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64-579: The Wairau Bar , or Te Pokohiwi , is a 19-hectare (47-acre) gravel bar formed where the Wairau River meets the sea in Cloudy Bay , Marlborough , north-eastern South Island , New Zealand. It is an important archaeological site, settled by explorers from East Polynesia who arrived in New Zealand about 1280. It is one of the earliest known human settlements in New Zealand. At the time of

128-487: A N(n,p) C reaction, direct uranium decay (though reported measured ratios of C/U in uranium-bearing ores would imply roughly 1 uranium atom for every two carbon atoms in order to cause the C/ C ratio, measured to be on the order of 10 ), or other unknown secondary sources of C production. The presence of C in the isotopic signature of a sample of carbonaceous material possibly indicates its contamination by biogenic sources or

192-504: A braid bar because they are often found in braided river channels. Braided river channels are broad and shallow and found in areas where sediment is easily eroded like at a glacial outwash , or at a mountain front with high sediment loads. These types of river systems are associated with high slope , sediment supply, stream power , shear stress , and bed load transport rates. Braided rivers have complex and unpredictable channel patterns, and sediment size tends to vary among streams. It

256-525: A direct comparison of carbon-14 levels in a sample, with tree ring or cave-deposit C levels of a known age, then gives the wood or animal sample age-since-formation. Radiocarbon is also used to detect disturbance in natural ecosystems; for example, in peatland landscapes, radiocarbon can indicate that carbon which was previously stored in organic soils is being released due to land clearance or climate change. Cosmogenic nuclides are also used as proxy data to characterize cosmic particle and solar activity of

320-442: A long and narrow boulder bank. There are two adze-making sites—one adjacent to the early occupation zone and the second adjacent to the later burial site. The most intensely studied indicates a right handed person sitting in the porch area of a small whare. They sat in front of a flat stone on a path cobbled with small round rocks, chipping off flakes of argillite with a hammer stone of quartzite. The limited studies done so far indicate

384-399: A more modern analysis by Buckley et al found the skeletons had a range of estimated ages. None of the skeletons were from elderly people. The oldest was 39 and the second oldest was 36. Most of the skeletons were from people aged in their 20s. No children and only 1 teenager's skeleton was found. This is consistent with younger people being buried elsewhere, a practice that was quite common in

448-440: A nuclear reactor) are summarized in the table. Another source of carbon-14 is cluster decay branches from traces of naturally occurring isotopes of radium , though this decay mode has a branching ratio on the order of 10 relative to alpha decay , so radiogenic carbon-14 is extremely rare. The above-ground nuclear tests that occurred in several countries in 1955-1980 (see List of nuclear tests ) dramatically increased

512-412: A sizeable village. It is apparent that bodies were commonly buried about 60 metres (200 ft) from the cooking and working zones. After being used for cooking, each umu had subsequently been used as a midden. The bottom layer of the midden showed that at the very earliest occupation time shellfish , such as mussels , were much larger, averaging 250 millimetres (9.8 in) long. The lower layers of

576-403: A slower rate to form CO 2 , radioactive carbon dioxide . The gas mixes rapidly and becomes evenly distributed throughout the atmosphere (the mixing timescale on the order of weeks). Carbon dioxide also dissolves in water and thus permeates the oceans , but at a slower rate. The atmospheric half-life for removal of CO 2 has been estimated at roughly 12 to 16 years in

640-464: A very different diet based on soft starchy food. The two other burial groups showed a very different, more varied diet consistent with being raised in New Zealand. Scientists found that there was a wide range of DNA mutations indicating that settlers were part of a reasonably large group. This indicated a planned migration rather than isolated random groups. One of the mutations was associated with insulin rejection as found in type 2 diabetes This reinforces

704-649: Is cosmic ray action on nitrogen in the atmosphere, and it is therefore a cosmogenic nuclide . However, open-air nuclear testing between 1955 and 1980 contributed to this pool. The different isotopes of carbon do not differ appreciably in their chemical properties. This resemblance is used in chemical and biological research, in a technique called carbon labeling : carbon-14 atoms can be used to replace nonradioactive carbon, in order to trace chemical and biochemical reactions involving carbon atoms from any given organic compound. Carbon-14 undergoes beta decay : By emitting an electron and an electron antineutrino , one of

