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51-678: Read Mountains is a group of rocky summits, the highest being Holmes Summit at 1,875 metres (6,152 ft), lying east of Glen Glacier in the south-central part of the Shackleton Range . The Read Mountains were first mapped in 1957 by the Commonwealth Trans-Antarctic Expedition . They are named for Professor Herbert Harold Read , Chairman of the Scientific Committee and member of the Committee of Management of

102-697: A supereon , but this is also an informal term, not defined by the ICS in its chronostratigraphic guide. Eozoic (from eo- "earliest") was a synonym for pre-Cambrian , or more specifically Archean . A specific date for the origin of life has not been determined. Carbon found in 3.8 billion-year-old rocks (Archean Eon) from islands off western Greenland may be of organic origin. Well-preserved microscopic fossils of bacteria older than 3.46 billion years have been found in Western Australia . Probable fossils 100 million years older have been found in

153-532: A basal sequence of quartzite and metalimestone resting unconformably on the metamorphic basement. The formation is over 2,500 metres (8,200 ft) thick, and overlays the Middle Precambrian Shackleton Range Metamorphic Complex of gneisses, schists and amphibolites. Ice-free terraces ( 80°43′S 22°41′W  /  80.717°S 22.683°W  / -80.717; -22.683 ) rising to 1,520 metres (4,990 ft) on

204-608: A pioneer of the theory of continental drift; Professor of Geophysics and Meteorology, University of Graz, Austria, 1924-30; Leader of German expeditions to Greenland in 1929 and 1930, losing life on the ice cap in November of that year. Mount Wegener gives its name to the Mount Wegener Formation of the Late Precambrian Turnpike Bluff Group. It consists of slate, quartzite and minor conglomerate overlying

255-713: A possible 2450 Ma red alga from the Kola Peninsula , 1650 Ma carbonaceous biosignatures in north China, the 1600 Ma Rafatazmia , and a possible 1047 Ma Bangiomorpha red alga from the Canadian Arctic. The earliest fossils widely accepted as complex multicellular organisms date from the Ediacaran Period. A very diverse collection of soft-bodied forms is found in a variety of locations worldwide and date to between 635 and 542 Ma. These are referred to as Ediacaran or Vendian biota . Hard-shelled creatures appeared toward

306-518: Is a stub . You can help Misplaced Pages by expanding it . Late Precambrian The Precambrian is an informal unit of geologic time, subdivided into three eons ( Hadean , Archean , Proterozoic ) of the geologic time scale . It spans from the formation of Earth about 4.6 billion years ago ( Ga ) to the beginning of the Cambrian Period, about 538.8 million years ago ( Ma ), when hard-shelled creatures first appeared in abundance. Relatively little

357-654: Is known about the Precambrian, despite it making up roughly seven-eighths of the Earth's history , and what is known has largely been discovered from the 1960s onwards. The Precambrian fossil record is poorer than that of the succeeding Phanerozoic , and fossils from the Precambrian (e.g. stromatolites ) are of limited biostratigraphic use. This is because many Precambrian rocks have been heavily metamorphosed , obscuring their origins, while others have been destroyed by erosion, or remain deeply buried beneath Phanerozoic strata. It

408-597: Is known to occur during the RNA replication of extant coronaviruses . Evidence of the details of plate motions and other tectonic activity in the Precambrian is difficult to interpret. It is generally believed that small proto-continents existed before 4280 Ma, and that most of the Earth's landmasses collected into a single supercontinent around 1130 Ma. The supercontinent, known as Rodinia , broke up around 750 Ma. A number of glacial periods have been identified going as far back as

459-514: Is thought that the Earth coalesced from material in orbit around the Sun at roughly 4,543 Ma, and may have been struck by another planet called Theia shortly after it formed, splitting off material that formed the Moon (see Giant-impact hypothesis ). A stable crust was apparently in place by 4,433 Ma, since zircon crystals from Western Australia have been dated at 4,404 ± 8 Ma. The term "Precambrian"

