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73-503: The Penarth Group is a Rhaetian age ( Triassic ) lithostratigraphic group (a sequence of rock strata ) which is widespread in Britain. It is named from the seaside town of Penarth near Cardiff in south Wales where strata of this age are exposed in coastal cliffs southwards to Lavernock Point . This sequence of rocks was previously known as the Rhaetic or Rhaetic Beds . It includes

146-411: A GSSP). A recent update of Newark stratigraphy by Kent, Olsen, & Muttoni (2017) combined magnetostratigraphy with astrochronology to form the longest astrochronostratigraphic polarity time scale (APTS) known in the fossil record. The Newark sequence was affected by astrochronological ( Milankovitch ) cycles as recorded by climate-induced changes in lake depth and geology, although depositional rate

219-653: A mountain chain stretching over parts of eastern Switzerland , northern Italy and western Austria . The stage was introduced in scientific literature by Austrian geologist Eduard Suess and German paleontologist Albert Oppel in 1856. In 2010, the Triassic subcommission of the ICS voted that the base of the Rhaetian should be defined by the first appearance of the conodont Misikella posthernsteini . M. posthernsteini 's direct ancestor Misikella hernsteini first appears shortly before

292-656: A pair of Triassic sequences in northern Italy: the Norian-Rhaetian Brumano section and the Rhaetian-Hettangian Italcementi section . In Brumano, M. posthernsteini first appeared quite a distance below the oldest reported magnetozone, BIT1n, which was correlated with E20n at Newark. The opposite is true in Pizzo Mondello, where M. posthersteini appears above the youngest complete magnetozone, PM12n (equivalent to E17n at Newark). This suggests that

365-497: A part of the Black Bear Ridge section of British Columbia which is considered early Rhaetian based on its conodont fauna. Their estimated 205.2 ± 0.9 Ma date for this early Rhaetian section agrees with the results of Wotzlaw et al. (2014). This compromise between "short-Rhaetian" and "long-Rhaetian" hypotheses has been supported by other studies. Maron et al. (2015) elaborated on the dating of an upcoming GSSP candidate for

438-758: Is a sequence of the Norian-Rhaetian Calcari con Selce (" Cherty limestone ") Formation named after two nearby towns. It preserves a diverse array of conodonts (including the Misikella hernsteini - posthernsteini morphocline) as well as pronounced radiolarian zones. The top of the Rhaetian (the base of the Hettangian Stage, the Lower Jurassic Series and the Jurassic System) is at the first appearance of ammonite genus Psiloceras . In

511-510: Is considered to lie approximately 60–140 thousand years after the extinction by most sources, and therefore the Rhaetian ended in the range of 201.5 to 201.4 Ma under the methodology of Blackburn et al . (2013). Tethys Ocean The Tethys Ocean ( / ˈ t iː θ ɪ s , ˈ t ɛ -/ TEETH -iss, TETH - ; Greek : Τηθύς Tēthús ), also called the Tethys Sea or the Neo-Tethys ,

584-486: Is remarkably consistent within the Newark basin. The most consistent and regular of these cycles are 405,000-year cycles known as McLaughlin cycles. By tracing McLaughlin cycles backwards from the radiometrically-dated CAMP basalts, the boundaries between each formation and magnetozone in the Newark sequence could be assigned a precise age. Magnetozone E20r.2r lasted from 206.03 to 204.65 Ma according to this method, suggesting that

657-684: Is still much debate over the age of this boundary, as well as the evolution of M. posthernsteini . The most comprehensive source of precise age data for the Late Triassic comes from astrochronologically -constrained terrestrial strata of the Newark basin in the eastern United States. Correlating the Newark basin to marine sections encompassing the Norian-Rhaetian boundary is mainly achieved via magnetostratigraphy , though such correlations are subject to debate and revision. Some authors have suggested that

730-674: Is what is thought to have allowed for upwelling in the Arabian Sea and led to the establishment of the modern South Asian Monsoon . It also caused major modifications to the functioning of the AMOC and ACC . During the Oligocene (33.9 to 23 Mya), large parts of central and eastern Europe were covered by a northern branch of the Tethys Ocean, called the Paratethys . The Paratethys was separated from

