The Miocene ( / ˈ m aɪ . ə s iː n , - oʊ -/ MY -ə-seen, -oh- ) is the first geological epoch of the Neogene Period and extends from about 23.03 to 5.333 million years ago (Ma). The Miocene was named by Scottish geologist Charles Lyell ; the name comes from the Greek words μείων ( meíōn , "less") and καινός ( kainós , "new") and means "less recent" because it has 18% fewer modern marine invertebrates than the Pliocene has. The Miocene followed the Oligocene and preceded the Pliocene.
175-701: As Earth went from the Oligocene through the Miocene and into the Pliocene, the climate slowly cooled towards a series of ice ages . The Miocene boundaries are not marked by distinct global events but by regionally defined transitions from the warmer Oligocene to the cooler Pliocene Epoch. During the Early Miocene, Afro-Arabia collided with Eurasia, severing the connection between the Mediterranean and Indian Oceans, and allowing
350-454: A proglacial lake above the valley created by an ice dam as a result of the 1815 eruption of Mount Tambora , which threatened to cause a catastrophic flood when the dam broke. Perraudin attempted unsuccessfully to convert his companions to his theory, but when the dam finally broke, there were only minor erratics and no striations, and Venetz concluded that Perraudin was right and that only ice could have caused such major results. In 1821 he read
525-590: A sea surface temperature (SST) drop of approximately 6 °C in the North Atlantic. The drop in benthic foraminiferal δO values was most noticeable in the waters around Antarctica, suggesting cooling was most intense there. Around this time the Mi3b glacial event (a massive expansion of Antarctic glaciers) occurred. The East Antarctic Ice Sheet (EAIS) markedly stabilised following the MMCT. The intensification of glaciation caused
700-415: A clade of large terrestrial predatory crocodyliformes distantly related to modern crocodilians, from which they likely diverged over 180 million years ago, are known from the Miocene of South America. The last Desmostylians thrived during this period before becoming the only extinct marine mammal order. The pinnipeds , which appeared near the end of the Oligocene, became more aquatic. A prominent genus
875-808: A consequence of the Han–Xiongnu War from 133 BC to 89 AD, the Tarim Basin region of Xinjiang in Northwest China, including the Saka-founded oasis city-state of Khotan and Kashgar, fell under Han Chinese influence, beginning with the reign of Emperor Wu (r. 141–87 BC) of the Han dynasty . Much like the neighboring people of the Kingdom of Khotan , people of Kashgar, the capital of the Shule Kingdom , spoke Saka , one of
1050-613: A decoherence of sediment deposition from the 405 kyr eccentricity cycle. The MMWI ended about 11 Ma, when the Late Miocene Cool Interval (LMCI) started. A major but transient warming occurred around 10.8-10.7 Ma. During the Late Miocene, the Earth's climate began to display a high degree of similarity to that of the present day. The 173 kyr obliquity modulation cycle governed by Earth's interactions with Saturn became detectable in
1225-520: A fertilizer that causes massive algal blooms that pulls large amounts of CO 2 out of the atmosphere. This in turn makes it even colder and causes the glaciers to grow more. In 1956, Ewing and Donn hypothesized that an ice-free Arctic Ocean leads to increased snowfall at high latitudes. When low-temperature ice covers the Arctic Ocean there is little evaporation or sublimation and the polar regions are quite dry in terms of precipitation, comparable to
1400-649: A flood, We went out among their cities, We tore down the idol-temples, We shat on the Buddha's head! In Turkic: kälginläyü aqtïmïz kändlär üzä čïqtïmïz furxan ävin yïqtïmïz burxan üzä sïčtïmïz The Buddhist Uyghurs of the Kingdom of Qocho and Turfan embraced Islam after conversion at the hands of the Muslim Chagatai Khizr Khwaja. Kara Del was a Mongolian ruled and Uighur populated Buddhist Kingdom. The Muslim Chagatai Khan Mansur invaded and used
1575-557: A geologist and professor of forestry at an academy in Dreissigacker (since incorporated in the southern Thuringian city of Meiningen ), adopted Esmark's theory. In a paper published in 1832, Bernhardi speculated about the polar ice caps once reaching as far as the temperate zones of the globe. In Val de Bagnes , a valley in the Swiss Alps , there was a long-held local belief that the valley had once been covered deep in ice, and in 1815
1750-618: A good analogue for future warmer climates caused by anthropogenic global warming , with this being especially true of the global climate during the Middle Miocene Climatic Optimum (MMCO), because the last time carbon dioxide levels were comparable to projected future atmospheric carbon dioxide levels resulting from anthropogenic climate change was during the MMCO. The Ross Sea margin of the East Antarctic Ice Sheet (EAIS)
1925-408: A local chamois hunter called Jean-Pierre Perraudin attempted to convert the geologist Jean de Charpentier to the idea, pointing to deep striations in the rocks and giant erratic boulders as evidence. Charpentier held the general view that these signs were caused by vast floods, and he rejected Perraudin's theory as absurd. In 1818 the engineer Ignatz Venetz joined Perraudin and Charpentier to examine
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#17328379718972100-577: A major expansion of Antarctic glaciers. This severed the connection between the Indian Ocean and the Mediterranean Sea and formed the present land connection between Afro-Arabia and Eurasia. The subsequent uplift of mountains in the western Mediterranean region and a global fall in sea levels combined to cause a temporary drying up of the Mediterranean Sea (known as the Messinian salinity crisis ) near
2275-463: A molten globe. In order to persuade the skeptics, Agassiz embarked on geological fieldwork. He published his book Study on Glaciers ("Études sur les glaciers") in 1840. Charpentier was put out by this, as he had also been preparing a book about the glaciation of the Alps. Charpentier felt that Agassiz should have given him precedence as it was he who had introduced Agassiz to in-depth glacial research. As
2450-534: A number of Mongol nomadic tribes. These tribes resented the conversion of khan Tarmashirin to Islam and the move of the khan to the sedentary areas of Transoxiana . They were behind the revolt that ended in Tarmashirin's death. One of the khans that followed Tarmashirin, Changshi , favored the east and was non-Muslim. In the 1340s as a series of ephemeral khans struggled to hold power in Transoxiana, little attention
2625-533: A prize-winning paper on the theory to the Swiss Society, but it was not published until Charpentier, who had also become converted, published it with his own more widely read paper in 1834. In the meantime, the German botanist Karl Friedrich Schimper (1803–1867) was studying mosses which were growing on erratic boulders in the alpine upland of Bavaria. He began to wonder where such masses of stone had come from. During
2800-488: A result of personal quarrels, Agassiz had also omitted any mention of Schimper in his book. It took several decades before the ice age theory was fully accepted by scientists. This happened on an international scale in the second half of the 1870s, following the work of James Croll , including the publication of Climate and Time, in Their Geological Relations in 1875, which provided a credible explanation for
2975-583: A route to India; Karakash ; Khotan , the main source of Chinese jade; eastward the land becomes more desolate; Keriya (Yutian); Niya (Minfeng); Qiemo (Cherchen); Charkilik (Ruoqiang). The modern road continues east to Tibet. There is currently no road east across the Kumtag Desert to Dunhuang, but caravans somehow made the crossing through the Yangguan pass south of the Jade Gate. The whole Tarim Basin and
3150-411: A significant causal factor of the 40 million year Cenozoic Cooling trend. They further claim that approximately half of their uplift (and CO 2 "scrubbing" capacity) occurred in the past 10 million years. There is evidence that greenhouse gas levels fell at the start of ice ages and rose during the retreat of the ice sheets, but it is difficult to establish cause and effect (see the notes above on
3325-690: A significant local decline along the northeastern coast of Australia during the Tortonian, most likely due to warming seawater. Cetaceans attained their greatest diversity during the Miocene, with over 20 recognized genera of baleen whales in comparison to only six living genera. This diversification correlates with emergence of gigantic macro-predators such as megatoothed sharks and raptorial sperm whales . Prominent examples are O. megalodon and L. melvillei . Other notable large sharks were O. chubutensis , Isurus hastalis , and Hemipristis serra . Crocodilians also showed signs of diversification during
3500-583: A southward shift of the subarctic front. Greenland may have begun to have large glaciers as early as 8 to 7 Ma, although the climate for the most part remained warm enough to support forests there well into the Pliocene. Zhejiang, China was noticeably more humid than today. In the Great Rift Valley of Kenya , there was a gradual and progressive trend of increasing aridification, though it was not unidirectional, and wet humid episodes continued to occur. Between 7 and 5.3 Ma, temperatures dropped sharply again in
3675-619: A tight-knit partnership, with intermarriage between Dunhuang and Khotan's rulers and Dunhuang's Mogao grottos and Buddhist temples being funded and sponsored by the Khotan royals, whose likenesses were drawn in the Mogao grottoes. Halfway in the 10th century Khotan came under attack by the Karakhanid ruler Musa, a long war ensued between the Turkic Karakhanid and Buddhist Khotan which eventually ended in
