeps it hot and mobile. Studies of the Ginkgo flow of

1134-476: A dead zone. However, not all large igneous provinces are connected with extinction events. The formation and effects of a flood basalt depend on a range of factors, such as continental configuration, latitude, volume, rate, duration of eruption, style and setting (continental vs. oceanic), the preexisting climate , and the biota resilience to change. Representative continental flood basalts and oceanic plateaus, arranged by chronological order, together forming

1296-510: A family of large-size fusuline foraminifera . The impact of the end-Guadalupian extinction on marine organisms appears to have varied between locations and between taxonomic groups – brachiopods and corals had severe losses. Marine invertebrates suffered the greatest losses during the P–Tr extinction. Evidence of this was found in samples from south China sections at the P–Tr boundary. Here, 286 out of 329 marine invertebrate genera disappear within

1458-539: A form and capabilities not possessed by the symbiont species alone (they can be experimentally isolated). The photobiont possibly triggers otherwise latent genes in the mycobiont. Trentepohlia is an example of a common green alga genus worldwide that can grow on its own or be lichenised. Lichen thus share some of the habitat and often similar appearance with specialized species of algae ( aerophytes ) growing on exposed surfaces such as tree trunks and rocks and sometimes discoloring them. Coral reefs are accumulated from

1620-415: A fungal origin for Reduviasporonites , diluting these critiques. Uncertainty exists regarding the duration of the overall extinction and about the timing and duration of various groups' extinctions within the greater process. Some evidence suggests that there were multiple extinction pulses or that the extinction was long and spread out over a few million years, with a sharp peak in the last million years of

1782-413: A high background extinction rate (by implication, taxa with a high turnover ). The extinction rate of marine organisms was catastrophic. Bioturbators were extremely severely affected, as evidenced by the loss of the sedimentary mixed layer in many marine facies during the end-Permian extinction. Surviving marine invertebrate groups included articulate brachiopods (those with a hinge), which had undergone

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1944-598: A lineage that eventually led to the higher land plants. The innovation that defines these nonalgal plants is the presence of female reproductive organs with protective cell layers that protect the zygote and developing embryo. Hence, the land plants are referred to as the Embryophytes . The term algal turf is commonly used but poorly defined. Algal turfs are thick, carpet-like beds of seaweed that retain sediment and compete with foundation species like corals and kelps , and they are usually less than 15 cm tall. Such

2106-602: A listing of large igneous provinces : Flood basalts are the dominant form of magmatism on the other planets and moons of the Solar System. The maria on the Moon have been described as flood basalts composed of picritic basalt. Individual eruptive episodes were likely similar in volume to flood basalts of Earth, but were separated by much longer quiescent intervals and were likely produced by different mechanisms. Extensive flood basalts are present on Mars. Trap rock

2268-560: A massive rearrangement of ecosystems does occur, with plant abundances and distributions changing profoundly and all the forests virtually disappearing. The dominant floral groups changed, with many groups of land plants entering abrupt decline, such as Cordaites ( gymnosperms ) and Glossopteris ( seed ferns ). The severity of plant extinction has been disputed. The Glossopteris -dominated flora that characterised high-latitude Gondwana collapsed in Australia around 370,000 years before

2430-468: A million years, with individual events each erupting hundreds of cubic kilometers of basalt. This highly fluid basalt lava can spread laterally for hundreds of kilometers from its source vents, covering areas of tens of thousands of square kilometers. Successive eruptions form thick accumulations of nearly horizontal flows, erupted in rapid succession over vast areas, flooding the Earth's surface with lava on

2592-423: A prominent examples of algae that have primary chloroplasts derived from endosymbiont cyanobacteria. Diatoms and brown algae are examples of algae with secondary chloroplasts derived from endosymbiotic red algae , which they acquired via phagocytosis . Algae exhibit a wide range of reproductive strategies, from simple asexual cell division to complex forms of sexual reproduction via spores . Algae lack

2754-483: A red dye derived from it. The Latinization, fūcus , meant primarily the cosmetic rouge. The etymology is uncertain, but a strong candidate has long been some word related to the Biblical פוך ( pūk ), 'paint' (if not that word itself), a cosmetic eye-shadow used by the ancient Egyptians and other inhabitants of the eastern Mediterranean. It could be any color: black, red, green, or blue. The study of algae

2916-621: A regional scale. These vast accumulations of flood basalt constitute large igneous provinces . These are characterized by plateau landforms, so that flood basalts are also described as plateau basalts . Canyons cut into the flood basalts by erosion display stair-like slopes, with the lower parts of flows forming cliffs and the upper part of flows or interbedded layers of sediments forming slopes. These are known in Dutch as trap or in Swedish as trappa , which has come into English as trap rock ,

3078-548: A severe bottleneck in diversity. Evidence from South China indicates the foraminiferal extinction had two pulses. Foraminiferal biodiversity hotspots shifted into deeper waters during the PTME. Approximately 93% of latest Permian foraminifera became extinct, with 50% of the clade Textulariina, 92% of Lagenida, 96% of Fusulinida, and 100% of Miliolida disappearing. Foraminifera that were calcaerous suffered an extinction rate of 91%. The reason why lagenides survived while fusulinoidean fusulinides went completely extinct may have been due to

3240-563: A silica content of around 52%. The magnesium number (the mol% of magnesium out of the total iron and magnesium content) is around 55, versus 60 for a typical MORB. The rare earth elements show abundance patterns suggesting that the original (primitive) magma formed from rock of the Earth's mantle that was nearly undepleted ; that is, it was mantle rock rich in garnet and from which little magma had previously been extracted. The chemistry of plagioclase and olivine in flood basalts suggests that

3402-520: A single province. For example, the flood basalts of the Parana Basin can be divided into a low phosphorus and titanium group (LPT) and a high phosphorus and titanium group (HPT). The difference has been attributed to inhomogeneity in the upper mantle, but strontium isotope ratios suggest the difference may arise from the LPT magma being contaminated with a greater amount of melted crust. Theories of

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3564-479: A slow decline in numbers since the P–Tr extinction; the Ceratitida order of ammonites ; and crinoids ("sea lilies"), which very nearly became extinct but later became abundant and diverse. The groups with the highest survival rates generally had active control of circulation , elaborate gas exchange mechanisms, and light calcification; more heavily calcified organisms with simpler breathing apparatuses suffered

3726-403: A specific region were more likely to go extinct than cosmopolitan taxa. There was little latitudinal difference in the survival rates of taxa. Organisms that inhabited refugia less affected by global warming experienced lesser or delayed extinctions. Among benthic organisms the extinction event multiplied background extinction rates , and therefore caused maximum species loss to taxa that had

3888-529: A study of coprolites in the Vyazniki fossil beds in Russia suggests it took only a few thousand years. Aridification induced by global warming was the chief culprit behind terrestrial vertebrate extinctions. There is enough evidence to indicate that over two thirds of terrestrial labyrinthodont amphibians , sauropsid ("reptile") and therapsid ("proto-mammal") taxa became extinct. Large herbivores suffered

4050-473: A term particularly used in the quarry industry. The great thickness of the basalt accumulations, often in excess of 1,000 meters (3,000 ft), usually reflects a very large number of thin flows, varying in thickness from meters to tens of meters, or more rarely to 100 meters (330 ft). There are occasionally very thick individual flows. The world's thickest basalt flow may be the Greenstone flow of

4212-468: A turf may consist of one or more species, and will generally cover an area in the order of a square metre or more. Some common characteristics are listed: Many algae, particularly species of the Characeae , have served as model experimental organisms to understand the mechanisms of the water permeability of membranes, osmoregulation , turgor regulation , salt tolerance , cytoplasmic streaming , and

