ABSOLUTE AND RELATIVE DATING
Chronological dating is the process of assigning a date in the past to an object or event, allowing that object or event to be located in a previously established chronology. This generally requires what is commonly known as a "dating method." There are several dating methods, depending on different criteria and techniques, and some well-known examples of disciplines that use such techniques are, for example, history, archaeology, geology, palaeontology, astronomy and even forensic science. Relative dating methods cannot determine the absolute age of an object or event, but can determine the impossibility of a particular event occurring before or after another event. Historians, for example, know that Shakespeare's work, 'Henry V', was not written before 1587 because Shakespeare's main source for writing his work was the second edition of The Chronicles of Raphael Holinshed, not published until 1587 (here it is assumed that this is correct).
The same inductive mechanism is applied in archaeology, geology and palaeontology, in many ways. For example, in a stratum that presents difficulties or ambiguities with absolute dating, paleopalinology can be used as a relative reference through the study of pollen found in the stratum. This is admitted for the simple reason that some botanical species, whether extinct or not, are well known for belonging to a certain position on the time scale (this is the assumption in this case).
A non-exhaustive list of relative dating methods and relative dating applications used in geology, palaeontology or archaeology is the following: cross-sectional relationships (the geological feature that cuts to another is the youngest of the two features), the law of included fragments (the clasts or components of the rock are older than the rock itself), Steno's law of superposition, principle of horizontality, principle of lateral continuity, principle of faunal succession, nitrogen dating (based on the decomposition and reliable release of bone sample amino acids to estimate the age of the object), dating by fluorine absorption (groundwater contains fluoride ions; elements such as bones found in the soil will absorb fluoride from groundwater over time), seriation (archaeology), palynology (pollen), morphology (in archaeology it’s the grouping by forms and styles), typology (archaeology), varnish micro-lamination (uses the slow accumulation of "varnish" or dark coating on exposed rock surfaces; this sedimentary deposition is slow -1 μm per 1000 years-), lead corrosion dating (used exclusively in archaeology), paleomagnetism, tephrochronology, isotope stages (occupy the same place in the Periodic Table) based on the marine cycle oxygen isotopes, etc.
Absolute dating methods, through the use of absolute reference criteria, mainly include radiometric dating methods. Some examples are: amino acid dating , archeomagnetic dating, Argon-Argon, Uranium-Lead, Samarium-Neodymium, Potassium-Argon, Rubidium-Strontium, Uranium-Thorium, C14 radiocarbon dating, fission track dating, optically stimulated luminescence OSL, thermoluminescence TLS (a type of luminescence dating), iodine-129, Lead-Lead (method for dating geological samples, based on samples of "whole rock" material such as granite; in general it has been replaced by Uranium-Lead, but in certain specialized situations -dated meteorites or the age of the Earth- it is more important than the U-Pb dating), oxidizable carbon ratio (to derive or estimate the age of the soil and sediment samples up to 35,000 years old), dating by rehydroxylation , cement-chronology (this method does not determine a precise moment in a time scale, but the age at death of a dead individual), 'Wiggle matching' , stones with dates (dates buildings in archaeology: a stone embedded with the date of engraving and other information carved on it, although it is not considered a very reliable source since cases of old houses destroyed and rebuilt with the ancient stones intact have been reported), hydration of the obsidian (affected by pressure and temperature), tephrochronology , molecular clock (used mainly in phylogeny and evolutionary biology), dendrochronology (affected among other factors by the Sun ), herb-chronology (dendrochronology for perennial herbs), and some others in development.
Other methods are used in geology and archaeology: AMS radiocarbon (accelerated mass spectrometry), cation ratio, amino acid racemization (changes in amino acids –Dextrorotation or levorotation- since its formation), OSL (optically stimulated luminescence), lichenometry, micro-erosion and micro-spatial analysis of the patina.
ICE CORE DATING
It is said that ice sheets have the special property of going back in time and sampling the accumulation, air temperature and air chemistry of another time. The ice core records allow us to generate continuous reconstructions of the past climate, which date back at least 800,000 years (some scientists believe there is enough ice in Antarctica to date 1.5 million). By observing past concentrations of greenhouse gases on layers in ice cores, scientists calculate how modern amounts of carbon dioxide and methane are compared with those of the past and relate previous concentrations of greenhouse gases to temperature. Ice sample extraction has been around since the 1950's. Ice cores have been drilled in ice sheets throughout the world, but especially in Greenland and Antarctica. High snow accumulation rates provide excellent weather resolution, and air bubbles in the ice retain samples of the ancient atmosphere.
As snow accumulates, each layer presses the lower layers, making them denser until they become firn. The firn is not dense enough to prevent air from escaping, but at a density of approximately 830 kg/m³ it becomes ice ('brittle ice' area), and the inner air is sealed in bubbles that capture the composition of the atmosphere at the time the ice formed. The depth at which this occurs varies by location, but in Greenland and Antarctica it ranges between 64 and 115 m. Because the snowfall rate varies from place to place, the age of snow when it changes to ice varies greatly. In Summit Camp (Greenland), the depth is 77 m and the ice is 230 years old; in Dome C in Antarctica, the depth is 95 m and the age of 2500 years. As additional layers build up, the pressure increases and, at approximately 1500 m, the crystalline structure of the ice changes from hexagonal to cubic, allowing air molecules to move towards the cubic crystals and form a clathrate. The bubbles disappear and the ice becomes more transparent.