803-681: The Alboran , Iberian , and Apulian plates. The high sea level in the Mesozoic flooded most of these continental domains, forming shallow seas. During the early Cenozoic, the Tethys Ocean could be divided into three sections: the Mediterranean Tethys (the direct predecessor to the Mediterranean Sea), the Peri-Tethys (a vast inland sea that covered much of eastern Europe and central Asia, and

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876-629: The Lilstock Formation and the underlying Westbury Formation . The Langport and Cotham Members, grey limestones of marine origin with associated mudstones, are recognised within the Lilstock Formation, itself named from Lilstock in west Somerset. The Westbury Formation is named from Westbury-on-Severn in Gloucestershire. In 1999, the discovery of an ichthyosaur from Langport Member mudstones exposed at Waterloo Bay , Larne , provided

949-504: The Paratethys when the Alpine front was still 100 km (62 mi) farther south. In 1885, the Austrian palaeontologist Melchior Neumayr deduced the existence of the Tethys Ocean from Mesozoic marine sediments and their distribution, calling his concept Zentrales Mittelmeer ( lit.   ' Central Mediterranean Sea ' ) and described it as a Jurassic seaway, which extended from

1022-644: The Pliocene (about 5 million years ago), when it largely dried out. The modern inland seas of Europe and Western Asia, namely the Black Sea and Caspian Sea, are remnants of the Paratethys Sea. The sea is named after Tethys , who, in ancient Greek mythology, is a water goddess, a sister and consort of Oceanus , mother of the Oceanid sea nymphs and of the world's great rivers, lakes and fountains. The eastern part of

1095-575: The Triassic , a new ocean began forming in the southern end of the Paleo-Tethys Ocean. A rift formed along the northern continental shelf of Southern Pangaea (Gondwana). Over the next 60 million years, that piece of shelf, known as Cimmeria , traveled north, pushing the floor of the Paleo-Tethys Ocean under the eastern end of northern Pangaea (early / proto- Laurasia ). The Neo-Tethys Ocean formed between Cimmeria and Gondwana, directly over where

1168-574: The "short-Rhaetian" hypothesis have been revived by radiometric dating of Peruvian bivalve extinctions and magnetostratigraphy at the Pignola-Abriola GSSP candidate. These studies suggest that the base of the Rhaetian was close to 205.5 Ma. During the Rhaetian, Pangaea began to break up, though the Atlantic Ocean was not yet formed. The Rhaetian is named after the Rhaetian Alps ,

1241-484: The 1960s, "fixist" geologists, however, regarded Tethys as a composite trough, which evolved through a series of orogenic cycles. They used the terms 'Paleotethys', 'Mesotethys', and 'Neotethys' for the Caledonian , Variscan , and Alpine orogenies, respectively. In the 1970s and 1980s, these terms and 'Proto-Tethys', were used in different senses by various authors, but the concept of a single ocean wedging into Pangea from

1314-829: The Aralo-Caspian Formation extending from close to the Danube delta across Crimea, up the east side of the Volga river to Samara, then south of the Urals to beyond the Aral Sea. Brackish and upper freshwater components (OSM) of the Miocene are now known to extend through the North Alpine foreland basin and onto the Swabian Jura with thickness of up to 250 m (820 ft); these were deposited in

1387-726: The Caribbean to the Himalayas. In 1893, the Austrian geologist Eduard Suess proposed the hypothesis that an ancient and extinct inland sea had once existed between Laurasia and the continents which formed Gondwana II. He named it the Tethys Sea after the Greek sea goddess Tethys. He provided evidence for his theory using fossil records from the Alps and Africa. He proposed the concept of Tethys in his four-volume work Das Antlitz der Erde ( The Face of

1460-473: The Earth ). In the following decades during the 20th century, " mobilist " geologists such as Uhlig (1911), Diener (1925), and Daque (1926) regarded Tethys as a large trough between two supercontinents which lasted from the late Palaeozoic until continental fragments derived from Gondwana obliterated it. After World War II , Tethys was described as a triangular ocean with a wide eastern end. From 1920s to

1533-520: The ICS Triassic subcommission had already voted in 2010 to certify the first appearance of M. posthernsteini as the defining event for the base of the Rhaetian. Partially inspired by the work of Hüsing et al . (2011), the ICS's 2012 Geologic Time Scale utilized a tentative 208.5 Ma date for the Norian-Rhaetian boundary. This date has been retained in ICS time scales as of 2020. The Norian-Rhaetian boundary