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#17328379718973850-658: A tomb dated to as early as the 7th century BC. According to the Sima Qian 's Shiji , the nomadic Indo-European Yuezhi originally lived between Tengri Tagh ( Tian Shan ) and Dunhuang in Gansu , China. However, the Yuezhi were assaulted and forced to flee from the Hexi Corridor of Gansu by the forces of the Xiongnu ruler Modu Chanyu , who conquered the area in 177–176 BC (decades before
4025-510: A town named after its Saka inhabitants (i.e. saγlâ ). Although the ancient Chinese called Khotan Yutian (于闐), its more native Iranian names during the Han period were Jusadanna (瞿薩旦那), derived from Indo-Iranian Gostan and Gostana , the names of the town and region around it, respectively. Around 200 BCE, the Yuezhi were overrun by the Xiongnu . The Xiongnu then tried to invade the western region of China, but ultimately failed and lost control of
4200-624: A zone of low rainfall in the Late Miocene. The Indian Plate continued to collide with the Eurasian Plate , creating new mountain ranges and uplifting the Tibetan Plateau , resulting in the rain shadowing and aridification of the Asian interior. The Tian Shan experienced significant uplift in the Late Miocene, blocking westerlies from coming into the Tarim Basin and drying it as a result. At
4375-556: Is a crossroads and former trading post. The Tarim Basin is the result of an amalgamation between an ancient microcontinent and the growing Eurasian continent during the Carboniferous to Permian periods, a process which ended in the earliest Triassic with the closure of the Palaeo-Asian Ocean. At present, deformation around the margins of the basin is resulting in the microcontinental crust being pushed under Tian Shan to
4550-532: Is actually the earliest fortified urban settlement in the entire region, covering 6 hectares, and developed in four phases between c. 770 BC and 80 AD. Spouted jars were found at this site, similar to those of Chawuhu culture, and buckles and moulds with animal motifs resemble steppe traditions. Another people in the region besides these Tarim people were the Indo-Iranian Saka people, who spoke various Eastern Iranian Khotanese Scythian or Saka dialects. In
4725-572: Is estimated to potentially outweigh the orbital forcing of the Milankovitch cycles for hundreds of thousands of years. Each glacial period is subject to positive feedback which makes it more severe, and negative feedback which mitigates and (in all cases so far) eventually ends it. An important form of feedback is provided by Earth's albedo , which is how much of the sun's energy is reflected rather than absorbed by Earth. Ice and snow increase Earth's albedo, while forests reduce its albedo. When
4900-661: Is of particular interest to geologists and palaeoclimatologists because major phases of the geology of the Himalaya occurred during that epoch, affecting monsoonal patterns in Asia, which were interlinked with glacial periods in the northern hemisphere. The Miocene faunal stages from youngest to oldest are typically named according to the International Commission on Stratigraphy : Regionally, other systems are used, based on characteristic land mammals; some of them overlap with
5075-465: Is of some importance historically. My own preference is for an explanation connecting it semantically with the name Saka, for the Iranian inhabitants of Khotan... In Northwest China , Khotanese-Saka-language documents, ranging from medical texts to Buddhist literature , have been found, primarily in Khotan and Tumshuq (northeast of Kashgar). They largely predate the arrival of Islam to the region under
5250-548: Is sometimes used synonymously to refer to the southern half of the province, that is, Southern Xinjiang or Nanjiang ( Chinese : 南疆 ; pinyin : Nánjiāng ), as opposed to the northern half of the province known as Dzungaria or Beijiang. Its northern boundary is the Tian Shan mountain range and its southern boundary is the Kunlun Mountains on the edge of the Tibetan Plateau . The Taklamakan Desert dominates much of
5425-580: Is that several factors are important: atmospheric composition , such as the concentrations of carbon dioxide and methane (the specific levels of the previously mentioned gases are now able to be seen with the new ice core samples from the European Project for Ice Coring in Antarctica (EPICA) Dome C in Antarctica over the past 800,000 years); changes in Earth's orbit around the Sun known as Milankovitch cycles ;
Miocene - Misplaced Pages Continue
5600-508: Is the increased aridity occurring with glacial maxima, which reduces the precipitation available to maintain glaciation. The glacial retreat induced by this or any other process can be amplified by similar inverse positive feedbacks as for glacial advances. According to research published in Nature Geoscience , human emissions of carbon dioxide (CO 2 ) will defer the next glacial period. Researchers used data on Earth's orbit to find
5775-686: The Achaemenid era Old Persian inscriptions found at Persepolis , dated to the reign of Darius I (r. 522–486 BC), the Saka are said to have lived just beyond the borders of Sogdiana . Likewise, an inscription dated to the reign of Xerxes I (r. 486–465 BC) has them coupled with the Dahae people of Central Asia. The contemporary Greek historian Herodotus noted that the Achaemenid Persians called all Indo-Iranian Scythian peoples "Saka". They were known as
5950-469: The Alps of Savoy . Two years later he published an account of his journey. He reported that the inhabitants of that valley attributed the dispersal of erratic boulders to the glaciers, saying that they had once extended much farther. Later similar explanations were reported from other regions of the Alps. In 1815 the carpenter and chamois hunter Jean-Pierre Perraudin (1767–1858) explained erratic boulders in
6125-516: The Bei Lu north of the mountains. Along it runs the modern highway and railroad while the middle Tarim River is about 100 km south. The caravans met in Kashgar before crossing the mountains. Bachu or Miralbachi; Uchturpan north of the main road; Aksu on the large Aksu River ; Kucha was once an important kingdom; Luntai ; Korla , now a large town; Karashar near Bosten Lake ; Turpan north of
6300-579: The Carboniferous and early Permian periods. Correlatives are known from Argentina, also in the center of the ancient supercontinent Gondwanaland . Although the Mesozoic Era retained a greenhouse climate over its timespan and was previously assumed to have been entirely glaciation-free, more recent studies suggest that brief periods of glaciation occurred in both hemispheres during the Early Cretaceous . Geologic and palaeoclimatological records suggest
6475-672: The Eastern Iranian languages . As noted by the Greek historian Herodotus, the contemporary Persians labelled all Scythians "Saka". Indeed, modern scholarly consensus is that the Saka language, ancestor to the Pamir languages in northern India and Khotanese in Xinjiang , belongs to the Scythian languages . During China's Tang dynasty (618–907 AD), the region once again came under Chinese suzerainty with
6650-743: The Four Garrisons of Anxi . Tang hegemony beyond the Pamir Mountains in modern Tajikistan and Afghanistan ended with revolts by the Turks, but the Tang retained a military presence in Xinjiang. These holdings were later invaded by the Tibetan Empire to the south in 670. For the remainder of the Tang dynasty, the Tarim Basin alternated between Tang and Tibetan rule as they competed for control of Central Asia. As
6825-864: The Han Chinese conquest and colonization of western tip of Gansu or the establishment of the Protectorate of the Western Regions ). In turn the Yuezi attacked and pushing the Sai (i.e. Saka) west into Sogdiana, where in the mid-2nd century BC the latter crossed the Syr Darya into Bactria , but also into the Fergana Valley where they settled in Dayuan , south towards northern India, and eastward as well, where they settled in some of
7000-601: The Himalayas are a major factor in the current ice age, because these mountains have increased Earth's total rainfall and therefore the rate at which carbon dioxide is washed out of the atmosphere, decreasing the greenhouse effect. The Himalayas' formation started about 70 million years ago when the Indo-Australian Plate collided with the Eurasian Plate , and the Himalayas are still rising by about 5 mm per year because
7175-513: The Kaidu river . Structures made of mud bricks were found at Xintala , showing building techniques similar to those seen in early oasis sites in western Central Asia, as well as in Yanbulake . There were no burials in Xintala culture, and its settlements were small. Autosomal genetic evidence suggests that the earliest Tarim people arose from locals of primarily Ancient North Eurasian descent with significant Northeast Asian admixture. The Tarim mummies have been found in various locations in
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7350-405: The Kara-Khanid Khanate in Semirechye , Western Tian Shan , and Kashgaria . The Karakhanids became the first Islamic Turkic dynasty in the tenth century when Sultan Satuq Bughra Khan converted to Islam in 966 while he controlled Kashgar. Satuq Bughra Khan and his son directed endeavors to preach Islam among the Turks and engage in conquests. Satok Bughra Khan's nephew or grandson Ali Arslan
7525-478: The Late Ordovician and the Silurian period. The evolution of land plants at the onset of the Devonian period caused a long term increase in planetary oxygen levels and reduction of CO 2 levels, which resulted in the late Paleozoic icehouse . Its former name, the Karoo glaciation, was named after the glacial tills found in the Karoo region of South Africa. There were extensive polar ice caps at intervals from 360 to 260 million years ago in South Africa during
7700-412: The Pleistocene Ice Age. Because this highland is at a subtropical latitude, with four to five times the insolation of high-latitude areas, what would be Earth's strongest heating surface has turned into a cooling surface. Kuhle explains the interglacial periods by the 100,000-year cycle of radiation changes due to variations in Earth's orbit. This comparatively insignificant warming, when combined with
