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38-621: With a potential radius of up to 4,500 km (2,800 mi), the CIMP was one of the larger volcanic events on Earth, similar in size to the 200 Ma Central Atlantic Magmatic Province . Evidences for the CIMP have also been found in Mexico, Morocco, and Svalbard. The CIMP coincides with the Marinoan and Gaskiers glaciations and precedes the so-called Cambrian explosion , the evolution of modern lineages. The CIMP left extensive traces along

76-467: A supercontinent . In 2013 the CAMP's connection to the end-Triassic extinction , with major extinctions that enabled dinosaur domination of land, became more firmly established. Until 2013, the uncertainties in the geochronologic dates had been too coarse to confirm that the volcanic eruptions were correlated with major climate changes. The work by Blackburn et al. demonstrated a tight synchroneity between

114-579: A CAMP–related (about 200 Ma) dike in North Carolina. Whiteside et al. (2007) suggest that reverse polarity intervals in this dike could be of post Triassic age and correlated with the same events in Morocco. The Tr-J boundary is not officially defined, but most workers recognise it in continental strata by the last appearance of index taxa such as Ovalipollis ovalis , Vallasporites ignatii and Patinasporites densus or, in marine sections, by

152-640: A certain correlation between the lower North American lava flows and the Lower Unit of the Moroccan CAMP, thus reinforcing the conclusion that the Moroccan basalts postdate the Tr-J boundary. Therefore, according to these data, CAMP basalts should not be included among the direct causes of the Tr-J mass extinction. Tholeiite The tholeiitic magma series ( / ˌ θ oʊ l i ˈ aɪ t ɪ k / )

190-618: A completely reliable constraint. CAMP lava flows of North America can be geochemically separated in three units: the older ones are classified as high titanium quartz normative (HTQ) basalts (TiO 2 = 1.0-1.3 wt%); these are followed by lava flows classified as low titanium quartz normative (LTQ) basalts (TiO 2 = ca. 0.8-1.3 wt%); and then by the youngest lava flow unit classified as high titanium iron quartz normative (HTIQ) basalts (TiO 2 = 1.4-1.6 wt%). According to Whiteside et al. (2007) , geochemical analyses based upon titanium, magnesium and silicon contents show

228-480: A composition indicative of a LIP, while the last pulse contains ocean island basalts and can therefore be associated with the opening Iapetus Ocean. Central Atlantic Magmatic Province The Central Atlantic magmatic province ( CAMP ) is the Earth's largest continental large igneous province , covering an area of roughly 11 million km . It is composed mainly of basalt that formed before Pangaea broke up in

266-483: A great lateral extension and a maximum thickness up to 1 km. The basaltic flows occur on top of continental fluvial and lacustrine sedimentary units of Triassic age. Ar/ Ar data (on plagioclase) indicate for these basaltic units an absolute age of 198–200 Ma bringing this magmatic event undoubtedly close to the Triassic-Jurassic (Tr-J) boundary. Thus it is necessary to determine whether it straddles

304-595: A palynologic turnover, interpreted as the Tr-J boundary. In Morocco, two reversals have been detected in two lava flow sequences. Two distinct correlations between the Moroccan and the Newark magnetostratigraphy have been proposed. Marzoli et al. (2004) suggest that the Tr-J boundary is located above the lower reverse polarity level which is positioned more or less at the base of the Intermediate basalt unit of Morocco. These two levels can be correlated with chron E23r of

342-514: A symposium held at the 1999 Spring Meeting of the American Geophysical Union. The CAMP volcanic eruptions occurred about 201 million years ago and split into four pulses lasting for over ~600,000 years. The resulting large igneous province is, in area covered, the most extensive on Earth. The volume of magma flow of between two and six million cubic kilometres makes it one of the most voluminous as well. This geologic event