The great ice sheets of Greenland and Antarctica have huge and high plateaus where snow accumulates in an orderly manner. The slow flow of ice in the centre of these ice sheets (near the ice division) means that the stratigraphy of snow and ice is preserved. Shallow ice-cores (100-200 m) can cover up to a few hundred years of accumulation, depending on the accumulation rates. Deeper cores require filling the well with drilling fluid to keep it open. The drilling fluid used is normally a petroleum-derived liquid such as kerosene. It must have a freezing point and adequate viscosity. The collection of the deepest ice cores (up to 3000 m) requires a semi-permanent scientific camp.
If we want to reconstruct past air temperatures, one of the most critical parameters is the age of the ice being analysed. Fortunately, ice cores preserve annual layers (which are an assumption), so it is easy to date the ice. "Seasonal" differences (another presumption) in snow properties create layers, as do tree rings. Unfortunately, the annual layers become harder to see deeper in the ice core. Other ways to date ice cores include geochemistry, ash layers (tephra), electrical conductivity and the use of numerical flow models to understand the relationships between age and depth. Although radiometric dating of ice cores has been difficult, uranium has been used to date the Dome C ice core of Antarctica. Powder is present in the ice cores and contains uranium. The disintegration of U238 to U234 in the ice matrix can be used to provide additional central chronology (see the radiometry chapter).
The thickness of the annual layers in ice cores can be used to obtain a precipitation rate (after correcting the glacial flow clearance). Precipitation rates in the past are an important paleo-environmental indicator, often related to climate change, and is an essential parameter for many past climate studies or numerical simulations of glaciers.
Ice cores provide information beyond the gas bubbles in the ice. Melting layers are related to summer temperatures (another assumption). More melting layers indicate warmer summer air temperatures. Melt layers form when the snow surface melts, releasing water to seep through the snow pack. They form layers of ice without bubbles, visible in the ice core. The distribution of the melted layers over time is a function of the past climate, and has been used, to show greater melting in the 20th century around the Antarctic Peninsula.
It is possible to discern past temperatures by the concentrations of CO2, CH4 and other greenhouse gases in the ice. Snow precipitation over Antarctica is mainly composed of H2O16 molecules (99.7%). There are also rarer stable isotopes: H2O18 (0.2%) and HDO16 (0.03%). Isotopic concentrations are expressed in thousand δ units (δD and δO16) respect to the standard middle ocean water. Past precipitation can be used to reconstruct the paleoclimatic temperatures. δD and δ18O are related to the surface temperature at medium and high latitudes. The relationship is consistent and linear over Antarctica. Snow falls on Antarctica and slowly turns to ice. Stable isotopes of oxygen (O16, O18) and hydrogen [D/H]) are trapped in ice cores. Stable isotopes are measured on ice through a mass spectrometer. Measuring the changing concentrations of δD and δO18 over time in layers through an ice core provides a detailed record of the temperature change, dating back hundreds of thousands of years (always assuming that the accumulation rate of snow would have remained, which is a lot to assume).
ICE CORES DATING TYPES
1) Annual layer count: The basis of this method is to look for elements that vary with the seasons in a constant way (they depend on the temperature, colder in winter and warmer in summer; and solar irradiation, lower in winter and more in summer). Once such markers of seasonal variations are found, they can be used to find the number of years that the ice core accumulated. This process is analogous to the counting of tree rings. A major disadvantage of this type of dating is that it consumes a lot of time.
a) Temperature dependent marker is the ratio of O18/O16. Water molecules composed of H2O18 evaporate less rapidly and condense easier than those of H2O16. Water that evaporates from the ocean is poor in H2O18. As water vapour travels to the poles, it becomes increasingly poor in H2O18 since heavier molecules tend to precipitate first (as long as there are no electrical charges in between, it could be an assumption). This depletion is a temperature dependent process: in winter the precipitation is more enriched H2O16 than in the case of summer. Therefore, each annual layer begins to be rich, becomes poor and ends up being rich. This process also depends on the relative temperatures of different years, which allows comparison with paleoclimatic data. For similar reasons, the ratio of deuterium to hydrogen acts in the same way. The main disadvantage of this dating method is that isotopes tend to spread as time goes by.
b) Irradiation-dependent markers are Be10 and Cl36. Both isotopes are produced by cosmic rays and solar irradiation that affects the upper atmosphere and both are rapidly washed from the atmosphere by precipitation. By comparing the proportions of these isotopes with their non-radioactive counterparts (Be9 and Cl35) the season of the year in which the precipitation occurred can be determined. Therefore, each annual layer begins Be10 and Cl36 poor, becomes rich in them, and then becomes poor again. Although this is true, its effect is minimal. Be10 and Cl36 are formed as charged ions in the ionosphere, the magnetic field traps them, allowing a "leak" of the isotopes into the lower atmosphere, which depends on the height of the ionosphere, which changes mainly in response to the solar cycle, with periods of maximum solar activity that correspond to the largest extent of the ionosphere .
