Geoscience Reference
In-Depth Information
the new radiometric dates should be used to interpret the sedimento-
logical record. Barrell examined in detail the various methods used to
date the Earth to that time, and their resulting figures, and in Part 4 of
the paper concluded that a minimum of 550 million years and a
maximum of 700 million years must have elapsed since the beginning
of the Cambrian, and that the underlying igneous and sedimentary
rocks termed the Laurentian were at least 1,400 million years old. The
Earth, he surmised, was much older even than this.