4374-496: Is comparable with the rate of extrusion of lava at mid-ocean ridges and much higher than the rate of extrusion by hotspots. However, extrusion at mid-ocean ridges is relatively steady, while extrusion of flood basalts is highly episodic. Flood basalts create new continental crust at a rate of 0.1 to 8 cubic kilometers (0.02 to 2 cu mi) per year, while the eruptions that form oceanic plateaus produce 2 to 20 cubic kilometers (0.5 to 5 cu mi) of crust per year. Much of

4536-533: Is difficult to know whether the end-Capitanian had finished, depending on the factor considered. Many of the extinctions once dated to the Permian-Triassic boundary have more recently been redated to the end- Capitanian . Further, it is unclear whether some species who survived the prior extinction(s) had recovered well enough for their final demise in the Permian-Triassic event to be considered separate from Capitanian event. A minority point of view considers

4698-561: Is episodic, and each episode has its own chemical signature. There is some tendency for lava within a single eruptive episode to become more silica-rich with time, but there is no consistent trend across episodes. Large Igneous Provinces (LIPs) were originally defined as voluminous outpourings, predominantly of basalt, over geologically very short durations. This definition did not specify minimum size, duration, petrogenesis, or setting. A new attempt to refine classification focuses on size and setting. LIPs characteristically cover large areas, and

4860-597: Is likely attributable to their ability to thrive in a wide range of environmental conditions. Conodonts saw a rapid recovery during the Induan, with anchignathodontids experiencing a diversity peak in the earliest Induan. Gondolellids diversified at the end of the Griesbachian; this diversity spike was most responsible for the overall conodont diversity peak in the Smithian. Segminiplanate conodonts again experienced

5022-449: Is likely that post-extinction microbial mats played a vital, indispensable role in the survival and recovery of various bioturbating organisms. The microbialite refuge hypothesis has been criticised as reflecting a taphonomic bias due to the greater preservation potential of microbialite deposits, however, rather than a genuine phenomenon. Ichnocoenoses show that marine ecosystems recovered to pre-extinction levels of ecological complexity by

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5184-550: Is most commonly called phycology (from Greek phykos  'seaweed'); the term algology is falling out of use. One definition of algae is that they "have chlorophyll as their primary photosynthetic pigment and lack a sterile covering of cells around their reproductive cells ". On the other hand, the colorless Prototheca under Chlorophyta are all devoid of any chlorophyll. Although cyanobacteria are often referred to as "blue-green algae", most authorities exclude all prokaryotes , including cyanobacteria, from

5346-591: Is now Jordan, known from fossils near the Dead Sea , showed unusual stability over the Permian-Triassic transition, and appears to have been only minimally affected by the crisis. The tempo of the terrestrial vertebrate extinction is disputed. Some evidence from the Karoo Basin indicates a protracted extinction lasting a million years. Other evidence from the Karoo deposits suggest it took 50,000 years or less, while

5508-544: Is quite different from those of reds and browns, because they have distinct nodes, separated by internode 'stems'; whorls of branches reminiscent of the horsetails occur at the nodes. Conceptacles are another polyphyletic trait; they appear in the coralline algae and the Hildenbrandiales , as well as the browns. Most of the simpler algae are unicellular flagellates or amoeboids , but colonial and nonmotile forms have developed independently among several of

5670-419: Is required for so much magma to be generated in so short a time. This is widely believed to have been supplied by a mantle plume impinging on the base of the Earth's lithosphere , its rigid outermost shell. The plume consists of unusually hot mantle rock of the asthenosphere , the ductile layer just below the lithosphere, that creeps upwards from deeper in the Earth's interior. The hot asthenosphere rifts

5832-528: Is the Latin word for 'seaweed' and retains that meaning in English. The etymology is obscure. Although some speculate that it is related to Latin algēre , 'be cold', no reason is known to associate seaweed with temperature. A more likely source is alliga , 'binding, entwining'. The Ancient Greek word for 'seaweed' was φῦκος ( phŷkos ), which could mean either the seaweed (probably red algae) or

5994-423: Is the dinoflagellate genus Lepidodinium , which has replaced its original endosymbiont of red algal origin with one of green algal origin. A nucleomorph is present, and the host genome still have several red algal genes acquired through endosymbiotic gene transfer. Also the euglenid and chlorarachniophyte genome contain genes of apparent red algal ancestry) These groups have chloroplasts containing chlorophylls

6156-560: Is the most durable construction aggregate of all rock types, because the interlocking crystals are oriented at random. Alga Algae ( UK : / ˈ æ l ɡ iː / AL -ghee , US : / ˈ æ l dʒ iː / AL -jee ; sg. : alga / ˈ æ l ɡ ə / AL -gə ) is an informal term for any organisms of a large and diverse group of photosynthetic eukaryotes , which include species from multiple distinct clades . Such organisms range from unicellular microalgae such as Chlorella , Prototheca and

6318-473: Is uncommon in flood basalt provinces. One possibility is that a primitive melt stagnates when it reaches the mantle-crust boundary, where it is not buoyant enough to penetrate the lower-density crust rock. As a tholeiitic magma differentiates (changes in composition as high-temperature minerals crystallize and settle out of the magma) its density reaches a minimum at a magnesium number of about 60, similar to that of flood basalts. This restores buoyancy and permits

6480-526: The Charophyta , a division of green algae which includes, for example, Spirogyra and stoneworts . Algae that are carried passively by water are plankton , specifically phytoplankton . Algae constitute a polyphyletic group since they do not include a common ancestor , and although their chlorophyll -bearing plastids seem to have a single origin (from symbiogenesis with cyanobacteria ), they were acquired in different ways. Green algae are

6642-573: The Araguainha crater and caused seismic release of methane and the destruction of the ozone layer with increased exposure to solar radiation. Previously, it was thought that rock sequences spanning the Permian–Triassic boundary were too few and contained too many gaps for scientists to reliably determine its details. However, it is now possible to date the extinction with millennial precision. U–Pb zircon dates from five volcanic ash beds from

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6804-523: The Bowen Basin of Queensland indicates numerous intermittent periods of marine environmental stress from the middle to late Lopingian leading up to the end-Permian extinction proper, supporting aspects of the gradualist hypothesis. Additionally, the decline in marine species richness and the structural collapse of marine ecosystems may have been decoupled as well, with the former preceding the latter by about 61,000 years according to one study. Whether

6966-751: The Calymmian period , early in Boring Billion , but it is difficult to track the key events because of so much time gap. Primary symbiogenesis gave rise to three divisions of archaeplastids , namely the Viridiplantae ( green algae and later plants ), Rhodophyta ( red algae ) and Glaucophyta ("grey algae"), whose plastids further spread into other protist lineages through eukaryote-eukaryote predation , engulfments and subsequent endosymbioses (secondary and tertiary symbiogenesis). This process of serial cell "capture" and "enslavement" explains

7128-480: The Global Stratotype Section and Point for the Permian–Triassic boundary at Meishan , China , establish a high-resolution age model for the extinction – allowing exploration of the links between global environmental perturbation, carbon cycle disruption, mass extinction, and recovery at millennial timescales. The first appearance of the conodont Hindeodus parvus has been used to delineate

7290-513: The Industrial Revolution was 280 ppm , and the amount today is about 422 ppm). There is also evidence of increased ultraviolet radiation reaching the earth, causing the mutation of plant spores. It has been suggested that the Permian–Triassic boundary is associated with a sharp increase in the abundance of marine and terrestrial fungi , caused by the sharp increase in the amount of dead plants and animals fed upon by

