beirut girl dating - Igneous rocks numerical dating
Some rock types look much the same regardless of their age (the 275 m.y.
Coconino Sandstone in Grand Canyon looks similar to the 160 m.y Navajo Sandstone in southern Utah) [see Photos 6a&b].
You can view these Global Boundary Stratotype Sections and Points online.
You can click on the "golden spike" to learn about the location, see a diagram of the sequence of rock types (click to enlarge), with the ranges of the various fossil species plotted, and the EXACT location of the boundaries between geologic periods.
The absolute ages of the rocks have been determined through radiometric dating where possible.