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Index to Creationist Claims,  edited by Mark Isaak,    Copyright © 2005
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Claim CD014.1:

The hawaiite lava flows from the Uinkaret Plateau of the Grand Canyon are dated by potassium-argon at about 1.2 million years, an age consistent with the lava flow being younger than the canyon itself. However, a Rb-Sr isochron plot of samples from the lava flow gives an age of 1.34 billion years, which is older than even the Cardenas Basalt, some of the oldest rock in the canyon. The data points are colinear, which is supposed to indicate a valid isochron. This result shows that the isochron method is invalid.


Austin, Steven A., 1992. Excessively old "ages" for Grand Canyon lava flows. Impact 224 (Feb.).


  1. One of the requirements for isochron dating is that the samples be cogenetic, that is, that they come from materials that were isotopically homogeneous (with respect to each other) when they formed. Austin's selection of samples violated this assumption. His five samples came from four different lava flows plus one phenocryst (which likely solidified in the magma chamber before the flow). Thus, Austin's conclusion, not the isochron method, is invalid.

  2. Noncogenetic samples such as Austin used are sometimes used intentionally to determine the age of the common source of the samples. Austin's results confirm that the lithospheric mantle underlying the Grand Canyon (the common source for his samples) is older than the Cardenas Basalt. Geologists have known this all along.

  3. Austin (1988) cited Brooks et al. (1976), showing Austin should have been aware that noncogenetic samples could produce an isochron for the age of their molten material's source. His misstatement of the significance of the isochron is just plain sloppy.


Stassen, Chris, 2003. A criticism of the ICR's Grand Canyon Dating Project.


  1. Austin, Steven A., 1988. Grand Canyon lava flows: A survey of isotope dating methods. Impact 178 (Apr.).
  2. Brooks, C., D. E. James and S. R. Hart, 1976. Ancient lithosphere: Its role in young continental volcanism. Science 193: 1086-1094.

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created 2003-8-4, modified 2004-9-8