7452-614: The Infusoria (microscopic organisms). Unlike macroalgae , which were clearly viewed as plants, microalgae were frequently considered animals because they are often motile. Even the nonmotile (coccoid) microalgae were sometimes merely seen as stages of the lifecycle of plants, macroalgae, or animals. Although used as a taxonomic category in some pre-Darwinian classifications, e.g., Linnaeus (1753), de Jussieu (1789), Lamouroux (1813), Harvey (1836), Horaninow (1843), Agassiz (1859), Wilson & Cassin (1864), in further classifications,

7614-612: The International Association for Lichenology to be "an association of a fungus and a photosynthetic symbiont resulting in a stable vegetative body having a specific structure". The fungi, or mycobionts, are mainly from the Ascomycota with a few from the Basidiomycota . In nature, they do not occur separate from lichens. It is unknown when they began to associate. One or more mycobiont associates with

7776-653: The Keweenaw Peninsula of Michigan , US, which is 600 meters (2,000 ft) thick. This flow may have been part of a lava lake the size of Lake Superior . Deep erosion of flood basalts exposes vast numbers of parallel dikes that fed the eruptions. Some individual dikes in the Columbia River Plateau are over 100 kilometers (60 mi) long. In some cases, erosion exposes radial sets of dikes with diameters of several thousand kilometers. Sills may also be present beneath flood basalts, such as

7938-589: The Late Cambrian / Early Ordovician period, from sessile shallow freshwater charophyte algae much like Chara , which likely got stranded ashore when riverine / lacustrine water levels dropped during dry seasons . These charophyte algae probably already developed filamentous thalli and holdfasts that superficially resembled plant stems and roots , and probably had an isomorphic alternation of generations . They perhaps evolved some 850 mya and might even be as early as 1  Gya during

8100-594: The Middle Triassic ) due to the severity of the extinction. However, studies in Bear Lake County , near Paris, Idaho , and nearby sites in Idaho and Nevada showed a relatively quick rebound in a localized Early Triassic marine ecosystem ( Paris biota ), taking around 1.3 million years to recover, while an unusually diverse and complex ichnobiota is known from Italy less than a million years after

8262-478: The Palisades Sill of New Jersey , US. The sheet intrusions (dikes and sills) beneath flood basalts are typically diabase that closely matches the composition of the overlying flood basalts. In some cases, the chemical signature allows individual dikes to be connected with individual flows. Flood basalt commonly displays columnar jointing , formed as the rock cooled and contracted after solidifying from

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8424-861: The Permian-Triassic boundary, the Triassic-Jurassic boundary, and in the Toarcian Age of the Jurassic correspond to the ages of large igneous provinces in Siberia, the Central Atlantic Magmatic Province, and the Karoo-Ferrar flood basalt. Some idea of the impact of flood basalts can be given by comparison with historical large eruptions. The 1783 eruption of Lakagígar was the largest in

8586-516: The Roadian (middle Permian), suffered a selective extinction pulse 10 million years before the main event, at the end of the Capitanian stage. In this preliminary extinction, which greatly reduced disparity , or the range of different ecological guilds, environmental factors were apparently responsible. Diversity and disparity fell further until the P–Tr boundary; the extinction here (P–Tr)

8748-986: The Vindhya basin have been dated to 1.6 to 1.7 billion years ago. Because of the wide range of algae types, they have increasingly different industrial and traditional applications in human society. Traditional seaweed farming practices have existed for thousands of years and have strong traditions in East Asia food cultures. More modern algaculture applications extend the food traditions for other applications, including cattle feed, using algae for bioremediation or pollution control, transforming sunlight into algae fuels or other chemicals used in industrial processes, and in medical and scientific applications. A 2020 review found that these applications of algae could play an important role in carbon sequestration to mitigate climate change while providing lucrative value-added products for global economies. The singular alga

8910-601: The apicomplexans are also parasites derived from ancestors that possessed plastids, but are not included in any group traditionally seen as algae. Algae are polyphyletic thus their origin cannot be traced back to single hypothetical common ancestor . It is thought that they came into existence when photosynthetic coccoid cyanobacteria got phagocytized by a unicellular heterotrophic eukaryote (a protist ), giving rise to double-membranous primary plastids . Such symbiogenic events (primary symbiogenesis) are believed to have occurred more than 1.5 billion years ago during

9072-435: The apicomplexans , are also derived from cells whose ancestors possessed chlorophyllic plastids, but are not traditionally considered as algae. Algae have photosynthetic machinery ultimately derived from cyanobacteria that produce oxygen as a byproduct of splitting water molecules , unlike other organisms that conduct anoxygenic photosynthesis such as purple and green sulfur bacteria . Fossilized filamentous algae from

9234-545: The calcareous exoskeletons of marine invertebrates of the order Scleractinia (stony corals ). These animals metabolize sugar and oxygen to obtain energy for their cell-building processes, including secretion of the exoskeleton, with water and carbon dioxide as byproducts. Dinoflagellates (algal protists) are often endosymbionts in the cells of the coral-forming marine invertebrates, where they accelerate host-cell metabolism by generating sugar and oxygen immediately available through photosynthesis using incident light and

9396-424: The diatoms , to multicellular macroalgae such as the giant kelp , a large brown alga which may grow up to 50 metres (160 ft) in length. Most algae are aquatic organisms and lack many of the distinct cell and tissue types, such as stomata , xylem and phloem that are found in land plants . The largest and most complex marine algae are called seaweeds . In contrast, the most complex freshwater forms are

9558-561: The ocean floor with basalt lava . Many flood basalts have been attributed to the onset of a hotspot reaching the surface of the Earth via a mantle plume . Flood basalt provinces such as the Deccan Traps of India are often called traps , after the Swedish word trappa (meaning "staircase"), due to the characteristic stairstep geomorphology of many associated landscapes. Michael R. Rampino and Richard Stothers (1988) cited eleven distinct flood basalt episodes occurring in

9720-404: The ocean acidification that resulted from increased atmospheric CO 2 . Organisms that relied on haemocyanin or haemoglobin for transporting oxygen were more resistant to extinction than those utilising haemerythrin or oxygen diffusion. There is also evidence that endemism was a strong risk factor influencing a taxon's likelihood of extinction. Bivalve taxa that were endemic and localised to

9882-720: The "algae" are seen as an artificial, polyphyletic group. Throughout the 20th century, most classifications treated the following groups as divisions or classes of algae: cyanophytes , rhodophytes , chrysophytes , xanthophytes , bacillariophytes , phaeophytes , pyrrhophytes ( cryptophytes and dinophytes ), euglenophytes , and chlorophytes . Later, many new groups were discovered (e.g., Bolidophyceae ), and others were splintered from older groups: charophytes and glaucophytes (from chlorophytes), many heterokontophytes (e.g., synurophytes from chrysophytes, or eustigmatophytes from xanthophytes), haptophytes (from chrysophytes), and chlorarachniophytes (from xanthophytes). With

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10044-606: The Anisian. Metazoan reefs became common again during the Anisian because the oceans cooled down then from their overheated state during the Early Triassic. Biodiversity amongst metazoan reefs did not recover until well into the Anisian, millions of years after non-reef ecosystems recovered their diversity. Microbially induced sedimentary structures (MISS) from the earliest Triassic have been found to be associated with abundant opportunistic bivalves and vertical burrows, and it

10206-772: The Atlantic Ocean, formed around 125 million years ago as the South Atlantic opened, while a second set of smaller flood basalts formed near the Triassic-Jurassic boundary in eastern North America as the North Atlantic opened. However, the North Atlantic flood basalts are not connected with any hot spot traces, but seem to have been evenly distributed along the entire divergent boundary. Flood basalts are often interbedded with sediments, typically red beds . The deposition of sediments begins before