510-693: Is used by geologists and paleontologists for general discussions not requiring a more specific eon name. However, both the United States Geological Survey and the International Commission on Stratigraphy regard the term as informal. Because the span of time falling under the Precambrian consists of three eons (the Hadean , the Archean , and the Proterozoic ), it is sometimes described as

561-853: The British Antarctic Survey in the period 1968–71. In association with the names of geologists grouped in this area, it was named by the UK Antarctic Place-Names Committee in 1971 after Professor Arthur Holmes , after whom the Holmes Hills in Palmer Land were also named. [REDACTED]  This article incorporates public domain material from "Holmes Summit" . Geographic Names Information System . United States Geological Survey . 80°40′S 24°40′W  /  80.667°S 24.667°W  / -80.667; -24.667 This Coats Land location article

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612-521: The Huronian epoch, roughly 2400–2100 Ma. One of the best studied is the Sturtian-Varangian glaciation, around 850–635 Ma, which may have brought glacial conditions all the way to the equator, resulting in a " Snowball Earth ". The atmosphere of the early Earth is not well understood. Most geologists believe it was composed primarily of nitrogen, carbon dioxide, and other relatively inert gases, and

663-739: The Paleoproterozoic were very similar to that of the Mawson Continent , which may mean that this continent extends over the Eastern Antarctic Shield and includes the Shackleton Range. Named features of the escarpment north of the range are, from west to east: A rock spur ( 80°38′S 24°26′W  /  80.633°S 24.433°W  / -80.633; -24.433 ) rising to c. 1,500 metres (4,900 ft) and bounded by screes (taluses), located northwest of Arkell Cirque on

714-482: The oxygen catastrophe . At first, oxygen would have quickly combined with other elements in Earth's crust, primarily iron, removing it from the atmosphere. After the supply of oxidizable surfaces ran out, oxygen would have begun to accumulate in the atmosphere, and the modern high-oxygen atmosphere would have developed. Evidence for this lies in older rocks that contain massive banded iron formations that were laid down as iron oxides. A terminology has evolved covering

765-782: The Commonwealth Trans-Antarctic Expedition, 1955–58. The Read Mountains form the southern rim of the eastern part of the Shackleton Range. To the north is the Shotton Snowfield . The Recovery Glacier runs west along the south face of the mountains. To the west the Cornwall Glacier separates the Read Mountains from the Stephenson Bastion . Isolated nunataks of the Pioneers Escarpment lie to

816-622: The Flett Crags Formation of the Late Precambrian Turnpike Bluff Group. The formation is over 1,500 metres (4,900 ft) thick and is mainly composed of slates, with minor quartzites and some pebble conglomerates. It overlays the Middle Precambrian Shackleton Range Metamorphic Complex of gneisses, schists and amphibolites. A group of nunataks ( 80°38′S 23°20′W  /  80.633°S 23.333°W  / -80.633; -23.333 ) 6 miles (9.7 km) north-north-east of Mount Wegener, rising to 1,470 metres (4,820 ft) near

867-512: The Read Mountains, Shackleton Range. Photographed from the air by the U.S. Navy, 1967. Surveyed by BAS, 1968-71. In association with the names of geologists grouped in this area, named by the UK-APC in 1971 after Norman Levi Bowen (1887-1956), American experimental petrologist who specialized in the phase equilibria of silicate melt systems. A cirque ( 80°44′S 23°08′W  /  80.733°S 23.133°W  / -80.733; -23.133 ) to

918-540: The Shackleton Range to join Recovery Glacier east of Ram Bow Bluff . First mapped in 1957 by the CTAE and named for Gen. Sir James H. Marshall-Cornwall , member of the Committee of Management of the CTAE, 1955-58. Glacier ( 80°44′S 25°16′W  /  80.733°S 25.267°W  / -80.733; -25.267 ) at least 7 miles (11 km) long, flowing south in the Shackleton Range to join Recovery Glacier to