7875-584: The Taklamakan Desert are surrounded by railroads. The Southern Xinjiang Railway branches from the Lanxin Railway near Turpan, follows the north side of the basin to Kashgar, and curves southeast to Khotan, while Hotan–Ruoqiang railway loops around the south and west side of the Traim. They are part of the Taklimakan Desert railway loop, joined together with sections of the Golmud–Korla railway , Hotan–Ruoqiang railway , Kashgar–Hotan railway , and Southern Xinjiang railway . The main road from eastern China reaches Ürümqi and continues as highway 314 along
8050-401: The Taklamakan Desert , one south, and a middle one connecting both through the Lop Nor region. In the early period, beginning around 2000 BC, there were six different cultural zones in the Tarim Basin, and bronze began to appear. One of these cultures was the Xintala culture ( c. 1700 –1500 BC), near the site of Yanqi, also known as Karashar , to the north and east of the Tarim, at
8225-405: The Torugart pass leads to the Ferghana Valley . Near Uchturpan the Bedel Pass leads to Lake Issyk-Kul and the steppes. Somewhere near Aksu the difficult Muzart Pass led north to the Ili River basin (Kulja). Near Korla was the Iron Gate Pass and now the highway and railway north to Ürümqi. From Turfan the easy Dabancheng pass leads to Ürümqi. The route from Charkilik to the Qaidam Basin
8400-454: The Turkic Kara-Khanids . Similar documents in the Khotanese-Saka language were found in Dunhuang dating mostly to the 10th century. After the collapse of the Uyghur Khaganate of modern-day Mongolia , Uyghur people migrated to the Tarim Basin and mixed with the Tocharians and converted to their religion, and adopted their method of oasis agriculture. In the tenth century, the Karluks , Yagmas , Chigils and other Turkic tribes founded
8575-400: The Turonian , otherwise the warmest period of the Phanerozoic, are disputed), ice sheets and associated sea ice appear to have briefly returned to Antarctica near the very end of the Maastrichtian just prior to the Cretaceous-Paleogene extinction event . The Quaternary Glaciation / Quaternary Ice Age started about 2.58 million years ago at the beginning of the Quaternary Period when
8750-465: The Turpan Depression and south of the Bogda Shan ; Hami ; then southeast to Anxi and the Gansu Corridor . Most of the basin is occupied by the Taklamakan Desert which is too dry for permanent habitation. The Yarkand , Kashgar and Aksu Rivers join to form the Tarim River which runs along the north side of the basin. Formerly it continued to Loulan , but some time after 330 AD it turned southeast near Korla toward Charkilik , and Loulan
8925-540: The 10th century "makes it likely that the ruler of Khotan was a speaker of Iranian ." Furthermore, he elaborated on the early name of Khotan: The name of Khotan is attested in a number of spellings, of which the oldest form is hvatana , in texts of approximately the 7th to the 10th century AD, written in an Iranian language itself called hvatana by the writers. The same name is attested also in two closely related Iranian dialects, Sogdian and Tumshuq ...Attempts have accordingly been made to explain it as Iranian, and this
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#17328379718979100-414: The 3rd century, bearing dual inscriptions in Chinese and Gandhari Prakrit in the Kharosthi script. Although Prakrit was the administrative language of nearby Shanshan , 3rd-century documents from that kingdom record the title hinajha (i.e. "generalissimo") for the king of Khotan, Vij'ida-simha, a distinctively Iranian-based word equivalent to the Sanskrit title senapati , yet nearly identical to
9275-558: The Afaqi (White Mountain) and the Ishaqi (Black Mountain). The Ishaqi defeated the Afaqi and the Afaq Khoja invited the 5th Dalai Lama (the leader of the Tibetans ) to intervene on his behalf in 1677. The Dalai Lama then called on his Dzungar Buddhist followers in the Dzungar Khanate to act on the invitation. The Dzungar Khanate conquered the Tarim Basin in 1678, during the Dzungar conquest of Altishahr , after which they set up Afaq Khoja as their puppet ruler. Xinjiang did not exist as one unit until 1884 under Qing rule. It consisted of
9450-423: The Alagou sites near the Turfan basin, and north to the region close to Ürümqi . Earlier diggings in the southern Tarim Basin, in the 1990s, suggested that Yuansha (Djoumbulak Koum) in the Keriya river valley was the earliest fortified urban site, from around 400 BC, but new surveys and excavations between 2018 and 2020, showed that the site Kuiyukexiehai'er (Koyuk Shahri), located in the northern Tarim Basin,
9625-403: The Atlantic, increasing heat transport into the Arctic, which melted the polar ice accumulation and reduced other continental ice sheets. The release of water raised sea levels again, restoring the ingress of colder water from the Pacific with an accompanying shift to northern hemisphere ice accumulation. According to a study published in Nature in 2021, all glacial periods of ice ages over
9800-417: The Central Paratethys, cut off from sources of freshwater input by its separation from the Eastern Paratethys. From 13.36 to 12.65 Ma, the Central Paratethys was characterised by open marine conditions, before the reopening of the Bârlad Strait resulted in a shift to brackish-marine conditions in the Central Paratethys, causing the Badenian-Sarmatian Extinction Event. As a result of the Bârlad Strait's reopening,
9975-419: The Early Miocene were very similar to those in the present. Global cooling caused the East Asian Summer Monsoon (EASM) to begin to take on its modern form during the Early Miocene. From 22.1 to 19.7 Ma, the Xining Basin experienced relative warmth and humidity amidst a broader aridification trend. The EMCI ended 18 million years ago, giving way to the Middle Miocene Warm Interval (MMWI), the warmest part of which
10150-719: The Early to the Middle Miocene. Europe's large mammal diversity significantly declined during the Late Miocene. In the Early Miocene, several Oligocene groups were still diverse, including nimravids , entelodonts , and three-toed equids. As in the previous Oligocene Epoch, oreodonts were still diverse, only to disappear in the earliest Pliocene. During the later Miocene mammals were more modern, with easily recognizable canids , bears , red pandas , procyonids , equids , beavers , deer , camelids , and whales , along with now-extinct groups like borophagine canids , certain gomphotheres , three-toed horses , and hornless rhinos like Teleoceras and Aphelos . The late Miocene also marks
10325-402: The Indo-Australian plate is still moving at 67 mm/year. The history of the Himalayas broadly fits the long-term decrease in Earth's average temperature since the mid-Eocene , 40 million years ago. Another important contribution to ancient climate regimes is the variation of ocean currents, which are modified by continent position, sea levels and salinity, as well as other factors. They have
10500-522: The Karakhanid leader. The "infidels" were defeated and driven towards Khotan by Yusuf Qadir Khan and the four Imams, but the Imams were assassinated by the Buddhists prior to the last Muslim victory. After Yusuf Qadir Khan's conquest of new land in Altishahr towards the east, he adopted the title "King of the East and China". In 1006, the Muslim Kara-Khanid ruler Yusuf Kadir (Qadir) Khan of Kashgar conquered Khotan, ending Khotan's existence as an independent state. The Islamic conquest of Khotan led to alarm in
10675-417: The Khotan River from Khotan to near Aksu . A road follows the Yarkant River from Yarkand to Baqu . East of the Korla-Charkilik road, travel continues to be very difficult. Rivers coming south from the Tien Shan join the Tarim, the largest being the Aksu . Rivers flowing north from the Kunlun are usually named for the town or oasis they pass through. Most dry up in the desert; only the Hotan River reaches
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#173283797189710850-415: The Khotanese Saka hīnāysa attested in contemporary documents. This, along with the fact that the king's recorded regnal periods were given in Khotanese as kṣuṇa , "implies an established connection between the Iranian inhabitants and the royal power", according to the late Professor of Iranian Studies Ronald E. Emmerick (d. 2001). He contended that Khotanese-Saka-language royal rescripts of Khotan dated to
11025-401: The Late Cretaceous, are known from the Miocene of Patagonia, represented by the mole-like Necrolestes . The youngest known representatives of metatherians (the broader grouping to which marsupials belong) in Europe, Asia and Africa are known from the Miocene, including the European herpetotheriid Amphiperatherium , the peradectids Siamoperadectes and Sinoperadectes from Asia, and
11200-421: The Late Miocene Cooling (LMC), most likely as a result of a decline in atmospheric carbon dioxide and a drop in the amplitude of Earth's obliquity, and the Antarctic ice sheet was approaching its present-day size and thickness. Ocean temperatures plummeted to near-modern values during the LMC; extratropical sea surface temperatures dropped substantially by approximately 7–9 °C. 41 kyr obliquity cycles became
11375-438: The Late Miocene. By 12 Ma, Oregon was a savanna akin to that of the western margins of the Sierra Nevada of northern California . Central Australia became progressively drier, although southwestern Australia experienced significant wettening from around 12 to 8 Ma. The South Asian Winter Monsoon (SAWM) underwent strengthening ~9.2–8.5 Ma. From 7.9 to 5.8 Ma, the East Asian Winter Monsoon (EAWM) became stronger synchronously with
11550-434: The Mediterranean refilled. That event is referred to as the " Zanclean flood ". Also during the early Miocene (specifically the Aquitanian and Burdigalian Stages), the apes first evolved, began diversifying, and became widespread throughout the Old World . Around the end of this epoch, the ancestors of humans had split away from the ancestors of the chimpanzees and had begun following their own evolutionary path during