10368-472: The Caribbean, Nauru, East Mariana, and Pigafetta provinces. Continental flood basalts (CFBs) or plateau basalts are the continental expressions of large igneous provinces. Flood basalts contribute significantly to the growth of continental crust. They are also catastrophic events, which likely contributed to many mass extinctions in the geologic record. The extrusion of flood basalts, averaged over time,

10530-485: The Columbia River Plateau, which is 30 to 70 meters (98 to 230 ft) thick, show that the temperature of the lava dropped by just 20 °C (68 °F) over a distance of 500 kilometers (310 mi). This demonstrates that the lava must have been insulated by a surface crust and that the flow was laminar , reducing heat exchange with the upper crust and base of the flow. It has been estimated that

10692-705: The Early Triassic; and they dominated many surviving communities across the recovery from the mass extinction. Microbialite deposits appear to have declined in the early Griesbachian synchronously with a significant sea level drop that occurred then. Metazoan-built reefs reemerged during the Olenekian, mainly being composed of sponge biostrome and bivalve builups. Keratose sponges were particularly noteworthy in their integral importance to Early Triassic microbial-metazoan reef communities, and they helped to create stability in heavily damaged ecosystems during early phases of biotic recovery. " Tubiphytes "-dominated reefs appeared at

10854-452: The Ginkgo flow advanced 500 km in six days (a rate of advance of about 3.5 km per hour). The lateral extent of a flood basalt flow is roughly proportional to the cube of the thickness of the flow near its source. Thus, a flow that is double in thickness at its source can travel roughly eight times as far. Flood basalt flows are predominantly pāhoehoe flows, with ʻaʻā flows much less common. Eruption in flood basalt provinces

11016-481: The Late Cretaceous to recover their full diversity. Crinoids ("sea lilies") suffered a selective extinction, resulting in a decrease in the variety of their forms. Though cladistic analyses suggest the beginning of their recovery to have taken place in the Induan, the recovery of their diversity as measured by fossil evidence was far less brisk, showing up in the late Ladinian. Their adaptive radiation after

11178-508: The Middle Triassic, with the exception of a notable Ladinian fauna from the Catalonian Basin. Microbial reefs were common across shallow seas for a short time during the earliest Triassic, predominating in low latitudes while being rarer in higher latitudes, occurring both in anoxic and oxic waters. Polybessurus -like microfossils often dominated these earliest Triassic microbialites . Microbial-metazoan reefs appeared very early in

11340-417: The PTME, being the most severely affected clade among the lophophorates. Deep water sponges suffered a significant diversity loss and exhibited a decrease in spicule size over the course of the PTME. Shallow water sponges were affected much less strongly; they experienced an increase in spicule size and much lower loss of morphological diversity compared to their deep water counterparts. Foraminifera suffered

11502-663: The PTME, but some tentative evidence suggests they may have survived into the Triassic. Freshwater and euryhaline fishes, having experienced minimal diversity losses before the PTME, were unaffected during the PTME and actually appear to have increased in diversity across the Permian-Triassic boundary. However, faunal turnovers in freshwater fish communities occurred in areas like the Kuznetsk Basin. The groups that survived suffered extremely heavy losses of species and some terrestrial vertebrate groups very nearly became extinct at

11664-652: The PTME. The Cordaites flora, which dominated the Angaran floristic realm corresponding to Siberia, collapsed over the course of the extinction. In the Kuznetsk Basin , the aridity-induced extinction of the regions's humid-adapted forest flora dominated by cordaitaleans occurred approximately 252.76 Ma, around 820,000 years before the end-Permian extinction in South China, suggesting that the end-Permian biotic catastrophe may have started earlier on land and that

11826-564: The Permian mass extinction event, both complex and simple marine ecosystems were equally common. After the recovery from the mass extinction, the complex communities outnumbered the simple communities by nearly three to one, and the increase in predation pressure and durophagy led to the Mesozoic Marine Revolution . Marine vertebrates recovered relatively quickly, with complex predator-prey interactions with vertebrates at

11988-441: The Permian-Triassic boundary are highly variable depending on the location and preservation quality of any given site. Plants are relatively immune to mass extinction, with the impact of all the major mass extinctions "insignificant" at a family level. Floral diversity losses were more superficial than those of marine animals. Even the reduction observed in species diversity (of 50%) may be mostly due to taphonomic processes. However,

12150-460: The Permian-Triassic boundary, with this flora's collapse being less constrained in western Gondwana but still likely occurring a few hundred thousand years before the boundary. The collapse of this flora is indirectly marked by an abrupt change in river morphology from meandering to braided river systems, signifying the widespread demise of rooted plants. Palynological or pollen studies from East Greenland of sedimentary rock strata laid down during

12312-484: The Permian-Triassic boundary. The extinction occurred between 251.941 ± 0.037 and 251.880 ± 0.031 million years ago, a duration of 60 ± 48 thousand years. A large, abrupt global decrease in δC , the ratio of the stable isotope carbon-13 to that of carbon-12 , coincides with this extinction, and is sometimes used to identify the Permian–Triassic boundary and PTME in rocks that are unsuitable for radiometric dating . The negative carbon isotope excursion's magnitude

12474-522: The Permian-Triassic mass extinction marked a key turning point in this ecological shift that began after the Capitanian mass extinction and culminated in the Late Jurassic . Typical taxa of shelly benthic faunas were now bivalves , snails , sea urchins and Malacostraca , whereas bony fishes and marine reptiles diversified in the pelagic zone . On land, dinosaurs and mammals arose in

12636-857: The Permian. Statistical analyses of some highly fossiliferous strata in Meishan, Zhejiang Province in southeastern China, suggest that the main extinction was clustered around one peak, while a study of the Liangfengya section found evidence of two extinction waves, MEH-1 and MEH-2, which varied in their causes, and a study of the Shangsi section showed two extinction pulses with different causes too. Recent research shows that different groups became extinct at different times; for example, while difficult to date absolutely, ostracod and brachiopod extinctions were separated by around 670,000 to 1.17 million years. Palaeoenvironmental analysis of Lopingian strata in

12798-519: The Permian–Triassic boundary. The best-known record of vertebrate changes across the Permian–Triassic boundary occurs in the Karoo Supergroup of South Africa , but statistical analyses have so far not produced clear conclusions. One study of the Karoo Basin found that 69% of terrestrial vertebrates went extinct over 300,000 years leading up to the Permian-Triassic boundary, followed by a minor extinction pulse involving four taxa that survived

12960-430: The Spathian and Anisian. Accordingly, low levels of interspecific competition in seafloor communities that are dominated by primary consumers correspond to slow rates of diversification and high levels of interspecific competition among nektonic secondary and tertiary consumers to high diversification rates. Other explanations state that life was delayed in its recovery because grim conditions returned periodically over

13122-541: The Spathian. Despite high taxonomic turnover, the ecological life modes of Early Triassic ostracods remained rather similar to those of pre-PTME ostracods. Bryozoans in the Early Triassic were restricted to the Boreal realm. They were also not diverse, represented mainly by members of Trepostomatida . During the Middle Triassic, there was a rise in bryozoan diversity, which peaked in the Carnian. However, bryozoans took until

13284-444: The Triassic, taking over niches that were filled primarily by brachiopods before the mass extinction event. Bivalves were once thought to have outcompeted brachiopods, but this outdated hypothesis about the brachiopod-bivalve transition has been disproven by Bayesian analysis . The success of bivalves in the aftermath of the extinction event may have been a function of them possessing greater resilience to environmental stress compared to

13446-675: The abandonment of plant-animal dichotomous classification, most groups of algae (sometimes all) were included in Protista , later also abandoned in favour of Eukaryota . However, as a legacy of the older plant life scheme, some groups that were also treated as protozoans in the past still have duplicated classifications (see ambiregnal protists ). Some parasitic algae (e.g., the green algae Prototheca and Helicosporidium , parasites of metazoans, or Cephaleuros , parasites of plants) were originally classified as fungi , sporozoans , or protistans of incertae sedis , while others (e.g.,

