ISOCHRONS AND EVOLUTIONARY DATING

by Dr. Steven Austin

As the media constantly tells us, the Grand Canyon is supposed to

be "Exhibit A" proving evolution. But have those Grand Canyon

rocks really been proved to be billions of years old? Is the

media giving us the correct story? I wrote the paper "Grand

Canyon Lava Flows: A Survey of Isotopic Dating Methods" (Institute

for Creation Research Impact No. 178, April 1988) to summarize

some of my recent work on potassium-argon (K-Ar) and rubidium-

strontium (Rb-Sr) dating of Grand Canyon rocks.

The Rb-Sr isochron date of 1.1 billion years for the deeply buried

Cardenas Lavas (Precambrian) has been considered by evolutionary

geologists to be the "most secure" isotopic date yet made for

Grand Canyon strata.

Several geologists have asked me if such a well

documented date can be questioned. They observe that the

isochron method appears to internally validate the assumptions of

the dating method which creationists have criticised. They even

note that the Rb-Sr isochron of 1.1 billion years for the Cardenas

Lavas overturned five K-Ar dates which gave a younger age (K-Ar

Lavas before the Rb-Sr isochron was generated).

I decided two years ago to generate my own "isochron dates" from

published isotopic ratios and elemental analyses. My computers

are able to do the data manipulation to plot isochrons. I have

started the project by working on Grand Canyon lava flows. The

Western Grand Canyon lava flows (Pleistocene) flowed over the rim

of the Grand Canyon and blocked the Colorado River. These lava

flows lie on the surface and look as fresh as recent Hawaiian

flows.

These Western Grand Canyon flows yielded a good "isochron

date" of 1.5 billion years, making them among the "oldest" strata

yet dated in the Grand Canyon. This isochron is shown in my

recent article (ICR Impact No. 178, April 1988).

Other geologists and I have referred to these erroneous dates as

"fictitious isochrons." These, I believe, cast severe doubts on

some of the "accepted" isochron dates. Fictitious isochrons need

to be recognized and discussed.

The subject of radiometric dating can become very theoretical and

may get to be a "can of worms" in a hurry. However, I do invite

your comments on my short article and want to discuss various

methods of dating Grand Canyon rocks. I recommend that we start

by keeping the discussion on real rocks from the Grand Canyon and

limit our discussion to the popular methods used by the media and

geologists to date Grand Canyon rocks. But please--no philosophy,

religious arguments, theoretical models, cosmological speculation

or polemics! I'm only interested in the facts.