11725-447: The Miocene. The largest form among them was a gigantic caiman Purussaurus which inhabited South America. Another gigantic form was a false gharial Rhamphosuchus , which inhabited modern age India . A strange form, Mourasuchus also thrived alongside Purussaurus . This species developed a specialized filter-feeding mechanism, and it likely preyed upon small fauna despite its gigantic size. The youngest members of Sebecidae ,
11900-410: The North American Great Plains and in Argentina . The global trend was towards increasing aridity caused primarily by global cooling reducing the ability of the atmosphere to absorb moisture, particularly after 7 to 8 million years ago. Uplift of East Africa in the late Miocene was partly responsible for the shrinking of tropical rain forests in that region, and Australia got drier as it entered
12075-447: The North Atlantic Ocean far enough to block the Gulf Stream. Ice sheets that form during glaciations erode the land beneath them. This can reduce the land area above sea level and thus diminish the amount of space on which ice sheets can form. This mitigates the albedo feedback, as does the rise in sea level that accompanies the reduced area of ice sheets, since open ocean has a lower albedo than land. Another negative feedback mechanism
12250-430: The North Atlantic during a warming cycle may also reduce the global ocean water circulation . Such a reduction (by reducing the effects of the Gulf Stream ) would have a cooling effect on northern Europe, which in turn would lead to increased low-latitude snow retention during the summer. It has also been suggested that during an extensive glacial, glaciers may move through the Gulf of Saint Lawrence , extending into
12425-513: The Oligocene and most of the Miocene. At the end of the Miocene, global temperatures rose again as the amplitude of Earth's obliquity increased, which caused increased aridity in Central Asia. Around 5.5 Ma, the EAWM underwent a period of rapid intensification. Life during the Miocene Epoch was mostly supported by the two newly formed biomes , kelp forests and grasslands. Grasslands allow for more grazers, such as horses , rhinoceroses , and hippos . Ninety-five percent of modern plants existed by
12600-700: The Oligocene–Miocene transgression. As the southern Andes rose in the Middle Miocene (14–12 million years ago) the resulting rain shadow originated the Patagonian Desert to the east. Far northern Australia was monsoonal during the Miocene. Although northern Australia is often believed to have been much wetter during the Miocene, this interpretation may be an artefact of preservation bias of riparian and lacustrine plants; this finding has itself been challenged by other papers. Western Australia, like today,
12775-595: The Qiongdongnan Basin in the northern South China Sea indicates the Pearl River was a major source of sediment flux into the sea during the Early Miocene and was a major fluvial system as in the present. During the Oligocene and Early Miocene, the coast of northern Brazil, Colombia, south-central Peru , central Chile and large swathes of inland Patagonia were subject to a marine transgression . The transgressions in
12950-630: The Sai (塞, sāi, sək in archaic Chinese) in ancient Chinese records. These records indicate that they originally inhabited the Ili and Chu River valleys of modern Kazakhstan . In the Chinese Book of Han , the area was called the "land of the Sai", i.e. the Saka. A people believed to be Saka has also been found in various locations in the Tarim Basin, for example in the Keriya region at Yumulak Kum (Djoumboulak Koum, Yuansha) around 200 km east of Khotan, with
13125-808: The Scandinavian peninsula. He regarded glaciation as a regional phenomenon. Only a few years later, the Danish-Norwegian geologist Jens Esmark (1762–1839) argued for a sequence of worldwide ice ages. In a paper published in 1824, Esmark proposed changes in climate as the cause of those glaciations. He attempted to show that they originated from changes in Earth's orbit. Esmark discovered the similarity between moraines near Haukalivatnet lake near sea level in Rogaland and moraines at branches of Jostedalsbreen . Esmark's discovery were later attributed to or appropriated by Theodor Kjerulf and Louis Agassiz . During
13300-538: The Swiss Alps with his former university friend Louis Agassiz (1801–1873) and Jean de Charpentier. Schimper, Charpentier and possibly Venetz convinced Agassiz that there had been a time of glaciation. During the winter of 1836–37, Agassiz and Schimper developed the theory of a sequence of glaciations. They mainly drew upon the preceding works of Venetz, Charpentier and on their own fieldwork. Agassiz appears to have been already familiar with Bernhardi's paper at that time. At
13475-458: The Tahe oil field. Below the level enriched with gas and oil is a complex Precambrian basement believed to be made up of the remnants of the original Tarim microplate , which accrued to the growing Eurasian continent in Carboniferous time. The snow on K2 , the second-highest mountain in the world, flows into glaciers which move down the valleys to melt. The melted water forms rivers which flow down
13650-814: The Tarim basin, rebelled against the Moghulistan Khanate and broke away. Five years later Sultan Said Khan , a brother of the Khan of Moghulistan in Turfan , conquered the Dughlats but established his own Yarkent Khanate instead. By the early 17th century, the Naqshbandi Sufi Khojas , descendants of Muhammad , had replaced the Chagatayid Khans as rulers of the Tarim Basin. There was a struggle between two Khoja factions:
13825-473: The Tarim in good years. An exception is the Qiemo River which flows northeast into Lop Nor. Ruins in the desert imply that these rivers were once larger. The original caravan route seems to have followed the south side. At the time of the Han dynasty conquest, it shifted to the center (Jade Gate-Loulan-Korla). When the Tarim changed course about 330 AD it shifted north to Hami . A minor route went north of
14000-730: The Tian Shan. When there was war on the Gansu Corridor trade entered the basin near Charkilik from the Qaidam Basin . The original route to India seems to have started near Yarkand and Kargilik, but it is now replaced by the Karakoram Highway south from Kashgar. To the west of Kashgar via the Irkeshtam border crossing is the Alay Valley , which was once the route to Persia. Northeast of Kashgar
14175-846: The Val de Bagnes in the Swiss canton of Valais as being due to glaciers previously extending further. An unknown woodcutter from Meiringen in the Bernese Oberland advocated a similar idea in a discussion with the Swiss-German geologist Jean de Charpentier (1786–1855) in 1834. Comparable explanations are also known from the Val de Ferret in the Valais and the Seeland in western Switzerland and in Goethe 's scientific work . Such explanations could also be found in other parts of
14350-511: The Yuezhi, albeit under slightly different names. After the Han dynasty, the kingdoms of the Tarim Basin began to have strong cultural influences on China as a conduit between the cultures of India and Central Asia and China. Indian Buddhists had previously travelled to China during the Han dynasty, but the Buddhist monk Kumārajīva from Kucha , who visited China during the Six Dynasties period
14525-609: The ability to cool (e.g. aiding the creation of Antarctic ice) and the ability to warm (e.g. giving the British Isles a temperate as opposed to a boreal climate). The closing of the Isthmus of Panama about 3 million years ago may have ushered in the present period of strong glaciation over North America by ending the exchange of water between the tropical Atlantic and Pacific Oceans. Analyses suggest that ocean current fluctuations can adequately account for recent glacial oscillations. During
14700-402: The air temperature decreases, ice and snow fields grow, and they reduce forest cover. This continues until competition with a negative feedback mechanism forces the system to an equilibrium. One theory is that when glaciers form, two things happen: the ice grinds rocks into dust, and the land becomes dry and arid. This allows winds to transport iron rich dust into the open ocean, where it acts as
14875-473: The amount found in mid-latitude deserts . This low precipitation allows high-latitude snowfalls to melt during the summer. An ice-free Arctic Ocean absorbs solar radiation during the long summer days, and evaporates more water into the Arctic atmosphere. With higher precipitation, portions of this snow may not melt during the summer and so glacial ice can form at lower altitudes and more southerly latitudes, reducing
15050-471: The aridity of the former. Unequivocally-recognizable dabbling ducks , plovers , typical owls , cockatoos and crows appear during the Miocene. By the epoch's end, all or almost all modern bird groups are believed to have been present; the few post-Miocene bird fossils which cannot be placed in the evolutionary tree with full confidence are simply too badly preserved, rather than too equivocal in character. Marine birds reached their highest diversity ever in
15225-524: The basin. The historical Uyghur name for the Tarim Basin is Altishahr ( Traditional Uyghur : آلتی شهر , Chinese : 六城 ), which means 'six cities' in Uyghur . The region was also called Little Bukhara or Little Bukharia . Xinjiang consists of two main geographically, historically, and ethnically distinct regions with different historical names, Dzungaria and the Tarim Basin ( Altishahr ), which Qing China unified into Xinjiang province in 1884. At
15400-474: The beginning of 1837, Schimper coined the term "ice age" ( "Eiszeit" ) for the period of the glaciers. In July 1837 Agassiz presented their synthesis before the annual meeting of the Swiss Society for Natural Research at Neuchâtel. The audience was very critical, and some were opposed to the new theory because it contradicted the established opinions on climatic history. Most contemporary scientists thought that Earth had been gradually cooling down since its birth as