13608-404: The bottom third of the flow. The greater hydrostatic pressure, due to the weight of overlying rock, also contributes to making the lower columns larger. By analogy with Greek temple architecture, the more regular lower columns are described as the colonnade and the more irregular upper fractures as the entablature of the individual flow. Columns tend to be larger in thicker flows, with columns of

13770-420: The brachiopods that they coexisted with, whilst other studies have emphasised the greater niche breadth of the former. The rise of bivalves to taxonomic and ecological dominance over brachiopods was not synchronous, however, and brachiopods retained an outsized ecological dominance into the Middle Triassic even as bivalves eclipsed them in taxonomic diversity. Some researchers think the brachiopod-bivalve transition

13932-451: The carbon dioxide produced by the host. Reef-building stony corals ( hermatypic corals ) require endosymbiotic algae from the genus Symbiodinium to be in a healthy condition. The loss of Symbiodinium from the host is known as coral bleaching , a condition which leads to the deterioration of a reef. Endosymbiontic green algae live close to the surface of some sponges, for example, breadcrumb sponges ( Halichondria panicea ). The alga

14094-420: The chloroplast has four membranes, retaining a nucleomorph in cryptomonads , and they likely share a common pigmented ancestor, although other evidence casts doubt on whether the heterokonts , Haptophyta , and cryptomonads are in fact more closely related to each other than to other groups. The typical dinoflagellate chloroplast has three membranes, but considerable diversity exists in chloroplasts within

14256-624: The composition of the three major groups of algae. Their lineage relationships are shown in the figure in the upper right. Many of these groups contain some members that are no longer photosynthetic. Some retain plastids, but not chloroplasts, while others have lost plastids entirely. Phylogeny based on plastid not nucleocytoplasmic genealogy: Cyanobacteria Glaucophytes Rhodophytes Stramenopiles Cryptophytes Haptophytes Euglenophytes Chlorarachniophytes Chlorophytes Charophytes Land plants (Embryophyta) These groups have green chloroplasts containing chlorophylls

14418-477: The course of the Triassic . The profound change in the taxonomic composition was partly a result of the selectivity of the extinction event, which affected some taxa (e.g., brachiopods ) more severely than others (e.g., bivalves ). However, recovery was also differential between taxa. Some survivors became extinct some million years after the extinction event without having rediversified ( dead clade walking , e.g.

14580-625: The course of the Early Triassic, causing further extinction events, such as the Smithian-Spathian boundary extinction . Continual episodes of extremely hot climatic conditions during the Early Triassic have been held responsible for the delayed recovery of oceanic life, in particular skeletonised taxa that are most vulnerable to high carbon dioxide concentrations. The relative delay in the recovery of benthic organisms has been attributed to widespread anoxia, but high abundances of benthic species contradict this explanation. A 2019 study attributed

14742-794: The crust, covering an area of 5 million square kilometres (1.9 million square miles), equal to 62% of the area of the contiguous states of the United States. The hot magma contained vast quantities of carbon dioxide and sulfur oxides , and released additional carbon dioxide and methane from deep petroleum reservoirs and younger coal beds in the region. The released gases created over 6400 diatreme -like pipes , each typically over 1.6 kilometres (1 mi) in diameter. The pipes emitted up to 160 trillion tons of carbon dioxide and 46 trillion tons of methane. Coal ash from burning coal beds spread toxic chromium , arsenic , mercury , and lead across northern Canada. Evaporite beds heated by

14904-512: The decline of the Gigantopteris flora of South China. In South China, the subtropical Cathaysian gigantopterid dominated rainforests abruptly collapsed. The floral extinction in South China is associated with bacterial blooms in soil and nearby lacustrine ecosystems, with soil erosion resulting from the die-off of plants being their likely cause. Wildfires too likely played a role in the fall of Gigantopteris . A conifer flora in what

15066-436: The definition of algae. The algae contain chloroplasts that are similar in structure to cyanobacteria. Chloroplasts contain circular DNA like that in cyanobacteria and are interpreted as representing reduced endosymbiotic cyanobacteria . However, the exact origin of the chloroplasts is different among separate lineages of algae, reflecting their acquisition during different endosymbiotic events. The table below describes

15228-444: The development of a large igneous province and marks a shift to more centralized volcanism. Flood basalts show a considerable degree of chemical uniformity across geologic time, being mostly iron-rich tholeiitic basalts. Their major element chemistry is similar to mid-ocean ridge basalts (MORBs), while their trace element chemistry, particularly of the rare earth elements , resembles that of ocean island basalt . They typically have

15390-422: The dissimilarity of recovery times between different ecological communities to differences in local environmental stress during the biotic recovery interval, with regions experiencing persistent environmental stress post-extinction recovering more slowly, supporting the view that recurrent environmental calamities were culpable for retarded biotic recovery. Recurrent Early Triassic environmental stresses also acted as

15552-425: The diversity of photosynthetic eukaryotes. Recent genomic and phylogenomic approaches have significantly clarified plastid genome evolution , the horizontal movement of endosymbiont genes to the "host" nuclear genome , and plastid spread throughout the eukaryotic tree of life . Fossils of isolated spores suggest land plants may have been around as long as 475  million years ago (mya) during

15714-572: The ecological crisis may have been more gradual and asynchronous on land compared to its more abrupt onset in the marine realm. In North China, the transition between the Upper Shihhotse and Sunjiagou Formations and their lateral equivalents marked a very large extinction of plants in the region. Those plant genera that did not go extinct still experienced a great reduction in their geographic range. Following this transition, coal swamps vanished. The North Chinese floral extinction correlates with

15876-491: The end of the Olenekian, representing the earliest platform-margin reefs of the Triassic, though they did not become abundant until the late Anisian, when reefs' species richness increased. The first scleractinian corals appear in the late Anisian as well, although they would not become the dominant reef builders until the end of the Triassic period. Bryozoans, after sponges, were the most numerous organisms in Tethyan reefs during

16038-439: The end of the Permian. Some of the surviving groups did not persist for long past this period, but others that barely survived went on to produce diverse and long-lasting lineages. However, it took 30   million years for the terrestrial vertebrate fauna to fully recover both numerically and ecologically. It is difficult to analyze extinction and survival rates of land organisms in detail because few terrestrial fossil beds span

16200-649: The end-Permian extinction. Additionally, the complex Guiyang biota found near Guiyang , China also indicates life thrived in some places just a million years after the mass extinction, as does a fossil assemblage known as the Shanggan fauna found in Shanggan, China, the Wangmo biota from the Luolou Formation of Guizhou, and a gastropod fauna from the Al Jil Formation of Oman. Regional differences in

16362-494: The expansion of more habitable climatic zones. Brachiopod taxa during the Anisian recovery interval were only phylogenetically related to Late Permian brachiopods at a familial taxonomic level or higher; the ecology of brachiopods had radically changed from before in the mass extinction's aftermath. Ostracods were extremely rare during the basalmost Early Triassic. Taxa associated with microbialites were disproportionately represented among ostracod survivors. Ostracod recovery began in

16524-412: The extinction event resulted in forms possessing flexible arms becoming widespread; motility , predominantly a response to predation pressure, also became far more prevalent. Though their taxonomic diversity remained relatively low, crinoids regained much of their ecological dominance by the Middle Triassic epoch. Stem-group echinoids survived the PTME. The survival of miocidarid echinoids such as Eotiaris