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1606-683: The Kiritehere section of New Zealand). It was construed to be related to the same event responsible for the Norian-Rhaetian extinction, which heavily impacted ammonoids, bivalves, conodonts, and radiolarians. The Norian-Rhaetian extinction may have been caused by the eruption of the Angayucham large igneous province in Alaska , or the asteroid responsible for the Rochechouart impact structure in France . However,

1679-882: The Mediterranean Sea, and the Paratethys . It was preceded by the Paleo-Tethys Ocean , which lasted between the Cambrian and the Early Triassic , while the Neotethys formed during the Late Triassic and lasted in some form up to the Oligocene – Miocene boundary (about 24–21 million years ago) when it completely closed. A portion known as the Paratethys was isolated during the Oligocene (34 million years ago) and lasted up to

1752-412: The Norian-Rhaetian boundary lies in the range of Newark magnetozones E17r to E19r, or 207-210 Ma. The authors expressed skepticism towards the substantial overlap between Oyuklu and Pizzo Mondello proposed by Gallet et al. (2007). Hounslow & Muttoni (2010) elaborated on this sentiment and correlated section A+ of Oyuklu with PM12n of Pizzo Mondello, indicating that the overlap between the two sections

1825-566: The Norian-Rhaetian boundary occurred somewhere between these ash beds, 205.50 ± 0.35 Ma. This date corresponds to "short-Rhaetian" predictions, but Wotzlaw et al. (2014) also agreed with "long-Rhaetian" proponents who argued that there was no good evidence for a hiatus in the Newark Basin sequence. Wotzlaw et al . (2014) estimated that the Norian-Rhaetian boundary was concurrent with a lengthy reverse polarity section (E20r.2r) of Newark magnetozone E20. Golding et al . (2016) utilized U-Pb dating at

1898-587: The Paleo-Tethys formerly rested. During the Jurassic period about 150 Mya, Cimmeria finally collided with Laurasia and stalled, so the ocean floor behind it buckled under , forming the Tethys Trench . Water levels rose, and the western Tethys shallowly covered significant portions of Europe, forming the first Tethys Sea. Around the same time, Laurasia and Gondwana began drifting apart , opening an extension of

1971-515: The Rhaetian began ~205.5 Ma. This agrees with the dates for the Norian-Rhaetian boundary obtained by Wotzlaw et al. (2014) and Maron et al. (2015). The accuracy of the Newark APTS has been supported by Li et al. (2017), who found astrochronological and magnetostratigraphic signatures in the Xujiahe Formation of China practically identical to those of the Newark sequence. The end date of

2044-516: The Rhaetian currently in use by the ICS (201.3 ±0.2 Ma) is based on a study by Schoene et al . (2010) involving ammonite -bearing strata in Peru . They used CA-ID-TIMS Uranium-Lead dating to date ash beds slightly below and slightly above the first appearance of Psiloceras in the Pucará Basin . The overlying ash bed was dated to 201.29 ±0.16 Ma while the underlying was 201.36 ±0.13 Ma. This allowed

2117-651: The Rhaetian in the form of the Pignola-Abriola section in Southern Italy. This section recorded the Norian-Rhaetian boundary as tracked by the first occurrence of Misikella posthernsteini , the base of the Proparvicingula moniliformis radiolarian zone, and a prominent negative δ C anomaly. Magnetostratigraphy correlated MPA5r (the Pignola-Abriola magnetozone surrounding the Norian-Rhaetian boundary) with

2190-484: The Rhaetian lasted less than 5 million years using magnetostratigraphy from Turkish strata and a presumed gap or unconformity in Newark strata. However, both of these lines of evidence have been met with skepticism. A commonly cited approximation of 208.5 Ma (used by the ICS since 2012) is based on a "long-Rhaetian" hypothesis reconstructed from the Steinbergkogel GSSP candidate. Most recently, aspects of

2263-465: The Rhaetian lasts under 5 million years) based on the Oyuklu section , a sequence from Turkey . This sequence was largely normal-polarity dominated, and presented two potential Norian-Rhaetian boundaries (since the defining biostratigraphy of the Rhaetian was not resolved at the time). Defining the boundary based on the appearance of Misikella posthernsteini placed it in a reverse-polarity section (B−) near

