Caribbean large igneous province

The Caribbean large igneous province (CLIP) consists of a major flood basalt, which created this large igneous province (LIP). It is the source of the current large eastern Pacific oceanic plateau, of which the Caribbean-Colombian oceanic plateau is the tectonized remnant. The deeper levels of the plateau have been exposed on its margins at the North and South American plates. The volcanism took place between 139 and 69 million years ago, with the majority of activity appearing to lie between 95 and 88 Ma. The plateau volume has been estimated as on the order of 4 x 106 km³. It has been linked to the Galápagos hotspot.[1]

Proto-Caribbean Seaway

Divergence between the North American and South American Plates began to create oceanic crust off Colombia's Pacific coast by the end of the Jurassic (150 Ma). This divergence, which continued until at least 66 Ma, first resulted in a "proto-Caribbean spreading ridge" between these plates flanked by a perpendicular transform zone on its Pacific side. By 135–130 Ma, the subduction of the Farallon Plate had begun along this transform zone, effectively modifying it into a subduction zone and beginning the creation of the Great Caribbean Arch. This arch was formed around 120-115 Ma but must have been intersected by the Caribbean spreading ridge until 66 Ma. Hence, the Farallon Plate fed the spreading zone and later became the Caribbean Plate.[2]

LIP formation

CLIP formed as a large igneous province and now forms a thickened zone of oceanic crust between the North American and South American Plates.[3] In some places the oceanic crust is 2–3 times as thick as normal oceanic crust (15–20 km (9.3–12.4 mi) vs 7 km (4.3 mi). Its composition is similar to that of the Ontong Java Plateau.[4]

Geochemical and geochronological evidences clearly indicate that the Galápagos hotspot initiated the formation of the CLIP 95-90 Ma in the eastern Pacific. From there it move north-east with the Farallon Plate between the two American plates until it collided with a volcanic arc, the Greater Antilles 60 million years later. Fragments of this voyage is preserved in accreted seamounts along the Central American coast and the Cocos and Carnegie Ridges. Isotopic profiles of Galápagos rocks can be matched with those from CLIP rocks.[3]

92–63 Ma 40Ar/39Ar ages have been reported for the Curaçao Lava Formation and 94–83 ma for the Dumisseau Formation in Haiti, dating both locations back to the original LIP formation 94 Ma. CLIP volcanism originates from the plume-like source distinct from a MORB (mid-ocean ridge basalt) mantle. The long duration of CLIP volcanism can be explained by the interaction between a plume and the Greater Antilles subduction zone.[5]

The margins of the CLIP have been uplifted and are exposed above sea level, which makes it unique among oceanic plateaus. It stretches 2,500 km (1,600 mi) east to west and 1,300 km (810 mi) north to south.[6][7] The CLIP is composed of irregularly thickened (up to 20 km (12 mi)) oceanic crust of the Caribbean Plate and the deformed associated magmatic terranes obducted onto the Pacific coasts of northern South America, Central America, and the Antilles. One of the least deformed parts is Gorgona Island off Colombia's Pacific coast.[6][7][8]

The CLIP was created during three phases of eruptions dating between the Aptian and the Maastrichtian: a first phase 124–112 Ma; the main magma production phase 94–83 Ma; and an 80–72 Ma phase. The youngest igneous rocks, in the Dominican Republic and Costa Rica, are from 63 Ma. That the CLIP originated in the Pacific is obvious because fragments of oceanic crust accreted to the margins of the Caribbean, for example on Hispaniola and Puerto Rico, contain fauna of Pacific provenance.[9]

The Farallon Plate's eastward movement forced the northern half of the CLIP into the ocean basin that had opened between North and South America starting in the Jurassic. However, the mechanisms causing the NE movement of the CLIP remains unclear, especially considering the subduction in the Costa Rica-Panama arc initiated during the Campanian (83–72 Ma). The Galápagos hotspot is probably responsible for the main plume-related magmatic event 90 Ma, whilst the 76 Ma and 55 Ma event are related to lithospheric thinning in the Central Caribbean.[9]

40Ar/39Ar dating have determined that the main magmatism occurred 95 to 83 million years ago (Ma) while a second pulse occurred 81-69 Ma. Around 86 Ma the arrival of a large plume initiated the Galápagos hotspot which resulted in volcanism over large parts of the Caribbean Plate and north-west South America. Renewed volcanism about 75 Ma has been attributed to either the Galápagos hotspot, thinning of the lithosphere coupled with associated melting and upwelling of plume-head material, or both.[6]