16686-550: The extinction event. Prior to the extinction, about two-thirds of marine animals were sessile and attached to the seafloor. During the Mesozoic, only about half of the marine animals were sessile while the rest were free-living. Analysis of marine fossils from the period indicated a decrease in the abundance of sessile epifaunal suspension feeders such as brachiopods and sea lilies and an increase in more complex mobile species such as snails , sea urchins and crabs . Before

16848-408: The extinction period indicate dense gymnosperm woodlands before the event. At the same time that marine invertebrate macrofauna declined, these large woodlands died out and were followed by a rise in diversity of smaller herbaceous plants including Lycopodiophyta , both Selaginellales and Isoetales . Data from Kap Stosch suggest that floral species richness was not significantly affected during

17010-584: The final extinction killed off only about 80% of marine species alive at that time, whereas the other losses occurred during the first pulse or the interval between pulses. According to this theory, one of these extinction pulses occurred at the end of the Guadalupian epoch of the Permian. For example, all dinocephalian genera died out at the end of the Guadalupian, as did the Verbeekinidae ,

17172-407: The final two sedimentary zones containing conodonts from the Permian. The decrease in diversity was probably caused by a sharp increase in extinctions, rather than a decrease in speciation . The extinction primarily affected organisms with calcium carbonate skeletons, especially those reliant on stable CO 2 levels to produce their skeletons. These organisms were susceptible to the effects of

17334-418: The first flood basalt eruptions, so that subsidence and crustal thinning are precursors to flood basalt activity. The surface continues to subside as basalt erupt, so that the older beds are often found below sea level. Basalt strata at depth ( dipping reflectors ) have been found by reflection seismology along passive continental margins. The composition of flood basalts may reflect the mechanisms by which

17496-432: The first to divide macroscopic algae into four divisions based on their pigmentation. This is the first use of a biochemical criterion in plant systematics. Harvey's four divisions are: red algae (Rhodospermae), brown algae (Melanospermae), green algae (Chlorospermae), and Diatomaceae. At this time, microscopic algae were discovered and reported by a different group of workers (e.g., O. F. Müller and Ehrenberg ) studying

17658-487: The flows are very homogeneous and rarely contain xenoliths , fragments of the surrounding rock ( country rock ) that have been entrained in the lava. Because the lavas are low in dissolved gases, pyroclastic rock is extremely rare. Except where the flows entered lakes and became pillow lava , the flows are massive (featureless). Occasionally, flood basalts are associated with very small volumes of dacite or rhyolite (much more silica-rich volcanic rock), which forms late in

17820-407: The formation of flood basalts must explain how such vast amounts of magma could be generated and erupted as lava in such short intervals of time. They must also explain the similar compositions and tectonic settings of flood basalts erupted across geologic time and the ability of flood basalt lava to travel such great distances from the eruptive fissures before solidifying. A tremendous amount of heat

17982-614: The full impact of the event. Many sedimentary sequences from South China show synchronous terrestrial and marine extinctions. Research in the Sydney Basin of the PTME's duration and course also supports a synchronous occurrence of the terrestrial and marine biotic collapses. Other scientists believe the terrestrial mass extinction began between 60,000 and 370,000 years before the onset of the marine mass extinction. Chemostratigraphic analysis from sections in Finnmark and Trøndelag shows

18144-403: The fungi. This "fungal spike" has been used by some paleontologists to identify a lithological sequence as being on or very close to the Permian–Triassic boundary in rocks that are unsuitable for radiometric dating or have a lack of suitable index fossils . However, even the proposers of the fungal spike hypothesis pointed out that "fungal spikes" may have been a repeating phenomenon created by

18306-538: The genera Volvox and Corallina , and a species of Acetabularia (as Madrepora ), among the animals. In 1768, Samuel Gottlieb Gmelin (1744–1774) published the Historia Fucorum , the first work dedicated to marine algae and the first book on marine biology to use the then new binomial nomenclature of Linnaeus. It included elaborate illustrations of seaweed and marine algae on folded leaves. W. H. Harvey (1811–1866) and Lamouroux (1813) were

18468-446: The generation of action potentials . Plant hormones are found not only in higher plants, but in algae, too. Some species of algae form symbiotic relationships with other organisms. In these symbioses, the algae supply photosynthates (organic substances) to the host organism providing protection to the algal cells. The host organism derives some or all of its energy requirements from the algae. Examples are: Lichens are defined by

18630-410: The great bulk of the magmatism occurs in less than 1 Ma. Principal LIPs in the ocean basins include Oceanic Volcanic Plateaus (OPs) and Volcanic Passive Continental Margins . Oceanic flood basalts are LIPs distinguished from oceanic plateaus by some investigators because they do not form morphologic plateaus, being neither flat-topped nor elevated more than 200 m above the seafloor. Examples include

18792-438: The greater range of environmental tolerance and greater geographic distribution of the former compared to the latter. Cladodontomorph sharks likely survived the extinction by surviving in refugia in the deep oceans, a hypothesis based on the discovery of Early Cretaceous cladodontomorphs in deep, outer shelf environments. Ichthyosaurs , which evolved immediately before the PTME, were also PTME survivors. The Lilliput effect ,

18954-417: The greatest loss of species diversity. In the case of the brachiopods, at least, surviving taxa were generally small, rare members of a formerly diverse community. Conodonts were severely affected both in terms of taxonomic and morphological diversity, although not as severely as during the Capitanian mass extinction. The ammonoids , which had been in a long-term decline for the 30 million years since

19116-538: The green algae Phyllosiphon and Rhodochytrium , parasites of plants, or the red algae Pterocladiophila and Gelidiocolax mammillatus , parasites of other red algae, or the dinoflagellates Oodinium , parasites of fish) had their relationship with algae conjectured early. In other cases, some groups were originally characterized as parasitic algae (e.g., Chlorochytrium ), but later were seen as endophytic algae. Some filamentous bacteria (e.g., Beggiatoa ) were originally seen as algae. Furthermore, groups like

19278-571: The group, and a number of endosymbiotic events apparently occurred. The Apicomplexa , a group of closely related parasites, also have plastids called apicoplasts , which are not photosynthetic, but appear to have a common origin with dinoflagellate chloroplasts. Linnaeus , in Species Plantarum (1753), the starting point for modern botanical nomenclature , recognized 14 genera of algae, of which only four are currently considered among algae. In Systema Naturae , Linnaeus described

19440-453: The groups. Some of the more common organizational levels, more than one of which may occur in the lifecycle of a species, are In three lines, even higher levels of organization have been reached, with full tissue differentiation. These are the brown algae, —some of which may reach 50 m in length ( kelps ) —the red algae, and the green algae. The most complex forms are found among the charophyte algae (see Charales and Charophyta ), in

19602-625: The heaviest losses. All Permian anapsid reptiles died out except the procolophonids (although testudines have morphologically -anapsid skulls, they are now thought to have separately evolved from diapsid ancestors). Pelycosaurs died out before the end of the Permian. Too few Permian diapsid fossils have been found to support any conclusion about the effect of the Permian extinction on diapsids (the "reptile" group from which lizards, snakes, crocodilians, and dinosaurs (including birds) evolved). Tangasaurids were largely unaffected. Gorgonopsians are traditionally thought to have gone extinct during

19764-577: The historical record, killing 75% of the livestock and a quarter of the population of Iceland. However, the eruption produced just 14 cubic kilometers (3.4 cu mi) of lava, which is tiny compared with the Roza Member of the Columbia River Plateau, erupted in the mid- Miocene , which contained at least 1,500 cubic kilometers (360 cu mi) of lava. During the eruption of the Siberian Traps , some 5 to 16 million cubic kilometers (1.2 to 3.8 million cubic miles) of magma penetrated

19926-418: The inarticulate brachiopod Lingularia , and the foraminifera Earlandia and Rectocornuspira kalhori , the latter of which is sometimes classified under the genus Ammodiscus . Their guild diversity was also low. Post-PTME faunas had a flat, insignificant latitudinal diversity gradient. The speed of recovery from the extinction is disputed. Some scientists estimate that it took 10 million years (until