15575-618: The beginning of the Miocene, the northern margin of the Arabian plate, then part of the African landmass, collided with Eurasia; as a result, the Tethys seaway continued to shrink and then disappeared as Africa collided with Eurasia in the Turkish – Arabian region. The first step of this closure occurred 20 Ma, reducing water mass exchange by 90%, while the second step occurred around 13.8 Ma, coincident with
15750-732: The campaigns of conquest by Emperor Taizong of Tang (r. 626–649). From the late 8th to 9th centuries, the region changed hands between the Chinese Tang Empire and the rival Tibetan Empire . By the early 11th century the region had fallen to the Muslim Turkic peoples of the Kara-Khanid Khanate , which led to both the Turkification of the region and its conversion from Buddhism to Islam . Suggestive evidence of Khotan's early link to India are minted coins from Khotan dated to
15925-495: The causes of ice ages. There are three main types of evidence for ice ages: geological, chemical, and paleontological. Geological evidence for ice ages comes in various forms, including rock scouring and scratching, glacial moraines , drumlins , valley cutting, and the deposition of till or tillites and glacial erratics . Successive glaciations tend to distort and erase the geological evidence for earlier glaciations, making it difficult to interpret. Furthermore, this evidence
16100-458: The concentrations of greenhouse gases) may alter the climate, while climate change itself can change the atmospheric composition (for example by changing the rate at which weathering removes CO 2 ). Maureen Raymo , William Ruddiman and others propose that the Tibetan and Colorado Plateaus are immense CO 2 "scrubbers" with a capacity to remove enough CO 2 from the global atmosphere to be
16275-728: The conquest of Khotan by Kashgar by the Karakhanid leader Yusuf Qadir Khan around 1006. Accounts of the Muslim Karakhanid war against the Khotanese Buddhists are given in Taẕkirah of the Four Sacrificed Imams written sometime in the period from 1700 to 1849 which told the story of four imams from Mada'in city (possibly in modern-day Iraq) who traveled to help the Islamic conquest of Khotan, Yarkand, and Kashgar by Yusuf Qadir Khan,
16450-691: The continental ice sheets are the Greenland and Antarctic ice sheets and smaller glaciers such as on Baffin Island . The definition of the Quaternary as beginning 2.58 Ma is based on the formation of the Arctic ice cap . The Antarctic ice sheet began to form earlier, at about 34 Ma, in the mid- Cenozoic ( Eocene-Oligocene Boundary ). The term Late Cenozoic Ice Age is used to include this early phase. Ice ages can be further divided by location and time; for example,
16625-405: The continents and pack ice on the oceans would inhibit both silicate weathering and photosynthesis , which are the two major sinks for CO 2 at present." It has been suggested that the end of this ice age was responsible for the subsequent Ediacaran and Cambrian explosion , though this model is recent and controversial. The Andean-Saharan occurred from 460 to 420 million years ago, during
16800-431: The continents are in positions which block or reduce the flow of warm water from the equator to the poles and thus allow ice sheets to form. The ice sheets increase Earth's reflectivity and thus reduce the absorption of solar radiation. With less radiation absorbed the atmosphere cools; the cooling allows the ice sheets to grow, which further increases reflectivity in a positive feedback loop. The ice age continues until
16975-564: The course of this epoch. The youngest representatives of Choristodera , an extinct order of aquatic reptiles that first appeared in the Middle Jurassic , are known from the Miocene of Europe, belonging to the genus Lazarussuchus , which had been the only known surviving genus of the group since the beginning of the Eocene. The last known representatives of the archaic primitive mammal order Meridiolestida , which dominated South America during
17150-527: The current glaciation, more temperate and more severe periods have occurred. The colder periods are called glacial periods , the warmer periods interglacials , such as the Eemian Stage . There is evidence that similar glacial cycles occurred in previous glaciations, including the Andean-Saharan and the late Paleozoic ice house. The glacial cycles of the late Paleozoic ice house are likely responsible for
17325-420: The deeper and richer grassland soils , with long-term burial of carbon in sediments, produced a carbon and water vapor sink. This, combined with higher surface albedo and lower evapotranspiration of grassland, contributed to a cooler, drier climate. C 4 grasses, which are able to assimilate carbon dioxide and water more efficiently than C 3 grasses, expanded to become ecologically significant near
17500-617: The deposition of cyclothems . Glacials are characterized by cooler and drier climates over most of Earth and large land and sea ice masses extending outward from the poles. Mountain glaciers in otherwise unglaciated areas extend to lower elevations due to a lower snow line . Sea levels drop due to the removal of large volumes of water above sea level in the icecaps. There is evidence that ocean circulation patterns are disrupted by glaciations. The glacials and interglacials coincide with changes in orbital forcing of climate due to Milankovitch cycles , which are periodic changes in Earth's orbit and
17675-439: The dominant orbital climatic control 7.7 Ma and this dominance strengthened 6.4 Ma. Benthic δO values show significant glaciation occurred from 6.26 to 5.50 Ma, during which glacial-interglacial cycles were governed by the 41 kyr obliquity cycle. A major reorganisation of the carbon cycle occurred approximately 6 Ma, causing continental carbon reservoirs to no longer expand during cold spells, as they had done during cold periods in
17850-613: The early Proterozoic Eon. Several hundreds of kilometers of the Huronian Supergroup are exposed 10 to 100 kilometers (6 to 62 mi) north of the north shore of Lake Huron, extending from near Sault Ste. Marie to Sudbury, northeast of Lake Huron, with giant layers of now-lithified till beds, dropstones , varves , outwash , and scoured basement rocks. Correlative Huronian deposits have been found near Marquette, Michigan , and correlation has been made with Paleoproterozoic glacial deposits from Western Australia. The Huronian ice age
18025-585: The early to mid Miocene (23–15 Ma). Oceans cooled partly due to the formation of the Antarctic Circumpolar Current , and about 15 million years ago the ice cap in the southern hemisphere started to grow to its present form. The Greenland ice cap developed later, in the Middle Pliocene time, about 3 million years ago. Ice age An ice age is a long period of reduction in the temperature of Earth 's surface and atmosphere, resulting in
18200-469: The east and Dunhuang's Cave 17, which contained Khotanese literary works, was closed shut possibly after its caretakers heard that Khotan's Buddhist buildings were razed by the Muslims, the Buddhist religion had suddenly ceased to exist in Khotan. The Karakhanid Turkic Muslim writer Mahmud al-Kashgari recorded a short Turkic language poem about the conquest: English translation: We came down on them like
18375-626: The eastern Tarim Basin such as Loulan , the Xiaohe Tomb complex , and Qäwrighul . These mummies have previously been suggested to be of Tocharian origin, but recent evidence suggests that the mummies belonged to a distinct population unrelated to later Indo-European pastoralists, such as Afanasievo. In the Iron Age , the Chawuhu culture (c. 1000–400 BC) flourished in the Yanqi (Karashar) oasis, and also reached
18550-567: The end of the Miocene between 6 and 7 million years ago, although they did not expand northward during the Late Miocene. The expansion of grasslands and radiations among terrestrial herbivores correlates to fluctuations in CO 2 . One study, however, has attributed the expansion of grasslands not to a CO 2 drop but to the increasing seasonality and aridity, coupled with a monsoon climate, which made wildfires highly prevalent compared to before. The Late Miocene expansion of grasslands had cascading effects on
18725-562: The end of the Miocene due to increased habitat uniformity. The expansion of grasslands in North America also led to an explosive radiation among snakes. Previously, snakes were a minor component of the North American fauna, but during the Miocene, the number of species and their prevalence increased dramatically with the first appearances of vipers and elapids in North America and the significant diversification of Colubridae (including
18900-537: The end of the Miocene. The Paratethys underwent a significant transgression during the early Middle Miocene. Around 13.8 Ma, during a global sea level drop, the Eastern Paratethys was cut off from the global ocean by the closure of the Bârlad Strait, effectively turning it into a saltwater lake. From 13.8 to 13.36 Ma, an evaporite period similar to the later Messinian salinity crisis in the Mediterranean ensued in
19075-517: The end of this epoch. Modern bony fish genera were established. A modern-style latitudinal biodiversity gradient appeared ~15 Ma. The coevolution of gritty , fibrous, fire-tolerant grasses and long-legged gregarious ungulates with high-crowned teeth , led to a major expansion of grass-grazer ecosystems . Herds of large, swift grazers were hunted by predators across broad sweeps of open grasslands , displacing desert, woodland, and browsers. The higher organic content and water retention of
