Isochron dating assumptions and critical thinking

Refuting "Radiometric Dating Methods Makes Untenable Assumptions!" | Debunking Denialism

isochron dating assumptions and critical thinking

The simplest way to think of it is this: Some rock materials (isotopes) decay, and First, let's take a hard look at the critical assumptions of the isochron model. This age is computed under the assumption that the parent substance (say, . In fact, I think this is a very telling argument against radiometric dating. Sr ( another non-radioactive isotope of strontium) that is critical to the situation. Apr 3, I would think that the older the sample, the larger the overestimate. This newly- pointed-out flaw in the isochron method is a stark reminder of that. .. that radiometric dating had some significant assumptions that warranted more . A Perfect Example of Critical Thinking · Homeschooling and Socialization.

That is, we can get both parent and daughter elements from the magma inherited into minerals that crystallize out of lava, making these minerals look old. Since the magma has old radiometric dates, depending on how much the clock gets reset, the crust can end up with a variety of younger dates just by partially inheriting the dates of the magma. Thus any method based on simple parent to daughter ratios such as Rb-Sr dating is bound to be unreliable, since there would have to be a lot of the daughter product in the magma already.

And Harold Coffin's book Creation by Design lists a study showing that Rb-Sr dates are often inherited from the magma. Even the initial ratios of parent and daughter elements in the earth do not necessarily indicate an age as old as 4. Radioactive decay would be faster in the bodies of stars, which is where scientists assume the heavy elements formed. Imagine a uranium nucleus forming by the fusion of smaller nucleii.

At the moment of formation, as two nucleii collide, the uranium nucleus will be somewhat unstable, and thus very likely to decay into its daughter element. The same applies to all nucleii, implying that one could get the appearance of age quickly. Of course, the thermonuclear reactions in the star would also speed up radioactive decay.

But isochrons might be able to account for pre-existing daughter elements. Furthermore, some elements in the earth are too abundant to be explained by radioactive decay in 4. Some are too scarce such as helium.

Scientist Realizes Important Flaw in Radioactive Dating – Proslogion

So it's not clear to me how one can be sure of the 4. Back to top In general, potassium-argon dates appear to be older the deeper one goes in the crust of the earth. We now consider possible explanations for this. There are at least a couple of mechanisms to account for this.

In volcano eruptions, a considerable amount of gas is released with the lava. This gas undoubtedly contains a significant amount of argon Volcanos typically have magma chambers under them, from which the eruptions occur.

It seems reasonable that gas would collect at the top of these chambers, causing artificially high K-Ar radiometric ages there. In addition, with each successive eruption, some gas would escape, reducing the pressure of the gas and reducing the apparent K-Ar radiometric age.

Thus the decreasing K-Ar ages would represent the passage of time, but not necessarily related to their absolute radiometric ages.

As a result, lava found in deeper layers, having erupted earlier, would generally appear much older and lava found in higher layers, having erupted later, would appear much younger.

This could account for the observed distribution of potassium-argon dates, even if the great sedimantary layers were laid down very recently.


In addition, lava emerging later will tend to be hotter, coming from deeper in the earth and through channels that have already been warmed up. This lava will take longer to cool down, giving more opportunity for enclosed argon to escape and leading to younger radiometric ages. A discussion of these mechanisms may be found at the Geoscience Research Institute site.

Another factor is that rocks absorb argon from the air. It is true that this can be accounted for by the fact that argon in the air has Ar36 and Ar40, whereas only Ar40 is produced by K-Ar decay. But for rocks deep in the earth, the mixture of argon in their environment is probably much higher in Ar40, since only Ar40 is produced by radioactive decay.

Scientist Realizes Important Flaw in Radioactive Dating

As these rocks absorb argon, their radiometric ages would increase. This would probably have a larger effect lower down, where the pressure of argon would be higher. Or it could be that such a distribution of argon pressures in the rocks occurred at some time in the past.

This would also make deeper rocks tend to have older radiometric ages. Recent lava flows often yield K-Ar ages of aboutyears. This shous that they contain some excess argon, and not all of it is escaping.

If they contained a hundred times more excess argon, their K-Ar ages would be a hundred times greater, I suppose. And faster cooling could increase the ages by further large factors. I also read of a case where a rock was K-Ar dated at 50 million years, and still susceptible to absorbing argon from the air. This shows that one might get radiometric ages of at least 50 million years in this way by absorbing Ar40 deep in the earth without much Ar36 or Ar38 present.