969-423: The air by the U.S. Navy, 1967, and surveyed by BAS, 1968-71. In association with the names of geologists grouped in this area, named by the UK-APC in 1971 after Professor Arthur Holmes ( Holmes Hills , q.v). A sharp-crested ridge ( 80°43′S 24°19′W  /  80.717°S 24.317°W  / -80.717; -24.317 ) rising to 1,600 metres (5,200 ft) between Murchison Cirque and Arkell Cirque on

1020-481: The air by the U.S. Navy, 1967, and surveyed by BAS, 1968-71. In association with the names of geologists grouped in this area, named by the UK-APC in 1971 after Sir Roderick Impey Murchison (1792-1871), British geologist; President, Royal Geographical Society, 1843-44, 1851-52, and 1855-58; Director-General, Geological Survey of Great Britain, 1855-71. A large cirque ( 80°41′S 24°08′W  /  80.683°S 24.133°W  / -80.683; -24.133 ) on

1071-477: The air by the U.S. Navy, 1967. Surveyed by BAS, 1968-71. In association with names of geologists grouped in this area, named by the UK-APC in 1971 after John Strachey (1671-1742), English geologist who made one of the first attempts to construct a geological cross-section, (in Chew Valley near Somerset coalfield ). He introduced a theory of rock formations known as Stratum , based on a pictorial cross-section of

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1122-484: The air by the U.S. Navy, 1967. Surveyed by the BAS, 1968-71. In association with the names of geologists grouped in this area, named by the UK-APC in 1971 after Pentti Eskola (1883–1964), Finnish geologist, an authority on the Precambrian rocks of Finland and on silicate melt systems. A cirque ( 80°42′S 23°27′W  /  80.700°S 23.450°W  / -80.700; -23.450 ) north-northeast of Mount Wegener in

1173-416: The central part of the Read Mountains, in the Shackleton Range. First mapped in 1957 by the CTAE. The name, given by the UK-APC, is descriptive of its shape when viewed from the west. Peak ( 80°40′S 24°40′W  /  80.667°S 24.667°W  / -80.667; -24.667 ) rising to 1,875 metres (6,152 ft), the highest elevation in the Read Mountains, Shackleton Range. Photographed from

1224-401: The current scheme based upon numerical ages. Such a system could rely on events in the stratigraphic record and be demarcated by GSSPs . The Precambrian could be divided into five "natural" eons, characterized as follows: The movement of Earth's plates has caused the formation and break-up of continents over time, including occasional formation of a supercontinent containing most or all of

1275-453: The early years of the Earth's existence, as radiometric dating has allowed absolute dates to be assigned to specific formations and features. The Precambrian is divided into three eons: the Hadean (4567.3–4031 Ma), Archean (4031-2500 Ma) and Proterozoic (2500-538.8 Ma). See Timetable of the Precambrian . It has been proposed that the Precambrian should be divided into eons and eras that reflect stages of planetary evolution, rather than

1326-666: The east end of the Read Mountains, Shackleton Range. Photographed from the air by the U.S. Navy, 1967. Surveyed by BAS, 1968-71. In association with the names of geologists grouped in this area, named by the UK-APC in 1971 after Paul Niggli (1888-1953), Swiss geologist who introduced the cataloguing of magma types by molecular or Niggli values; Professor of Geology, University of Zurich. A flat-topped mountain ( 80°41′S 23°10′W  /  80.683°S 23.167°W  / -80.683; -23.167 ) rising to 1,630 metres (5,350 ft), 5 miles (8.0 km) northeast of Mount Wegener in Read Mountains, Shackleton Range. Photographed from

1377-649: The east end of the Read Mountains, Shackleton Range. Photographed from the air by the U.S. Navy, 1967. Surveyed by the BAS, 1968-71. In association with the names of geologists grouped in this area, named by the UK-APC after Henry H. Swinnerton (1876-1966), British zoologist and paleontologist, Professor of Geology, University College of Nottingham (later Nottingham University), 1912–46; President, Geological Society, 1938-40. 81°10′S 28°00′W  /  81.167°S 28.000°W  / -81.167; -28.000 . Glacier, at least 60 miles (97 km) long and 40 miles (64 km) wide at its mouth, flowing west along