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768-490: Is 0.05 mm. Radiocarbon dating is a radiometric dating method that uses C to determine the age of carbonaceous materials up to about 60,000 years old. The technique was developed by Willard Libby and his colleagues in 1949 during his tenure as a professor at the University of Chicago . Libby estimated that the radioactivity of exchangeable C would be about 14 decays per minute (dpm) per gram of carbon, and this

832-447: Is also generated inside nuclear fuels (some due to transmutation of oxygen in the uranium oxide , but most significantly from transmutation of nitrogen-14 impurities), and if the spent fuel is sent to nuclear reprocessing then the C is released, for example as CO 2 during PUREX . After production in the upper atmosphere, the carbon-14 reacts rapidly to form mostly (about 93%) CO ( carbon monoxide ), which subsequently oxidizes at

896-418: Is believed the site was primarily a factory for making stone adze heads. It has been estimated from the adze heads found and the large area of stone flakes that about 12,000 adze heads were made here or about 400 to 500 per year. Argillite, the most common adze head material is hard, compressed mudstone. It is found at D'Urville Island only 100 kilometres (62 mi) away from Wairau Bar. A Maori argillite quarry

960-910: Is evidence for an unusually high production rate in AD 774–775 , caused by an extreme solar energetic particle event, the strongest such event to have occurred within the last ten millennia. Another "extraordinarily large" C increase (2%) has been associated with a 5480 BC event, which is unlikely to be a solar energetic particle event. Carbon-14 may also be produced by lightning but in amounts negligible, globally, compared to cosmic ray production. Local effects of cloud-ground discharge through sample residues are unclear, but possibly significant. Carbon-14 can also be produced by other neutron reactions, including in particular C (n,γ) C and O (n,α) C with thermal neutrons , and N (n,d) C and O (n, He) C with fast neutrons . The most notable routes for C production by thermal neutron irradiation of targets (e.g., in

1024-406: Is in the oceans. The following inventory of carbon-14 has been given: Many human-made chemicals are derived from fossil fuels (such as petroleum or coal ) in which C is greatly depleted because the age of fossils far exceeds the half-life of C. The relative absence of CO 2 is therefore used to determine the relative contribution (or mixing ratio ) of fossil fuel oxidation to

1088-463: Is located in the hills behind Nelson City. Such large numbers of adze heads have implications about trade in the early archaic period. One adze found in the 2009 study has been identified by archaeologist Richard Walter as Tahanga basalt from Tahanga Hill near Opito, a well known moahunter area. It was of quadrangular shape(known as Type 1), identical in design to those used in the Cook Island at

1152-430: Is small compared to the doses from K (0.39 mSv/year) and radon (variable). C can be used as a radioactive tracer in medicine. In the initial variant of the urea breath test , a diagnostic test for Helicobacter pylori , urea labeled with about 37  kBq (1.0  μCi ) C is fed to a patient (i.e. 37,000 decays per second). In the event of a H. pylori infection, the bacterial urease enzyme breaks down

1216-524: Is still used as the activity of the modern radiocarbon standard . In 1960, Libby was awarded the Nobel Prize in chemistry for this work. One of the frequent uses of the technique is to date organic remains from archaeological sites. Plants fix atmospheric carbon during photosynthesis; so the level of C in plants and animals when they die, roughly equals the level of C in the atmosphere at that time. However, it thereafter decreases exponentially; so

1280-436: Is the preferred method although more recently, accelerator mass spectrometry has become the method of choice; it counts all the carbon-14 atoms in the sample and not just the few that happen to decay during the measurements; it can therefore be used with much smaller samples (as small as individual plant seeds), and gives results much more quickly. The G-M counting efficiency is estimated to be 3%. The half-distance layer in water

1344-420: Is these features that are responsible for the formations of braid bars. Braided streams are often overfed with massive amounts of sediment which creates multiple stream channels within one dominant pair of flood bank plains. These channels are separated by mid-channel or braid bars. Anastomosing river channels also create mid-channel bars, however they are typically vegetated bars, making them more permanent than