Seismic and geochemical analyses, on the other hand, suggest the CLIP consists of several oceanic plateaus and palaeo-hotspot tracks formed 139-83 Ma some of which have been overprinted by later magmatism.[6][10] If these first volcanic activities were generated by the Galápagos hotspot, it would make it the oldest still active hotspot on Earth.[10]

See also

References

Notes

  1. ^ Courtillot & Renne 2003; Hoernle, Hauff & van den Bogaard 2004
  2. ^ Serrano et al. 2011, 5.2. Geodynamic setting during the formation of the CLIP, p. 332; Fig. 8, p. 333
  3. ^ a b Loewen et al. 2013, Introduction, pp. 4241–4242
  4. ^ Hauff et al. 2000, 2. Geological background, pp. 248–249
  5. ^ Loewen et al. 2013, Conclusions, pp. 4256–4257
  6. ^ a b c d Courtillot & Renne 2003, Introduction, p. 697
  7. ^ a b Geldmacher et al. 2003, Introduction
  8. ^ Serrano et al. 2011, Introduction, pp. 324–325
  9. ^ a b Escuder-Viruete et al. 2011, The Caribbean large igneous province, p. 309
  10. ^ a b Courtillot & Renne 2003, p. 700

Sources

Andean orogeny

The Andean orogeny (Spanish: Orogenia andina) is an ongoing process of orogeny that began in the Early Jurassic and is responsible for the rise of the Andes mountains. The orogeny is driven by a reactivation of a long-lived subduction system along the western margin of South America. On a continental scale the Cretaceous (90 Ma) and Oligocene (30 Ma) were periods of re-arrangements in the orogeny. Locally the details of the nature of the orogeny varies depending on the segment and the geological period considered.

Anoxic event

Oceanic anoxic events or anoxic events (anoxia conditions) were intervals in the Earth's past where portions of oceans became depleted in oxygen (O2) at depths over a large geographic area. During some of these events, euxinia, waters that contained hydrogen sulfide, H2S, developed. Although anoxic events have not happened for millions of years, the geological record shows that they happened many times in the past. Anoxic events coincided with several mass extinctions and may have contributed to them. These mass extinctions include some that geobiologists use as time markers in biostratigraphic dating. Many geologists believe oceanic anoxic events are strongly linked to slowing of ocean circulation, climatic warming, and elevated levels of greenhouse gases. Researchers have proposed enhanced volcanism (the release of CO2) as the "central external trigger for euxinia".

Caribbean Plate

The Caribbean Plate is a mostly oceanic tectonic plate underlying Central America and the Caribbean Sea off the north coast of South America.

Roughly 3.2 million square kilometers (1.2 million square miles) in area, the Caribbean Plate borders the North American Plate, the South American Plate, the Nazca Plate and the Cocos Plate. These borders are regions of intense seismic activity, including frequent earthquakes, occasional tsunamis, and volcanic eruptions.

Cenomanian-Turonian boundary event

The Cenomanian-Turonian boundary event, or the Cenomanian-Turonian extinction event, the Cenomanian-Turonian anoxic event (OAE 2), and referred also as the Bonarelli Event, was one of two anoxic extinction events in the Cretaceous period. (The other being the earlier Selli Event, or OAE 1a, in the Aptian.) The OAE 2 occurred approximately 91.5 ± 8.6 Ma, though other estimates are given as 93–94 Ma. The Cenomanian-Turonian boundary has recently been refined to 93.9 ± 0.15 Ma There was a large carbon disturbance during this time period. However, apart from the carbon cycle disturbance, there were also large disturbances in the oxygen and sulfur cycles of the ocean.

The event brought about the extinction of the Pliosauridae, and most Ichthyosauria. Coracoids of Maastrichtian age were once interpreted by some authors as belonging to ichthyosaurs, but these have since been interpreted as plesiosaur elements instead. Although the cause is still uncertain, the result starved the Earth's oceans of oxygen for nearly half a million years, causing the extinction of approximately 27 percent of marine invertebrates, including certain planktic and benthic foraminifera, mollusks, bivalves, dinoflagellates and calcareous nannofossils. The global environmental disturbance that resulted in these conditions increased atmospheric and oceanic temperatures. Boundary sediments show an enrichment of trace elements, and contain elevated δ13C values.The Cenomanian and Turonian stages were first noted by D'Orbigny between 1843 and 1852. The global type section for this boundary is located in the Bridge Creek Limestone Member of the Greenhorn formation near Pueblo, Colorado, which are bedded with the Milankovitch orbital signature. Here, a positive carbon-isotope event is clearly shown, although none of the characteristic, organic-rich black shale is present. It has been estimated that the isotope shift lasted approximately 850 kyrs longer than the black shale event, which may be the cause of this anomaly in the Colorado type-section. A significantly expanded OAE2 interval from southern Tibet documents a complete, more detailed, and finer-scale structures of the positive carbon isotope excursion that contains multiple shorter-term carbon isotope stages amounting to a total duration of 820±25 kyrs.The boundary is also known as the Bonarelli event because of 1- to 2-meter layer of thick black shale that marks the boundary and was first studied by Guido Bonarelli in 1891. It is characterized by interbedded black shale, chert and radiolarian sands is estimated to span a 400,000-year interval. Planktic foraminifera do not exist in this Bonarelli level, and the presence of radiolarians in this section indicates relatively high productivity and an availability of nutrients.