1428-737: The east side of Goldschmidt Cirque, near the east end of Read Mountains, Shackleton Range. Photographed from the air by the U.S. Navy, 1967, and surveyed by BAS, 1968-71. In association with the names of geologists grouped in this area, named by the UK-APC after Sir Arthur E. Trueman (1895-1956), British geologist, who worked on the coal measures and their correlation by marine bands, and on the introduction of statistical methods into paleontology; Professor of Geology, Glasgow University, 1937-46; President, Geological Society of London, 1945–47. A flat-topped ridge ( 80°43′S 22°28′W  /  80.717°S 22.467°W  / -80.717; -22.467 ) rising to c. 1,500 metres (4,900 ft) and marking

1479-741: The end of that time span, marking the beginning of the Phanerozoic Eon. By the middle of the following Cambrian Period, a very diverse fauna is recorded in the Burgess Shale , including some which may represent stem groups of modern taxa. The increase in diversity of lifeforms during the early Cambrian is called the Cambrian explosion of life. While land seems to have been devoid of plants and animals, cyanobacteria and other microbes formed prokaryotic mats that covered terrestrial areas. Tracks from an animal with leg-like appendages have been found in what

1530-496: The geology under his estate at Bishop Sutton and Stowey in the Chew Valley and coal seams in nearby coal works of the Somerset coalfield , projecting them according to their measured thicknesses and attitudes into unknown areas between the coal workings. The purpose was to enhance the value of his grant of a coal-lease on parts of his estate. This work was later developed by William Smith . Download coordinates as: Cirques on

1581-541: The landmass. The earliest known supercontinent was Vaalbara . It formed from proto-continents and was a supercontinent 3.636 billion years ago. Vaalbara broke up c. 2.845–2.803 Ga ago. The supercontinent Kenorland was formed c. 2.72 Ga ago and then broke sometime after 2.45–2.1 Ga into the proto-continent cratons called Laurentia , Baltica , Yilgarn craton and Kalahari . The supercontinent Columbia , or Nuna, formed 2.1–1.8 billion years ago and broke up about 1.3–1.2 billion years ago. The supercontinent Rodinia

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1632-479: The metagranites gives ages of around 1,760 and 1,600 million years. Rb–Sr and K-Ar mineral cooling ages are 1650–1550 million years. The Southern Terrane has detritus up to 2,850 million years old that experienced magmatism from 1,850 to 1,810 million years ago, a metamorphic event between 1,710 and 1,680 years ago, and another metamorphic event 510 million years ago. Tectonics in the Southern Terrane during

1683-412: The names of geologists grouped in this area, named by the UK-APC in 1971 after Professor Hisashi Kuno (1910–69), Japanese petrologist, who worked on basaltic magmas. A glacier-filled cirque ( 80°42′S 24°33′W  /  80.700°S 24.550°W  / -80.700; -24.550 ) between Kuno Cirque and Arkell Cirque on the south side of the Read Mountains, Shackleton Range. Photographed from

1734-496: The north side of the Read Mountains, Shackleton Range. Photographed from the air by the U.S. Navy, 1967, and surveyed by BAS, 1968-71. In association with the names of geologists grouped in this area, named by the UK-APC in 1971 after Gideon A. Mantell (1790–1852), English surgeon and geologist, known for his discovery of the iguanodon and three other fossil reptiles. Rock crags ( 80°39′S 23°35′W  /  80.650°S 23.583°W  / -80.650; -23.583 ) on

1785-512: The north slope of Read Mountains, 5 miles (8.0 km) north of Mount Wegener, in the Shackleton Range. Photographed from the air by the U.S. Navy in 1967. Surveyed by BAS, 1968-71. In association with the names of geologists grouped in this area, named by the UK-APC after Sir John Smith Flett (1869-1947), British geologist who worked on Scottish geology and volcanoes; Director, Geological Survey and Museum of Practical Geology (later British Geological Survey), 1920–35. Flett Crags gives its name to