20088-405: The late Olenekian. Anisian ichnocoenoses show slightly lower diversity than Spathian ichnocoenoses, although this was likely a taphonomic consequence of increased and deeper bioturbation erasing evidence of shallower bioturbation. Flood basalt A flood basalt (or plateau basalt ) is the result of a giant volcanic eruption or series of eruptions that covers large stretches of land or

20250-417: The late phase of the Boring Billion . A range of algal morphologies is exhibited, and convergence of features in unrelated groups is common. The only groups to exhibit three-dimensional multicellular thalli are the reds and browns , and some chlorophytes . Apical growth is constrained to subsets of these groups: the florideophyte reds, various browns, and the charophytes. The form of charophytes

20412-403: The lava prior to its being erupted to the surface, which are often present in other extrusive igneous rocks. Phenocrysts are more abundant in the dikes that fed lava to the surface. Flood basalts are most often quartz tholeiites . Olivine tholeiite (the characteristic rock of mid-ocean ridges ) occurs less commonly, and there are rare cases of alkali basalts . Regardless of composition,

20574-419: The lava. The rock fractures into columns, typically with five to six sides, parallel to the direction of heat flow out of the rock. This is generally perpendicular to the upper and lower surfaces, but rainwater infiltrating the rock unevenly can produce "cold fingers" of distorted columns. Because heat flow out of the base of the flow is slower than from its upper surface, the columns are more regular and larger in

20736-784: The lithosphere above the plume, allowing magma produced by decompressional melting of the plume head to find pathways to the surface. The swarms of parallel dikes exposed by deep erosion of flood basalts show that considerable crustal extension has taken place. The dike swarms of west Scotland and Iceland show extension of up to 5%. Many flood basalts are associated with rift valleys, are located on passive continental plate margins, or extend into aulacogens (failed arms of triple junctions where continental rifting begins.) Flood basalts on continents are often aligned with hotspot volcanism in ocean basins. The Paraná and Etendeka traps , located in South America and Africa on opposite sides of

20898-436: The magma reaches the surface. The original melt formed in the upper mantle (the primitive melt ) cannot have the composition of quartz tholeiite, the most common and typically least evolved volcanic rock of flood basalts, because quartz tholeiites are too rich in iron relative to magnesium to have formed in equilibrium with typical mantle rock. The primitive melt may have had the composition of picrite basalt , but picrite basalt

21060-694: The magma released hydrochloric acid , methyl chloride , methyl bromide , which damaged the ozone layer and reduced ultraviolet shielding by as much as 85%. Over 5 trillion tons of sulfur dioxide was also released. The carbon dioxide produced extreme greenhouse conditions, with global average sea water temperatures peaking at 38 °C (100 °F), the highest ever seen in the geologic record. Temperatures did not drop to 32 °C (90 °F) for another 5.1 million years. Temperatures this high are lethal to most marine organisms, and land plants have difficulty continuing to photosynthesize at temperatures above 35 °C (95 °F). The Earth's equatorial zone became

21222-460: The magma to complete its journey to the surface, and also explains why flood basalts are predominantly quartz tholeiites. Over half the original magma remains in the lower crust as cumulates in a system of dikes and sills. As the magma rises, the drop in pressure also lowers the liquidus , the temperature at which the magma is fully liquid. This likely explains the lack of phenocrysts in erupted flood basalt. The resorption (dissolution back into

21384-471: The magma was only slightly contaminated with melted rock of the Earth's crust , but some high-temperature minerals had already crystallized out of the rock before it reached the surface. In other words, the flood basalt is moderately evolved . However, only small amounts of plagioclase appear to have crystallized out of the melt. Though regarded as forming a chemically homogeneous group, flood basalts sometimes show significant chemical diversity even with in

21546-718: The mass extinction, exemplifying the Lilliput effect's opposite, which has been dubbed the Brobdingnag effect. The Permian had great diversity in insect and other invertebrate species, including the largest insects ever to have existed. The end-Permian is the largest known mass extinction of insects; according to some sources, it may well be the only mass extinction to significantly affect insect diversity. Eight or nine insect orders became extinct and ten more were greatly reduced in diversity. Palaeodictyopteroids (insects with piercing and sucking mouthparts) began to decline during

21708-408: The melt) of a mixture of solid olivine, augite, and plagioclase—the high-temperature minerals likely to form as phenocrysts—may also tend to drive the composition closer to quartz tholeiite and help maintain buoyancy. Once the magma reaches the surface, it flows rapidly across the landscape, literally flooding the local topography. This is possible in part because of the rapid rate of extrusion (over

21870-510: The mid-Permian; these extinctions have been linked to a change in flora. The greatest decline occurred in the Late Permian and was probably not directly caused by weather-related floral transitions. However, some observed entomofaunal declines in the PTME were biogeographic changes rather than outright extinctions. The geological record of terrestrial plants is sparse and based mostly on pollen and spore studies. Floral changes across

22032-438: The more rapidly cooling lava close to the base of the flow forms a thin chilled margin of glassy rock, and the more rapidly crystallized rock just above the glassy margin contains vesicles trapped as the rock was rapidly crystallizing. These have a distinctive appearance likened to a clay tobacco pipe stem, particularly as the vesicle is usually subsequently filled with calcite or other light-colored minerals that contrast with

22194-440: The most voluminous of all extrusive igneous rocks , forming enormous deposits of basaltic rock found throughout the geologic record. They are a highly distinctive form of intraplate volcanism , set apart from all other forms of volcanism by the huge volumes of lava erupted in geologically short time intervals. A single flood basalt province may contain hundreds of thousands of cubic kilometers of basalt erupted over less than

22356-505: The new crust formed during flood basalt episodes takes the form of underplating , with over half the original magma crystallizing out as cumulates in sills at the base of the crust. The eruption of flood basalts has been linked with mass extinctions. For example, the Deccan Traps , erupted at the Cretaceous-Paleogene boundary , may have contributed to the extinction of the non-avian dinosaurs. Likewise, mass extinctions at

22518-480: The ocean-atmosphere system during this period. Several other contributing factors have been proposed, including the emission of carbon dioxide from the burning of oil and coal deposits ignited by the eruptions; emissions of methane from the gasification of methane clathrates ; emissions of methane by novel methanogenic microorganisms nourished by minerals dispersed in the eruptions; longer and more intense El Niño events; and an extraterrestrial impact which created

22680-470: The pace of biotic recovery existed, which suggests that the impact of the extinction may have been felt less severely in some areas than others, with differential environmental stress and instability being the source of the variance. In addition, it has been proposed that although overall taxonomic diversity rebounded rapidly, functional ecological diversity took much longer to return to its pre-extinction levels; one study concluded that marine ecological recovery

22842-475: The parameters were now shared differently among clades . Ostracods experienced prolonged diversity perturbations during the Changhsingian before the PTME proper, when immense proportions of them abruptly vanished. At least 74% of ostracods died out during the PTME itself. Bryozoans had been on a long-term decline throughout the Late Permian epoch before they suffered even more catastrophic losses during

23004-569: The past 250 million years, creating large igneous provinces , lava plateaus , and mountain ranges . However, more have been recognized such as the large Ontong Java Plateau , and the Chilcotin Group , though the latter may be linked to the Columbia River Basalt Group . Large igneous provinces have been connected to five mass extinction events, and may be associated with bolide impacts. Flood basalts are