19250-611: The enigmatic Saint Bathans Mammal . Microbial life in the igneous crust of the Fennoscandian Shield shifted from being dominated by methanogens to being primarily composed of sulphate-reducing prokaryotes . The change resulted from fracture reactivation during the Pyrenean-Alpine orogeny, enabling sulphate-reducing microbes to permeate into the Fennoscandian Shield via descending surficial waters. Diatom diversity
19425-461: The evolution of both groups into modern representatives. The early Miocene Saint Bathans Fauna is the only Cenozoic terrestrial fossil record of the landmass, showcasing a wide variety of not only bird species, including early representatives of clades such as moa , kiwi and adzebills , but also a diverse herpetofauna of sphenodontians , crocodiles and turtles as well as a rich terrestrial mammal fauna composed of various species of bats and
19600-691: The existence of glacial periods during the Valanginian , Hauterivian , and Aptian stages of the Early Cretaceous. Ice-rafted glacial dropstones indicate that in the Northern Hemisphere , ice sheets may have extended as far south as the Iberian Peninsula during the Hauterivian and Aptian. Although ice sheets largely disappeared from Earth for the rest of the period (potential reports from
19775-759: The extinction of the last-surviving members of the hyaenodonts . Islands began to form between South and North America in the Late Miocene, allowing ground sloths like Thinobadistes to island-hop to North America. The expansion of silica-rich C 4 grasses led to worldwide extinctions of herbivorous species without high-crowned teeth . Mustelids diversified into their largest forms as terrestrial predators like Ekorus , Eomellivora , and Megalictis and bunodont otters like Enhydriodon and Sivaonyx appeared. Eulipotyphlans were widespread in Europe, being less diverse in Southern Europe than farther north due to
19950-436: The final Messinian Stage (7.5–5.3 Ma) of the Miocene. As in the Oligocene before it, grasslands continued to expand, and forests to dwindle. In the seas of the Miocene, kelp forests made their first appearance and soon became one of Earth's most productive ecosystems. The plants and animals of the Miocene were recognizably modern. Mammals and birds were well established. Whales , pinnipeds , and kelp spread. The Miocene
20125-423: The finding of a vast, carbon-rich underground sea beneath the basin. It is speculated that the Tarim Basin may be one of the last places in Asia to have become inhabited: It is surrounded by mountains and irrigation technologies might have been necessary. The Northern Silk Road on one route bypassed the Tarim Basin north of the Tian Shan mountains and traversed it on three oases-dependent routes: one north of
20300-600: The findings of marine invertebrate fossils of both Atlantic and Pacific affinity in La Cascada Formation . Connection would have occurred through narrow epicontinental seaways that formed channels in a dissected topography . The Antarctic Plate started to subduct beneath South America 14 million years ago in the Miocene, forming the Chile Triple Junction . At first the Antarctic Plate subducted only in
20475-509: The first person to suggest drifting sea ice was a cause of the presence of erratic boulders in the Scandinavian and Baltic regions. In 1795, the Scottish philosopher and gentleman naturalist, James Hutton (1726–1797), explained erratic boulders in the Alps by the action of glaciers. Two decades later, in 1818, the Swedish botanist Göran Wahlenberg (1780–1851) published his theory of a glaciation of
20650-554: The following years, Esmark's ideas were discussed and taken over in parts by Swedish, Scottish and German scientists. At the University of Edinburgh Robert Jameson (1774–1854) seemed to be relatively open to Esmark's ideas, as reviewed by Norwegian professor of glaciology Bjørn G. Andersen (1992). Jameson's remarks about ancient glaciers in Scotland were most probably prompted by Esmark. In Germany, Albrecht Reinhard Bernhardi (1797–1849),
20825-417: The geographical distribution of fossils. During a glacial period, cold-adapted organisms spread into lower latitudes, and organisms that prefer warmer conditions become extinct or retreat into lower latitudes. This evidence is also difficult to interpret because it requires: Despite the difficulties, analysis of ice core and ocean sediment cores has provided a credible record of glacials and interglacials over
21000-678: The global carbon cycle, evidenced by the imprint it left in carbon isotope records. Cycads between 11.5 and 5 million years ago began to rediversify after previous declines in variety due to climatic changes, and thus modern cycads are not a good model for a "living fossil". Eucalyptus fossil leaves occur in the Miocene of New Zealand , where the genus is not native today, but have been introduced from Australia . Both marine and continental fauna were fairly modern, although marine mammals were less numerous. Only in isolated South America and Australia did widely divergent fauna exist. In Eurasia, genus richness shifted southward to lower latitudes from
21175-434: The historical warm interglacial period that looks most like the current one and from this have predicted that the next glacial period would usually begin within 1,500 years. They go on to predict that emissions have been so high that it will not. The causes of ice ages are not fully understood for either the large-scale ice age periods or the smaller ebb and flow of glacial–interglacial periods within an ice age. The consensus
21350-458: The human lineage) appeared in Africa at the very end of the Miocene, including Sahelanthropus , Orrorin , and an early form of Ardipithecus ( A. kadabba ). The chimpanzee–human divergence is thought to have occurred at this time. The evolution of bipedalism in apes at the end of the Miocene instigated an increased rate of faunal turnover in Africa. In contrast, European apes met their end at
21525-575: The interchange of fauna between Eurasia and Africa, including the dispersal of proboscideans and hominoids into Eurasia. During the late Miocene, the connections between the Atlantic and Mediterranean closed, causing the Mediterranean Sea to almost completely evaporate. This event is referred to as the " Messinian salinity crisis ". Then, at the Miocene–Pliocene boundary, the Strait of Gibraltar opened, and
21700-529: The lake levels of the Eastern Paratethys dropped as it once again became a sea. The Fram Strait opened during the Miocene and acted as the only throughflow for Atlantic Water into the Arctic Ocean until the Quaternary period. Due to regional uplift of the continental shelf, this water could not move through the Barents Seaway in the Miocene. The modern day Mekong Delta took shape after 8 Ma. Geochemistry of
21875-496: The last 1.5 million years were associated with northward shifts of melting Antarctic icebergs which changed ocean circulation patterns, leading to more CO 2 being pulled out of the atmosphere . The authors suggest that this process may be disrupted in the future as the Southern Ocean will become too warm for the icebergs to travel far enough to trigger these changes. Matthias Kuhle 's geological theory of Ice Age development
22050-422: The last glacial period the sea-level fluctuated 20–30 m as water was sequestered, primarily in the Northern Hemisphere ice sheets. When ice collected and the sea level dropped sufficiently, flow through the Bering Strait (the narrow strait between Siberia and Alaska is about 50 m deep today) was reduced, resulting in increased flow from the North Atlantic. This realigned the thermohaline circulation in
22225-490: The last vestiges of the Indo-Greek Kingdom, expanded back into the Tarim Basin in the 1st–2nd centuries CE, where they established a kingdom in Kashgar and competed for control of the area with nomads and Chinese forces. The Yuezhi or Rouzhi ( Chinese : 月氏 ; pinyin : Yuèzhī ; Wade–Giles : Yüeh -chih , [ɥê ʈʂɻ̩́] ) were an ancient people first reported in Chinese histories as nomadic pastoralists living in an arid grassland area in
22400-457: The latest Quaternary Ice Age ). Outside these ages, Earth was previously thought to have been ice-free even in high latitudes; such periods are known as greenhouse periods . However, other studies dispute this, finding evidence of occasional glaciations at high latitudes even during apparent greenhouse periods. Rocks from the earliest well-established ice age, called the Huronian , have been dated to around 2.4 to 2.1 billion years ago during
22575-812: The long run, supplying one-fifth of the country's total oil supply by 2010, with an annual output of 35 million tonnes . On June 10, 2010, Baker Hughes announced an agreement to work with PetroChina Tarim Oilfield Co. to supply oilfield services, including both directional and vertical drilling systems, formation evaluation services, completion systems and artificial lift technology for wells drilled into foothills formations greater than 7,500 meters (24,600 feet) deep with pressures greater than 20,000 psi (1,400 bar) and bottom-hole temperatures of approximately 160 °C (320 °F). Electrical submersible pumping (ESP) systems will be employed to dewater gas and condensate wells. PetroChina will fund any joint development. In 2015, Chinese researchers published
22750-433: The lowering of the Nordic inland ice areas and Tibet due to the weight of the superimposed ice-load, has led to the repeated complete thawing of the inland ice areas. Tarim Basin The Tarim Basin is an endorheic basin in Xinjiang , Northwestern China occupying an area of about 888,000 km (343,000 sq mi) and one of the largest basins in Northwest China. Located in China's Xinjiang region, it
22925-484: The most recent glacial periods, ice cores provide climate proxies , both from the ice itself and from atmospheric samples provided by included bubbles of air. Because water containing lighter isotopes has a lower heat of evaporation , its proportion decreases with warmer conditions. This allows a temperature record to be constructed. This evidence can be confounded, however, by other factors recorded by isotope ratios. The paleontological evidence consists of changes in