1836-531: The northeast and east of the mountains. The Reid Mountains are a group of arêtes extending south from the 200 to 400 metres (660 to 1,310 ft) high escarpment along the southern edge of the Shotton Snowfield. Between the arêtes there are cirques floored with blue ice that slope gently down to the Recovery Glacier. The mountains are mostly made up of schists and gneisses , but Mount Wegener and

1887-588: The ridges east are topped with slates . These flat-topped ridges are remains of a peneplain that had an elevation of around 1,500 metres (4,900 ft) in this area. The southern belt of the Shackleton Range is exposed in the Read Mountains. It has medium- to high-grade metamorphic rocks classified as the Read Group. They are mainly composed of partly migmatised quartzitic, basic, calcareous and pelitic rocks. In places they are interlayered with gneissic granites, and intruded by granites and basic rocks. Dating of

1938-526: The same area. However, there is evidence that life could have evolved over 4.280 billion years ago. There is a fairly solid record of bacterial life throughout the remainder (Proterozoic Eon) of the Precambrian. Complex multicellular organisms may have appeared as early as 2100 Ma. However, the interpretation of ancient fossils is problematic, and "... some definitions of multicellularity encompass everything from simple bacterial colonies to badgers." Other possible early complex multicellular organisms include

1989-444: The south edge of the range, facing the Recovery Glacier to the south, are (from west to east): A glacier-filled cirque ( 80°40′S 24°55′W  /  80.667°S 24.917°W  / -80.667; -24.917 ) between Glen Glacier and Murchison Cirque on the south side of the Read Mountains, Shackleton Range. The feature was photographed from the air by the U.S. Navy, 1967, and surveyed by BAS, 1968-71. In association with

2040-580: The south face of the central Read Mountains, Shackleton Range. Photographed from the air by U.S. Navy in 1967 and surveyed from the ground by BAS, 1968-71. Named by the UK-APC after William J. Arkell (1904-58), English geologist; specialist in Jurassic stratigraphy and paleontology. A cirque ( 80°43′S 23°49′W  /  80.717°S 23.817°W  / -80.717; -23.817 ) 2 miles (3.2 km) wide between Arkell Cirque and Bowen Cirque in central Read Mountains, Shackleton Range. Photographed from

2091-450: The south of Arkell Cirque in the Read Mountains, Shackleton Range. Photographed from the air by the U.S. Navy, 1967, and surveyed by BAS, 1968-71. In association with the names of geologists grouped in this area, named by the UK-APC in 1971 after William Nicol (c. 1768-1851), Scottish natural philosopher who devised the Nicol prism and the preparation of thin rock sections, thus contributing to

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2142-565: The south side of Read Mountains, Shackleton Range. Photographed from the air by the U.S. Navy, 1967, and surveyed by BAS, 1968-71. In association with the names of geologists grouped in this area, named in 1971 by the UK-APC after Sir Henry Thomas de la Beche (1796-1855), English geologist, first Director-General, Geological Survey of Great Britain (later Institute of Geological Sciences), 1835–55. Rock crags ( 80°44′S 24°05′W  /  80.733°S 24.083°W  / -80.733; -24.083 ) rising to c. 1,300 metres (4,300 ft) to

2193-580: The south side of the Shackleton Range. First seen from the air and examined from the ground by the CTAF in 1957, and so named because of the recovery of the expedition's vehicles which repeatedly broke into bridged crevasses on this glacier during the early stages of the crossing of Antarctica. Not: Glaciar Expedicion Polar Argentina, Glaciar Falucho. 80°47′S 26°16′W  /  80.783°S 26.267°W  / -80.783; -26.267 . Glacier 9 miles (14 km) long, flowing south from Crossover Pass in