One possible cause of this event is sub-oceanic volcanism, possibly the Caribbean large igneous province, with increased activity approximately 500,000 years earlier. During that period, the rate of crustal production reached its highest level for 100 million years. This was largely caused by the widespread melting of hot mantle plumes under the oceans at the base of the lithosphere. This resulted in the thickening of the oceanic crust in the Pacific and Indian Oceans. This volcanism would have sent large quantities of carbon dioxide into the atmosphere, leading to global warming. Within the oceans, the emission of SO2, H2S, CO2, and halogens would have increased the acidity of the water, causing the dissolution of carbonate, and a further release of carbon dioxide. When the volcanic activity declined, this run-away greenhouse effect would have likely been put into reverse. The increased CO2 content of the oceans could have increased organic productivity in the ocean surface waters. The consumption of this newly abundant organic life by aerobic bacteria would produce anoxia and mass extinction. The resulting elevated levels of carbon burial would account for the black shale deposition in the ocean basins.

Chortis Block

The Chortis Block is a 400–600 km (250–370 mi)-wide continental fragment in Central America (Honduras, Nicaragua, El Salvador, Guatemala, and the off-shore Nicaragua Rise) located in the northwest corner of the oceanic Caribbean Plate.

Curaçao

Curaçao ( KEWR-əss-oh, -⁠ow, -⁠OH, -⁠OW, Dutch: [kyraːˈsʌu, kur-] (listen); Papiamento: Kòrsou [ˈkɔrsɔu̯]) is a Lesser Antilles island in the southern Caribbean Sea and the Dutch Caribbean region, about 65 km (40 mi) north of the Venezuelan coast. It is a constituent country (Dutch: land) of the Kingdom of the Netherlands.The country was formerly part of the Curaçao and Dependencies colony in 1815–1954 and later the Netherlands Antilles in 1954–2010, as "Island Territory of Curaçao" (Dutch: Eilandgebied Curaçao, Papiamento: Teritorio Insular di Kòrsou) and is now formally called the Country of Curaçao (Dutch: Land Curaçao, Papiamento: Pais Kòrsou). It includes the main island of Curaçao and the much smaller, uninhabited island of Klein Curaçao ("Little Curaçao"). Curaçao has a population of 149,600 (July 2017 est.) and an area of 444 km2 (171 sq mi); its capital is Willemstad.

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.

Geography of Aruba

Aruba is an island in the south of the Caribbean in the Caribbean Sea. It is westernmost island of the ABC Islands and of the Leeward Antilles. It is located 25 km north of the coast of Venezuela and 68 km northwest of Curaçao. The island has a total area of 193 km2 (75 sq mi) and a coast line of 68.5 km (42.6 mi). Mount Jamanota of 188 m (617 ft) is the highest point.

Politically, Aruba is a constituent country of the Kingdom of the Netherlands. Oranjestad is the largest settlement with a population of 32,748.

Hotspot (geology)

In geology, the places known as hotspots or hot spots are volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle. Their position on the Earth's surface is independent of tectonic plate boundaries. There are two hypotheses that attempt to explain their origins. One suggests that hotspots are due to mantle plumes that rise as thermal diapirs from the core–mantle boundary. The other hypothesis is that lithospheric extension permits the passive rising of melt from shallow depths. This hypothesis considers the term "hotspot" to be a misnomer, asserting that the mantle source beneath them is, in fact, not anomalously hot at all. Well-known examples include the Hawaii, Iceland and Yellowstone hotspots.

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.

