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Concordance of dates

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To look at one dating method is like looking at a clock. Imagine that you have just woken up and look at your clock. You think the clock has the wrong time. There are many reasons the clock may be incorrect. The power may have gone out during the night, it may have been set wrong in the first place, it may be broken and no longer keeping time correctly. The same sorts of things happen to any dating method.

However, in order to determine the true time, what do you do? You consult another clock. If both clocks agree that is much stronger evidence for the correct time then one clock alone. One clock might be dismissed, several clocks are a lot harder to dismiss.

Measuring Clocks of Rocks

In the case of these different measurements of the ages of rocks, the earth, and the universe, we are being told that all of these clocks show pretty much the same time. All of the dating methods agree on the dates.

However, there are a few responses to this:

  • Methods which give young earth dates are dismissed, i.e. we ignore clocks that give "undesirable" ates;
  • The different methods have been calibrated based on one another, i.e. the clocks have been synchronized; and
  • The methods are not as consistent as generally portrayed.

Concordant Radiometric "ages" from Isua Series rock of Greenland[1]

Method "Date" in Billions of years
U-Pb 3.60+/-0.05
Pb-Pb 3.56+/-0.10
Lu-Hf 3.55+/-0.22
SM-Nd 3.56+/-0.20
Rb-Dr 3.62+/-0.06

Charts such as this are often used to illustrate the consistency of radiometric dating. The claim is that the agreement among such dates shows the legitimacy of the dates. Now concordance (agreement) does occur, sometimes very closely, but this proves nothing about the accuracy of the dates. The first assumption is that the odds of coincidental concordance are extremely small. The second is that the only process that would produce concordant dates is radioactive decay over time.

Curiously, it is difficult to find charts of radiometric dates on the internet such as the one above except on sites that are attacking young earth creationism. What such sites don't show you is that vast disagreements in dates can be demonstrated as well.

Dating data from the Alaska Division of Geological & Geophysical Surveys illustrates a different story. The data was collected from various locations scattered over Alaska and reported with no interpretation beyond the date calculations. Now 62% of the locations had only one date and so there was nothing to compare the dates to. Another 35% were remeasured by the same method and therefore they only show the isotopic consistency of the rock. Only 3% of the locations had dates by different methods.[2]

Percent difference between dates Occurrences %
Identical 2 14
<5% 3 22
5-10% 1 7
10-25% 4 29
25-50% 2 14
>50% 2 14

The result is that after evaluating the radiometric dates from 509 locations scattered over Alaska, that there is no statistical indication of a trend favoring concordance. Yes, this is based on only 14 samples, but that shows how seldom more than one dating method is used (or reported) in radiometric dating.

Dr. Walter Brian Harland lists some 800 dates to support the existence of the geological column, however only a few dozen samples even come from the same site.[3]

Disagreements of Radiometric Dates

Vast disagreements in radiometric dates can be demonstrated as well. The following is data on three different rock formations in the Grand Canyon. The isochron ages are from the K-Ar and Rb-Sr model ages next to them.

Uinkaret Plateau

Ages of Rocks in Millions of Years

K-Ar Rb-Sr Rb-Sr Isochron Pb-Pb Isochron
0.01 1230 - 1310 1300 - 1380 2390 - 2810
1.0 - 1.4 1260 - 1380
2.63 1310 - 1370
3.6 1320 - 1440
3.67 1360 - 1420

The Uinkaret Plateau samples are from lava flows on the plateau, at the top of the Grand Canyon and some flows down into the canyon so that the eruption must have occurred after the canyon was formed. These are indisputably some of the youngest rock in the canyon, yet it's radiometric age ranges from a 10,000 years K-Ar date to a 2.81 billion year Pb-Pb Isochron date.