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2336-781: The Tethyan domain, the Rhaetian contains two ammonite biozones. The highest ammonite biozone is that of Choristoceras marshi , the lower one that of Rhabdoceras suesii . The end of this period is marked by the Triassic-Jurassic extinction event . The GSSP marking the beginning of the Hettangian (and the end of the Rhaetian) is located at Kuhjoch, a geological section near the base of the Kendelbach Formation in Austria . This site records

2409-630: The Tethys Ocean is sometimes referred to as Eastern Tethys. The western part of the Tethys Ocean is called Tethys Sea, Western Tethys Ocean, or Paratethys or Alpine Tethys Ocean. The Black , Caspian , and Aral seas are thought to be its crustal remains, though the Black Sea may, in fact, be a remnant of the older Paleo-Tethys Ocean . The Western Tethys was not simply a single open ocean. It covered many small plates, Cretaceous island arcs , and microcontinents . Many small oceanic basins ( Valais Ocean , Piemont-Liguria Ocean , Meliata Ocean ) were separated from each other by continental terranes on

2482-612: The Tethys Sea between them which today is the part of the Atlantic Ocean between the Mediterranean and the Caribbean . As North and South America were still attached to the rest of Laurasia and Gondwana, respectively, the Tethys Ocean in its widest extension was part of a continuous oceanic belt running around the Earth between about latitude 30°N and the Equator . Thus, ocean currents at

2555-728: The Tethys oceans should be confused with the Rheic Ocean , which existed to the west of them in the Silurian Period. To the north of the Tethys, the then-land mass is called Angaraland and to the south of it, it is called Gondwanaland . From the Ediacaran (600  Mya ) into the Devonian (360 Mya ), the Proto-Tethys Ocean existed and was situated between Baltica and Laurentia to

2628-417: The Tethys were eventually closed off in what is now the Middle East during the Miocene , as a consequence of the northern migration of Africa/Arabia and global sea levels falling due to the concurrent formation of the Antarctic Ice Sheet . This decoupling occurred in two steps, first around 20 Mya and another around 14 Mya. The complete closure of the Tethys led to a global reorganization of currents, and

2701-417: The Tethys with the formation of the Alps, Carpathians , Dinarides , Taurus , and Elburz mountains during the Alpine orogeny . During the late Miocene , the Paratethys gradually disappeared, and became an isolated inland sea. Separation from the wider Tethys during the early Miocene initially led to a boost in primary productivity for the Paratethys, but this gave way to a total ecosystem collapse during

2774-420: The base of Oyuklu. Defining the boundary based on the extinction of Epigondolella bidentata placed it at magnetozone G+, the first of several major normal-polarity sections. The early reverse-polarity zones (B− to D−) were correlated with PM11r, a reverse-polarity section at the top of Pizzo Mondello , a similar Carnian-Norian sequence in Sicily . The inferred overlap between these reverse-polarity sections

2847-407: The base of the Rhaetian. In the boreal domain (i.e. the area of the Northern ocean), the base of the Cochloceras (Paracochloceras) amoenum biozone is used instead. Extinctions at the beginning of the Rhaetian include the ammonite Metasibirites and almost all species of the large bivalve Monotis , which was abundant throughout the world in the Norian but only persisted into the Rhaetian in

2920-491: The biostratigraphers who argue in favor of a Newark hiatus use similar techniques to support a "long Tuvalian" hypothesis, in which the Tuvalian (late Carnian) extends into a period of time commonly believed to be early Norian. When the International Commission on Stratigraphy updated their Geologic Time Scale in 2012, the "short Rhaetian" and "long Tuvalian" hypotheses were equated with each other. The combined "short Rhaetian/long Tuvalian" hypothesis as described by Ogg (2012)

2993-439: The boundary. Around the same time is the first occurrence of the more extravagant conodont species Epigondolella mosheri ( also called Mockina mosheri), which may be used as a proxy in areas where M. posthernsteini is uncommon or occurs later in time than it does elsewhere. In the Tethyan domain (i.e. the area of the Tethys ocean), the Sagenites reticulatus and Paracochloceras suessi ammonite biozones begin at

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3066-434: The conodonts Misikella hernsteini and M. posthernsteini (sensu lato) and the ammonoid Paracochloceras suessi . It also record the extinction of large Monotis bivalves and the disappearance of ammonoids including Metasibirites and some Sagenites forms with lateral nodes. A second formal GSSP candidate was not provided until Rigo et al. (2015) proposed the Pignola-Abriola section of southern Italy . This