2244-671: The southwest end of the ridge east of Glen Glacier, in the Read Mountains, Shackleton Range. Photographed from the air by the U.S. Navy, 1967, and surveyed by BAS, 1968-71. In association with the names of geologists grouped in this area, named by the UK-APC in 1971 after William Whitehead Watts (1860–1947), British geologist who worked particularly on the Precambrian rocks of the English midlands; Professor of Geology, Imperial College, London, 1906-30. Rock summit ( 80°43′S 24°47′W  /  80.717°S 24.783°W  / -80.717; -24.783 ) rising to 1,790 metres (5,870 ft) in

2295-500: The techniques of microscopy. Mountain ( 80°44′S 23°31′W  /  80.733°S 23.517°W  / -80.733; -23.517 ) rising to 1,385 metres (4,544 ft) in central Read Mountains, Shackleton Range. The feature was photographed from the air by the U.S. Navy, 1967. Surveyed by BAS, 1968-71. Named by the UK-APC in association with the names of geologists grouped in this area after Alfred L. Wegener (1880-1930), German astronomer, meteorologist, and Arctic explorer;

2346-451: The west end of the Read Mountains, Shackleton Range. Photographed from the air by the U.S. Navy, 1967, and surveyed by the BAS, 1968-71. In association with the names of geologists grouped in this area, named by the UK-APC after Alexander Logie du Toit , South African geologist. A needle-shaped peak ( 80°44′S 24°59′W  /  80.733°S 24.983°W  / -80.733; -24.983 ) rising to 1,450 metres (4,760 ft)) at

2397-663: The west of Goldschmidt Cirque in the east portion of Read Mountains, Shackleton Range. Photographed from the air by the U.S. Navy, 1967. Surveyed by BAS, 1968-71. In association with the names of geologists grouped in this area, named by the UK-APC in 1971 after Charles Lapworth (1842-1920), British geologist who established the stratigraphic succession in south Scotland and who defined the Ordovician system ; Professor of Geology and Physiography, Birmingham University , 1881–1913. A cirque ( 80°44′S 22°48′W  /  80.733°S 22.800°W  / -80.733; -22.800 ) at

2448-522: The west of Read Mountains. First mapped in 1957 by the CTAE and named for Alexander R. Glen, member of the Committee of Management of the CTAE, 1955–58. Holmes Summit Holmes Summit is a peak rising to 1,875 metres (6,150 ft), the highest elevation in the Read Mountains of the Shackleton Range in Antarctica. It was photographed from the air by the U.S. Navy in 1967 and was surveyed by

2499-612: The west side of Trueman Terraces in the east portion of the Read Mountains, Shackleton Range. Photographed from the air by the U.S. Navy, 1967. Surveyed by the BAS, 1968-71. In association with the names of geologists grouped in this area, named by the UK-APC after Victor M. Goldschmidt (1888-1947), Norwegian geochemist and pioneer in the field of crystal chemistry. Mountains, ridges and escarpments include, from west to east: A group of nunataks ( 80°43′S 25°50′W  /  80.717°S 25.833°W  / -80.717; -25.833 ) between Cornwall Glacier and Glen Glacier, marking

2550-482: Was lacking in free oxygen . There is, however, evidence that an oxygen-rich atmosphere existed since the early Archean. At present, it is still believed that molecular oxygen was not a significant fraction of Earth's atmosphere until after photosynthetic life forms evolved and began to produce it in large quantities as a byproduct of their metabolism . This radical shift from a chemically inert to an oxidizing atmosphere caused an ecological crisis , sometimes called

2601-846: Was mud 551 million years ago. The RNA world hypothesis asserts that RNA evolved before coded proteins and DNA genomes. During the Hadean Eon (4,567–4,031 Ma) abundant geothermal microenvironments were present that may have had the potential to support the synthesis and replication of RNA and thus possibly the evolution of a primitive life form. It was shown that porous rock systems comprising heated air-water interfaces could allow ribozyme - catalyzed RNA replication of sense and antisense strands that could be followed by strand-dissociation, thus enabling combined synthesis, release and folding of active ribozymes. This primitive RNA replicative system also may have been able to undergo template strand switching during replication ( genetic recombination ) as

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