If the pressure of Ar40 were greater, one could obtain even greater ages. Yet another mechanism that can lead to decreasing K-Ar ages with time is the following, in a flood model: One can assume that at the beginning of the flood, many volcanoes erupted and the waters became enriched in Ar Then any lava under water would appear older because its enclosed Ar40 would have more trouble escaping. As time passed, this Ar40 would gradually pass into the atmosphere, reducing this effect and making rocks appear younger.

In addition, this would cause a gradient of Ar40 concentrations in the air, with higher concentrations near the ground. This also could make flows on the land appear older than they are, since their Ar40 would also have a harder time escaping. Back to top Let us consider the question of how much different dating methods agree on the geologic column, and how many measurements are anomalous, since these points are often mentioned as evidences of the reliability of radiometric dating.

It takes a long time to penetrate the confusion and find out what is the hard evidence in this area. In the first place, I am not primarily concerned with dating meteorites, or precambrian rocks. What I am more interested in is the fossil-bearing geologic column of Cambrian and later age. Now, several factors need to be considered when evaluating how often methods give expected ages on the geologic column. Some of these are taken from John Woodmoreappe's article on the subject, but only when I have reason to believe the statements are also generally believed.

First, many igneous formations span many periods, and so have little constraint on what period they could belong to. The same applies to intrusions. In addition, some kinds of rocks are not considered as suitable for radiometric dating, so these are typically not considered.

Furthermore, it is at least possible that anomalies are under-reported in the literature. Finally, the overwhelming majority of measurements on the fossil bearing geologic column are all done using one method, the K-Ar method. And let me recall that both potassium and argon are water soluble, and argon is mobile in rock.

Thus the agreement found between many dates does not necessarily reflect an agreement between different methods, but rather the agreement of the K-Ar method with itself. For example, if 80 percent of the measurements were done using K-Ar dating, and the other 20 percent gave random results, we still might be able to say that most of the measurements on a given strata agree with one another reasonably well.

So to me it seems quite conceivable that there is no correlation at all between the results of different methods on the geologic column, and that they have a purely random relationship to each other.

Let us consider again the claim that radiometric dates for a given geologic period agree with each other. I would like to know what is the exact or approximate information content of this assertion, and whether it could be or has been tested statistically. It's not as easy as it might sound. Let's suppose that we have geologic periods G Let's only include rocks whose membership in the geologic period can be discerned independent of radiometric dating methods. Let's also only include rocks which are considered datable by at least one method, since some rocks I believe limestone are considered not to hold argon, for example.

Now, we can take a random rock from Gi. We will have to restrict ourselves to places where Gi is exposed, to avoid having to dig deep within the earth. Let's apply all known dating methods to Gi that are thought to apply to this kind of rock, and obtain ages from each one. Then we can average them to get an average age for this rock. We can also compute how much they differ from one another. Now we have to be careful about lava flows -- which geologic period do they belong to? What about rocks that are thought not to have their clock reset, or to have undergone later heating episodes?

Just to make the test unbiased, we will assign altitude limits to each geologic period at each point on the earth's surface at least in principle and include all rocks within these altitude limits within Gi, subject to the condition that they are datable.

The measurements should be done in a double-blind manner to insure lack of unconscious bias. For each geologic period and each dating method, we will get a distribution of values.

isochron dating assumptions and critical thinking

We will also get a distribution of averaged values for samples in each period. Now, some claim is being made about these distributions. It is undoubtedly being claimed that the mean values ascend as one goes up the geologic column. It is also being claimed that the standard deviations are not too large. It is also being claimed that the different methods have distributions that are similar to one another on a given geologic period.

The only correlation I know about that has been studied is between K-Ar and Rb-Sr dating on precambrian rock. And even for this one, the results were not very good.

isochron dating assumptions and critical thinking

This was a reference by Hurley and Rand, cited in Woodmorappe's paper. As far as I know, no study has been done to determine how different methods correlate on the geologic column excluding precambrian rock.

The reason for my request is that a correlation is not implied by the fact that there are only 10 percent anomalies, or whatever. I showed that the fact that the great majority of dates come from one method K-Ar and the fact that many igneous bodies have very wide biostratigraphic limits, where many dates are acceptable, makes the percentage of anomalies irrelevant to the question I am asking.

isochron dating assumptions and critical thinking

And since this agreement is the strongest argument for the reliability of radiometric dating, such an assumption of agreement appears to be without support so far. The question of whether different methods correlate on the geologic column is not an easy one to answer for additional reasons.

