Laws of Relative Rock DatingRelative dating and radiometric dating are used to determine age of fossils and geologic features, but with different methods. Relative dating uses observation of location within rock layers, while radiometric dating uses data from the decay of radioactive substances within an object. Relative dating observes the placement of fossils and rock in layers known as strata. Basically, fossils and rock found in lower strata are older than those found in higher strata because lower objects must have been deposited first, while higher objects were deposited last. Relative dating helps determine what came first and what followed, but doesn't help determine actual age. Radiometric dating, or numeric dating, determines an actual or approximate age of an object by studying the rate of decay of radioactive isotopes, such as uranium, potassium, rubidium and carbon within that object. Radioactive isotopes decay at a fixed rate.
ES Uploaded By SuzyQ Compare and contrast relative age dating with radiometric dating. What are the strengths and limitations if any of each?
Some techniques measure the absolute age and some measure relative age of our earth and the foundations in it. Relative age dating is used to determine the age of a fossil when looking at its position by the layers of sedimentary rocks. Relative dating is somewhat less precise than radiometric dating. For example, everywhere in the world, trilobites were found lower in the stratigraphy than marine reptiles.
Dinosaurs were found after the first occurrence of land plants, insects, and amphibians. Spore-bearing land plants like ferns were always found before the occurrence of flowering plants. And so on. The observation that fossils occur in a consistent succession is known as the "principle of faunal and floral succession".
The study of the succession of fossils and its application to relative dating is known as "biostratigraphy". Each increment of time in the stratigraphy could be characterized by a particular assemblage of fossil organisms, formally termed a biostratigraphic "zone" by the German paleontologists Friedrich Quenstedt and Albert Oppel.
These zones could then be traced over large regions, and eventually globally. Groups of zones were used to establish larger intervals of stratigraphy, known as geologic "stages" and geologic "systems". The time corresponding to most of these intervals of rock became known as geologic "ages" and "periods", respectively. By the end of the s, most of the presently-used geologic periods had been established based on their fossil content and their observed relative position in the stratigraphy e.
These terms were preceded by decades by other terms for various geologic subdivisions, and although there was subsequent debate over their exact boundaries e. By the s, fossil succession had been studied to an increasing degree, such that the broad history of life on Earth was well understood, regardless of the debate over the names applied to portions of it, and where exactly to make the divisions. All paleontologists recognized unmistakable trends in morphology through time in the succession of fossil organisms.
This observation led to attempts to explain the fossil succession by various mechanisms. Perhaps the best known example is Darwin's theory of evolution by natural selection. Note that chronologically, fossil succession was well and independently established long before Darwin's evolutionary theory was proposed in Fossil succession and the geologic time scale are constrained by the observed order of the stratigraphy -- basically geometry -- not by evolutionary theory.
For almost the next years, geologists operated using relative dating methods, both using the basic principles of geology and fossil succession biostratigraphy. Various attempts were made as far back as the s to scientifically estimate the age of the Earth, and, later, to use this to calibrate the relative time scale to numeric values refer to "Changing views of the history of the Earth" by Richard Harter and Chris Stassen.
Most of the early attempts were based on rates of deposition, erosion, and other geological processes, which yielded uncertain time estimates, but which clearly indicated Earth history was at least million or more years old. A challenge to this interpretation came in the form of Lord Kelvin's William Thomson's calculations of the heat flow from the Earth, and the implication this had for the age -- rather than hundreds of millions of years, the Earth could be as young as tens of million of years old.
This evaluation was subsequently invalidated by the discovery of radioactivity in the last years of the 19th century, which was an unaccounted for source of heat in Kelvin's original calculations.
With it factored in, the Earth could be vastly older. Estimates of the age of the Earth again returned to the prior methods. The discovery of radioactivity also had another side effect, although it was several more decades before its additional significance to geology became apparent and the techniques became refined.
Because of the chemistry of rocks, it was possible to calculate how much radioactive decay had occurred since an appropriate mineral had formed, and how much time had therefore expired, by looking at the ratio between the original radioactive isotope and its product, if the decay rate was known.
Many geological complications and measurement difficulties existed, but initial attempts at the method clearly demonstrated that the Earth was very old. In fact, the numbers that became available were significantly older than even some geologists were expecting -- rather than hundreds of millions of years, which was the minimum age expected, the Earth's history was clearly at least billions of years long. Radiometric dating provides numerical values for the age of an appropriate rock, usually expressed in millions of years.