2) Use predetermined ages as markers: Pre-determined ages are used for several points in the ice core. The main advantage of these methods is that they can be completed relatively quickly. The main disadvantage is that if the default age markers are incorrect, the age assigned to the ice core will also be incorrect.
a) If we take previously measured ice cores, certain inclusions in an ice core whose age has been determined are compared with a separate method for similar inclusions in an ice core of an undetermined age. These inclusions are typically ash from volcanic eruptions and acidic layers. The main disadvantage of this method is that, to begin with, you must have a previously dated ice core.
b) Oceanic cores with related inclusions found in the ice core of an undetermined age are used, for example, a decrease (or increase) in temperature over a period of years that can be determined from flora and fauna found in the ocean core and a decrease (increase) in the enrichment of O18 during this same period of years. Another example is volcanic ash. The main disadvantages of this method are that different signatures of climate change that correspond to the same event and that there is no certainty of the delay times (if applicable) between ocean reactions and glacial reactions to the same climatic changes must be compared.
c) After the eruption of volcanoes, volcanic ashes and chemicals are removed from the atmosphere by precipitation. These eruptions leave a distinctive marker within the snow, and we can use recorded eruptions to gauge the age of the ice core. Ash and acidity are good indicators. The cons of the method are that one must first know the date of the rash, which is generally not the case. In addition, alkaline precipitants of ice ages limit this measure to approximately 8000 BC.
d) Precipitation during glaciations is markedly alkaline. This is due to the fact that the ice ages tied a large amount of available water, thus exposing a larger portion of the continental shelves (this is a creationist assumption). From these shelves, huge clouds of alkaline dust (mainly CaCO3) were swept through the landscape. The main disadvantage of this method is that it only provides very approximate age ranges (this ice was deposited during the ice age). In addition, the delay time between the onset of glaciation and the increase in alkalinity is uncertain.
e) Long-range climatic changes (for example, ice ages and interglacial warming) are compared by means of paleoclimatic comparisons with markers (such as the O18/O16 ratios) found within the ice cores.
3) Radioactive dating of gaseous inclusions: a quantity of glacial material of a certain depth is melted, and the gases that were trapped inside are collected; using standard dating C14 and Cl-36. The main disadvantage of this method is that a large amount of ice must be melted to gather the necessary amount of gases {and assuming radiometric dating is a valid method}.
4) Ice flow calculation: the length of the ice core is measured and computes how many years it must have taken for a glacier of that thickness to form. This is the most inaccurate of the methods used to date ice cores. First one must know how the thickness of the annual layer changes with depth. After this, some assumptions should be made about the original thickness of the annual layer to date (the amount of precipitation that fell on the area in a year).
Excerpt from http://www.talkorigins.org/faqs/icecores.html .
ASSUMPTIONS
The use of predetermined ages as markers is based on trusting other main methods that are the ones to be valued, and therefore, it is not reliable in itself. The use of radiometric dating will be seen later. The calculation of ice flows is not only inaccurate as orthodox scientists recognise, but it is reckless given the amount of assumptions it makes (such as a rate of 1 layer of firn per year). Regarding the direct count of annual layers, they admit that elements whose variations are constant and consistent are necessary, such as seasonal cycles, stability of the lithosphere (if the poles had changed their location both methods would be futile no matter how slight the variation would have been), and the electrical charge of the atmosphere and the ionosphere.
Ice samples taken from kilometres below the surface of the Greenland glaciers have long served as a historical thermometer, adding temperature data to studies of local conditions, and even the climate of the northern hemisphere. But the method, which compares the proportion of buried oxygen isotopes while snow fell for millennia, may not be such a direct indicator of air temperature.
The geologist at the University of Wisconsin-Madison, AE Carlsson, published in a study in Nature that says: "We do not believe that ice cores can be interpreted simply as a temperature signal... You should consider where the precipitation that formed the ice came from". They say that the Greenland ice record shifted significantly from other temperature records in the northern hemisphere during the Younger Dryas, almost 13,000 years ago, and has not coincided since then. “In terms of temperature during Dryas, the only thing that looks like Greenland's ice cores is Greenland's ice cores. They are supposed to be iconic for the northern hemisphere, but we have four other records that disagree with Greenland's ice cores. The abrupt cooling is there, but not in the same degree”.
As the Younger Dryas approached, the Laurentian ice sheet that covered North America melted, and allowed more moisture from the Pacific Ocean to cross the continent towards Greenland. The two oceans have clearly different rates of oxygen isotopes, which allowed a different ratio when it snows. According to the findings of the study, Greenland temperatures did not cool as much during the transition between the Older and the Younger Dryas due to the increase in carbon dioxide in the atmosphere . There have been abrupt climatic changes, but they come with complex changes in the way the climatic variables like humidity changed. "You cannot take a difference and interpret it only as temperature changes, and that is what we are seeing here in the Greenland ice cores".