Since the bulk of K-Ar dates are generally accepted as correct, one may say that certain minerals are reliable if they tend to give similar dates, and unreliable otherwise. We can also say that certain formations tend to give reliable dates and others do not, depending on whether the dates agree with K-Ar dates.

Thus we can get an apparent correlation of different methods without much of a real correlation in nature. It's also possible for other matter to be incorporated into lava as it rises, without being thoroughly melted, and this matter may inherit all of its old correlated radiometric dates.

Coffin mentions that fission tracks can survive transport through lava, for example. It may also be that lava is produced by melting the bottom of continents and successively different layers are melted with time, or there could be a tendency for lighter isotopes to come to the top of magma chambers, making the lava there appear older.

But anyway, I think it is important really to know what patterns appear in the data to try to understand if there is a correlation and what could be causing it. Not knowing if anomalies are always published makes this harder.

It is often mentioned that different methods agree on the K-T boundary, dated at about 65 million years ago. This is when the dinosaurs are assumed to have become extinct. This agreement of different methods is taken as evidence for a correlation between methods on the geologic column. One study found some correlated dates from bentonite that are used to estimate the date of the K-T boundary.

I looked up some information on bentonite. It is composed of little glass beads that come from volcanic ash. This is formed when lava is sticky and bubbles of gas in it explode.

  • Isochron Dating

So these small particles of lava cool very fast. The rapid cooling might mean that any enclosed argon is retained, but if not, the fact that this cooling occurs near the volcano, with a lot of argon coming out, should guarantee that these beads would have excess argon.

As the gas bubble explodes, its enclosed argon will be rushing outward along with these tiny bubbles as they cool. This will cause them to retain argon and appear too old. In addition, the rapid cooling and the process of formation means that these beads would have Rb, Sr, U, and Pb concentrations the same as the lava they came from, since there is no chance for crystals to form with such rapid cooling. So to assume that the K-Ar dates, Rb-Sr dates, and U-Pb dates all reflect the age of the lava, one would have to assume that this lava had no Sr, no Pb, and that all the argon escaped when the beads formed.

Since the magma generally has old radiometric ages, I don't see how we could have magma without Pb or Sr. So to me it seems to be certain that these ages must be in error. Furthermore, the question arises whether bentonite always gives correlated ages, and whether these ages always agree with the accepted ages for their geologic period.

I believe that bentonite occurs in a number of formations of different geologic periods, so this could be checked. If bentonite does not always give correlate and correct ages, this calls into question its use for dating the K-T boundary.

Back to top Note that if there are small pockets in crystals where both parent and daughter product can accumulate from the lava, then one can inherit correlated ages from the lava into minerals. Thus even the existence of correlations is not conclusive evidence that a date is correct.

Back to top If a date does not agree with the expected age of its geologic period, and no plausible explanation can be found, then the date is called anomalous. But if we really understand what is going on, then we should be able to detect discrepant dates as they are being measured, and not just due to their divergence from other dates.

Geologists often say that the percentage of anomalies is low. But there are quite a number of rather outstanding anomalies in radiometric dating that creationists have collected. These anomalies are reported in the scientific literature.

For example, one isochron yielded a date of 10 billion years. A Rb-Sr isochron yielded a date of 34 billion years. K-Ar dates of 7 to 15 billion years have been recorded. It's also not uncommon for two methods to agree and for the date to be discarded anyway.

Samples with flat plateaus which should mean no added argon can give wrong dates. Samples giving no evidence of being disturbed can give wrong dates. Samples that give evidence of being disturbed can give correct dates. The number of dates that disagree with the expected ages is not insignificant.

Refuting “Radiometric Dating Methods Makes Untenable Assumptions!”

I don't know what the exact percentage is. Many dates give values near the accepted ones. But even these often differ from one another by 10 or 20 percent. And quite a few other dates are often much, much farther off. Whatever is making some of these dates inaccurate could be making all of them inaccurate. It's interesting to note that in a few cases, old radiometric dates are above young ones. The fact that different methods often give different dates is noted by geologists.

Here are some quotes from http: Age estimates on a given geological stratum by different radiometric methods are often quite different sometimes by hundreds of millions of years. There is not absolutely reliable long-term radiological "clock". The uncertainties inherent in radiometric dating are disturbing to geologists and evolutionists One example is the rocks from the Kaupelehu Flow, Hualalai Volcano in Hawaii which was known to have erupted in These rocks were dated by a variety of different methods.

