The Talk.Origins Archive

A Criticism of the
ICR's Grand Canyon Dating Project
Copyright © 1994-2003 by Chris Stassen
[Last Update: February 18, 2003]

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Jonathan Sarfati of Answers in Genesis attempts to address this FAQ, but it appears that he read only the fragment submitted to AiG's feedback system. As a result, Sarfati raises no substantive issues, and many of his criticisms are refuted by the full text.


  1. General information on the Grand Canyon
  2. ICR's claims
  3. Background on ICR's claims and isochrons
  4. Criticism of ICR's claims
  5. Summary
  6. Response to Criticisms
  7. References

General information on the Grand Canyon

The Grand Canyon looks something like this:

Grand Canyon figure

Figure 1. Idealized and simplified diagram of the Grand Canyon

There are a number of lava flows on the plateau that the canyon is cut into (yellow in Figure 1, above). These lava flows are Cenozoic in age, and some of them spill into the canyon. The walls of the canyon are mostly cut into horizontal rock layers of Paleozoic age (green in Figure 1, above). There is an angular unconformity at the bottom of the Paleozoic layers. An angular unconformity is the result of tilting and eroding of the lower layers before the upper ones are deposited. These tilted and eroded layers are Precambrian in age (blue in Figure 1, above).

The geological relationships of the various formations are quite clear. The lava flows which spill into the canyon must be younger than the canyon. The canyon must be younger than the rock layers that it cuts into. The sediments above the angular unconformity must be younger than the sediments below it.

Grand Canyon figure The ordering of events which resulted in Figure 1 must be:
  1. The blue layers are deposited.
  2. The blue layers are tilted and eroded.
  3. The green layers are deposited.
  4. The canyon is cut into the green and blue layers.
  5. The lava flows occur.

Even young-earth creationists would agree with this relative sequencing of events. They would argue for a much shorter absolute timescale than mainstream geologists would accept, but the relative sequence is agreed upon by all parties.

ICR's claims

Dr. Steven Austin, chairman of the Geology Department at the Institute for Creation Research, claimed (1992) that he had derived an Rb/Sr isochron for the plateau flows, which indicates an age of about 1.3 billion years.

One particular Precambrian layer known as the Cardenas Basalt has been dated by radiometric methods to about 1.1 billion years in age. The Cenozoic flows sampled by ICR thus are claimed to yield an age which is about 200 million years older than the Cardenas Basalt. But the Cardenas Basalt cannot be younger than the plateau flows, due to the geological relationships discussed in the first section of this document.

Austin says that his isochron age is the result of a "research project" (1992, p. i) undertaken by the ICR to "test the ages assigned by the best radioactive isotope dating methods" (1992, p. i). Dr. Austin suggests that the slope of his isochron line (indicating great age) is "unexpected" (1992, p. iii) and that his result "challenges the basic assumptions upon which the isochron dating method is based" (1992, p. iv).

In other words, Austin claims that he has produced a seemingly reliable isochron age which must necessarily be wrong, and therefore the Rb-Sr isochron dating method, which is considered to be among the more reliable of radiometric dating methods, must be considered suspect.

Background on ICR's claims and isochrons

Criticism of ICR's claims


The ICR's Grand Canyon Dating Project does not strike a telling blow against the reliability of isochron dating. The conditions which caused the "false isochron" in this case are fairly well-understood, and easy to avoid by proper sample selection. In fact, the resulting age in this case may well be meaningful and accurate. The problem is not the age itself but rather Austin's sleight-of-hand in trying to pass off the result as necessarily the age of the flows rather than a minimum age of their source.

The attempt to abuse the meaning of a single contrived date -- which was produced only by a sample selection geared to dating a different event, and only for samples whose results were known by Austin in advance -- says a lot more about the level of competence or honesty in this creation "science" research program, than it says about the validity of isochron dating methods.

Even if given credit for discovering this case (which he clearly doesn't deserve, as his use of Leeman's data proves), Austin has only managed to "call into question" a particular sampling technique. However, this sampling technique was known by mainstream geologists to behave in this manner long before Austin published on the topic, and this behavior is often intentionally used by geologists. Austin was aware of this, as his 1988 reference to Faure shows.

Response to Criticisms

I recently received a critique of this FAQ. Unfortunately, it was submitted anonymously and it didn't address the key issues above. Since I couldn't get permission to reproduce the claims verbatim, I will summarize the creationist claims, and respond to them here. I would recommend that future prospective critics attempt to deal directly and explicitly with the three items in the "criticisms" section above.

The "type" of rock is not sufficient to establish the samples being cogenetic. Since the stratigraphic evidence indicates that the flows did not all occur at the same time, the case could only be made by other isotopic analysis such as taking internal isochrons of the individual flows. That data is lacking from Austin's published works.

Besides, this line of argument does not address the fact that the result is a known and expected behavior of isochrons. As discussed above, whole-rock samples of multiple flows yields the time since their common source was isotopically homogeneous. It could also be the age of the flows, but it does not have to be. If it is not the flows' age, that is not a "problem" with isochron dating, and it is not relevant to the large number of Rb/Sr isochrons which were computed from mineral separations of a single object.

At the GSA meeting, Austin discussed the inheritance of a mantle age. He didn't pretend that the age of the flows was the expected result, and he didn't make the false claim that his result was sufficient to call all isochron dating into question. This is a transparent attempt to place a GSA "seal of approval" on Austin's unsupportable Impact claims. (In my opinion, the anonymous critic is engaging in a little sleight-of-hand of his own.) The length of the medium is not a legitimate excuse for a blatant falsehood (the claim that Austin set out to "test" Rb/Sr dating) or for the shenanigans involving the sampling technique versus the expected meaning of the resulting age. Further, there is no material in Austin's book which legitimizes the false and misleading claims in his Impact article.

In addition, the Impact articles (which are free and available online) receive much wider distribution than Austin's book (which costs $20). At least a dozen creationists arguing against isotope geology have referred me to the Impact articles, and not a single one of them had ever looked at the book. The claims in Impact are all that most creationists ever see. Therefore they must be accurate on their own.


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