Radiometric Dating Study by Richard Overman

This past August was the International Conference on Creationism in Pittsburgh, Pennsylvania, and I had the opportunity to attend the event and meet some great creationist speakers. There were a number of sessions occurring at the same time, so I missed some of the sessions I was interested in. I was very pleased, however, when they made these sessions available to those who attended, so now I’m going back and listening to those that I missed.

The session I just listened to was by Richard Overman, M.S., titled, The Temporal Geographical and Geological Ubiquity of Excess Argon with a Young Earth Analysis. This is a bit technical, but if you’ve ever wondered about how radiometric dating works, this provides a good overview.

One of the most key issues in the creation evolution debate is the age of the earth, and it’s this issue that led Richard Overman to analyze the secular literature on argon dating- a common method for dating rocks and minerals. He searched, reviewed and downloaded over 500 articles from secular journals on the topic of excess argon for this study.

The significance of excess argon is an important concept because it impacts the accepted date of rock samples. So where did the excess argon come from, and exactly how does it impact the various dating methods?

According to Overman, researchers cannot tell the difference between argon 40 in the rock due to radioactive decay (the transformation of potassium into argon) and argon 40 that was there to begin with. The only way to tell the difference is to compare the apparent age they get to some other dating method, or to the strata. But an underlying assumption is that all of the argon 40 in existence (even if the result of contamination) is from radioactive decay or from the atmosphere.

Once the apparent date is compared to another method or strata, scientists can then determine if there’s excess argon. If there is excess argon, it had to come from somewhere. But, according to a 1976 article by Lanphere and Dalrymple, it is attributed to some process other than radioactive decay and atmospheric contamination.

Excess argon, therefore, is a problem for those who accept that the earth is billions of years old, and it’s for this reason that Overman wanted to see how prevalent excess argon was in the secular literature. For creationists, however, the amount of argon in a rock isn’t representative of the date, so it doesn’t have much meaning. The problem of excess argon only pertains to an old earth.

Overman presented three examples where we know when the rocks were solidified: Mt. St. Helens, Mt. Erebus, and Mt. Ngauruhoe. And in every case the lava gave an apparent age of hundreds of thousands of years: 1: Mt. St. Helen’s lava solidified in 1986 gives an apparent age of 350,000 years. 2: Mt. Erebus lava solidified in 1984 gives an apparent age of 700,000 years. 3: Mt. Ngauruhoe lava solidified in 1949, 1954, and 1975 gives an apparent age of 270,000 years or more.

Overman then addressed some of his critics, who claim that the wrong dating method was used; they claim that the scientists should have used the Argon-Argon dating method rather than the Potassium- Argon method. But Overman points out that scientists actually did publish both methods on Mt. Erebus, and both methods gave ages of 700,000 years. So this criticism doesn’t hold any merit.

The difference in the two dating methods is a direct measurement (model ages) vs. an indirect measurement (Isochron ages). The Potassium-Argon method measures the various elements in the rock and then calculates the age. The Argon-Argon method calculates the apparent age based on the amount of Argon 40 released during the testing and estimates the initial amount of the daughter element. In fact the Argon-Argon method was developed due to the problem of excess argon identified as early as the 1950s. But according to published results by Harrison et al in 1994, the Argon-Argon method hasn’t provided a complete solution to the problem of excess argon in minerals.

The isochron method isn’t typically used for potassium-argon dating because there’s an assumption of zero-daughter element; it’s assumed that all the argon in the lava percolates out before it solidifies. But the fact that excess argon is found is an indication that all the argon doesn’t percolate out while the lava is molten.

Geochronologist T. Mark Harrison and his co-workers  published the following remark in the journal, Chemical Geology, in 1990: “In a discipline which well understands precision as a product of repetition, appreciation of the spectral nature of Ar40 to Ar39 results may not be intuitive. In contrast to virtually all other geochronological methods, the daughter product is obtained from a sample in an indirect manner during which time experimental artifacts can complicate or obscure the primary chronological information. Although the challenge to ensure ideal behavior, or at least understand this behavior should guarantee full employment for some time, mastery comes slowly that at times our response is more expedient than patient.”

This remark leads Overman to conclude that there’s still a lot not understood about this dating method, and that a correction needs to be made for the Ar40 in the atmosphere. Therefore the atmospheric contamination issue is far from settled.

Overman also reviewed published comments by Rene et al regarding the fundamental importance of atmospheric argon, which may be the most critical limitation of accuracy. Rene et al pointed out that the ratio of atmospheric composition was adopted in 1976 from a study published in 1950, and the composition has increased according to publications by Lee et al in 2006 (295.5 vs. 298.56). According to Rene et al, this apparent increase in ratio is significant.

Criticism of radiometric dating was expressed in a 1967 article by Morvath, who was critical of the assumption that there’s been no gain or loss of parent or daughter nuclei in the mineral or rock since the time of crystallization (closed system assumption).

Overman explains that radiometric dates of millions of years only means that millions of years worth of radioactive transformations have apparently occurred under specific conditions, not that the radioactive transformations have occurred over millions of years.

During his research of excess argon in the scientific literature, he found that the problem of excess argon has increased over time (since the 1960s) and hasn’t been solved. Excess argon has been a universal problem for decades; it has been documented on every continent and in over 92 countries. He’s also found that excess argon is found in every geologic layer, and he concludes that the geologic column is infested with excess argon.

In an attempt to solve the problem of excess argon due to atmospheric contamination, geochronologists must adjust the argon 40 extracted from the sample and the amount in the atmosphere. But the problem with this is that the amount of argon 40 in the atmosphere isn’t constant; there’s evidence that it has increased over time and isn’t stable; that’s a problem if one is trying to obtain absolute ages. Nonetheless, researchers have used the same ratio over the years.

Another method to deal with excess argon is to handpick the minerals, but this is cherry picking, and Udagawa et al in 1999 indicate that excess argon may still be a possibility.

Overman suggests that the retention of argon in molten lava would be a good area of study for creationists. He pointed out that Dr. Andrew Snelling reported on a reservoir of argon in the mantle, which is also discussed in secular literature. One possible mechanism would be due to olivine entrapment; olivine is one of the first minerals to crystallize when lava cools, and it has interesting properties (such as forming a lattice) that could help it capture argon before it escapes.

In conclusion, Overman suggests that argon dating techniques don’t provide meaningful information, and aren’t useful for obtaining absolute ages for rocks.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s