Even still the Rubidium-Strontium dates place the rocks at about 1.3 billion years. This would make them pre-Cambrian rocks, rather than the modern Quaternary rocks that they obviously are. There is overlapping of the Rb-Sr dates, meaning that they are concordant, as is the Rb-Sr Isochron date but yet the dates are clearly wrong. Also the bottom two K-Ar dates are concordant but disagree dramatically from the concordant Rb-S date. None of the dates from different methods overlap, other than the Rb-Sr and Rb-Sr Isochron.[4]

Cardenas Basalt

Ages of Rocks in Millions of Years

K-Ar K-Ar Isochron Rb-Sr Rb-Sr Isochron
771 - 811 682 - 748 920 -1040 1000 - 1140
809 - 877 990 -1130
838 - 868 990 -1190
780 - 820 1010 -1170
800 - 840 1030 -1110
1050 -1150

The Cardenas Basalts are classified as late pre-Cambrian rocks and the radiometric dates reflect this but there is such disagreement among the dates that we need to ask which age should you believe? The only overlap in method is between the Rb-Sr and Rb-Sr Isochron. Once again we have concordance among the dates of a given method but not between methods, so which is correct?[4]

Diabase Sills

Ages of Rocks in Millions of Years

K-Ar K-Ar Isochron Rb-Sr Rb-Sr Isochron
874 - 954 926 680 - 1020 1000 - 1140
924 - 984 740 - 1100
1030 - 1070
1030 - 1090
1100 - 1280
1300 - 1440

The Diabase Sills are some of the deepest rocks in the Grand Canyon and so they should be the oldest, yet they yield some of the youngest Rb-Sr dates. Now it did yield the oldest K-Ar Isochron dates, but they were not old enough, since they should be several billion years. Curiously the Rb-Sr Isochrons of both Cardenas Basalts and Diabase Sills are the same. This one is better on the concordance of dates between different methods but only because Rb-Sr dates spans about 800 million years, but internally the Rb-Sr dates are hardly concordant at all.[4]

Geologist often change and alter the time scale they want us all to believe in. In 2004, a Nature paper was published that "corrected" time line, putting the Jurassic at 145.5 million years ago. The paper was heavily endorsed by the International Union of Geological Sciences Geologic Timescale. To quote Mr. Gradstein, [5]

Most people will tell you that a measurement more than five years old is obsolete.

Such a selective nature of data casts doubt on the true nature of so-called "concordance".


The real question is how likely is coincidental concordance of dates. This question was first dealt with in a study using completely random data, by John Woodmorappe. The study shows a high likelihood of fortunate concordance, mathematically explained by the birthday paradox.

Each trial consisted of strings of 100 random numbers. The range for concordance was defined as +/- 2.5%, so that overlapping ranges were considered concordant.

In his book The Mythology of Modern Dating Methods, trying this little exercise produced the following results. First tried were concordant pairs which are at the same point in their respective lists occurred about 4.75% of the time. When the position on the lists were not important the odds of getting concordant pairs in random data were vary good. In fact one needs to go to more than 6 concordant pairs before the odds of concordance drops below 50%.

Number of concordant pairs on the other list. Percent of time concordant pairs occur.
2 90%
3 80%
4 70%
5 60%
6 52%
7 41%

The fact is that the odds of fortunate concordance in random data are quite good. This is particularly true given the large number of available samples of radiometric dates.

Now real radiometric "dates" are definitely not this random; at the very least, the physical processes that affect isotope ratios limit date ranges, increasing the odds of fortunate concordance. So the odds are sufficiently in favor of fortunate concordance that such agreement of dates can not be used to claim accuracy.

Related References

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  1. Radiometric Dating II, lecture slides by Dr. Ben Waggoner, Biology 4415, "Evolution", University of Central Arkansas (Originally accessed April 2006; link broken, June 2010)
  2. Radiometric Dates from Alaska - A 1975 Compilation (Special Report 10), By Donald L. Turner, Donald Grybeck, and Frederick H. Wilson, published by the Alaska Department of Natural Resources, Division of Geological & Geophysical Surveys, College, Alaska, 1975
  3. Harland, et al 1990, "A Geologic Time Scale 1989," Cambridge University Press, Cambridge
  4. 4.0 4.1 4.2 Radioactive Dating Explained - Part 2, by Do-While Jones, Science Against Evolution
  5. "Time Lords", Nature 429, pp. 124-125 (13 May 2004), as cited in "Radioactive Dating Explained - Part 2"