3139-408: The dating of these geological events and their effects on life are uncertain at best. The Rhaetian does not yet have an official GSSP, but two candidates have been formally proposed. Krystyn et al. (2007) proposed the Austrian Steinbergkogel section, a Norian-Rhaetian limestone sequence near Hallstatt . It records many potential Norian-Rhaetian biostratigraphic events, such as the appearance of

3212-547: The direct predecessor to the Paratethys Sea), and the Indian Tethys (the direct predecessor to the Indian Ocean). The Turgai Strait extended out of the Peri-Tethys, connecting the Tethys with the Arctic Ocean . As theories have improved, scientists have extended the "Tethys" name to refer to three similar oceans that preceded it, separating the continental terranes: in Asia, the Paleo-Tethys (Devonian–Triassic), Meso-Tethys (late Early Permian –Late Cretaceous), and Ceno-Tethys (Late-Triassic–Cenozoic) are recognized. None of

3285-480: The early M. posthernsteini specimens present at Steinbergkogel are actually an older transitional form ( M. posthernsteini sensu lato) which lies between M. hernsteini and M. posthernsteini in the evolution of Triassic conodonts. The Pignola-Abriola form ( M. posthernsteini sensu stricto) is considered morphologically more similar to the original fossils of the species, described from Slovakia in 1974. This debate has led some biostratigraphers to suggest avoiding

3358-414: The early part of Newark's E20. This provided an estimated date of 205.7 Ma for the Norian-Rhaetian boundary, very similar to Wotzlaw et al. (2014)'s estimate. Some controversy over the date of the Norian-Rhaetian boundary has resulted from differing interpretations of the conodont used to define it, Misikella posthernsteini . Paleontologists working on the Pignola-Abriola GSSP candidate have argued that

3431-648: The first CAMP eruptions. However, the lithology and astrochronology of Newark seem to be continuous and this precludes any assumed unconformity. In addition, the magnetic signature of at the end of Newark basin has been found worldwide, with sequences in Morocco, Nova Scotia, Italy, the U.K., and possibly Turkey all preserving E23r-equivalent magnetozones underlying the Rhaetian-Hettangian boundary. It would be very improbable for all of these sites of varying geology and deposition rates to experience an unconformity erasing an equivalent amount of time. Kent, Olsen, & Muttoni (2017) additionally found convincing correlations between

3504-479: The first appearance of Misikella posthernsteini (sensu stricto) and the Proparvicingula moniliformis radiolarian zone. Rigo et al. (2020) found this same pattern in the nearby Mt Volturino and Madonna del Sirino sections, as well as the Kastelli section of Greece. They also found it in East Panthalassan sediments (Kennecott Point of British Columbia and New York Canyon of Nevada) and West Panthalassan sediments (Wombat and northern Carnarvon Basins of Australia and

3577-449: The first appearance of Psiloceras to be given a date of 201.31 ±0.18/0.43 Ma (assuming minimum/maximum uncertainty). Blackburn et al . (2013) instead estimated a slightly older end date. They used a combination of radiometric dates and astrochronology (via Triassic Milankovitch cycles ) to constrain the end-Triassic extinction to 201.564 ±0.015/0.22 Ma. The biostratigraphically-defined Triassic-Jurassic (Rhaetian-Hettangian) boundary

3650-412: The first appearance of Psiloceras spelae , Cerebropollenites thiergartii (a palynomorph ), Praegubkinella turgescens (a foraminifer ), Cytherelloidea buisensis (an ostracod ), and a positive δ C spike marking a recovery from the underlying large negative δ C spike which marks the Triassic-Jurassic extinction event. Gallet et al . (2007) argued in support of a "short Rhaetian" (where

3723-430: The form of a few miniaturized species endemic to the Tethys ocean. The Norian-Rhaetian boundary also experienced an overturn in radiolarian species, with the beginning of the Proparvicingula moniliformis biozone. Maron et al. (2015) provided a chemostratigraphic option for defining the base of the Rhaetian at the Pignola-Abriola section. This sequence records a pronounced negative spike in δ C just before