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1408-496: Is usually associated with the far north of New Zealand but may have been grown further south during the warmer climatic period associated with early Polynesian settlement. A geophysics study showed that it was only one of six such pits in a rough horseshoe shape on the edge of a lagoon. The study also showed the site to be much bigger than previously thought—at least 11 hectares (27 acres) and possibly larger as two boundaries have not been accurately plotted. At least 50 percent of

1472-496: The Kermadecs ) by Roger Duff, as being typical Polynesian umu ti. The purpose of the large pit was to cook the taproot of the ti plant . This was a common method of reducing the tuberous root to a sugary pulp. The ti can be cultivated easily but is slow growing. The root is about 900 millimetres (35 in) long by 90 millimetres (3.5 in) wide, to a point. It is cooked very slowly in an umu for 12 to 24 hours. The plant

1536-564: The Northern Hemisphere. The transfer between the ocean shallow layer and the large reservoir of bicarbonates in the ocean depths occurs at a limited rate. In 2009 the activity of C was 238 Bq per kg carbon of fresh terrestrial biomatter, close to the values before atmospheric nuclear testing (226 Bq/kg C; 1950). The inventory of carbon-14 in Earth's biosphere is about 300 megacuries (11  E Bq ), of which most

1600-609: The South Pacific. There was only one child's skeleton. The 21 skeletons with teeth all exhibited some developmental enamel disorders, showing they had suffered long stressful periods during childhood but survived to reasonably healthy adulthood. Tooth decay was rare, especially amongst males (a similar trait to neolithic people of the Americas (North American Indians). Many of the skeletons showed multiple signs of stress such as Harris lines (on X-rays of long bones such as

1664-634: The above-ground nuclear tests of the 1950s and 1960s. Though the extra C generated by those nuclear tests has not disappeared from the atmosphere, oceans and biosphere, it is diluted due to the Suess effect . Carbon-14 is produced in coolant at boiling water reactors (BWRs) and pressurized water reactors (PWRs). It is typically released into the air in the form of carbon dioxide at BWRs, and methane at PWRs. Best practice for nuclear power plant operator management of carbon-14 includes releasing it at night, when plants are not photosynthesizing . Carbon-14

1728-593: The amount of C in tooth enamel , or the carbon-14 concentration in the lens of the eye. In 2019, Scientific American reported that carbon-14 from nuclear testing has been found in animals from one of the most inaccessible regions on Earth, the Mariana Trench in the Pacific Ocean. The concentration of C in atmospheric CO 2 , reported as the C/ C ratio with respect to a standard, has (since about 2022) declined to levels similar to those prior to

1792-425: The amount of C in the atmosphere and subsequently the biosphere; after the tests ended, the atmospheric concentration of the isotope began to decrease, as radioactive CO 2 was fixed into plant and animal tissue, and dissolved in the oceans. One side-effect of the change in atmospheric C is that this has enabled some options (e.g. bomb-pulse dating ) for determining the birth year of an individual, in particular,

1856-404: The amount of material that can be carried there. Point bars are usually crescent shaped and located on the inside curve of the river bend. The excess material falls out of transport and, over time, forms a point bar. Point bars are typically found in the slowest moving, shallowest parts of rivers and streams , and are often parallel to the shore and occupy the area farthest from the thalweg , on

1920-425: The area even further. Over time, the bar can eventually attach to one side of the channel bank and merge into the flood plain . A point bar is an area of deposition typically found in meandering rivers. Point bars form on the inside of meander bends in meandering rivers. As the flow moves around the inside of the bend in the river, the water slows down because of the shallow flow and low shear stresses there reduce

1984-673: The area was intact. By 2007 only 2 percent of the site had been scientifically investigated. "Intact" skeletons (many minus the head) were found in four groups, with the oldest (1-7) being closer to the sea and at the western end of the site. These have been shown by DNA studies to be people who had lived in East Polynesia. The largest group of skeletons (15-43) were in an area to the east which covered an oval area 30 by 50 metres (98 by 164 ft). These people are believed to be moa hunters who lived their lives in New Zealand, based on bone and teeth DNA analysis. The main habitation area