Therefore, by dating a series of rocks in a vertical succession of strata previously recognized with basic geologic principles see Stratigraphic principles and relative timeit can provide a numerical calibration for what would otherwise be only an ordering of events -- i. The integration of relative dating and radiometric dating has resulted in a series of increasingly precise "absolute" i. Given the background above, the information used for a geologic time scale can be related like this:.
A continuous vertical stratigraphic section will provide the order of occurrence of events column 1 of Figure 2. These are summarized in terms of a "relative time scale" column 2 of Figure 2.
Geologists can refer to intervals of time as being "pre-first appearance of species A" or "during the existence of species A", or "after volcanic eruption 1" at least six subdivisions are possible in the example in Figure 2.
For this type of "relative dating" to work it must be known that the succession of events is unique or at least that duplicate events are recognized -- e. Unique events can be biological e. Ideally, geologists are looking for events that are unmistakably unique, in a consistent order, and of global extent in order to construct a geological time scale with global significance.
Some of these events do exist. For example, the boundary between the Cretaceous and Tertiary periods is recognized on the basis of the extinction of a large number of organisms globally including ammonites, dinosaurs, and othersthe first appearance of new types of organisms, the presence of geochemical anomalies notably iridiumand unusual types of minerals related to meteorite impact processes impact spherules and shocked quartz.
These types of distinctive events provide confirmation that the Earth's stratigraphy is genuinely successional on a global scale. Even without that knowledge, it is still possible to construct local geologic time scales.
Although the idea that unique physical and biotic events are synchronous might sound like an "assumption", it is not. It can, and has been, tested in innumerable ways since the 19th century, in some cases by physically tracing distinct units laterally for hundreds or thousands of kilometres and looking very carefully to see if the order of events changes.
Geologists do sometimes find events that are "diachronous" i. Because any newly-studied locality will have independent fossil, superpositional, or radiometric data that have not yet been incorporated into the global geological time scale, all data types serve as both an independent test of each other on a local scaleand of the global geological time scale itself. The test is more than just a "right" or "wrong" assessment, because there is a certain level of uncertainty in all age determinations.
For example, an inconsistency may indicate that a particular geological boundary occurred 76 million years ago, rather than 75 million years ago, which might be cause for revising the age estimate, but does not make the original estimate flagrantly "wrong".
It depends upon the exact situation, and how much data are present to test hypotheses e. Whatever the situation, the current global geological time scale makes predictions about relationships between relative and absolute age-dating at a local scale, and the input of new data means the global geologic time scale is continually refined and is known with increasing precision.
This trend can be seen by looking at the history of proposed geologic time scales described in the first chapter of [Harland et al,p. The unfortunate part of the natural process of refinement of time scales is the appearance of circularity if people do not look at the source of the data carefully enough.
Most commonly, this is characterised by oversimplified statements like:. Even some geologists have stated this misconception in slightly different words in seemingly authoritative works e. When a geologist collects a rock sample for radiometric age dating, or collects a fossil, there are independent constraints on the relative and numerical age of the resulting data. Stratigraphic position is an obvious one, but there are many others.
There is no way for a geologist to choose what numerical value a radiometric date will yield, or what position a fossil will be found at in a stratigraphic section. Every piece of data collected like this is an independent check of what has been previously studied. The data are determined by the rocksnot by preconceived notions about what will be found.
Every time a rock is picked up it is a test of the predictions made by the current understanding of the geological time scale. The time scale is refined to reflect the relatively few and progressively smaller inconsistencies that are found.
This is not circularity, it is the normal scientific process of refining one's understanding with new data. It happens in all sciences. If an inconsistent data point is found, geologists ask the question: "Is this date wrong, or is it saying the current geological time scale is wrong?
However, this statistical likelihood is not assumed, it is testedusually by using other methods e. Geologists search for an explanation of the inconsistency, and will not arbitrarily decide that, "because it conflicts, the data must be wrong.
If it is a small but significant inconsistency, it could indicate that the geological time scale requires a small revision.