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3796-434: The hiatus. Estimating the duration of Oyuklu by comparing Pizzo Mondello with equivalent sections of Newark led Gallet et al . (2007) to the conclusion that the Rhaetian lasted only 2 million years (if the boundary was at G+) or 4.5 million years (if it was at B−). Some biostratigraphic studies have also supported a hiatus at Newark. The conchostracan Shipingia olseni , which in Europe is found in Norian rocks, occurs in

3869-411: The historic æra, a vast region of Europe and Asia was covered by a Mediterranean Sea of brackish water, of which the present Caspian is the diminished type. ... To render the distinction between these accumulations and all others clear and unambiguous, we have adopted the term Aralo-Caspian, first applied in a geographical sense, by our great precursor Humboldt, to this region of the globe. ... Judging from

3942-412: The late Miocene as a result of rapid dissolution of carbonate . In Chapter 13 of his 1845 book, Roderick Murchison described a distinctive formation extending from the Black Sea to the Aral Sea in which the creatures differed from those of the purely marine period that preceded them. The Miocene deposits of Crimea and Taman (south of the Sea of Azov ) are identical with formations surrounding

4015-484: The magnetozones of the upper Passaic Formation and Rhaetian strata in England. They suggest that the apparent delay between Newark and Europe fauna and flora may instead be biogeographic differences due to climatic variation over time and latitude, a factor which has manifested at other points in the Triassic. Various studies have supported a "long Rhaetian" hypothesis (where the Rhaetian lasts 5–10 million years) based on magnetostratigraphy. Muttoni et al. (2010) studied

4088-406: The masses of water now separated from each other, from the Aral to the Black Sea inclusive, were formerly united in this vast pre-historical Mediterranean ; which (even if we restrict its limits to the boundaries we already know, and do not extend them eastward, amid low regions untrodden by geologists) must have exceeded in size the present Mediterranean! On the accompanying map, Murchison shows

4161-414: The most complete example of this in Northern Ireland . This article about a specific stratigraphic formation in the United Kingdom is a stub . You can help Misplaced Pages by expanding it . Rhaetian In 2010, the base of the Rhaetian (i.e. the Norian-Rhaetian boundary) was voted to be defined based on the first appearance of Misikella posthernsteini , a marine conodont . However, there

4234-403: The north and Gondwana to the south. From the Silurian (440 Mya ) through the Jurassic periods, the Paleo-Tethys Ocean existed between the Hunic terranes and Gondwana. Over a period of 400 million years, continental terranes intermittently separated from Gondwana in the Southern Hemisphere to migrate northward to form Asia in the Northern Hemisphere. About 250 Mya, during

4307-400: The ocean, a land barrier to the flow of currents between the Indian and Mediterranean basins, and the orogenies of the Alpide belt (including the Alps , Himalayas , Zagros , and Caucasus Mountains ). All of these geological events, in addition to a drop in sea level rise from Antarctic glaciation, brought an end to the Tethys as it previously existed, fragmenting it into the Indian Ocean,

4380-403: The opening of the Indian and Atlantic oceans during the Cretaceous Period and the breakup of these continents over the same period, it came to be defined as the ocean bordered by the continents of Africa, Eurasia, India, and Australasia. During the early-mid Cenozoic, the Indian, African, Australian and Arabian plates moved north and collided with the Eurasian plate, which created new borders to

4453-434: The present Caspian Sea , in which the univalves of freshwater origin are associated with forms of Cardiacae and Mytili that are common to partially saline or brackish waters. This distinctive fauna has been found throughout all the enormously developed Tertiary formations of the southern and south-eastern steppes. ... and leads at once to the conviction, that during long periods antecedent, as will be hereafter explained, to

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4526-422: The recital of travellers and from specimens of the rock, we have no doubt that it extended to Khivah and the Aral Sea ; beyond which the low level of the adjacent eastern deserts would lead us to infer, that it spread over wide tracts in Asia now inhabited by the Turkomans and Kirghis , and was bounded only by the mountains of the Hindoo Kusk and Chinese Tartary . ... there can be no sort of doubt, that all

4599-422: The time around the Early Cretaceous ran very differently from the way they do today. Between the Jurassic and the Late Cretaceous , which started about 100 Mya, Gondwana began breaking up, pushing Africa and India north across the Tethys and opening up the Indian Ocean. Throughout the Cenozoic (66 million to the dawn of the Neogene, 23 Mya), the connections between the Atlantic and Indian Oceans across

