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 km2. It is composed mainly of basalt that formed before Pangaea broke up in 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 and provided a legacy of basaltic dikes, sills, and lavas over a vast area around the present central North Atlantic Ocean, including large deposits in northwest Africa, southwest Europe, as well as northeast South and southeast North America (found as continental thoeliitic basalts in subaerial flows and intrusive bodies). The name and CAMP acronym were proposed by Andrea Marzoli (Marzoli et al. 1999) and adopted at 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 ~2–3 × 106 km3 makes it one of the most voluminous as well.

This geologic event is associated with the Triassic–Jurassic extinction event.

Connected magma flows

CAMP Magmatism in the context of Pangea
Location of large residual elements of the Central Atlantic magmatic province

Although some connections among these basalts had long been recognized, in 1988 they were linked as constituting a single major flood basalt province (Rampino & Stothers 1988). 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 the province in 1999 (Marzoli et al. 1999). Remnants of CAMP have been identified on four continents (Africa, Europe, North America and South America) and consist of thoeliitic basalts formed during the opening of the Atlantic Ocean basin during the breakup of the Pangean supercontinent (Blackburn et al. 2013).

Geographical extent

The province has been described as extending within Pangaea from present-day central Brazil northeastward about 5000 km across western Africa, Iberia, and northwestern France, and from the interior of western Africa westward for 2500 km through eastern and southern North America (McHone 2000). If not the largest province by volume, the CAMP certainly encompasses the greatest area known, roughly 11 million km², 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 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 a supercontinent (Wilson 1997), (McHone 2000).

Connection with the Triassic-Jurassic boundary and the associated mass extinction event

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 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 (Blackburn et al. 2013).

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 (e.g., Marzoli et al. 2004), whereas 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 (Whiteside et al. 2007), respectively.

Morocco

Affioramento CAMP2
A basaltic lava flow section from the Middle Atlas, Morocco

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 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:

  • a progressive decrease of eruption rate (the Lower and the Intermediate units represent over 80% of preserved lava volume);
  • a trend going from intersertal to porphyritic texture;
  • a progressive depletion of incompatible element contents in the basalts, possibly linked to a progressive depletion of their mantle source.

Isotopic analyses

Ages were determined by 40Ar/39Ar analysis on plagioclase (Knight et al. 2004), (Verati et al. 2007), (Marzoli et al. 2004). These data show indistinguishable ages (199.5±0.5 Ma) from Lower to Upper lava flows, from central to northern Morocco. Therefore, CAMP is 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.

Magnetostratigraphy

According to magnetostratigraphic data, the Moroccan CAMP events were divided into five groups, differing in paleomagnetic orientations (declination and inclination) (Knight et al. 2004). Each group 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 the High Atlas CAMP.

Palynological analyses

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 (Marzoli et al. 2004). 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 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.

Conclusions

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 the Tr-J boundary climatic and biotic crisis that led to the mass-extinction.

Eastern North America

CAMP North America
Basal contact of the North Mountain section of Fundy basin, Nova Scotia, Canada

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 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. 40Ar/39Ar data (on plagioclase) indicate for these basaltic units an absolute age of 198-200 Ma (Hames et al. 2003) bringing this magmatic event undoubtedly close to the Triassic-Jurassic (Tr-J) boundary. Thus it is necessary to determine whether it straddles 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.

Magnetostratigraphy

In the Newark basin a magnetic reversal (E23r) is observed just below the oldest basalts and more or less in the same position as a palynologic turnover, interpreted as the Tr-J boundary. In Morocco, two reversal 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 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 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: 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.

Palynological analyses

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 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 the lowest lava flows (Marzoli et al. 2004). 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 a completely reliable constraint.

Geochemical analyses

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 (TiO2 = 1.0-1.3 wt%); these are followed by lava flows classified as low titanium quartz normative (LTQ) basalts (TiO2 = ca. 0.8-1.3 wt%); and then by the youngest lava flow unit classified as high titanium iron quartz normative (HTIQ) basalts (TiO2 = 1.4-1.6 wt%). According to Whiteside et al. 2007, geochemical analyses based upon titanium, magnesium and silicon contents show 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 shouldn’t be included among the direct causes of the Tr-J mass extinction.