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2048-422: The atmosphere. C and C are both stable; C is unstable, with half-life 5700 ± 30 years. Carbon-14 has a specific activity of 62.4 mCi/mmol (2.31 GBq/mmol), or 164.9 GBq/g. Carbon-14 decays into nitrogen-14 ( N ) through beta decay . A gram of carbon containing 1 atom of carbon-14 per 10 atoms, emits ~0.2 beta (β) particles per second. The primary natural source of carbon-14 on Earth

2112-436: The bars found in a braided river channel which have high rates of change because of the large amounts of non-cohesive sediment, lack of vegetation, and high stream powers found in braided river channels. Bars can also form mid-channel due to snags or logjams . For example, if a stable log is deposited mid-channel in a stream, this obstructs the flow and creates local flow convergence and divergence . This causes erosion on

2176-404: The combination of deposition along point bars, and erosion along cut banks can lead to the formation of an oxbow lake . A mouth bar is an elevated region of sediment typically found at a river delta which is located at the mouth of a river where the river flows out to the ocean. Sediment is transported by the river and deposited, mid channel, at the mouth of the river. This occurs because, as

2240-421: The date of death or fixation can be estimated. The initial C level for the calculation can either be estimated, or else directly compared with known year-by-year data from tree-ring data ( dendrochronology ) up to 10,000 years ago (using overlapping data from live and dead trees in a given area), or else from cave deposits ( speleothems ), back to about 45,000 years before present. A calculation or (more accurately)

2304-554: The decay of radioactive material in surrounding geologic strata. In connection with building the Borexino solar neutrino observatory, petroleum feedstock (for synthesizing the primary scintillant) was obtained with low C content. In the Borexino Counting Test Facility, a C/ C ratio of 1.94×10 was determined; probable reactions responsible for varied levels of C in different petroleum reservoirs , and

2368-674: The distant past. Carbon-14 is produced in the upper troposphere and the stratosphere by thermal neutrons absorbed by nitrogen atoms. When cosmic rays enter the atmosphere, they undergo various transformations, including the production of neutrons . The resulting neutrons (n) participate in the following n-p reaction (p is proton ): The highest rate of carbon-14 production takes place at altitudes of 9 to 15 kilometres (30,000 to 49,000 ft) and at high geomagnetic latitudes . The rate of C production can be modeled, yielding values of 16,400 or 18,800 atoms of C per second per square meter of Earth's surface, which agrees with

2432-447: The early Polynesian colonial period. (The other is the early East Polynesian pearl lure found at Tairua identified by A. Powell of Auckland Museum.) The shell tool is a modified spiral gastropod shell. These tools were used as small chisels or gouges, possibly for enlarging holes. The point of the turret shell was removed and the remains honed to a chisel point of about 60 degrees by grinding. Although found in various East Polynesian Islands

2496-561: The global carbon budget that can be used to backtrack, but attempts to measure the production time directly in situ were not very successful. Production rates vary because of changes to the cosmic ray flux caused by the heliospheric modulation (solar wind and solar magnetic field), and, of great significance, due to variations in the Earth's magnetic field . Changes in the carbon cycle however can make such effects difficult to isolate and quantify. Occasional spikes may occur; for example, there

2560-464: The local megafauna . At the time of the latest investigation the local Rangitāne Iwi reburied 60 skeletons claimed to be their forebears in a formal ceremony at the lagoon site. A study of a turret shell artifact completed in 2011 shows a direct link between the Wairau Bar site and East Polynesia. This is only the second artifact found in New Zealand originating from East Polynesia dated to

2624-578: The lower C levels in methane, have been discussed by Bonvicini et al. Since many sources of human food are ultimately derived from terrestrial plants, the relative concentration of C in human bodies is nearly identical to the relative concentration in the atmosphere. The rates of disintegration of potassium-40 ( K) and C in the normal adult body are comparable (a few thousand decays per second). The beta decays from external (environmental) radiocarbon contribute about 0.01  mSv /year (1 mrem/year) to each person's dose of ionizing radiation . This

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2688-471: The making of waka. The stone head was lashed to an L-shaped natural crook and swung so the blade struck the wood more or less horizontally. An investigation by a team from Otago University found a huge stone-lined umu or hāngī pit (earth oven) 1.5 metres (4.9 ft) deep by 4 metres (13 ft) across—estimated to be big enough to feed 1000 people by a local Maori familiar with modern hangi. However, these large hangi or umu pits were identified in 1968 (in