METHODS AND PRESUMPTIONS. PROS & CONS
Counting firn layers.
Methods:
Rain and snow fall at an undetermined rate and, with them, drag dust and ash. For a certain period of time small microscopic air cavities form and are finally sealed (Note that initially there is or there may be an air current that communicates them). Then they are counted and dated.
It is assumed that each snowfall season produces a layer easy to differentiate from the following one by a strip of molten ice during the summer.
The O18/O16 ratio depends on the Temperature at the time of precipitation.
Pros:
The dating of ice cores must be crossed and contrasted by numerous other methods to be published (sediments, eruptions other ice-cores NGRIP, GRIP DYE-3...).
Counting of the layers (initially visual) is done by several techniques:
Electrical conductivity of ashes and other materials.
Cloudy bands of dust particles, according to grains size (subjective).
Laser dispersion by dust in the cores.
Other methods to cross dating are dendrochronology or coral dating (C14).
Cons:
The age of air bubbles and firn is different (100-3,000 years).
A single foundation spends more than 400 million$ on Arctic research.
The reliability of counting decreases significantly with the compaction of the firn, being only valid in the upper layers.
Before the snow and ice are compacted, the air flow prevents a clear count of the ‘annual’ layers.
To use the methods described, they must assume an alleged thickness of a layer . From this you can count the density of grains, dust or impurities of certain chemical elements statistically.
When we have a model that describes how ice deforms, it is possible to calculate an Age/Depth ratio (ice-core time scale) assuming we know the amount of snowfall and the melting on the surface of the ice sheet, and any fusion in the bedrock (basal and surface mass balances). This is called Direct Modeling .
Sometimes fragments in cores are missing, and the number of layers is extrapolated from the supposed thickness of the missing section .
Predetermined ages by other ice-cores as independent markers:
Methods:
Are trustable if the other ones are.
Tephras and pyroclasts are used to compare.
Pros:
A priori, crossing and comparing data seems positive.
Other methods such as radiometry, corals and dendrochronology are employed to re-calibrate.
Cons:
Coral dating has the same problems tan radiometric dating.
Tree rings might vary depending on factors as Temp or solar activity (sunspots).
Solar, volcanic and ocean activity (Thermohaline current CTH) affect the ratio SnowAccumulation /Temperature, especially in the Holocene .
Calculation of ice flux:
Methods:
Continuous Flux Analysis (CFA) allows detecting small variations of CH4, Ca, Na and other elements.
Pros:
Elements as Be10 o C14 in tree rings are influenced by solar activity, which might render them useful to synchronise different ice-cores (Antarctic and Greenland).
Cons:
Alleged thickness of annual layers is important as it determines how many measurements of every variable are made along the ice core trepan. According to expected annual thickness uniformitarian scientists get enough measurements to elucidate what they believe are yearly cycles .
Due to diffusion processes, the O18/O16 ratio only allows dating trustworthily until 8.500 years.
THE LOST SQUADRON
From a secret air base of the US Army six P-38 Lightning fighter planes and two gigantic B-17 Flying Fortress bombers rose at dawn on July 15, 1942, and headed to a British airfield to join the war against Hitler. Heading east on the polar cap, they found a massive blizzard. Flying blindly, and unable to reach Iceland, where they were going to refuel, they were forced to return to their base of operations. Critically low on fuel, they had to make emergency landings on the icy plains of the east coast of Greenland. All crew members were rescued unharmed by dog sledding nine days later. However, the planes had to be abandoned.
In 1980, the Greenland Society of Atlanta and US air trafficker Patrick Epps and his friend, architect Richard Taylor, thought the planes would be like new. Remove the snow from the wings, fill them with gasoline, land and collect them. It took them many years, money and several failed expeditions before the first real track arrived. Using a sophisticated form of radar with the help of an Icelandic geophysicist, they located eight large forms under the ice in 1988. A small and improvised steam probe, began to melt a hole in the ice, and the members of the expedition watched stunned how more and more extensions were added to the hose, about 75 m, before arriving at the first plane . None of the discoverers thought the planes could be buried under more than a light layer of snow and ice. And why would they do it? After all, the impression that the general public has is that the accumulation of glacial ice takes a long time (the published figures of the average ice accumulation rates are a little lower than 1½ m / year). In 1990 they returned with more machinery and continued digging to create a cavern around one of the B-17 by hot water, but the device was shattered by pressure. Two years later they returned with more funding thinking that the most robust P-38 would be in condition, and after hard efforts they managed to recover part of the device and reuse 80% of the pieces. What was clear, is that if in 46 years, 75 meters of snow were deposited, to deposit the less than 3,000 of the Greenland icefield, it would only take about 1,840 years instead of the hundreds of thousands that orthodoxy claims.
