Lava rock dating
Their abundant, closely spaced crystallites (microscopic embryonic crystal growths) are so numerous that the glass is opaque except on thin edges.
Many samples of obsidian contain spherical clusters of radially arranged, needlelike crystals called spherulites.
The geological relationships of the various formations are quite clear.
The lava flows which spill into the canyon must be younger than the canyon.
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. Steven Austin, chairman of the Geology Department at the Institute for Creation Research, claimed (1992) that he had derived an isochron for the plateau flows, which indicates an age of about 1.3 billion years.
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.
The conditions which caused the "false isochron" in this case are fairly well-understood, and easy to avoid by proper sample selection.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.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.