References

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  • Hames, W.E., McHone, J.G., Renne, P., and Ruppel, C., eds. (2003). The Central Atlantic Magmatic Province: Insights from Fragments of Pangea. 136. American Geophysical Union Monograph. p. 267. ISBN 978-0-87590-995-0.CS1 maint: uses editors parameter (link)
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  • McHone, J.G. (2000). "Non-plume magmatism and rifting during the opening of the Central Atlantic Ocean". Tectonophysics. 316 (3–4): 287–296. Bibcode:2000Tectp.316..287M. doi:10.1016/S0040-1951(99)00260-7.
  • McHone, J.G. (2003). "Volatile emissions of Central Atlantic Magmatic Province basalts: Mass assumptions and environmental consequences" (PDF). In Hames, W.E.; Mchone, J.G.; Renne, P.; et al. (eds.). The Central Atlantic Magmatic Province: Insights from Fragments of Pangea. Washington DC American Geophysical Union Geophysical Monograph Series. American Geophysical Union Monograph. 136. pp. 241–254. Bibcode:2003GMS...136..241M. doi:10.1029/136GM013. ISBN 978-0-87590-995-0. Retrieved 8 August 2015.
  • Marzoli, A.; Renne, P.R.; Piccirillo, E.M.; Ernesto, M.; Bellieni, G.; De Min, A. (1999). "Extensive 200 million-year-old continental flood basalts of the central Atlantic magmatic province". Science. 284 (5414): 616–618. Bibcode:1999Sci...284..616M. doi:10.1126/science.284.5414.616. PMID 10213679.
  • Marzoli, A.; Bertrand, H.; Knight, K.B.; Cirilli, S.; N. Buratti; C. Vérati; S. Nomade; P.R. Renne; N. Youbi; R. Martini; K. Allenbach; R. Neuwerth; C. Rapaille; L. Zaninetti; G. Bellieni (2004). "Synchrony of the Central Atlantic magmatic province and the Triassic-Jurassic boundary climatic and biotic crisis" (PDF). Geology. 32-11 (11): 973–976. Bibcode:2004Geo....32..973M. doi:10.1130/G20652.1. Archived from the original (PDF) on 2011-06-13.
  • Rampino, Michael R.; Stothers, Richard B. (5 Aug 1988). "Flood Basalt Volcanism During the Past 250 Million Years". Science. 241 (4866): 663–668. Bibcode:1988Sci...241..663R. doi:10.1126/science.241.4866.663. PMID 17839077.
  • Veratia, Chrystèle; Rapaille, Cédric; Férauda, Gilbert; Marzoli, Andrea; Bertrand, Hervé; Youbi, Nasrrddine (9 February 2007). "40Ar/39Ar ages and duration of the Central Atlantic Magmatic Province volcanism in Morocco and Portugal and its relation to the Triassic–Jurassic boundary". Palaeogeography, Palaeoclimatology, Palaeoecology. Triassic-Jurassic Boundary events: problems, progress, possibilities. 244 (1–4): 308–325. Bibcode:2007PPP...244..308V. doi:10.1016/j.palaeo.2006.06.033.
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External links

Atlantic Ocean

The Atlantic Ocean is the second largest of the world's oceans, with an area of about 106,460,000 square kilometers (41,100,000 square miles). It covers approximately 20 percent of Earth's surface and about 29 percent of its water surface area. It separates the "Old World" from the "New World".

The Atlantic Ocean occupies an elongated, S-shaped basin extending longitudinally between Europe and Africa to the east, and the Americas to the west. As one component of the interconnected World Ocean, it is connected in the north to the Arctic Ocean, to the Pacific Ocean in the southwest, the Indian Ocean in the southeast, and the Southern Ocean in the south (other definitions describe the Atlantic as extending southward to Antarctica). The Equatorial Counter Current subdivides it into the North(ern) Atlantic Ocean and the South(ern) Atlantic Ocean at about 8°N.Scientific explorations of the Atlantic include the Challenger expedition, the German Meteor expedition, Columbia University's Lamont-Doherty Earth Observatory and the United States Navy Hydrographic Office.

CAMP

CAMP or cAMP may stand for:

CAMP:

Cathelicidin, or Cathelicidin antimicrobial peptide

Campaign Against Marijuana Planting

CAMP, Center for Architecture and Metropolitan Planning in Prague

Central Atlantic magmatic province

CAMP (company), an Italian manufacturer of climbing equipment

cAMP:

Cyclic adenosine monophosphate (cAMP)

(+)-cis-2-Aminomethylcyclopropane carboxylic acid, a GABAA-ρ agonist

Conodont

Conodonts (Greek kōnos, "cone", + odont, "tooth") are extinct agnathan chordates resembling eels, classified in the class Conodonta. For many years, they were known only from tooth-like microfossils found in isolation and now called conodont elements. Knowledge about soft tissues remains limited. The animals are also called Conodontophora (conodont bearers) to avoid ambiguity.

