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27-540: The Alert Bay Volcanic Belt is a heavily eroded Neogene volcanic belt in northern Vancouver Island , British Columbia , Canada . The belt is now north of the Nootka Fault , but may have been directly above the fault at the time it last erupted. Eruptions of basaltic to rhyolitic volcanoes and hypabyssal rocks of the Alert Bay Volcanic Belt are probably linked with the subducted margin flanked by

54-466: A stub . You can help Misplaced Pages by expanding it . Neogene During this period, mammals and birds continued to evolve into modern forms, while other groups of life remained relatively unchanged. The first humans ( Homo habilis ) appeared in Africa near the end of the period. Some continental movements took place, the most significant event being the connection of North and South America at

81-795: A decrease in global temperatures termed the Late Miocene Cooling (LMC) ensued, driven by decreases in carbon dioxide concentrations. During the Pliocene, from about 5.3 to 2.7 Ma, another warm interval occurred, being known as the Pliocene Warm Interval (PWI), interrupting the longer-term cooling trend. The Pliocene Thermal Maximum (PTM) occurred between 3.3 and 3.0 Ma. During the Pliocene, Green Sahara phases of wet conditions in North Africa were frequent and occurred about every 21 kyr, being especially intense when Earth's orbit's eccentricity

108-545: A positive feedback as sea levels dropped and the ITF diminished and further limited the heat transported southward by the Leeuwin Current . By the end of the period the first of a series of glaciations of the current Ice Age began. Marine and continental flora and fauna have a modern appearance. The reptile group Choristodera went extinct in the early part of the period, while the amphibians known as Allocaudata disappeared at

135-595: A zonal and meridional level. In southern Africa, summer and winter precipitation zones shifted poleward by ∼1°, while precipitation was reduced by about 0.5 mm/day. The coast of Ecuador became drier. Subtropical South Africa became dominated by fynbos and Afrotemperate forest vegetation. Carbon dioxide concentration during the Middle Pliocene has been estimated at around 400 ppmv from C/ C ratio in organic marine matter and stomatal density of fossilised leaves, although lower estimates of between 330 and 394 ppm over

162-475: Is due to the comparatively fine divisibility of time units as time approaches the present, and due to geological preservation that causes the youngest sedimentary geological record to be preserved over a much larger area and to reflect many more environments than the older geological record. By dividing the Cenozoic Era into three (arguably two) periods ( Paleogene , Neogene, Quaternary ) instead of seven epochs,

189-686: Is subdivided into two ages: The Miocene Epoch is subdivided into six ages: In different geophysical regions of the world, other regional names are also used for the same or overlapping ages and other timeline subdivisions. The terms Neogene System (formal) and Upper Tertiary System (informal) describe the rocks deposited during the Neogene Period . The continents in the Neogene were very close to their current positions. The Isthmus of Panama formed, connecting North and South America . The Indian subcontinent continued to collide with Asia , forming

216-596: The Explorer and Juan de Fuca plates at the Cascadia subduction zone . The Alert Bay Volcanic Belt is poorly studied, but appears to have been active in Miocene to Pliocene time. No Holocene eruptions are known, and volcanic activity in the belt has most likely ceased. The features within the belt include: This article about a location on the Coast of British Columbia , Canada is

243-507: The Himalayas . Sea levels fell, creating land bridges between Africa and Eurasia and between Eurasia and North America. The global climate became more seasonal and continued an overall drying and cooling trend which began during the Paleogene . The Early Miocene was relatively cool; Early Miocene mid-latitude seawater and continental thermal gradients were already very similar to those of

270-771: The Isthmus of Panama , late in the Pliocene. This cut off the warm ocean currents from the Pacific to the Atlantic Ocean, leaving only the Gulf Stream to transfer heat to the Arctic Ocean . The global climate cooled considerably throughout the Neogene, culminating in a series of continental glaciations in the Quaternary Period that followed. In ICS terminology, from upper (later, more recent) to lower (earlier): The Pliocene Epoch

297-531: The mammoths and woolly rhinoceros were common in Pliocene . With lower levels of CO 2 in the atmosphere, C 4 plants expanded and reached ecological dominance in grasslands during the last 10 million years. Also Asteraceae (daisies) went through a significant adaptive radiation . Eucalyptus fossil leaves occur in the Miocene of New Zealand, where the genus is not native today, but have been introduced from Australia. The Neogene traditionally ended at

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324-631: The East Asian Summer Monsoon (EASM) did not extend as far into the interior of East Asia as it does today, causing a much drier climate to occur in the Chinese Loess Plateau relative to the present day. In the Nihewan Basin , a stable and warm climate predominated from 3.58 Ma to 3.31 Ma. From 3.31 Ma to 3.10 Ma, the warmth continued but with greater instability, with three major cool events occurring during this interval. After 3.10 Ma,

351-756: The Gelasian Age, which was formerly considered part of the Neogene Period and Pliocene Epoch. Thus the Neogene Period ends bounding the succeeding Quaternary Period at 2.58 Mya. Middle Pliocene Warm Period The Mid-Piacenzian Warm Period ( mPWP ) (prior to 2009 known as the Middle Pliocene Warm Period ), or the Pliocene Thermal Maximum , was an interval of warm climate during the Pliocene epoch that lasted from 3.3 to 3.0 million years ago (Ma). The global average temperature in

378-741: The Neogene and the Pliocene end at 2.58 Ma, that the Gelasian be transferred to the Pleistocene, and the Quaternary be recognized as the third period in the Cenozoic, citing key changes in Earth's climate, oceans, and biota that occurred 2.58 Ma and its correspondence to the Gauss-Matuyama magnetostratigraphic boundary . In 2006 ICS and INQUA reached a compromise that made Quaternary a sub-era, subdividing Cenozoic into