4672-437: The top of a normal-polarity section while M. posthernsteini (sensu lato) first appeared at the base of a shorter overlying reverse-polarity section. These sections were correlated with magnetozones E16n and E16r of the Newark Basin. Hüsing et al . (2011) preferred to define the Rhaetian based on M. hernsteini , and estimated a date for the Norian-Rhaetian boundary of 209.8 Ma based on that of Newark's magnetozone E16n. However,

4745-484: The upper portion of the Passaic Formation , the last pre- CAMP section of the Newark basin. Typical Rhaetian conchostracans such as Euestheria brodieana only appear in the last few layers of the Catharpin Creek Formation , a late Triassic unit in the Culpeper Basin which is likely equivalent to the upper Passaic formation. Palynomorph turnovers and changes in tetrapod faunas similar to Norian events in Europe have also been used to support this hypothesis. Many of

4818-415: The use of conodonts in Triassic chronostratigraphy altogether, a proposal which itself has been criticized by Triassic conodont specialists. Writing on behalf of the ICS, Ogg (2016) stated that there were two possible dates for the Norian-Rhaetian boundary: 209.5 Ma (using M. posthernsteini sensu lato and Steinbergkogel as a GSSP) or 205.8 Ma (using M. posthernsteini sensu stricto and Pignola-Abriola as

4891-426: Was a missing period of time or "hiatus" at the end of the Newark sequence, which would have resembled part of Oyuklu had it not been eroded away. If the base of Oyuklu (A+) was equivalent to E21n, then the upper half of Oyuklu would be equivalent to the Newark "hiatus", B− was equivalent to E21r, and G+ was equivalent to E23n. If A+ was instead equivalent to E23n, then practically all of Oyuklu (B− and up) would represent

4964-443: Was a prehistoric ocean during much of the Mesozoic Era and early-mid Cenozoic Era . It was the predecessor to the modern Indian Ocean , the Mediterranean Sea , and the Eurasian inland marine basins (primarily represented today by the Black Sea and Caspian Sea ). During the early Mesozoic, as Pangaea broke up, the Tethys Ocean was defined as the ocean located between the ancient continents of Gondwana and Laurasia . After

5037-465: Was a prominent study arguing in favor of a long Rhaetian. This was based on biostratigraphy and magnetostratigraphy of the Steinbergkogel section in Austria, which is a candidate GSSP for the base of the Rhaetian. They proposed two options for defining the base of the Rhaetian, either at the first occurrence of Misikella hernsteini or the first appearance datum of Misikella posthernsteini (sensu lato) . At Steinbergkogel, M. hernsteini first occurred at

5110-453: Was finally provided with radiometric dating in a study by Wotzlaw et al. (2014). They studied a sequence of the Aramachay Formation in Peru which records the extinction of large Monotis bivalves . This prominent biotic event is closely associated with the Norian-Rhaetian boundary. The last Monotis specimens lie between ash beds which are Uranium-Lead dated to 205.70 ± 0.15 Ma and 205.30 ± 0.14 Ma. This allowed them to conclude that

5183-465: Was located above a normal-polarity section (A+ in Oyuklu and PM11n in Pizzo Mondello). This underlying normal-polarity section was correlated with either magnetozone E21n or E23n of the Newark sequence. Although the upper portion of Oyuklu was mostly normal, it did have a few reverse sections (H− and J−) which were at odds with the almost entirely-normal last few Triassic magnetozones of Newark. Gallet et al. (2007) explained this by suggesting that there

5256-407: Was ultimately not chosen by the ICS when compared to its competition, which was supported by a more diverse array of methods. The "short Rhaetian" hypothesis has been criticized for its reliance on the assumption that a hiatus existed at Newark. This hiatus was presumed to lie within the normal polarity-dominated end of the Rhaetian, after a very short reverse polarity section (E23r) and just before

5329-535: Was very narrow. They also noted that a thrust fault at Oyuklu artificially lengthens B−, the magnetozone containing the Norian-Rhaetian boundary at that section. Ikeda & Tada (2014) provided an astrochronologically -constrained chert sequence in Japan which suggested that the Norian-Rhaetian boundary occurred 208.5 ± 0.3 Ma, based on the extinction of the Norian radiolarian Betraccium deweveri . Hüsing et al . (2011)

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