23100-473: The motion of tectonic plates resulting in changes in the relative location and amount of continental and oceanic crust on Earth's surface, which affect wind and ocean currents ; variations in solar output ; the orbital dynamics of the Earth–Moon system; the impact of relatively large meteorites and volcanism including eruptions of supervolcanoes . Some of these factors influence each other. For example, changes in Earth's atmospheric composition (especially
23275-453: The mountains and into the Tarim Basin, never reaching the sea. Surrounded by desert, some rivers feed the oases where the water is used for irrigation while others flow to salt lakes and marshes. Lop Nur is a marshy , saline depression at the east end of the Tarim Basin. The Tarim River ends in Lop Nur. The Tarim Basin is believed to contain large potential reserves of petroleum and natural gas . Methane comprises over 70 percent of
23450-407: The names Riss (180,000–130,000 years bp ) and Würm (70,000–10,000 years bp) refer specifically to glaciation in the Alpine region . The maximum extent of the ice is not maintained for the full interval. The scouring action of each glaciation tends to remove most of the evidence of prior ice sheets almost completely, except in regions where the later sheet does not achieve full coverage. Within
23625-405: The natural gas reserve, with variable contents of ethane (<1% – c. 18%) and propane (<0.5% – c. 9%). China National Petroleum Corporation 's comprehensive exploration of the Tarim basin between 1989 and 1995 led to the identification of 26 oil- and gas-bearing structures. These occur at deeper depths and in scattered deposits. Beijing aims to develop Xinjiang into China's new energy base for
23800-432: The north side to Kashgar. Highway 315 follows the south side from Kashgar to Charkilik and continues east to Tibet. There are currently four north–south roads across the desert. 218 runs from Charkilik to Korla along the former course of the Tarim, forming an oval whose other end is Kashgar. The Tarim Desert Highway , a major engineering achievement, crosses the center from Niya to Luntai . The new Highway 217 follows
23975-468: The north, and Kunlun Shan to the south. A thick succession of Paleozoic , Mesozoic and Cenozoic sedimentary rocks occupy the central parts of the basin, locally exceeding thicknesses of 15 km (9 mi). The source rocks of oil and gas tend to be mostly Permian mudstones and, less often, Ordovician strata which experienced an intense and widespread early Hercynian karstification . The effect of this event are e.g. paleokarst reservoirs in
24150-437: The oasis city-states of the Tarim Basin. Whereas the Yuezhi continued westward and conquered Daxia around 177–176 BC, the Sai (i.e. Saka), including some allied Tocharian peoples , fled south to the Pamirs before heading back east to settle in Tarim Basin sites like Yanqi (焉耆, Karasahr ) and Qiuci (龜茲, Kucha ). The Saka are recorded as inhabiting Khotan by at least the 3rd century and also settled in nearby Shache (莎車),
24325-419: The oceans, the lysocline shoaled by approximately half of a kilometre during warm phases that corresponded to orbital eccentricity maxima. The MMCO ended around 14 million years ago, when global temperatures fell in the Middle Miocene Climate Transition (MMCT). Abrupt increases in opal deposition indicate this cooling was driven by enhanced drawdown of carbon dioxide via silicate weathering. The MMCT caused
24500-520: The origin of many modern genera such as Nerodia , Lampropeltis , Pituophis and Pantherophis ). Arthropods were abundant, including in areas such as Tibet where they have traditionally been thought to be undiverse. Neoisopterans diversified and expanded into areas they previously were absent from, such as Madagascar and Australia. In the oceans, brown algae , called kelp , proliferated, supporting new species of sea life, including otters , fish and various invertebrates . Corals suffered
24675-521: The past few million years. These also confirm the linkage between ice ages and continental crust phenomena such as glacial moraines, drumlins, and glacial erratics. Hence the continental crust phenomena are accepted as good evidence of earlier ice ages when they are found in layers created much earlier than the time range for which ice cores and ocean sediment cores are available. There have been at least five major ice ages in Earth's history (the Huronian , Cryogenian , Andean-Saharan , late Paleozoic , and
24850-460: The possible herpetotheriid Morotodon from the late Early Miocene of Uganda. Approximately 100 species of apes lived during this time, ranging throughout Africa, Asia and Europe and varying widely in size, diet, and anatomy. Due to scanty fossil evidence it is unclear which ape or apes contributed to the modern hominid clade, but molecular evidence indicates this ape lived between 18 and 13 million years ago. The first hominins ( bipedal apes of
25025-668: The preceding Oligocene and following Pliocene Epochs: Continents continued to drift toward their present positions. Of the modern geologic features, only the land bridge between South America and North America was absent, although South America was approaching the western subduction zone in the Pacific Ocean , causing both the rise of the Andes and a southward extension of the Meso-American peninsula. Mountain building took place in western North America , Europe , and East Asia . Both continental and marine Miocene deposits are common worldwide with marine outcrops common near modern shorelines. Well studied continental exposures occur in
25200-563: The presence or expansion of continental and polar ice sheets and alpine glaciers . Earth's climate alternates between ice ages, and greenhouse periods during which there are no glaciers on the planet. Earth is currently in the ice age called Quaternary glaciation . Individual pulses of cold climate within an ice age are termed glacial periods ( glacials, glaciations, glacial stages, stadials, stades , or colloquially, ice ages ), and intermittent warm periods within an ice age are called interglacials or interstadials . In glaciology ,
25375-449: The reduction in weathering causes an increase in the greenhouse effect . There are three main contributors from the layout of the continents that obstruct the movement of warm water to the poles: Since today's Earth has a continent over the South Pole and an almost land-locked ocean over the North Pole, geologists believe that Earth will continue to experience glacial periods in the geologically near future. Some scientists believe that
25550-458: The region to the Chinese. The Han Chinese wrested control of the Tarim Basin from the Xiongnu at the end of the 1st century under the leadership of General Ban Chao (32–102 CE), during the Han-Xiongnu War . The Chinese administered the Tarim Basin as the Protectorate of the Western Regions . The Tarim Basin was later under many foreign rulers, but ruled primarily by Turkic, Han, Tibetan, and Mongolic peoples. The powerful Kushans , who conquered
25725-421: The role of weathering). Greenhouse gas levels may also have been affected by other factors which have been proposed as causes of ice ages, such as the movement of continents and volcanism. The Snowball Earth hypothesis maintains that the severe freezing in the late Proterozoic was ended by an increase in CO 2 levels in the atmosphere, mainly from volcanoes, and some supporters of Snowball Earth argue that it
25900-530: The southernmost tip of Patagonia, meaning that the Chile Triple Junction lay near the Strait of Magellan . As the southern part of Nazca Plate and the Chile Rise became consumed by subduction the more northerly regions of the Antarctic Plate begun to subduct beneath Patagonia so that the Chile Triple Junction advanced to the north over time. The asthenospheric window associated to the triple junction disturbed previous patterns of mantle convection beneath Patagonia inducing an uplift of ca. 1 km that reversed
26075-429: The spread of ice sheets in the Northern Hemisphere began. Since then, the world has seen cycles of glaciation with ice sheets advancing and retreating on 40,000- and 100,000-year time scales called glacial periods , glacials or glacial advances, and interglacial periods, interglacials or glacial retreats. Earth is currently in an interglacial, and the last glacial period ended about 11,700 years ago. All that remains of
26250-441: The summer of 1835 he made some excursions to the Bavarian Alps. Schimper came to the conclusion that ice must have been the means of transport for the boulders in the alpine upland. In the winter of 1835–36 he held some lectures in Munich. Schimper then assumed that there must have been global times of obliteration ("Verödungszeiten") with a cold climate and frozen water. Schimper spent the summer months of 1836 at Devens, near Bex, in
26425-437: The sword to make the population convert to Islam. After being converted to Islam, the descendants of the previously Buddhist Uyghurs in Turfan believed that the "infidel Kalmuks" ( Dzungars ) were the ones who built Buddhist monuments in their area, in opposition to the current academic theory that it was their own ancestral legacy. The eastern regions of the Chagatai Khanate in the early 14th century had been inhabited by
26600-408: The temperatures over land by increased albedo as noted above. Furthermore, under this hypothesis the lack of oceanic pack ice allows increased exchange of waters between the Arctic and the North Atlantic Oceans, warming the Arctic and cooling the North Atlantic. (Current projected consequences of global warming include a brief ice-free Arctic Ocean period by 2050 .) Additional fresh water flowing into
26775-425: The term ice age is defined by the presence of extensive ice sheets in the northern and southern hemispheres. By this definition, the current Holocene period is an interglacial period of an ice age. The accumulation of anthropogenic greenhouse gases is projected to delay the next glacial period. In 1742, Pierre Martel (1706–1767), an engineer and geographer living in Geneva , visited the valley of Chamonix in