380-481: Is associated with the Triassic–Jurassic extinction event . Although some connections among these basalts had long been recognized, in 1988 they were linked as constituting a single major flood basalt province . The basaltic sills of similar age (near 200 Ma, or earliest Jurassic) and composition (intermediate-Ti quartz tholeiite) which occur across the vast Amazon River basin of Brazil were linked to

418-424: Is composed by a smaller number of lava flows (i.e., a lower volume) than the preceding one. These data suggest that they were created by five short magma pulses and eruption events, each one possibly <400 (?) years long. All lava flow sequences are characterized by normal polarity, except for a brief paleomagnetic reversal yielded by one lava flow and by a localized interlayered limestone in two distinct section of

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456-461: Is one of two main magma series in subalkaline igneous rocks , the other being the calc-alkaline series. A magma series is a chemically distinct range of magma compositions that describes the evolution of a mafic magma into a more evolved, silica rich end member. Rock types of the tholeiitic magma series include tholeiitic basalt , ferro-basalt, tholeiitic basaltic andesite , tholeiitic andesite , dacite and rhyolite . The variety of basalt in

494-592: The Appalachians in eastern North America to which the Baltoscandian margin a conjugate. No traces of the CIMP have been found in Amazonia, however, and it is possible Laurentia and Amazonia separated during 1000 Ma-rifting events. Four pulses of magmatism associated with the CIMP have been identified: It is unclear whether the CIMP was a single plume centre event or not. The first two pulses have

532-463: The Earth's mantle . Tholeiitic basalt constituting the oceanic crust is termed MORB: m id- o cean- r idge b asalt. Throughout the process of igneous differentiation , the oceanic crust acts to reduce the magma, producing the tholeiitic trend. In contrast, alkali basalts are not typical of ocean ridges, but are erupted on some oceanic islands and on continents, as also is tholeiitic basalt. Because

570-884: The Mesozoic Era, near the end of the Triassic and the beginning of the Jurassic periods. The subsequent breakup of Pangaea created the Atlantic Ocean , but the massive igneous upwelling provided a legacy of basaltic dikes , sills , and lavas now spread over a vast area around the present central North Atlantic Ocean, including large deposits in northwest Africa , southwest Europe , as well as northeast South America and southeast North America (found as continental tholeiitic basalts in subaerial flows and intrusive bodies ). The name and CAMP acronym were proposed by Andrea Marzoli (Marzoli et al. 1999) and adopted at

608-620: The High Atlas CAMP. Palynological data from sedimentary layers samples at the base of four lava flow sequences constrain the onset of the CAMP, since there is no evidence of depositional hiatus or tectonic deformation at the bottom of the lava flow piles. The palynological assemblage observed in these basal layers is typical of Late Triassic age, similar to that of the uppermost Triassic sedimentary rocks of eastern North America. Samples from interlayered limestone in lava flows provided unreliable palynological data. One limestone bed from

646-977: The Newark Basin, therefore the North American CAMP Basalts postdate the Tr–J boundary whereas part of the Moroccan CAMP was erupted within the Triassic. Contrarily, Whiteside et al. (2007) propose that these two levels could be earliest Jurassic intervals of reverse polarity not sampled in the Newark Basin Sequence (many more lava flows are present in the Moroccan Succession than in the Newark Basin), but observed in Early Jurassic sedimentary sequences of

684-710: The Paris Basin of France. Reverse polarity intervals in America could be present within North Mountain (Fundy basin, Nova Scotia) which are poorly sampled even if previous magnetostratigraphy analysis in this sequence showed only normal polarity, or in the Scots Bay Member of the Fundy basin which have never been sampled. There is only one outcrop in the CAMP of America where reverse polarity is observable:

722-657: The Tr-J boundary climatic and biotic crisis that led to the mass-extinction . The North American portion of the CAMP lava flows crop out in various sections in the basins of Newark, Culpeper, Hartford, Deerfield, i.e. the Newark Supergroup in New England (USA), and in the Fundy Basin in Nova Scotia (Canada). The CAMP is here constituted by rare olivine - and common quartz-normative basalts showing

