Review by Greg Neyman
© Old Earth Ministries
Published May 2006
In this chapter, DeYoung summarizes the work of Steven Austin concerning discordant radiometric dates.
SELECTIVITY OF RADIOISOTOPE DATA
As DeYoung points out, many thousands of reports on rock ages have been accomplished. And he is correct...when a rock sample gives a bad date, which is not consistent with the other dates, it is filed away and not used. But rather than seeing this as a good process, DeYoung describes this as "bias" against dates that do not agree. He is correct, but this bias is required in this case.
DeYoung makes an interesting statement in the first paragraph. Some items do not show up in geologic reports, such as "how and why were particular rock samples chosen for analysis and reporting?" In my study of young earth radiometric studies, one must ask the same question...why did the young earth author choose this particular sample to date? Typically, the answer is because the young earth author knew in advance that it would give a bad date. It was chosen because he knew it would fail in advance. As we examine this chapter, we will see if this is the case.
To verify that there are discordant dates, RATE conducted examinations based upon two rock samples. Naturally, the larger your sample size, the better your results, therefore one must ask why only two sites were examined. Clearly, they were "stacking the deck" in their favor.
The term "discordant" means that two different radioisotope methods do not agree with each other. For instance, the Potassium-Argon method may yield an age of 1 billion years, but the Rubidium-Strontium method yields an age of 100 million years. Geologists familiar with dating know how to get discordant dates...they could tell you what types of rocks/what locations to sample. The young earth creationists know this as well.
If the RATE group truly wanted to show that radiometric dating was discordant, they should have used a large sample size. However, they would have discovered many more dates that were not discordant, which would undermine their entire purpose.
RATE SAMPLE COLLECTION
The RATE rock samples were taken from Precambrian rocks, one is in the Beartooth Mountains of Wyoming, and the other is a diabase sill located at Bass Rapids in the Grand Canyon. The sites were chosen because previous studies were accomplished on these rocks. It should be noted that the Beartooth site involves metamorphic rocks.
ROCK SAMPLE PREPARATION
ICR scientists prepared the rock samples for analysis. Nothing of interest here, other than the fact that this is not a normal procedure that is accomplished by ICR. Although they may know how it is done from reading guides, they have little practical experience. For the purposes of this review, we will assume that they did this procedure properly.
BEARTOOTH MOUNTAINS SAMPLE RESULTS
The rock samples were analyzed using four radioisotope pairs. They used potassium-argon (K-Ar), rubidium-strontium (Rb-Sr), samarium-neodymium (Sm-Nd), and lead-lead (Pb-Pb). The work was contracted out to commercial labs, and isochron graphs were plotted for all data.
RATE quotes a previous dating study which puts the age of this rock unit at about 2,790 million years, using the Rb-Sr method. In RATE's results, the Rb-Sr yielded an age of about 2,515 million years. The discordance comes with the comparisons of the other methods. K-Ar yielded ages, depending on how the data was obtained, from 1.52 to 2.6 billion years. The Sm-Nd (2.886 billion years) and Pb-Pb (2.689 billion years) was close to the results obtained with the other methods, with the exception of the K-Ar.
It should be noted that if one wants to disprove radiometric dating, geologists knows that the K-Ar method should be used, since it is known that excess argon is a factor that throws off the dating results (usually dates appear as "too old", although laboratory corrections for this anomaly can overcorrect and make them appear too young). This may be the case here. Notice the chart on page 115. RATE gives four different dates obtained from four methods of sampling of the rock using K-Ar dating. They apparently did not do these four methods with the Rb-Sr, Sm-Nd, or Pb-Pb method. Why not? Because the RATE scientists know that K-Ar will give the desired result...a "different" answer from the other methods.
CATEGORIES OF DISCORDANCE
DeYoung mentions four categories of discordance, and says that the Beartooth samples fit all four categories. Yes, but the deck is stacked in their favor.
How does one get discordance? A secular geologist can sample a rock and have it dated, and another geologist can do the same thing, right in behind the other geologist, and they get different dates. This could be due to any number of factors, such as how the samples were prepared by the two different scientists, the laboratories the samples are sent to, the quality of the laboratory equipment used during the procedure, and whether any contamination occurred anywhere along this process. Geologists understand these limitations, and work within them. Young earth creationists take these same limitations, and use them to their advantage. In doing so, they have merely proved that you can get discordant dates from the same rock. They have not proved overall that radiometric dating is unreliable.
BASS RAPIDS SILL RESULTS
The secular, old earth age given to the Bass Rapids sill is about 1.07 billion years. The data obtained from the RATE study shows ranges from 656 million years to 1.379 billion years, depending upon the method used. The most divergent dates given are the ranges for the K-Ar, which read as younger than the accepted age, and the Pb-Pb and Sm-Nd methods, which reads older than the accepted age. The same limitations apply here...differences could be in sample preparation, contamination, or the laboratory equipment, or even laboratory procedures. Although the results do vary and show discordance, such discordance does not disprove radiometric dating.
DISCORDANCE AT OTHER LOCATIONS
RATE shows that the geologic literature reveals there is discordance at other locations as well. This is no surprise, as discordance is a known factor in dealing with radiometric dates.
POSSIBLE EXPLANATIONS OF DISCORDANCE
DeYoung lists three possible explanations for discordance.
First, he alludes to a mixing of isotopes between the magma and the rock body into which the magma intrudes. He will deal with this issue more in the next chapter, thus we will defer discussion of it until then.
Second, some have suggested that cooling rates vary, and thus some minerals form more quickly than others, leading to these being older. Of course, this alludes to the belief that magma may take millions of years to cool. DeYoung dismisses this out of hand, saying there is no evidence of such slow cooling. However, if true, the different dates by themselves are indeed evidence of such a phenomenon. DeYoung dismisses it for two reasons...first and foremost in his mind, the earth is young, and therefore it could not have been cooling for millions of years, and second, nobody has ever observed it cooling for millions of years (as none of us are millions of years old). However, he presents no direct evidence against this slow cooling, and it remains a valid possibility.
Finally, he says the decay rates for the radioisotopes were different in the past. This is the preferred young earth explanation, although this accelerated nuclear decay is an unworkable theory, as you will see in the discussions for Chapter 9.
In this section, the RATE scientists note that in the Bass Rapids sill, dating methods based on alpha particle decay yield older dates than those based on beta particle decay. They say it may be due to the "accelerated nuclear decay" which accelerated the alpha decay at a faster rate than the beta decay. While nice to know, there is still no evidence to support their theory of accelerated decay.
One other thing should be mentioned. From a statistical standpoint, the RATE group sampled two locations. There are literally millions of locations they could have chosen. Their sample size of only two is insignificant. You cannot have a "significant trend" based on only two sample locations. Assuming ten million locations that we could date (the number is much higher), that's a ratio of 1 to 5 million ( .0000002 percent). Without a larger sample size, the RATE data is meaningless.
In essence, they knew from previous studies that these two locations would yield discordant dates. They even admitted up front that the locations were chosen because they had already been dated. In other words, they picked two locations that they knew would give discordant dates. In doing so, they have proven nothing concerning the overall reliability of radioisotope dating.
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