However, 'mainstream' scientists remember that factors such as compaction of firn on ice due to gravity must be taken into account, and believe that the average annual thickness of the ice at Camp Century, located near the northern tip of Greenland, varies about 35 cm near the surface less than 5 cm near the bottom. If, for simplicity, we assume that the average annual thickness is the average between the annual thickness at the top and bottom (about 20 cm), this would still take 15,000 years to compact all snow on ice. This is presuming the idea of Hammer et al. In the same paper, they say that it is possible with a high degree of precision to verify the count of the annual layers with occasional peaks in acidity and particles from historical volcanic events. Hammer and company correlate the peaks in the average acidity of the annual layers from 553 to 1972 AD, with historical volcanic events. About a dozen historical volcanic eruptions are evident in the ice core of Crete in central Greenland. Several unknown eruptions are also documented in the ice core registry. However, the deeper the ice drill, the less the trust in chronology. The amplitude of the annual oscillations decreases slowly in relation to other factors, and the historical markers are less and are more spaced. Glaciologists estimate that uncertainties in the identification of layers will likely limit the number of accounting layers to less than approximately 8,500.
The claims that the deep ice sheets are 160,000 years ago come mainly from the interpretation of Antarctica . The Soviet expeditions at Vostok recovered an ice core of almost 2,100 meters long in a region where the total thickness of the ice is approximately 3600 m. Since the current precipitation rate is much lower than that of Greenland (of the order of 1 inch/year or 2.5 cm/year), the gross calculation of age, without corrections for compression and horizontal movement for the lower layers, is more than 100,000 years.
However, such estimates are based on the assumption that the accumulation rate has not changed much in the past. Unlike the Greenland ice cores, the annual oscillations of O18 and other parameters cannot be traced deeply in the ice sheet in Antarctica. In Greenland, high precipitation rates not only provide relatively thick annual layers for analysis, but the accumulation of snow quickly seals the ice beneath and protects the metamorphosis record by changes in pressure and temperature in the atmosphere. In Antarctica, at the time when ice has been buried enough to stop being influenced by the atmosphere, annual variations have been greatly attenuated by diffusion .
The technique used to estimate the age of a deep ice sheet is to measure its O18 content and calculate the atmospheric temperature that is observed to produce such concentrations today. Through a second known relationship between temperature and precipitation rate, observed again in the current atmosphere, the accumulation rate for a given layer is calculated. These methods and techniques would be reliable if they could be supported by markers such as volcanic eruptions, of which there are only a few thousand years record, or if the accumulation rates had been constant over long periods of time in the past, which is very doubtful.
Richard Alley himself, the ice cores guru, acknowledged the existence of abrupt changes in the climate and that, in many places, the annual firn layers are not preserved as snowfall and rainfall are unimportant given that the climate is arid. He added that there were no events older than 2000 years, reliably dated by historical records with clear signs on ice cores.
The NOAA website (ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/ice-cores.pdf) contains a document detailing numerous sources of uncertainty regarding core data of ice. Finally, there are dozens of modern papers that speak of an increase in the rate of ice accumulation both in Antarctica , in Patagonia , and several anomalies in them in the very base camp of Lake Vostok .
RADIOMETRIC DATING
New data makes us doubt radioisotope dating. A team from Purdue and Stanford universities showed that radioactive decay varies with the rotation of the Sun . Jenkins and Fischbach suggest that changes in decay rates are due to interactions with solar neutrinos. Muons are elementary particles similar to e- (electric charge, they seem to have a zero radius, fractional spin...). Unlike electrons, they are not stable, but rather decay (usually within a few microseconds). They occur naturally in the upper part of the atmosphere after collisions of high-energy cosmic rays with O2 or N. They shoot towards the surface at relativistic speeds and, thanks to temporary dilation, some reach the ground and disintegrate. The reduction of the present resting mass will be compensated with an increase in kinetic energy, so that the total mass of energy remains constant. The important thing is that the rates are affected by the distance to the Sun.
The GSI anomaly was discovered in 2007 following an experiment in Germany that reported the observation of an unexpected modulation over time of the electron capture rate of highly ionized atoms ¹⁴²Pr⁵⁸⁺ (Promethium), which have a half-life of 3.39 min. These findings were soon repeated by the same group, and extended to include the decrease of ¹⁴²Pm⁶⁰⁺ (Praseodymium) (half-life 40.5 s) . The oscillations in the decay speed had periods of time close to 7 seconds and amplitudes of approximately 20%. Such a phenomenon had not been previously observed, and was difficult to understand. The experimental group considered it very unlikely that the occurrence of the phenomenon is due to a technical failure because it says that its detection technique provides, throughout the entire observation time, complete and uninterrupted information on the status of each ion stored. Since this type of weak deterioration involves the production of an electron-neutrino, attempts have been made to relate the observed oscillations to the neutrino oscillations, but this proposal was very controversial.