760-411: The alkali corner as they cool. In the tholeiitic magma, magnesium-rich crystals are produced preferentially, the magnesium content of the magma plummets, causing the magma to move away from the magnesium corner until it runs low on magnesium and simply moves towards the alkali corner as it loses iron and any remaining magnesium. With the calc-alkaline series, however, the precipitation of magnetite causes

798-468: The aluminium content, with tholeiitic basalts containing 12% to 16% Al 2 O 3 versus 16% to 20% Al 2 O 3 for calc-alkali basalts. Like all basalt, the rock type is dominated by olivine , clinopyroxene and plagioclase , with minor iron- titanium oxides. Orthopyroxene or pigeonite may also be present in tholeiitic basalt, and olivine, if present, may be rimmed by either of these calcium-poor pyroxenes. Tridymite or quartz may be present in

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836-809: The best preserved and most complete basaltic lava piles are exposed. According to geochemical, petrographic and isotopic data four distinct tholeiitic basaltic units were recognized and can be placed throughout the Central High Atlas: Lower, Intermediate, Upper and Recurrent basalts. The Lower and Intermediate units are constituted by basaltic andesites , whereas the Upper and Recurrent units have basaltic composition. From Lower to Recurrent unit, we observe: Ages were determined by Ar/ Ar analysis on plagioclase . These data show indistinguishable ages (199.5±0.5 Ma) from Lower to Upper lava flows, from central to northern Morocco. Therefore, CAMP

874-529: The boundary or not: if not, then the CAMP could not be a cause of the Late Triassic extinction event . For example, according to Whiteside et al. (2007) there are palynological, geochemical, and magnetostratigraphic evidences that the CAMP postdates the Tr-J boundary. In the Newark Basin , a magnetic reversal (E23r) is observed just below the oldest basalts and more or less in the same position as

912-461: The earliest volcanism and extinction of large populations using zircon uranium-lead (U-Pb) dating. They further demonstrated that the magmatic eruptions as well as the accompanying atmospheric changes were split into four pulses lasting for over ~600,000 years. Before that integration, two hypotheses were in debate. One hypothesis was based especially on studies on Triassic-Jurassic basins from Morocco where CAMP lava flows are outcropping, whereas

950-482: The fine-grained groundmass of tholeiitic basalt, and feldspathoids are absent. Tholeiitic rocks may have a fine, glassy groundmass , as may other types of basalt. Tholeiitic rocks are the most common igneous rocks in Earth's crust , produced by submarine volcanism at mid-ocean ridges and make up much of the ocean crust. Tholeiitic basaltic magmas are initially generated as partial melts of peridotite ( olivine and pyroxene ) produced by decompression melting of

988-520: The first appearance of the ammonite Psiloceras planorbis . In the Newark basin the palynological turnover event (hence the Tr-J boundary mass extinction) occurs below the oldest CAMP lava flows. The same can be said for the Fundy, Hartford and Deerfield Basins. In the investigated Moroccan CAMP sections (Central High Atlas Basin), sedimentary layers sampled immediately below the oldest basaltic lava flows, apparently contain Triassic taxa (e.g., P. densus ), and were thus defined as Triassic in age as at least

1026-553: The interior of western Africa westward for 2,500 kilometres (1,600 mi) through eastern and southern North America . If not the largest province by volume, the CAMP certainly encompasses the greatest area known, roughly 11,000,000 square kilometres (4,200,000 sq mi), of any continental large igneous province . Nearly all CAMP rocks are tholeiitic in composition, with widely separated areas where basalt flows are preserved, as well as large groups of diabase (dolerite) sills or sheets, small lopoliths , and dikes throughout

1064-425: The iron content of the magma to remain more steady as it cools than with a tholeiitic magma. The difference between these two magma series can be seen on an AFM diagram, a ternary diagram showing the relative proportions of the oxides Na 2 O + K 2 O (A), FeO + Fe 2 O 3 (F), and MgO (M). As magmas cool, they precipitate out significantly more iron and magnesium than alkali, causing the magmas to move towards