23166-499: The phenomenon of dwarfing of species during and immediately following a mass extinction event, has been observed across the Permian-Triassic boundary, notably occurring in foraminifera, brachiopods, bivalves, and ostracods. Though gastropods that survived the cataclysm were smaller in size than those that did not, it remains debated whether the Lilliput effect truly took hold among gastropods. Some gastropod taxa, termed "Gulliver gastropods", ballooned in size during and immediately following

23328-561: The post-extinction ecosystem during the earliest Triassic. The very idea of a fungal spike has been criticized on several grounds, including: Reduviasporonites , the most common supposed fungal spore, may be a fossilized alga ; the spike did not appear worldwide; and in many places it did not fall on the Permian–Triassic boundary. The Reduviasporonites may even represent a transition to a lake-dominated Triassic world rather than an earliest Triassic zone of death and decay in some terrestrial fossil beds. Newer chemical evidence agrees better with

23490-403: The previous extinction interval. Another study of latest Permian vertebrates in the Karoo Basin found that 54% of them went extinct due to the PTME. In the wake of the extinction event, the ecological structure of present-day biosphere evolved from the stock of surviving taxa. In the sea, the "Palaeozoic evolutionary fauna" declined while the "modern evolutionary fauna" achieved greater dominance;

23652-453: The quick recovery seen in nektonic organisms such as ammonoids , which exceeded pre-extinction diversities already two million years after the crisis, and conodonts, which diversified considerably over the first two million years of the Early Triassic. Recent work suggests that the pace of recovery was intrinsically driven by the intensity of competition among species, which drives rates of niche differentiation and speciation . That recovery

23814-405: The same phycobiont species, from the green algae, except that alternatively, the mycobiont may associate with a species of cyanobacteria (hence "photobiont" is the more accurate term). A photobiont may be associated with many different mycobionts or may live independently; accordingly, lichens are named and classified as fungal species. The association is termed a morphogenesis because the lichen has

23976-410: The sequence of environmental disasters to have effectively constituted a single, prolonged extinction event, perhaps depending on which species is considered. This older theory, still supported in some recent papers, proposes that there were two major extinction pulses 9.4 million years apart, separated by a period of extinctions that were less extensive, but still well above the background level, and that

24138-412: The snail family Bellerophontidae ), whereas others rose to dominance over geologic times (e.g., bivalves). A cosmopolitanism event began immediately after the end-Permian extinction event. Marine post-extinction faunas were mostly species-poor and were dominated by few disaster taxa such as the bivalves Claraia , Unionites , Eumorphotis , and Promyalina , the conodonts Clarkina and Hindeodus ,

24300-534: The surrounding dark basalt. At still smaller scales, the texture of flood basalts is aphanitic , consisting of tiny interlocking crystals. These interlocking crystals give trap rock its tremendous toughness and durability. Crystals of plagioclase are embedded in or wrapped around crystals of pyroxene and are randomly oriented. This indicates rapid emplacement so that the lava is no longer flowing rapidly when it begins to crystallize. Flood basalts are almost devoid of large phenocrysts , larger crystals present in

24462-427: The terrestrial and marine extinctions were synchronous or asynchronous is another point of controversy. Evidence from a well-preserved sequence in east Greenland suggests that the terrestrial and marine extinctions began simultaneously. In this sequence, the decline of animal life is concentrated in a period approximately 10,000 to 60,000 years long, with plants taking an additional several hundred thousand years to show

24624-414: The terrestrial extinction occurred after the marine extinction in the tropics. Studies of the timing and causes of the Permian-Triassic extinction are complicated by the often-overlooked Capitanian extinction (also called the Guadalupian extinction), just one of perhaps two mass extinctions in the late Permian that closely preceded the Permian-Triassic event. In short, when the Permian-Triassic starts it

24786-498: The terrestrial floral turnover occurred before the large negative δC shift during the marine extinction. Dating of the boundary between the Dicynodon and Lystrosaurus assemblage zones in the Karoo Basin indicates that the terrestrial extinction occurred earlier than the marine extinction. The Sunjiagou Formation of South China also records a terrestrial ecosystem demise predating the marine crisis. Other research still has found that

24948-416: The top of the food web being known from coprolites five million years after the PTME. Post-PTME hybodonts exhibited extremely rapid tooth replacement. Ichthyopterygians appear to have ballooned in size extremely rapidly following the PTME. Bivalves rapidly recolonised many marine environments in the wake of the catastrophe. Bivalves were fairly rare before the P–Tr extinction but became numerous and diverse in

25110-842: The various structures that characterize plants (which evolved from freshwater green algae), such as the phyllids (leaf-like structures) and rhizoids of bryophytes ( non-vascular plants ), and the roots , leaves and other xylemic / phloemic organs found in tracheophytes ( vascular plants ). Most algae are autotrophic , although some are mixotrophic , deriving energy both from photosynthesis and uptake of organic carbon either by osmotrophy , myzotrophy or phagotrophy . Some unicellular species of green algae, many golden algae , euglenids , dinoflagellates , and other algae have become heterotrophs (also called colorless or apochlorotic algae), sometimes parasitic , relying entirely on external energy sources and have limited or no photosynthetic apparatus. Some other heterotrophic organisms, such as

25272-409: The very thick Greenstone flow, mentioned earlier, being around 10 meters (30 ft) thick. Another common small-scale feature of flood basalts is pipe-stem vesicles . Flood basalt lava cools quite slowly, so that dissolved gases in the lava have time to come out of solution as bubbles (vesicles) that float to the top of the flow. Most of the rest of the flow is massive and free of vesicles. However,

25434-474: Was 4-7% and lasted for approximately 500 kyr, though estimating its exact value is challenging due to diagenetic alteration of many sedimentary facies spanning the boundary. Further evidence for environmental change around the Permian-Triassic boundary suggests an 8 °C (14 °F) rise in temperature, and an increase in CO 2 levels to 2,500  ppm (for comparison, the concentration immediately before

25596-585: Was attributable not only to the end-Permian extinction but also the ecological restructuring that began as a result of the Capitanian extinction. Infaunal habits in bivalves became more common after the PTME. Linguliform brachiopods were commonplace immediately after the extinction event, their abundance having been essentially unaffected by the crisis. Adaptations for oxygen-poor and warm environments, such as increased lophophoral cavity surface, shell width/length ratio, and shell miniaturisation, are observed in post-extinction linguliforms. The surviving brachiopod fauna

25758-409: Was non-selective, consistent with a catastrophic initiator. During the Triassic, diversity rose rapidly, but disparity remained low. The range of morphospace occupied by the ammonoids, that is, their range of possible forms, shapes or structures, became more restricted as the Permian progressed. A few million years into the Triassic, the original range of ammonoid structures was once again reoccupied, but

25920-423: Was slow in the Early Triassic can be explained by low levels of biological competition due to the paucity of taxonomic diversity, and that biotic recovery explosively accelerated in the Anisian can be explained by niche crowding, a phenomenon that would have drastically increased competition, becoming prevalent by the Anisian. Biodiversity rise thus behaved as a positive feedback loop enhancing itself as it took off in

26082-516: Was still ongoing 50 million years after the extinction, during the latest Triassic, even though taxonomic diversity had rebounded in a tenth of that time. The pace and timing of recovery also differed based on clade and mode of life. Seafloor communities maintained a comparatively low diversity until the end of the Early Triassic, approximately 4 million years after the extinction event. Epifaunal benthos took longer to recover than infaunal benthos. This slow recovery stands in remarkable contrast with

26244-433: Was very low in diversity and exhibited no provincialism whatsoever. Brachiopods began their recovery around 250.1 ± 0.3 Ma, as marked by the appearance of the genus Meishanorhynchia , believed to be the first of the progenitor brachiopods that evolved after the mass extinction. Major brachiopod rediversification only began in the late Spathian and Anisian in conjunction with the decline of widespread anoxia and extreme heat and

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