Of 12 dates reported the youngest was million years and the oldest was 2. The dates average 1. Geologists explain the Kaupelehu date by the lava being cooled rapidly in deep ocean water and not being able to get rid of its enclosed argon.

Instead, the uncertainty grows as more and more data is accumulated In addition, Woodmorappe gives over sets of dates "that are in gross conflict with one another and with expected values for their indicated paleontological positions.

This does not include dates from minerals that are thought to yield bad dates, or from igneous bodies with wide biostrategraphic ranges, where many dates are acceptable. He states that the number of dates within range are less than the number of anomalies, except for the Cenozoic and Cretaceous. When one adds in the fact that many anomalies are unreported, which he gives evidence for, the true distribution is anyone's guess.

There have been criticisms of John Woodmorappe's study, but no one has given any figures from the literature for the true percentage of anomalies, with a definition of an anomaly, or the degree of correlation between methods. Steven Schimmrich's review of this study often concerns itself with John W's presentation of geologists explanation for anomalies, and not with the percentage of anomalies; the later is my main concern.

Here are a couple of more quotes about anomalies: The carbon age of the buried trees is only years, but some of the overlying volcanic material has a ,year potassium-argon age. Still another evidence for problems with radiometric dating was given in a recent talk I attended by a man who had been an evolutionist and taken a course in radiometric dating.

The teacher gave 14 assumptions of radiometric dating and said something like "If creationists got a hold of these, they could cut radiometric dating to pieces.

Many sedimentary uranium ores are not. On another point, if we can detect minerals that were not molten with the lava, as has been claimed, then this is one more reason why there should be no anomalies, and radiometric dating should be a completely solved problem. But that does not appear to be the case, at least especially on the geologic column. I'm not claiming that anomalous results are being hidden, just that the agreement of a mass of results, none of which has much claim to reliability, does not necessarily mean much.

Picking out a few cases where radiometric dates appear to be well-behaved reminds me of evolutionary biologists focusing on a few cases where there may be transitional sequences. It does not answer the overall question. And as I said above, I'm also interested to know how much of the fossil-bearing geologic column can be dated by isochrons, and how the dates so obtained compare to others. Concerning K-Ar anomalies, here is a quote from Woodmorappe's paper cited above, p.

Gerling et al called attention to some chlorites yielding K-Ar dates of 7 to 15 b. It had been noted that some minerals which yield such dates as beryl, cordierite, etc. They also pointed out that for the anomalies to be accounted for by excess argon, unreasonably high partial pressures of Ar during crystallization would have to be required.

isochron dating assumptions and critical thinking

They concluded by suggesting some unknown nuclear process which no longer operates to have generated the Ar. Here is another quote from Woodmorappe about isochrons, since some people think that mixing scenarios or other age-altering scenarios are unlikely: If this condition does not hold, invalid ages and intercepts are obtained.

Models yield isochron ages that are too high, too low, or in the future, sometimes by orders of magnitude. The fact that the only "valid" K-Ar isochrons are those for which the concentration of non-radiogenic argon Ar36 is constant, seems very unusual. This suggests that what is occuring is some kind of a mixing phenomenon, and not an isochron reflecting a true age. The following quote is from http: We have analyzed several devitrified glasses of known age, and all have yielded ages that are too young.

A brief study conducted in showed a high degree of correlation to this mixing test in the isochrons being published. The caution for the geochronologist would be to suspect any isochron, since there is no way to rule out mixing. It is now clear, however, that there is at least one positive test for mixing.

It is the whole-rock isochron itself. If the whole rock yields samples that give a linear plot, whether the slope is positive or negative, or whether the slope signifies an age that fits a preconceived model or not, there is no other known mechanism outside of mixing to which the data may be rationally ascribed.

Discussion Mixing is an unfortunate misnomer that has become popular for describing rocks formed from two or more original melts, or from a melt becoming contaminated by isolated incorporation of local rock. Understand it to mean partial mixing, with resulting heterogeneity. Complete mixing would result in homogeneity, and would give only a single point to plot. No curve of any kind, nor even a scattering of points would occur. This homogeneity is the assumed starting point in the history of the rock being dated.