This happens regularly. The continued revision of the time scale as a result of new data demonstrates that geologists are willing to question it and change it. The geological time scale is far from dogma. If the new data have a large inconsistency by "large" I mean orders of magnitudeit is far more likely to be a problem with the new data, but geologists are not satisfied until a specific geological explanation is found and tested.Relative dating methods (ANT)
An inconsistency often means something geologically interesting is happening, and there is always a tiny possibility that it could be the tip of a revolution in understanding about geological history. Admittedly, this latter possibility is VERY unlikely. There is almost zero chance that the broad understanding of geological history e. The amount of data supporting that interpretation is immense, is derived from many fields and methods not only radiometric datingand a discovery would have to be found that invalidated practically all previous data in order for the interpretation to change greatly.
So far, I know of no valid theory that explains how this could occur, let alone evidence in support of such a theory, although there have been highly fallacious attempts e. It contains a mixture of minerals from a volcanic eruption and detrital mineral grains eroded from other, older rocks.
If the age of this unit were not so crucial to important associated hominid fossils, it probably would not have been dated at all because of the potential problems. After some initial and prolonged troubles over many years, the bed was eventually dated successfully by careful sample preparation that eliminated the detrital minerals. Lubenow's work is fairly unique in characterising the normal scientific process of refining a difficult date as an arbitrary and inappropriate "game", and documenting the history of the process in some detail, as if such problems were typical.
Another example is "John Woodmorappe's" paper on radiometric datingwhich adopts a "compilation" approach, and gives only superficial treatment to the individual dates. Among other problems documented in an FAQ by Steven Schimmrichmany of Woodmorappe's examples neglect the geological complexities that are expected to cause problems for some radiometrically-dated samples.
This section is important because it places a limit on the youngest age for a specific ammonite shell -- Baculites reesidei -- which is used as a zonal fossil in western North America. It consistently occurs below the first occurrence of Bacultes jenseni and above the occurrence of Baculites cuneatus within the upper part of the Campanian, the second to last "stage" of the Cretaceous Period in the global geological time scale.
The biostratigraphic situation can be summarized as a vertically-stacked sequence of "zones" defined by the first appearance of each ammonite species:. About 40 of these ammonite zones are used to subdivide the upper part of the Cretaceous Period in this area.
Dinosaurs and many other types of fossils are also found in this interval, and in broad context it occurs shortly before the extinction of the dinosaurs, and the extinction of all ammonites. The Bearpaw Formation is a marine unit that occurs over much of Alberta and Saskatchewan, and it continues into Montana and North Dakota in the United States, although it adopts a different name in the U. The numbers above are just summary values. Other examples yield similar results - i.
The result? Radiometric dating methods are more recent than dendrochronology. However, dendrochronology provides an important calibration technique for radiocarbon dating techniques. All radiometric-dating techniques are based on the well-established principle from physics that large samples of radioactive isotopes decay at precisely known rates. The rate of decay of a radioactive isotope is usually given by its half-life.
The decay of any individual nucleus is completely random.
The half-life is a measure of the probability that a given atom will decay in a certain time. The shorter the half-life, the more likely the atom will decay. This probability does not increase with time. If an atom has not decayed, the probability that it will decay in the future remains exactly the same. This means that no matter how many atoms are in a sample, approximately one-half will decay in one half-life. The remaining atoms have exactly the same decay probability, so in another half-life, one half of the remaining atoms will decay.
The amount of time required for one-half of a radioactive sample to decay can be precisely determined. The particular radioisotope used to determine the age of an object depends on the type of object and its age. Radiocarbon is the most common and best known of radiometric dating techniques, but it is also possibly the most misunderstood. It was developed at the University of Chicago in by a group of American scientists led by Willard F.
Radiocarbon dating has had an enormous impact on archaeology. In the last 50 years, radiocarbon dating has provided the basis for a worldwide cultural chronology. Recognizing the importance of this technique, the Nobel Prize committee awarded the Prize in Chemistry to Libby in The physics behind radiocarbon dating is straightforward. Earth 's atmosphere is constantly bombarded with cosmic rays from outer space. Cosmic-ray neutrons collide with atoms of nitrogen in the upper atmosphere, converting them to atoms of radioactive carbon The carbon atom quickly combines with an oxygen molecule to form carbon dioxide.
This radioactive carbon dioxide spreads throughout Earth's atmosphere, where it is taken up by plants along with normal carbon As long as the plant is alive, the relative amount ratio of carbon to carbon remains constant at about one carbon atom for every one trillion carbon atoms. Some animals eat plants and other animals eat the plant-eaters. As long as they are alive, all living organisms have the same ratio of carbon to carbon as in the atmosphere because the radioactive carbon is continually replenished, either through photosynthesis or through the food animals eat.