2752-487: The mathematical modelling done in the past that shows the same pattern. Work will now begin on tracing East Polynesian populations that have the same DNA mutations in order to discover the specific homelands of the Wairau Bar settlers. The DNA pattern is very similar to that found in the Marquesas Islands in East Polynesia at the same time. The later 2009–2010 study, using more precise modern methods, resulted in

2816-458: The maximum distance traveled is estimated to be 22 cm in air and 0.27 mm in body tissue. The fraction of the radiation transmitted through the dead skin layer is estimated to be 0.11. Small amounts of carbon-14 are not easily detected by typical Geiger–Müller (G-M) detectors ; it is estimated that G-M detectors will not normally detect contamination of less than about 100,000 decays per minute (0.05 μCi). Liquid scintillation counting

2880-405: The midden also showed that early moa bones were not smashed to get at the marrow as was common in the upper layers. Whale bones were found in the lower layer. Mainly moa leg bones were found indicating that moa were hunted inland and brought to the site for cooking. More than 4000 moa were consumed at the site. Bones from all five moa species located in the upper South Island were found. As well as

2944-476: The most common site by far is Fa'ahia, Huahine, in the Society Islands , where many have been located from the same period. The significance of the find that was dug up 60 years ago was not realised until recently. 41°30′33.7″S 174°03′49.7″E  /  41.509361°S 174.063806°E  / -41.509361; 174.063806 Gravel bar A mid-channel bar, is also often referred to as

3008-533: The mouth of the river, it builds up to eventually create a sand bar that has the potential to extend the entire length of the river mouth and block the flow. Carbon-14 Carbon-14 , C-14 , C or radiocarbon , is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons . Its presence in organic matter is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues (1949) to date archaeological, geological and hydrogeological samples. Carbon-14

3072-425: The neutrons in carbon-14 decays to a proton and the carbon-14 ( half-life of 5700 ± 30 years ) decays into the stable (non-radioactive) isotope nitrogen-14 . As usual with beta decay, almost all the decay energy is carried away by the beta particle and the neutrino. The emitted beta particles have a maximum energy of about 156 keV, while their weighted mean energy is 49 keV. These are relatively low energies;

3136-402: The occupation it is believed to have been a low scrub-covered island 2 to 3 metres (7 to 10 ft) high, 1.1 kilometres (0.68 mi) long and 0.4 kilometres (0.25 mi) wide. The site was discovered in 1939 by then schoolboy Jim Eyles who, in 1942, found more artefacts. Early investigations with Roger Duff unearthed a burial site . Bones were scattered and close to the surface. This

3200-487: The ocean. River mouth bars stagnate, or cease to prograde when the water depth above the flow is shallow enough to create a pressure on the upstream side of the bar strong enough to force the flow around the deposit rather than over the top of the bar. This divergent channel flow around either side of the sediment deposit continuously transports sediment, which over time is deposited on either side of this original mid channel deposit. As more and more sediment accumulates across

3264-416: The outside curve of the river bend in a meandering river. Here, at the deepest and fastest part of the stream is the cut bank , the area of a meandering river channel that continuously undergoes erosion. The faster the water in a river channel, the better it is able to pick up greater amounts of sediment, and larger pieces of sediment, which increases the river's bed load . Over a long enough period of time,

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3328-638: The partial skeletons of several children were found in shallow graves but these were in such poor condition and scattered that Duff was either unable or unwilling to keep the fragments using the methods of those days. The examination showed that the people were using the same cultural methods as those in eastern Polynesia , particularly the Marquesas Islands . Sixty-nine adzes were found at Wairau Bar, of which only three were made of greenstone . Eighty small, one-piece, triangular, stone or bone fishing lures with lashed unbarbed hook were found. In 2009

3392-417: The remains of numerous butchered moa, seals , porpoises , the extinct Haast's eagle , Eyles' harrier , New Zealand swan and New Zealand raven , kurī (Maori dogs), tuatara , kiore , shellfish such as pipi , pāua , cockles , and marine bones from eels , skate , sunfish and sharks were found there. Anderson and Smith in their 1996 study stated that the first colonists enjoyed a sustained assault on