Low frequency EM resonances seem to affect rates . Therefore, Schumann resonance could be related (speculation) to it. Not only can ß-decay be accelerated, but also the Alfa. The U-232 rate has been accelerated by laser with Au nanoparticles . C. Rolfs accelerated the decay rates by 1% by embedding (wrapping) Na22 in super-cooled metals, but it could be done with heavy materials (radioactive waste). In Type Ia supernovae, the radioactive decay rate Ni56 and Co56 is reduced when the nuclei are completely ionized . Other scientists doubt whether the decay rates are really exponential (as the statistical theory says for elements with large half-life periods) for slow ratios. There are theories based on the ‘Quantum Tunnelling’ property which claim that decay can be accelerated by observing atomic nuclei [quantum Zeno-or anti-Zeno effect].
FISSION TRACKS
Fission Track dating is a radiometric dating technique based on the analysis of damage traces, or clues, that leave fission fragments in certain minerals and crystals that contain uranium. Fission fingerprint dating is a relatively simple method of radiometric dating that has had a significant impact on the understanding of the thermal history of the continental crust, the timing of volcanic events and the source and age of different archaeological artefacts. The method involves the use of the amount of fission events produced by the spontaneous decomposition of Uranium-238 in common accessory minerals until the date of rocks cooling below the closing temperature. Fission tracks are sensitive to heat and, therefore, the technique is useful for unravelling the thermal evolution of rocks and minerals. Most current research that uses fission tracks is intended to: understand the evolution of mountain belts; determine the source or origin of the sediments; study the thermal evolution of the basins; determine the age of poorly dated strata; and determine dates and provenances of archaeological artefacts.
Unlike other isotopic dating methods, the daughter element in fission track dating is an effect on the crystal rather than a daughter isotope. Uranium-238 experiences spontaneous disintegration at a known (really assumed) rate, and is the only isotope with a decay rate that is relevant for the significant production of natural fission tracks; other isotopes have fission decay rates that are too slow to produce visible effects. The fragments emitted by this fission process leave traces of damage (fossil tracks or ion tracks) in the crystalline structure of the uranium-containing mineral. The follow-up production process is essentially the same by which fast heavy ions produce ionic tracks. The chemical etching of polished internal surfaces of these minerals reveals spontaneous fission tracks and path density can be determined. Because of the recorded tracks are relatively large (in the range of 1 to 15 micro-meters), the counting can be done by optical microscopy, although other imaging techniques are used. The density of the fossil tracks correlates with the cooling age of the sample and with the uranium content, which must be determined independently.
To determine the uranium content, several methods have been used. One method is by neutron irradiation, where the sample is irradiated with thermal neutrons in a nuclear reactor, with an external detector, such as mica, fixed to the surface of the grain. Neutron irradiation induces fission of U-235 in the sample, and the resulting induced clues are used to determine the uranium content of the sample because the U-235/U-238 ratio is well known and assumed constant in nature. To determine the number of induced fission events that occurred during neutron irradiation, an external detector joins the sample and both the sample and the detector are simultaneously irradiated by thermal neutrons. The external detector is typically a low uranium mica scale, but plastics such as CR-39 have also been used. The resulting induced fission of U-235 in the sample creates induced tracks in the superimposed external detector, which is then revealed by chemical etching. The proportion of spontaneous to induced clues is proportional to age. Another method to determine the uranium concentration is through LA-ICPMS, a technique where the crystal is struck with a laser beam and sectioned, and then the material is passed through an AMS mass spectrometer.
But it turns out that there are several paths of decay: U235-Pb207 and U238-Pb206. Scientists take uranium as distributed in the same way since the beginning of the solar system: they calculated 137.8 parts of U238 for one part of U235. Based on that technique they could know the distribution of parent elements in their analysis meteorite. However, in 2012 it was discovered that this proportion is not fixed . Curie-247 decays in U235, and although uranium has been distributed evenly in the solar system initially, it is not the case of Cm247. This could make dating vary by a small percentage.
Fossils are buried in the sediments and if we can know the age of the sedimentary rocks, then we can give the fossils an age. The main problem with radio isotope dating is that we have no means to know the exact amount of father and daughter isotopes present at the beginning . In addition, it is assumed that the system is closed so that none of the father and daughter isotopes are filtered into the environment. Most uranium salts are soluble in water . The rocks are exposed to rain and moisture. Therefore, there is a huge possibility that they can dissolve and get lost in the atmosphere. In such cases we will get erroneous results when we use the sample to date. In addition, radioactivity is considered independent of temperature and pressure and, therefore, this technique cannot be used to calculate the time required for solidification of magma. Finally, the assumption of constant decay rate faces many recent challenges .
In Brookhaven (New York), two experiments were carried out with Si-32 , Cl-36 and Radio-226 that detected seasonal variations of 0.3% in decay rates. Effects of eruptions and solar flares on rates were also published . Ra226 is part of the decay chain of U-238.
ACCELERATED MASS SPECTROMETRY AMS
It is a form of mass spectrometry that accelerates ions to extremely high kinetic energies before mass analysis. Its power lies in its great ability to separate a rare isotope from an abundant neighbouring mass (for example, 14C to 12C). The method suppresses molecular isobars (same molecular weight) completely and in many cases can separate atomic isobars (for example, 14N from 14C) as well. This makes it possible to detect naturally occurring long-lasting radioisotopes, such as 10Be, 36Cl, 26Al and 14C. The typical ranges of isotopic abundance (abundance in nature) range from 10-12 to 10-18. AMS outperforms the decay counting technique for all isotopes where the half-life is long enough. The AMS is appropriate for samples that provide between 25 milligrams and 0.3 grams of final carbon.