405-581: The Yermak Plateau in the Arctic Ocean shows that the thermophilic and moist boreal Tsuga-Thuja- Cupressaceae -Betula-Ilex community became dominant in the Arctic during the mPWP. At the lagerstatte of Camp del Ninots in northeastern Spain, a MAT of 14.3 ± 2.6°C and a mean annual precipitation (MAP) of 846.8 ± 165.4 mm prevailed. The East Asian Winter Monsoon (EAWM) strengthened during the mPWP. The influence of

432-670: The course of the whole mPWP and 391 ppm in the KM5c interglacial, during the warmest phase of the mPWP, have been given. The mPWP is considered a potential analogue of future climate. The intensity of the sunlight reaching the Earth, the global geography, and carbon dioxide concentrations were similar to present. Furthermore, many mid-Pliocene species are extant, helping calibrate paleotemperature proxies . Model simulations of mid-Pliocene climate produce warmer conditions at middle and high latitudes, as much as 10–20 °C warmer than today above 70°N. They also indicate little temperature variation in

459-499: The dominant terrestrial vertebrates, and took many forms as they adapted to various habitats. An explosive radiation of ursids took place at the Miocene-Pliocene boundary. The first hominins , the ancestors of humans, may have appeared in southern Europe and migrated into Africa. The first humans (belonging to the species Homo habilis ) appeared in Africa near the end of the period. About 20 million years ago gymnosperms in

486-405: The end of it. Neogene also marked the end of the reptilian genera Langstonia and Barinasuchus , terrestrial predators that were the last surviving members of Sebecosuchia , a group related to crocodiles. The oceans were dominated by large carnivores like megalodons and livyatans , and 19 million years ago about 70% of all pelagic shark species disappeared. Mammals and birds continued to be

513-603: The end of the Pliocene Epoch, just before the older definition of the beginning of the Quaternary Period; many time scales show this division. However, there was a movement amongst geologists (particularly marine geologists ) to also include ongoing geological time (Quaternary) in the Neogene, while others (particularly terrestrial geologists) insist the Quaternary to be a separate period of distinctly different record. The somewhat confusing terminology and disagreement amongst geologists on where to draw what hierarchical boundaries

540-451: The form of some conifer and cycad groups started to diversify and produce more species due to the changing conditions. In response to the cooler, seasonal climate, tropical plant species gave way to deciduous ones and grasslands replaced many forests. Grasses therefore greatly diversified, and herbivorous mammals evolved alongside it, creating the many grazing animals of today such as horses , antelope , and bison . Ice age mammals like

567-527: The mid-Pliocene was 2–3 °C higher than today, global sea level 25 meters higher, and the Northern Hemisphere ice sheet was ephemeral before the onset of extensive glaciation over Greenland that occurred in the late Pliocene around 3 Ma. Near-surface permafrost extent was substantially lower relative to the present. Global precipitation was marginally increased by 0.09 mm/yr according to CCSM4 simulations. Annual Northern Hemisphere Hadley circulation

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594-595: The old classical Tertiary and Quaternary, a compromise that was rejected by International Union of Geological Sciences because it split both Neogene and Pliocene in two. Following formal discussions at the 2008 International Geological Congress in Oslo, Norway, the ICS decided in May 2009 to make the Quaternary the youngest period of the Cenozoic Era with its base at 2.58 Mya and including

621-616: The periods are more closely comparable to the duration of periods in the Mesozoic and Paleozoic Eras. The International Commission on Stratigraphy (ICS) once proposed that the Quaternary be considered a sub-era (sub-erathem) of the Neogene, with a beginning date of 2.58 Ma, namely the start of the Gelasian Stage . In the 2004 proposal of the ICS, the Neogene would have consisted of the Miocene and Pliocene Epochs. The International Union for Quaternary Research (INQUA) counterproposed that

648-713: The present. During the Middle Miocene , Earth entered a warm phase known as the Middle Miocene Climatic Optimum (MMCO), which was driven by the emplacement of the Columbia River Basalt Group . Around 11 Ma, the Middle Miocene Warm Interval gave way to the much cooler Late Miocene. The ice caps on both poles began to grow and thicken, a process enhanced by positive feedbacks from increased formation of sea ice. Between 7 and 5.3 Ma,

675-527: The region's climate cooled significantly. In the Qaidam Basin, annual precipitation was about ten times higher than in the present, and it varied in 20-kyr precessional cycles and was likely related to the fluctuation of the EASM in response to Antarctic ice sheet dynamics and insolation forcing. The Kuroshio Current Extension (KCE) shifted northwards. The South Asian Summer Monsoon (SASM) became strengthened on both

702-539: Was high. The PWI had similar levels of atmospheric carbon dioxide to contemporary times and is often seen as an analogous climate to the projected climate of the near future as a result of anthropogenic global warming . Towards the end of the Pliocene, decreased heat transport towards the Antarctic resulting from a weakening of the Indonesian Throughflow (ITF) cooled the Earth, a process that exacerbated itself in

729-487: Was weakened, but annual Southern Hemisphere Hadley circulation was enhanced. As during the Quaternary glaciation , glacial-interglacial cycles existed during the mPWP and it was not a uniform and stable climatic interval. Polar amplification during the mPWP was considerable. The mean annual temperature (MAT) of eastern interior Alaska was about 7-9 °C higher than its present day MAT of -6.4 °C. Palynological evidence from

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