However, when the plant or animal dies, the intake of carbon stops and the ratio of carbon to carbon immediately starts to decrease.
nuclides formed by radioactive disintegration of the parent nuclide. Radiometric Dating. technique used to measure absolute time in which the amounts of a parent Absolute dating provides a computed numerical age in contrast with relative. Relative dating and radiometric dating are used to determine age of fossils and geologic features, but with different methods. Basically, fossils and rock found in lower strata are older than those found in higher strata because lower objects. Does radiometric dating via liquid form, within those rocks and theology ca relative dating methods, like rocks and absolute age markers. Radioactive.
The half-life of carbon is 5, years. After 5, years, about one-half of the carbon atoms will have decayed. After another 5, years, one-half of the remaining atoms will have decayed. So after 11, years, only one-fourth will remain. After 17, years, one-eighth of the original carbon will remain.
After 22, years, one-sixteenth will remain. Radiocarbon dating has become the standard technique for determining the age of organic remains those remains that contain carbon. There are many factors that must be taken into account when determining the age of an object.
The best objects are bits of charcoal that have been preserved in completely dry environments. The worst candidates are bits of wood that have been saturated with sea water, since sea water contains dissolved atmospheric carbon dioxide that may throw off the results. Radiocarbon dating can be used for small bits of clothing or other fabric, bits of bone, baskets, or anything that contains organic material. There are well over labs worldwide that do radiocarbon dating.
In the early twenty-first century, the dating of objects up to about 10 half-lives, or up to about 50, years old, is possible. However, objects less than years old cannot be reliably dated because of the widespread burning of fossil fuels, which began in the nineteenth century, and the production of carbon from atmospheric testing of nuclear weapons in the s and s. Another problem with radiocarbon dating is that the production of carbon in the atmosphere has not been constant, due to variation in solar activity.
For example, in the s, solar activity dropped a phenomenon called the "Maunder Minimum"so carbon production also decreased during this period. To achieve the highest level of accuracy, carbon dates must be calibrated by comparison to dates obtained from dendrochronology. Calibration of Radiocarbon Dates.
Samples of Bristlecone pine, a tree with a very long life span, have been dated using both dendrochronology and radiocarbon dating. The results do not agree, but the differences are consistent.
That is, the radiocarbon dates were always wrong by the same number of years. Consequently, tree-ring chronologies have been used to calibrate radiocarbon dates to around 12, years ago.
When radiocarbon dating was first put into use, it was decided that dates would always be reported as B. That way, dates reported in magazine articles and books do not have to be adjusted as the years pass.
So if a lab determines that an object has a radiocarbon age of 1, years inits age will be given as B. Calibrated dates are given using the actual date, such as c. Potassium-Argon Dating. If an object is too old to be dated by radiocarbon dating, or if it contains no organic material, other methods must be used.
One of these is potassium-argon dating. All naturally occurring rocks contain potassium. Some of the potassium in rocks is the radioactive isotope potassium Potassium gradually decays to the stable isotope argon, which is a gas. When the rock is melted, as in a volcano, any argon gas trapped in the rock escapes.
When the rock cools, the argon will begin to build up. So this method can be used to measure the age of any volcanic rock, fromyears up to around 5 billion years old.
This method is not widely used in archaeology, since most archaeological deposits are not associated with volcanic activity. However, Louis and Mary Leakey successfully used the method to determine the ages of fossils in Olduvai Gorge in Tanzania by examining rocks from lava flows above and below the fossils.
They were able to establish an absolute chronology for humans and human ancestors extending back two million years. At Laetolli, in Tanzania, volcanic ash containing early hominid footprints was dated by this method at 3.
Uranium is present in most rocks. This isotope of uranium spontaneously undergoes fission. The fission fragments have a lot of energy, and they plow through the rock, leaving a track that can be made visible by treating the rock.
So by counting fission tracks, the age of the rock can be determined. Like potassium-argon datingthis can only be used to determine the age of the rock, not the age of the artifact itself. Thermoluminescence is a recently developed technique that uses the property of some crystals to "store" light. Sometimes an electron will be knocked out of its position in a crystal and will "stick" somewhere else in the crystal.