The advantages of AMS radiocarbon dating over radiometric analysis by LSC (scintillation counting) are:
A small sample size (only 20 mg) is needed, so it is recommended for radiocarbon dating of blood particles, grains, seeds, small artifacts or very expensive or rare materials.
It takes less time than the radiometric method (less than 24 hours).
Greater precision than radiometric techniques, especially in samples over 10,000 years old.
The sample size required by the laboratory is a conservative estimate. The usual pre-treatment procedures can eliminate 30% to 70% of the original material sent. Water, adhered minerals and the loss of carbon in chemical preparations are basic factors to consider when determining the amount of material required. For example, only 25% of the weight of a sample of clean carbon presented is available for analysis (1 gram of final carbon of 4 grams presented).
MAIN ASSUMPTIONS OF RADIOMETRIC DATING
The initial conditions of the rock sample are known exactly (parent and daughter isotopes quantities).
The amount of parent or daughter elements in a sample has not been altered by processes other than radioactive decay (the system is closed or isolated). Sample contamination is well documented . In Ngauruhoe, New Zealand, lava from 50 years ago gave an age of 133 million by Rb-St, 197 by Samario-Neodymium, and by U-Pb of 3,900 million .
The decay rate of the parent isotope has remained constant since the rock formed.
It is true that when small amounts of matter decay, large amounts of energy/heat (nuclear explosions) are released. The Earth's core is partially melted by the heat generated by the decay of radioactive elements. Theoretically, if the decay rate is accelerated, more heat emissions occur. This argument is used by scientists against creationists.
On the one hand, the U has a high melting point and it does not take long to reach the mantle, decreasing the dating, while Pb has a low melting point which translates into it less remaining material which increases the age. The segregation of materials in magma is due to geological processes that separate different elements which can also affect the U-Pb ratio for example. In addition, U is very soluble in water which could provide much older ages.
It is assumed that the decay rate cannot be altered (otherwise there would be no radioactive waste), but that man cannot, does not mean that nature cannot.
CIRCUMSTANTIAL ARGUMENTS
A fossil skull that suffered from tuberculosis was dated to 500 thousand years (apparently using faunal association methods –index fossil-) . The point is that evolutionary biologists claim that tuberculosis began just a few thousand years ago, therefore, theories would not fit.
As radiocarbon dating (C14) is only possible for 'living' organisms until 70,000 years ago, and cases of C14 findings have been reported in bones of extinct animals millions of years ago (supposedly ) and even soft tissues or collagen in your bones, or dating techniques do not work or evolutionary biology is wrong. The aggressive orthodox reaction is that the samples must have been contaminated. Therefore, it is difficult to publish the results of these findings in the main journals.
There have been discoveries of C14 in diamonds (it should not be not living organisms). Orthodoxy blames it on typical measurement errors, incorrect manipulations and contamination . An alternative source of C14 from N14 must be considered as in the atmosphere, or obtained from C13.
THERMOLUMINESCENCE (TL) AND OSL
Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) are two new methods developed at the end of the 20th century, related to Radiometry but with slight differences that make them more interesting as comparative methods. While being statistical methods, numerous anomalies have been detected, measuring different ages for crystals of the same material, and even samples that had no radiation (TL) in them .
Thermoluminescence (TL) is a well-established archaeological dating technique, but the most common mineral in volcanic rocks, feldspar plagioclase, is affected by "anomalous fading" that prevents its use for lava flow dating. There are well-known controversies such as the findings of Aboriginal humans from Western Australia (near Darwin) that some place in 10,000 years and others at 176,000 through TL procedures .
The process begins when crystalline material is buried by geological processes and supposedly isolated from the environment (light, water, radiation, Tª pressure...). Since that moment, radiation coming from the Earth heats the material (or, sunlight, in the case of the optical luminescence OSL). In both cases, this energizes the particles creating what they call "trapped electrons". With current measurements, a Radiation Absorption Ratio (RDR) is measured that is assumed constant for aeons. Subsequently, the samples unearthed by archaeologists are stimulated by heat (TL) or laser (light, OSL) so that the material releases stored radiation (TMRD, Total Measured Radiation Dose). Dividing TMRD between RDR would provide us with the age of the samples.
How do we know that RDR is constant for billions of years without having measured those ratios more than a few decades ago?
How do we know that TMRD is correct and that the system remained isolated from the environment (for example, it was not exposed to light or radiation temporarily) and was always in the state in which it was found?
There are few papers and scientists who recognise such limitations, and that there are not too many assumptions about the alleged balance of the samples throughout their history. In any case, RDRs seem to depend on other factors .