List of largest volcanic eruptions

In a volcanic eruption, lava, volcanic bombs and ash, and various gases are expelled from a volcanic vent and fissure. While many eruptions only pose dangers to the immediately surrounding area, Earth's largest eruptions can have a major regional or even global impact, with some affecting the climate and contributing to mass extinctions. Volcanic eruptions can generally be characterized as either explosive eruptions, sudden ejections of rock and ash, or effusive eruptions, relatively gentle outpourings of lava. A separate list is given below for each type.

There have probably been many such eruptions during Earth's history beyond those shown in these lists. However erosion and plate tectonics have taken their toll, and many eruptions have not left enough evidence for geologists to establish their size. Even for the eruptions listed here, estimates of the volume erupted can be subject to considerable uncertainty.

Magma supply rate

The magma supply rate measures the production rate of magma at a volcano. Global magma production rates on Earth are about 20–25 cubic kilometres per year (4.8–6.0 cu mi/a).

Paleocene

The Paleocene, ( PAL-ee-ə-seen, -⁠ee-oh-, PAY-lee-, -⁠lee-oh-) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name derives from the combining of the Ancient Greek palæo- meaning "old" and the Eocene Epoch (which succeeds the Paleocene), translating to "the old part of the Eocene".

The epoch is bracketed by two major events in Earth's history: the K-Pg extinction event and the Paleocene–Eocene thermal maximum. The K-Pg extinction event, brought on by an asteroid impact and an ensuing impact winter, marked the beginning of the Paleocene and killed off 75% of life on Earth, most famously the non-avian dinosaurs. The end of the epoch was marked by the Paleocene–Eocene thermal maximum, which was a major climatic event wherein about 2,500–4,500 gigatons of carbon was released into the atmosphere and ocean systems en masse, causing a spike in global temperatures and ocean acidification.

The Paleocene continued many geological processes initiated in Mesozoic, and the continents continued moving towards their present positions. The Northern Hemisphere continents were still connected via some land bridges as well as the Southern Hemisphere continents, the Rocky Mountains were being uplifted, the Americas had not yet joined, and the Indian Plate had begun its collision with Asia. In the oceans, the thermohaline circulation probably was much different than it is today, with downwellings occurring in the North Pacific rather than the North Atlantic, and water density was mainly controlled by salinity rather than temperature.

The extinction event caused a floral and faunal turnover of species, with previously abundant species being replaced by previously uncommon ones. With a global average temperature of about 24–25 °C (75–77 °F), compared to 14 °C (57 °F) in more recent times, the Earth had a greenhouse climate without permanent ice sheets at the poles. As such, there were forests worldwide–including at the poles–with low species richness in regards to plant life, populated by mainly small creatures which were rapidly evolving to take advantage of the recently-emptied Earth. Though some animals attained enormous size, most remained rather small. The forests grew quite dense in the general absence of large herbivores. Mammals proliferated in the Paleocene, and the earliest placentals and marsupials are recorded from this time, but most Paleocene taxa have ambiguous affinities. In the seas, ray-finned fish rose to dominate open ocean and reef ecosystems.

Pilavo

Pilavo is a volcano in Ecuador. It is more a shield volcano than a stratovolcano and was active about 20,000/40,000 - 8,000 years before present with basaltic andesite-andesite lava flows.

Western Interior Seaway anoxia

Three Western Interior Seaway anoxic events occurred during the Cretaceous in the shallow inland seaway that divided North America in two island continents, Appalachia and Laramidia (see map). During these anoxic events much of the water column was depleted in dissolved oxygen. While anoxic events impact the world's oceans, Western Interior Seaway anoxic events exhibit a unique paleoenvironment compared to other basins. The notable Cretaceous anoxic events in the Western Interior Seaway mark the boundaries at the Aptian-Albian, Cenomanian-Turonian, and Coniacian-Santonian stages, and are identified as Oceanic Anoxic Events I, II, and III respectively. The episodes of anoxia came about at times when very high sea levels coincided with the nearby Sevier orogeny that affected Laramidia to the west and Caribbean large igneous province to the south, which delivered nutrients and oxygen-adsorbing compounds into the water column.

Most anoxic events are recognized using the 13C isotope as a proxy to indicate total organic carbon preserved in sedimentary rocks. If there is very little oxygen, then organic material that settles to the bottom of the water column will not be degraded as readily compared to normal oxygen settings and can be incorporated into the rock. 13Corganic is calculated by comparing the amount of 13C to a carbon isotope standard, and using multiple samples can track changes (δ) in organic carbon content through rocks over time, forming a δ13Corganic curve. The δ13Corganic, as a result, serves as a benthic oxygen curve.

The excellent organic carbon preservation brought about by these successive anoxic events makes Western Interior Seaway strata some of the richest source rocks for oil and gas.

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