3456-417: The river widens at the mouth, the flow slows, and sediment settles out and is deposited. After initial formation of a river mouth bar, they have the tendency to prograde . This is caused by the pressure from the flow on the upstream face of the bar. This pressure creates erosion on that face of the bar, allowing the flow to transport this sediment over or around, and re-deposit it farther downstream, closer to

3520-508: The same time. Also found were chert from Kaikoura, which was commonly used for making holes, pumice from the volcanic plateau, which was used as floats and for making small handheld fire bowls and small amounts of greenstone from the West Coast which was made into two adze heads. This indicates that the Wairau Bar moa hunters travelled extensively through New Zealand exploring the land. Adze heads are associated with shaping wood, especially in

3584-640: The site being more accurately dated by the radiocarbon method to 1288–1300 CE . The site appeared to be occupied twice over a period of about 20 years, which is consistent with information from other early Polynesian colonisation sites in New Zealand. Accurate dates were obtained from moa egg fragments found in grave and midden sites. Buried with the skeletons were moa bone reel necklaces , whole moa eggs (used as water carriers), argillite adze heads, carved serpentine that looked like shark and whale teeth, harpoon heads and tattoo chisels . Few nephrite (jade or greenstone) artefacts were found. It

3648-430: The tibia) caused by either infection or a poor diet. Tooth wear was substantial among older individuals, with teeth worn to the roots, but this did not seem to be due to bracken fern root chewing. All the adults showed healed bone fractures, indicating a well-balanced diet and a supportive community structure. Several skeletons showed features that are interpreted as being caused by tuberculosis (TB). The presence of TB

3712-458: The total carbon dioxide in a given region of Earth's atmosphere . Dating a specific sample of fossilized carbonaceous material is more complicated. Such deposits often contain trace amounts of C. These amounts can vary significantly between samples, ranging up to 1% of the ratio found in living organisms (an apparent age of about 40,000 years). This may indicate contamination by small amounts of bacteria, underground sources of radiation causing

3776-461: The upstream side of the obstruction and deposition on the downstream side. The deposition that occurs on the downstream side can create a central bar, and an arcuate bar can be formed as flow diverges upstream of the obstruction. Continuous deposition downstream can build up the central bar to form an island . Eventually the logjam can become partially buried, which protects the island from erosion, allowing for vegetation to begin to grow, and stabilize

3840-399: Was central, about 25 to 50 metres (82 to 164 ft) from the southern lagoon edge. There were three zones of cooking and surface midden debris, all about 100 by 30 metres (328 by 98 ft) approximately. The earliest zone was alongside the lagoon and the latter on the ocean side of the island. At the time of the second occupation of the island, the second site was protected from the ocean by

3904-592: Was discovered on February 27, 1940, by Martin Kamen and Sam Ruben at the University of California Radiation Laboratory in Berkeley, California . Its existence had been suggested by Franz Kurie in 1934. There are three naturally occurring isotopes of carbon on Earth: carbon-12 ( C), which makes up 99% of all carbon on Earth; carbon-13 ( C), which makes up 1%; and carbon-14 ( C), which occurs in trace amounts, making up about 1-1.5 atoms per 10 atoms of carbon in

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3968-422: Was originally believed to have been due to ploughing , but work by Bruce McFadgen shows that at some stage, probably between the two periods of occupation, the site was subject to either large storm surge waves or a tsunami which probably contributed to the scattering. Using the techniques of the time about 2,000 artefacts and 44 human skeletons were removed and examined in detail. The record seems to show that

4032-448: Was the practice in eastern Polynesia. The archaeological layers were shallow. Lisa Matisoo-Smith and Michael Knapp from New Zealand's Otago University have released the results of a recent bone and teeth DNA study carried out on early Polynesian migrants to New Zealand who lived at Wairau Bar about 1285–1300 AD. The results of DNA analysis reinforce the idea that some of these people were original settlers from East Polynesia, as they had

4096-401: Was yet to be confirmed by DNA analysis in 2010. Anaemia was common, as was arthritis . The average height of the males was 175 centimetres (69 in) and the females 161 centimetres (63 in). These figures show the early colonisers were tall compared to most Polynesians. The skeletons were all found in shallow graves, with the heads pointing towards the east and the feet to the west, as

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