Conodonts are considered index fossils, fossils used to define and identify geological periods.

Flood basalt

A flood basalt is the result of a giant volcanic eruption or series of eruptions that covers large stretches of land or the ocean floor with basalt lava. Flood basalt provinces such as the Deccan Traps of India are often called traps, after the Swedish word trappa (meaning "stairs"), 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 the past 250 million years, creating large volcanic 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.

Geology of Guyana

Guyana occurs within the northern part of the Guiana Shield.The Guiana Shield forms the northern part of the Amazonian Craton, the core of the South American continent.

Most of the geology of northern Guyana consists of Palaeoproterozoic Orosirian greenstone belts (Barama and Mazaruni Supergroups) intruded by granites. These are overlain unconformably by the Statherian Burro-Burro Group, which consist of the Muruwa Formation sandstones and Iwokrama Formation felsic volcanics. Both are intruded by granites associated with the Iwokrama Formation. Some folding occurred before these were overlain by the locally unconformable almost flat lying Roraima Group.

Major mafic sills and dykes of the Avanavero Suite intrude all of the older rocks, and are part of a Large Igneous Province (LIP). Numerous mafic dykes intruded the basement in the late Permian and Early Jurassic, associated with the start of the separation of Africa from South America. These are part of the Central Atlantic Magmatic Province (CAMP).

The northern Guiana Shield, including Guyana is separated from Southern Guiana Shield by ENE to NE trending Tumbes /Guayaquil - Tacutu Tectonic Lineament. This is a major regional pre-Cambrian shear zone / mega-shear which is believed to have been re-activated several times. At the beginning of the Mesozoic when Africa and South America started to separate this re-activated again and was involved in formation of the Takutu Graben in the lower Rupununi area and the Guyana-Suriname basin near the coast and offshore. Both these sedimentary basins have oil potential, and in 2015 significant oil was found in a deep water area off Guyana. During the Mesozoic the headwaters of the Upper Orinoco and Rio Branco flowed through the Takutu Graben via the Essequibo either to the current river mouth, to the Corentyne, the Berbice or the Canje Rivers. Tilting associated with rifting of the Atlantic Ocean resulted in complex patterns of river capture, so now the headwaters of the Rio Branco flow to the south via the Amazon, and the headwaters of the Upper Orinoco flow to the west and north. Water and sediment volumes directly flowing east are now much reduced.

Gondwana

Gondwana ( ) or Gondwanaland was a supercontinent that existed from the Neoproterozoic (about 550 million years ago) until the Jurassic (about 180 million years ago).

It was formed by the accretion of several cratons. Eventually, Gondwana became the largest piece of continental crust of the Paleozoic Era, covering an area of about 100,000,000 km2 (39,000,000 sq mi). During the Carboniferous Period, it merged with Euramerica to form a larger supercontinent called Pangaea. Gondwana (and Pangaea) gradually broke up during the Mesozoic Era. The remnants of Gondwana make up about two thirds of today's continental area, including South America, Africa, Antarctica, Australia, Indian Subcontinent and Arabia.

The formation of Gondwana began c. 800 to 650 Ma with the East African Orogeny, the collision of India and Madagascar with East Africa, and was completed c. 600 to 530 Ma with the overlapping Brasiliano and Kuunga orogenies, the collision of South America with Africa and the addition of Australia and Antarctica, respectively.

Guizhouichthyosaurus

Guizhouichthyosaurus ("Guizhou fish lizard") is an extinct genus of Ichthyosaur which existed during the lower Carnian stage of the Late Triassic in southwest China. The genus contains the single species Guizhouichthyosaurus tangae. It had been referred to the genus Shastasaurus in the past, but later study showed that it is likely distinct, since it lacks the characteristically short snout of that genus. Originally named as a species of Cymbospondylus (Cymbospondylus asiaticus) in 2002, and again in 2003 with Panjiangsaurus (Panjiangsaurus epicharis) before finally being placed within its own genus. Size estimates based on the preserved collection of 86 presacral vertebrae and 110 caudal vertebrae brings its total length to 10 metres (33 ft).