1102-502: The iron-magnesium ratio to remain relatively constant, so the magma moves in a straight line towards the alkali corner on the AFM diagram. The AFM plot distinguishes the intermediate members of the tholeiitic and calc-alkali magma series quite well. However, the felsic end members of the two series are nearly indistinguishable, so granitic rocks are generally assigned to the calc-alkali magma series. The mafic end members may be distinguished by

1140-461: The lowest lava flows . Still, a different interpretation is suggested by Whiteside et al. (2007) : the sampled sedimentary strata are quite deformed and this can mean that some sedimentary units could be lacking (eroded or structurally omitted). With respect to the Triassic pollens found in some sedimentary units above the Upper Unit basalts, they could have been reworked, so they don’t represent

1178-455: The oceanic crust. Almost all the basalt found on the Moon is tholeiitic basalt. Rocks in the tholeiitic magma series are classified as subalkaline (they contain less sodium than some other basalts) and are distinguished from rocks in the calc-alkaline magma series by the redox state of the magma they crystallized from (tholeiitic magmas are reduced; calc-alkaline magmas are oxidized ). When

Central Iapetus Magmatic Province - Misplaced Pages Continue

1216-460: The other was based on end-Triassic extinction data from eastern North American basins and lava flows showing an extremely large turnover in fossil pollen, spores (sporomorphs), and vertebrates, respectively. The thickest lava flow sequences of the African CAMP are in Morocco, where there are basaltic lava piles more than 300 metres thick. The most-studied area is Central High Atlas , where

1254-400: The parent magmas of basalts crystallize, they preferentially crystallize the more magnesium-rich and iron-poor forms of the silicate minerals olivine and pyroxene , causing the iron content of tholeiitic magmas to increase as the melt is depleted of iron-poor crystals. However, a calc-alkaline magma is oxidized enough to precipitate significant amounts of the iron oxide magnetite , causing

1292-598: The province in 1999. Remnants of CAMP have been identified on four continents (Africa, Europe, North America and South America) and consist of tholeiitic basalts formed during the opening of the Atlantic Ocean basin during the breakup of the Pangean supercontinent. The province has been described as extending within Pangaea from present-day central Brazil northeastward about 5,000 kilometres (3,100 mi) across western Africa , Iberia , and northwestern France , and from

1330-494: The province. Dikes occur in very large individual swarms with particular compositions and orientations. CAMP activity is apparently related to the rifting and breakup of Pangaea during the Late Triassic through Early Jurassic periods, and the enormous province size, varieties of basalt, and brief time span of CAMP magmatism invite speculation about mantle processes that could produce such a magmatic event as well as rift

1368-512: The series was originally called tholeiite but the International Union of Geological Sciences recommends that tholeiitic basalt be used in preference to that term. Tholeiitic rock types tend to be more enriched in iron and less enriched in aluminium than calc-alkaline rock types. They are thought to form in a less oxidized environment than calc-alkaline rocks. Tholeiitic basalt is formed at mid-ocean ridges and makes up much of

1406-555: The top to the central High Atlas upper basalts yielded a Late Triassic palynological assemblage. However, the observed sporomorphs in this sample are rare and poorly preserved. All of these data indicate that the basaltic lava flows of the Central Atlantic magmatic province in Morocco were erupted at c. 200 Ma and spanned the Tr - J boundary. Thus, it is very possible that there is a connection between this magmatic event and

1444-519: Was an intense, short magmatic event. Basalts of the Recurrent unit are slightly younger (mean age: 197±1 Ma) and represent a late event. Consistently, the Upper and Recurrent basalts are separated by a sedimentary layer that locally reaches a thickness of circa 80 m. According to magnetostratigraphic data, the Moroccan CAMP events were divided into five groups, differing in paleomagnetic orientations (declination and inclination). Each group

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