These displaced electrons will accumulate over time. If the sample is heated, the electrons will fall back to their normal positions, emitting a small flash of light. By measuring the light emitted, the time that has passed since the artifact was heated can be determined. This method should prove to be especially useful in determining the age of ceramics, rocks that have been used to build fire rings, and samples of chert and flint that have been deliberately heated to make them easier to flake into a projectile point.
Science continues to develop new methods to determine the age of objects. As our knowledge of past chronologies improves, archaeologists will be better able to understand how cultures change over time, and how different cultures interact with each other. As a result, this knowledge will enable us to achieve a progressively better understanding of our own culture. Baillie, M.
London U. Taylor, R. Radiocarbon Dating : An Archaeological Perspective. Orlando, FL: Academic Press, Long, and R. New York : Springer-Verlag, Wood, Michael. In Search of the Trojan War. New York : New American Library, Dating techniques are procedures used by scientists to determine the age of an object or a series of events.
The two main types of dating methods are relative and absolute. Relative dating methods are used to determine only if one sample is older or younger than another. Absolute dating methods are used to determine an actual date in years for the age of an object.
Before the advent of absolute dating methods in the twentieth century, nearly all dating was relative. The main relative dating method is stratigraphy pronounced stra-TI-gra-feewhich is the study of layers of rocks or the objects embedded within those layers.
This method is based on the assumption which nearly always holds true that deeper layers of rock were deposited earlier in Earth 's history, and thus are older than more shallow layers. The successive layers of rock represent successive intervals of time. Since certain species of animals existed on Earth at specific times in history, the fossils or remains of such animals embedded within those successive layers of rock also help scientists determine the age of the layers. Similarly, pollen grains released by seed-bearing plants became fossilized in rock layers.
If a certain kind of pollen is found in an archaeological site, scientists can check when the plant that produced that pollen lived to determine the relative age of the site.
Absolute dating methods are carried out in a laboratory. The most widely used and accepted form of absolute dating is radioactive decay dating. Radioactive decay dating. Radioactive decay refers to the process in which a radioactive form of an element is converted into a nonradioactive product at a regular rate.
The nucleus of every radioactive element such as radium and uranium spontaneously disintegrates over time, transforming itself into the nucleus of an atom of a different element.
In the process of disintegration, the atom gives off radiation energy emitted in the form of waves. Hence the term radioactive decay. Each element decays at its own rate, unaffected by external physical conditions. By measuring the amount of original and transformed atoms in an object, scientists can determine the age of that object. Cosmic rays: Invisible, high-energy particles that constantly bombard Earth from all directions in space. Dendrochronology: Also known as tree-ring dating, the science concerned with determining the age of trees by examining their growth rings.
Half-life: Measurement of the time it takes for one-half of a radioactive substance to decay. Radioactive decay: The predictable manner in which a population of atoms of a radioactive element spontaneously disintegrate over time.
The age of the remains of plants, animals, and other organic material can be determined by measuring the amount of carbon contained in that material. Carbon, a radioactive form of the element carbon, is created in the atmosphere by cosmic rays invisible, high-energy particles that constantly bombard Earth from all directions in space. When carbon falls to Earth, it is absorbed by plants. These plants are eaten by animals who, in turn, are eaten by even larger animals.
Eventually, the entire ecosystem community of plants and animals of the planet, including humans, is filled with a concentration of carbon As long as an organism is alive, the supply of carbon is replenished. When the organism dies, the supply stops, and the carbon contained in the organism begins to spontaneously decay into nitrogen The time it takes for one-half of the carbon to decay a period called a half-life is 5, years.
By measuring the amount of carbon remaining, scientists can pinpoint the exact date of the organism's death. The range of conventional radiocarbon dating is 30, to 40, years. With sensitive instrumentation, this range can be extended to 70, years.
In addition to the radiocarbon dating technique, scientists have developed other dating methods based on the transformation of one element into another.
These include the uranium-thorium method, the potassium-argon method, and the rubidium-strontium method. Thermoluminescence pronounced ther-moeloo-mi-NES-ence dating is very useful for determining the age of pottery.
The older the pottery, the brighter the light that will be emitted. Using thermoluminescence, pottery pieces as old asyears can be dated with precision. Tree-ring dating. Known as dendrochronology pronounced den-dro-crow-NOL-o-geetree-ring dating is based on the fact that trees produce one growth ring each year. Narrow rings grow in cold or dry years, and wide rings grow in warm or wet years.