26950-440: The tilt of Earth's rotational axis. Earth has been in an interglacial period known as the Holocene for around 11,700 years, and an article in Nature in 2004 argues that it might be most analogous to a previous interglacial that lasted 28,000 years. Predicted changes in orbital forcing suggest that the next glacial period would begin at least 50,000 years from now. Moreover, anthropogenic forcing from increased greenhouse gases
27125-457: The time of the Qing conquest in 1759, Dzungaria was inhabited by steppe-dwelling, nomadic Mongolic-speaking , Tibetan Buddhist Dzungars , while the Tarim Basin (Altishahr) was inhabited by sedentary, oasis-dwelling, Turkic-speaking Uyghur Muslim farmers. Dzungaria and the Tarim Basin were each governed separately until the creation of Xinjiang in 1884 . The Chinese called this the Tien Shan Nan Lu or Tien Shan South Road, as opposed to
27300-562: The two separate political entities of Dzungaria and the Tarim Basin (Eastern Turkestan). Dzungharia or Ili was called Zhunbu 準部 (Dzungar region) Tianshan Beilu 天山北路 (Northern March), "Xinjiang" 新疆 (New Frontier), or "Kalmykia" (La Kalmouquie in French). It was formerly the area of the Dzungar (or Zunghar) Khanate 準噶爾汗國, the land of the Dzungar people . The Tarim Basin was known as "Tianshan Nanlu 天山南路 (southern March), Huibu 回部 (Muslim region), Huijiang 回疆 (Muslim frontier), Chinese Turkestan , Kashgaria, Little Bukharia, East Turkestan ", and
27475-462: The warm conditions of the MMCO. The MMCO saw the expansion of the tropical climatic zone to much larger than its current size. The July ITCZ, the zone of maximal monsoonal rainfall, moved to the north, increasing precipitation over southern China whilst simultaneously decreasing it over Indochina during the EASM. Western Australia was at this time characterised by exceptional aridity. In Antarctica, average summer temperatures on land reached 10 °C. In
27650-438: The west coast of South America are thought to be caused by a regional phenomenon while the steadily rising central segment of the Andes represents an exception. While there are numerous registers of Oligocene–Miocene transgressions around the world it is doubtful that these correlate. It is thought that the Oligocene–Miocene transgression in Patagonia could have temporarily linked the Pacific and Atlantic Oceans, as inferred from
27825-504: The western part of the modern Chinese province of Gansu during the 1st millennium BC. After a major defeat by the Xiongnu, in the 2nd century BC, the Yuezhi split into two groups: the Greater Yuezhi ( Dà Yuèzhī 大月氏) and Lesser Yuezhi ( Xiǎo Yuèzhī 小月氏). They introduced the Brahmi script, the Indian Prakrit language for administration, and Buddhism , playing a central role in the Silk Road transmission of Buddhism to Eastern Asia. Three pre-Han texts mention peoples who appear to be
28000-433: The world. When the Bavarian naturalist Ernst von Bibra (1806–1878) visited the Chilean Andes in 1849–1850, the natives attributed fossil moraines to the former action of glaciers. Meanwhile, European scholars had begun to wonder what had caused the dispersal of erratic material. From the middle of the 18th century, some discussed ice as a means of transport. The Swedish mining expert Daniel Tilas (1712–1772) was, in 1742,
28175-422: Was Allodesmus . A ferocious walrus , Pelagiarctos may have preyed upon other species of pinnipeds including Allodesmus . Furthermore, South American waters witnessed the arrival of Megapiranha paranensis , which were considerably larger than modern age piranhas . New Zealand 's Miocene fossil record is particularly rich. Marine deposits showcase a variety of cetaceans and penguins , illustrating
28350-419: Was captured by the Tang in 644 and the kingdom of Kucha was conquered in 649 . The expansion into Central Asia continued under Taizong's successor, Emperor Gaozong , who dispatched an army in 657 led by Su Dingfang against the Western Turk qaghan Ashina Helu . Ashina was defeated and the khaganate was absorbed into the Tang empire. The Tarim Basin was administered through the Anxi Protectorate and
28525-455: Was abandoned. The Tarim ended at the now-dry Lop Nur, which occupied a shifting position east of Loulan. Eastward is the fabled Jade Gate which the Chinese considered the gateway to the Western Regions . Beyond that was Dunhuang with its ancient manuscripts and then Anxi at the west end of the Gansu Corridor . Settlements include Kashgar; Yangi Hissar , famous for its knives; Yarkand , once larger than Kashgar; Karghalik (Yecheng), with
28700-403: Was arid, particularly so during the Middle Miocene. Climates remained moderately warm, although the slow global cooling that eventually led to the Pleistocene glaciations continued. Although a long-term cooling trend was well underway, there is evidence of a warm period during the Miocene when the global climate rivalled that of the Oligocene . The climate of the Miocene has been suggested as
28875-492: Was caused by the elimination of atmospheric methane , a greenhouse gas , during the Great Oxygenation Event . The next well-documented ice age, and probably the most severe of the last billion years, occurred from 720 to 630 million years ago (the Cryogenian period) and may have produced a Snowball Earth in which glacial ice sheets reached the equator, possibly being ended by the accumulation of greenhouse gases such as CO 2 produced by volcanoes. "The presence of ice on
29050-429: Was caused in the first place by a reduction in atmospheric CO 2 . The hypothesis also warns of future Snowball Earths. In 2009, further evidence was provided that changes in solar insolation provide the initial trigger for Earth to warm after an Ice Age, with secondary factors like increases in greenhouse gases accounting for the magnitude of the change. The geological record appears to show that ice ages start when
29225-455: Was difficult to date exactly; early theories assumed that the glacials were short compared to the long interglacials. The advent of sediment and ice cores revealed the true situation: glacials are long, interglacials short. It took some time for the current theory to be worked out. The chemical evidence mainly consists of variations in the ratios of isotopes in fossils present in sediments and sedimentary rocks and ocean sediment cores. For
29400-491: Was highly dynamic during the Early Miocene. The Miocene began with the Early Miocene Cool Event (Mi-1) around 23 million years ago, which marked the start of the Early Miocene Cool Interval (EMCI). This cool event occurred immediately after the Oligocene-Miocene Transition (OMT) during a major expansion of Antarctica's ice sheets, but was not associated with a significant drop in atmospheric carbon dioxide levels. Both continental and oceanic thermal gradients in mid-latitudes during
29575-513: Was inversely correlated with carbon dioxide levels and global temperatures during the Miocene. Most modern lineages of diatoms appeared by the Late Miocene. There is evidence from oxygen isotopes at Deep Sea Drilling Program sites that ice began to build up in Antarctica about 36 Ma during the Eocene . Further marked decreases in temperature during the Middle Miocene at 15 Ma probably reflect increased ice growth in Antarctica. It can therefore be assumed that East Antarctica had some glaciers during
29750-402: Was of some importance when Tibet was an empire. North of the mountains is Dzungaria with its central Gurbantünggüt Desert , Ürümqi, and the Karamay oil fields. The Kulja territory is the upper basin of the Ili River and opens out onto the Kazakh Steppe with several roads east. The Dzungarian Gate was once a migration route and is now a road and rail crossing . Tacheng or Tarbaghatay
29925-408: Was paid by the Chagatayids to the eastern regions. As a result, the eastern tribes there were virtually independent. The most powerful of the tribes, the Dughlats , controlled extensive territories in Moghulistan and the western Tarim Basin. In 1347 the Dughlats decided to appoint a khan of their own, and raised the Chagatayid Tughlugh Timur to the throne. In 1509 the Dughlats, vassal rulers of
30100-421: Was particularly renowned. Music and dances from Kucha were also popular in the Sui and Tang periods. During the Tang dynasty , a series of military expeditions were conducted against the oasis states of the Tarim Basin, then vassals of the Western Turkic Khaganate . The campaigns against the oasis states began under Emperor Taizong with the annexation of Gaochang in 640. The nearby kingdom of Karasahr
30275-463: Was slain by the Buddhists during the war. Buddhism lost territory to the Turkic Karakhanid Satok Bughra Khan during the Karakhanid reign around Kashgar. The Tarim Basin became Islamicized over the next few centuries. In the tenth century, the Buddhist Iranic Saka Kingdom of Khotan was the only city-state that was not conquered yet by the Turkic Uyghur (Buddhist) and the Turkic Karakhanid (Muslim) states. The Buddhist entitites of Dunhuang and Khotan had
30450-406: Was suggested by the existence of an ice sheet covering the Tibetan Plateau during the Ice Ages ( Last Glacial Maximum ?). According to Kuhle, the plate-tectonic uplift of Tibet past the snow-line has led to a surface of c. 2,400,000 square kilometres (930,000 sq mi) changing from bare land to ice with a 70% greater albedo . The reflection of energy into space resulted in a global cooling, triggering
30625-479: Was the MMCO that began 16 million years ago. As the world transitioned into the MMCO, carbon dioxide concentrations varied between 300 and 500 ppm. Global annual mean surface temperature during the MMCO was about 18.4 °C. MMCO warmth was driven by the activity of the Columbia River Basalts and enhanced by decreased albedo from the reduction of deserts and expansion of forests. Climate modelling suggests additional, currently unknown, factors also worked to create
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