Large igneous province

A large igneous province (LIP) is an extremely large accumulation of igneous rocks, including intrusive (sills, dikes) and extrusive (lava flows, tephra deposits), arising when magma travels through the crust towards the surface. The formation of LIPs is variously attributed to mantle plumes or to processes associated with divergent plate tectonics. The formation of some of the LIPs the past 500 million years coincide in time with mass extinctions and rapid climatic changes, which has led to numerous hypotheses about the causal relationships. LIPs are fundamentally different from any other currently active volcanoes or volcanic systems.

Late Triassic

The Late Triassic is the third and final of three epochs of the Triassic Period in the geologic timescale. The Triassic-Jurassic extinction event began during this epoch and is one of the five major mass extinction events of the Earth. The corresponding series is known as the Upper Triassic. In Europe the epoch was called the Keuper, after a German lithostratigraphic group (a sequence of rock strata) that has a roughly corresponding age. The Late Triassic spans the time between 237 Ma and 201.3 Ma (million years ago). The Late Triassic is divided into the Carnian, Norian and Rhaetian ages.

Many of the first dinosaurs evolved during the Late Triassic, including Plateosaurus, Coelophysis, and Eoraptor.

The extinction event that began during the Late Triassic resulted in the disappearance of about 76% of all terrestrial and marine life species, as well as almost 20% of taxonomic families. Although the Late Triassic Epoch did not prove to be as destructive as the preceding Permian Period, which took place approximately 50 million years earlier and destroyed about 70% of land species, 57% of insect families as well as 95% of marine life, it resulted in great decreased in population sizes of many living organism populations.

Specifically, the Late Triassic had negative effects on the conodonts and ammonoid groups. These groups once served as vital index fossils, which made it possible to identify feasible life span to multiple strata of the Triassic strata. These groups were severely affected during the epoch, and became extinct soon after. Despite the large populations that withered away with the coming of the Late Triassic, many families, such as the pterosaurs, crocodiles, mammals and fish were very minimally affected. However, such families as the bivalves, gastropods, marine reptiles and brachiopods were greatly affected and many species became extinct during this time.

Mantle plume

A mantle plume is a proposed mechanism of convection of abnormally hot rock within the Earth's mantle. Because the plume head partly melts on reaching shallow depths, a plume is often invoked as the cause of volcanic hotspots, such as Hawaii or Iceland, and large igneous provinces such as the Deccan and Siberian traps. Some such volcanic regions lie far from tectonic plate boundaries, while others represent unusually large-volume volcanism near plate boundaries or in large igneous provinces.

The hypothesis of mantle plumes from depth is not universally accepted as explaining all such volcanism. It has required progressive hypothesis-elaboration leading to variant propositions such as mini-plumes and pulsing plumes. Another hypothesis for unusual volcanic regions is the "Plate model". This proposes shallower, passive leakage of magma from the mantle onto the Earth's surface where extension of the lithosphere permits it, attributing most volcanism to plate tectonic processes, with volcanoes far from plate boundaries resulting from intraplate extension.

Mid-Atlantic Ridge

The Mid-Atlantic Ridge (MAR) is a mid-ocean ridge, a divergent tectonic plate or constructive plate boundary located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. In the North Atlantic, it separates the Eurasian and North American plates, and in the South Atlantic, it separates the African and South American plates. The ridge extends from a junction with the Gakkel Ridge (Mid-Arctic Ridge) northeast of Greenland southward to the Bouvet Triple Junction in the South Atlantic. Although the Mid-Atlantic Ridge is mostly an underwater feature, portions of it have enough elevation to extend above sea level. The section of the ridge that includes Iceland is known as the Reykjanes Ridge. The ridge has an average spreading rate of about 2.5 centimetres (0.98 in) per year.

Noronha hotspot

Noronha hotspot is a hypothesized hotspot in the Atlantic Ocean. It has been proposed as the candidate source for volcanism in the Fernando de Noronha archipelago of Brazil, as well as of other volcanoes also in Brazil and even the Bahamas and the Central Atlantic Magmatic Province.

The presence of a mantle plume is controversial owing to equivocal seismic tomography images of the mantle and the inconsistent age progression in the volcanoes, especially the Brazilian ones.