Thus, the growth pattern of a tree of a known age can be used as a standard to determine the age of similar trees. The ages of buildings and archaeological sites can also be determined by examining the ring patterns of the trees used in their construction. Dendrochronology has a range of 1 to 10, years or more.
Relative dating techniques date specimens in relation to one another; for example, stratigraphy is used to establish the succession of fossils. Absolute or chronometric techniques give an absolute estimate of the age and fall into two main groups. The first depends on the existence of something that develops at a seasonally varying rate, as in dendrochronology and varve dating.
The other uses some measurable change that occurs at a known rate, as in chemical datingradioactive or radiometric dating see carbon dating ; fission-track dating ; potassium—argon dating ; rubidium—strontium dating ; uranium—lead datingand thermoluminescence.
Compare and contrast the techniques of relative dating to those of radiometric dating
Depositional rates of sediments have also been employed as a dating method, but only recently has absolute dating been made possible through the use of radioactive isotopes. Of the various methods the last is obviously the most precise, but fossilslithologiesand cross-cutting relationships do enable the geologist to give an approximate relative age in field studies.
Start studying Relative Dating, Fossils, and Radiometric Dating. that have shaped Earth in the past are essentially the same as those operating today. What is. Compare and contrast relative age dating with radiometric dating. What are the The relative age dating techniques that were developed are used to this day. The textbooks speak of the radiometric dating techniques, and the Relative ages are assigned to rocks based on the idea that rock Certain types of rocks, especially those that form from magma (igneous), contain radioactive isotopes of . Comparing the amount of a parent isotope to the amount of its.
A relative time scale, constructed in the last century, is based on correlations between palaeontological and stratigraphic data. The rate at which sediments accumulate can also be used for dating see varve. Absolute dating relies on the decay of radioactive isotopes of elements present in the material to be dated see decay constant ; decay curve ; decay series ; isotopic dating; radiocarbon dating ; and radiometric dating.
Dating techniques are procedures used by scientists to determine the age of rocks, fossils, or artifacts.
Relative vs Absolute Dating Dating is a technique used in Compare and Contrast- What are the differences between relative dating and absolute dating? What is the difference between relative dating and radiometric dating? Basically, fossils and rock found in lower strata are older than those found. It is not about the theory behind radiometric dating methods, it is . and the strata towards the bottom are older, those towards the top are Other workers in the rest of Europe, and eventually the rest of the world, were able to compare directly to the Radiometric Dating: Calibrating the Relative Time Scale. Relative dating methods tell only if one sample is older or younger than Many absolute dating techniques take advantage of radioactive decay, Stratigraphy is the study of layers of rocks or the objects embedded within those layers. . to a known amount of light and compare these grains with the unknown sediment.
Relative dating methods tell only if one sample is older or younger than another; absolute dating methods provide an approximate date in years. Many absolute dating techniques take advantage of radioactive decaywhereby a radioactive form of an element decays into a non-radioactive product at a regular rate. In recent years, a few of these methods have come under close scrutiny as scientists strive to develop the most accurate dating techniques possible. It is based on the assumption which nearly always holds true that deeper layers were deposited earlier, and thus are older, than more shallow layers.
Although these units may be sequential, they are not necessarily continuous due to erosional removal of some intervening. Stratigraphy is the principle method of relative dating, and in the early years of dating studies was virtually the only method available to scientists.
The technique works best if the animals belonged to species, which evolved quickly, expanded rapidly over a large area, or suffered a mass extinction. The unit of the calendar is the pollen zone. In most cases, this tells us about the climate of the period, because most plants only thrive in specific climatic conditions. This dating technique was first conducted by Hare and Mitterer inand was popular in the s.
Amino acid racimization is based on the principle that amino acids except glycine, which is a very simple amino acid exist in two mirror image forms called stereoisomers. This may form a D-amino acid instead of an L-amino acid. The rate at which the reaction occurs is different for each amino acid; in addition, it depends upon the moisture, temperature, and pH of the postmortem conditions. It can be used to obtain dates that would be unobtainable by more conventional methods such as radio-carbon dating.
Although cation-ratio dating has been widely used, recent studies suggest it has many problems.