WATER RELATED EFFECTS
Now, Italian research shows evidence that a process called “cavitation” accelerated the nuclear decay of thorium (Th228). In particular, it seems that cavitation caused radioactive thorium decay to accelerate by a factor of 10,000 times during a 90-minute experiment. Cavitation can occur when water flows so fast that vapour bubbles are produced. These bubbles collapse to produce shock waves—very powerful on tiny scales—that have been known to rapidly destroy boat propellers and pump parts, catastrophically erode water tunnels, and create light sparks. Cavitation may also affect the nuclei of atoms in heavily resonating solutions.
The marine reservoir effect is a phenomenon affecting radiocarbon dating. Because much of the carbon consumed by organisms in the ocean is older than that consumed by organisms on land, samples from marine life and from organisms that consumed a lot of sea-based foods while alive may appear older when tested than they truly are. It is necessary to account for changes in the Earth's oceans to correct for the marine reservoir effect .
When a carbon reservoir has lower radiocarbon content than the atmosphere, this is referred to as a reservoir effect. This is expressed as an offset between the radiocarbon ages of samples from the two reservoirs at a single point in time. The marine reservoir effect (MRE) and the freshwater reservoir effect (FRE) are similar.
The mineralization of ancient dissolved organic carbon (DOC) (e.g., derived from peats), is likely to increase the radiocarbon ages of DIC in freshwater systems (Olsson, 1983, 1996), leading to elevated ΔR values. In theory, the same would happen in marine systems, but experimental data showing significant DOC influence are lacking. Discussions on these topics are available in Godwin (1951), Deevey et al. (1954), Little (1993), Heier-Nielsen et al. (1995), Ulm (2002), and Olsen et al. (2017).
Marine radiocarbon ages must be interpreted with care. Whereas calibration with global marine curves accounts for the global average of the MRE, research illustrates the necessity of taking into account local deviations from this mean. A discussion of the MRE requires the analysis of local ocean dynamics for these values are a product of the physical, chemical, and biological processes responsible for the uptake and distribution of radiocarbon in the heterogeneous marine realm. Discussions on oceanic configurations and climate changes known to have demonstrably changed the MRE would make the database even more practical. Notes by the authors of the original publications warning on very local hardwater and/or freshwater effects could also be added. Hardwater and/or freshwater effects can affect estuaries in an extremely local scale. After the recognition of the disequilibrium in radiocarbon content between atmosphere and oceans, the amount of research being published on the topic increased, yielding new data for different world regions and providing a better understanding of the time dependency of MREs. The quantification of this disequilibrium has been the main objective of many papers, which then use the MRE values as a proxy for changes in circulation, freshwater input and air-sea exchange, and/or for the correct calibration of marine 14C ages.
In summary, MRE and FRE are proved to produce older dates on bones, pottery and sedimentary rocks and any organic material.
USAGE OF SPECIFIC DATING SCHEMES
Uranium-Lead (U238-Pb206; U235-Pb207): Coal (petrified wood, for instance), meteorites, zircons, biotite crystals, metamorphic rocks.
Potasium40-Argon40 (and Ar-Ar): Seafloor spreading, Igneous rocks, meteorites, lava.
Rubidium87-Strontium87: mica.
Uranium234-Thorium230: biotite crystals and metamorphic rocks in general.
C14-C12: Fossils with bone or collagen (not petrified), pottery, sedimentary rocks, organic material.
LATITUDE EFFECT-TREE RINGS
Two different trends can be seen in the tree ring series. First, there is a long-term oscillation with a period of about 9,000 years, which causes radiocarbon dates to be older than true dates for the last 2,000 years and too young before that. The known fluctuations in the strength of the earth's magnetic field match up quite well with this oscillation: cosmic rays are deflected by magnetic fields, so when there is a weaker magnetic field, more 14C is produced, leading to a younger apparent age for samples from those periods. Conversely, a stronger magnetic field leads to lower 14C production and an older apparent age. A secondary oscillation is thought to be caused by variations in sunspot activity, which has two separate periods: a longer-term, 200-year oscillation, and a shorter 11-year cycle. Sunspots cause changes in the solar system's magnetic field and corresponding changes to the cosmic ray flux, and hence to the production of 14C.
There are two kinds of geophysical event which can affect 14C production: geomagnetic reversals and polarity excursions. In a geomagnetic reversal, the Earth's geomagnetic field weakens and stays weak for thousands of years during the transition to the opposite magnetic polarity and then regains strength as the reversal completes. A polarity excursion, which can be either global or local, is a shorter-lived version of a geomagnetic reversal. A local excursion would not significantly affect 14C production. During either a geomagnetic reversal or a global polarity excursion, 14C production increases during the period when the geomagnetic field is weak. It is fairly certain, though, that in the last 50,000 years there have been no geomagnetic reversals or global polarity excursions.
Since the earth's magnetic field varies with latitude, the rate of 14C production changes with latitude, too, but atmospheric mixing is rapid enough that these variations amount to less than 0.5% of the global concentration. This is close to the limit of detectability in most years, but the effect can be seen clearly in tree rings from years such as 1963, when 14C from nuclear testing rose sharply through the year. The latitudinal variation in 14C was much larger than normal that year, and tree rings from different latitudes show corresponding variations in their 14C content.
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