North Mountain (Nova Scotia)

North Mountain (French: Montagne du Nord; Gaelic: Beinn a Tuath) is a narrow southwest-northeast trending volcanic ridge on the mainland portion of southwestern Nova Scotia, stretching from Brier Island to Cape Split. It forms the northern edge of the Annapolis Valley along the shore of the Bay of Fundy. Together with South Mountain, the two ranges form the Annapolis Highlands region.North Mountain rises dramatically from the valley floor and tapers somewhat more gradually to the north and west where it meets the coast, although many parts of this coast have vertical cliffs rising higher than 30 metres, most notably at Cape Split. A break occurs at Digby Gut where a gap in the mountain ridge is filled by a deep tidal channel separating the eastern end of the mountain from Digby Neck.

The highest point on the ridge is at Mount Rose in Annapolis County, north of Lawrencetown.

Taylorsville Basin

The Taylorsville Basin is an early Mesozoic rift basin that either outcrops, or is present beneath younger deposits, in Virginia and Maryland. It is part of the chain of rift basins along the eastern part of North America that formed during the break-up of the Pangaea supercontinent. It is filled by a fluvial and lacustrine sedimentary sequence of the Newark Supergroup.

The Palisades (Hudson River)

The Palisades, also called the New Jersey Palisades or the Hudson River Palisades, are a line of steep cliffs along the west side of the lower Hudson River in Northeastern New Jersey and Southeastern New York in the United States. The cliffs stretch north from Jersey City about 20 miles (32 km) to near Nyack, New York, and visible at Haverstraw, New York. They rise nearly vertically from near the edge of the river, and are about 300 feet (90 m) high at Weehawken, increasing gradually to 540 feet (160 m) high near their northern terminus. North of Fort Lee, the Palisades are part of Palisades Interstate Park and are a National Natural Landmark.The Palisades are among the most dramatic geologic features in the vicinity of New York City, forming a canyon of the Hudson north of the George Washington Bridge, as well as providing a vista of the Manhattan skyline. They sit in the Newark Basin, a rift basin located mostly in New Jersey.

Palisade is derived from the same root as the word pale, ultimately from the Latin word palus, meaning stake. A "palisade" is, in general, a defensive fence or wall made up of wooden stakes or tree trunks. The Lenape called the cliffs "rocks that look like rows of trees", a phrase that became "Weehawken", the name of a town in New Jersey that sits at the top of the cliffs across from Midtown Manhattan.

Triassic

The Triassic ( try-ASS-ik) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.9 million years ago (Mya), to the beginning of the Jurassic Period 201.3 Mya. The Triassic is the first and shortest period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events.Triassic began in the wake of the Permian–Triassic extinction event, which left the Earth's biosphere impoverished; it was well into the middle of the Triassic before life recovered its former diversity. Therapsids and archosaurs were the chief terrestrial vertebrates during this time. A specialized subgroup of archosaurs, called dinosaurs, first appeared in the Late Triassic but did not become dominant until the succeeding Jurassic Period.The first true mammals, themselves a specialized subgroup of therapsids, also evolved during this period, as well as the first flying vertebrates, the pterosaurs, who, like the dinosaurs, were a specialized subgroup of archosaurs. The vast supercontinent of Pangaea existed until the mid-Triassic, after which it began to gradually rift into two separate landmasses, Laurasia to the north and Gondwana to the south.

The global climate during the Triassic was mostly hot and dry, with deserts spanning much of Pangaea's interior. However, the climate shifted and became more humid as Pangaea began to drift apart. The end of the period was marked by yet another major mass extinction, the Triassic–Jurassic extinction event, that wiped out many groups and allowed dinosaurs to assume dominance in the Jurassic.

The Triassic was named in 1834 by Friedrich von Alberti, after the three distinct rock layers (tri meaning "three") that are found throughout Germany and northwestern Europe—red beds, capped by marine limestone, followed by a series of terrestrial mud- and sandstones—called the "Trias".

Triassic–Jurassic extinction event

The Triassic–Jurassic extinction event marks the boundary between the Triassic and Jurassic periods, 201.3 million years ago, and is one of the major extinction events of the Phanerozoic eon, profoundly affecting life on land and in the oceans. In the seas, a whole class (conodonts) and 23–34% of marine genera disappeared. On land, all archosaurs other than crocodylomorphs (Sphenosuchia and Crocodyliformes) and Avemetatarsalia (pterosaurs and dinosaurs), some remaining therapsids, and many of the large amphibians became extinct.

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