But now, years later, we dig up 6 adjacent meter cubes of the rock, and discover that the normalized ratio of the parent and incidentally of the daughter is different in each cube, sufficient to plot as an "isochron". How can we rationally accept the assumed initial homogeneity? What is needed but missing in the whole rock isochron is a mechanism to establish initial homogeneity, and then to extract heterogeneous samples. The mineral crystals do the job in an elegant way.

Each type accepts a different level of contamination of the parent isotope, chemically determined. One cannot rationally extend this process back to the whole rock. It has been tried, but there is a fallacy. This is much larger than the average crystal size. Thus the original constituents of each crystal will lie nearby. By taking samples of cm dimensions, one could assure that the entire content of the original crystals are well represented by the sample, with very small error.

However, this matrix is the original melt that was theorized to be homogeneous. The ability to find differences in the rubidium content among the samples violates the assumption of original homogeneity. Original inhomogeneity is the only possible explanation: This method of justifying the whole-rock isochron on the basis of the mineral is logically unsound.

Within the larger matrix the tiny crystals may incorporate discrete trace elements and return them over time. But they are powerless to alter the composition of the whole-rock matrix. It is claimed that fractional crystallization of magmas and separation of crystals from the remaining liquid result in suites of comagmatic rocks of differing composition. This may be true, but there is no experimental evidence that this can generally be applied to trace elements that are foreign to the crystals.

Add the fact that trace elements are not securely held by crystals until temperatures are well below the melting points, and this postulate falls far short of explaining the variation in rubidium in whole-rock isochrons.

Mixing is much preferred, particularly when it is noted that many data sets have negative slope, where mixing is always the accepted explanation. Often the negative-slope data pertain to large formations that particularly fit the hypothesis of slow cooling from a melt. As the crystals form, their differential solubility will move their individual points on the diagram horizontallydifferent distances. Only horizontally, since the vertical is a ratio of two isotopes of the same element.

The large volume of whole-rock isochrons, however, shows the general case to be an initial heterogeneous melt represented by the kind of diagram published as an isochron, and which we conclude is actually a mixing line. Any point in the melt can be represented as a point on the straight line. When mineral crystals form, each crystal will move its point off the straight line in one or the other horizontal directions.

The result is a scattering of the points. The geochronologist discards it as one of the following: A three or more part mixture, Subsequent metamorphosis, Not a closed system: In this case he recognizes that crystals really cannot be expected to be a closed system.

They tend to continue to reject contaminants long after formation, the mobilities of foreign elements in crystals being a whole school of scientific study. The retention of trace elements in crystals is so inadequate that it has been possible to construct "Isochrons" from various parts of the same crystal. The ability to obtain a whole-rock diagram, straight-line or not, can be considered proof that the data represent a "mixing line" rather than an "isochron".

If mixing has not occurred, and the system has remained closed, then the whole-rock data must all lie on a single point. In fact, even if the whole-rock data show scatter, either mixing is indicated -- but of a complex nature, with more than two components -- or there have been subsequent alterations described as the system being open, or both.

Has any legitimate isochron ever been formed? There is ample evidence for mixing. Any "isochron" could be mixing. There is no way to rule it out. Many of the remaining mineral "isochrons" have a whole-rock point located close enough to the straight line to discredit them.

Why should we expect any of the others to be "true isochrons", since mixing has the strongest probability? If one possesses a strong faith in the antiquity of the rocks, one could rationally expect that an occasional mineral isochron is legitimate. But it would also require the whole-rock diagram to be concentrated in a single point. Neither a straight line or scattered. Often a whole rock point is put on a mineral diagram. That does not meet the criterion.

Several whole-rock samples must be obtained, using the same techniques required for the whole-rock method. Their individual data points must be identical, i. At that point mixing would not have been ruled out, but all available tests requiring mixing would have been eliminated.

In the dialog with Dalrymple [4] it was noted that he is unwilling to defend the whole-rock isochron. In his latest book [7] on the age of the earth he has included a section that describes the elegant process with which crystals minerals give the necessary heterogeneity to make the system work.

He also shows why the mineral isochron cannot be relied upon for dating, but does not state that conclusion. He carefully avoids describing the whole-rock method, which leads the casual reader to conclude that it is validated by the same processes as is the mineral method.

Nothing could be farther from the case. Dalrymple has seen our initial critique of the whole-rock method, [5] and is obviously reluctant to forthrightly claim any scientific merit for it. He has clearly sidestepped the issue. Dalrymple [7] does not depend directly on isochron dating of rocks to date the earth, but rather on the lead-isotope ratios.