Dating Methods

* In your otherwise excellent Nov. 28 editorial, “Science Through a Prism,” it was suggested that the radiocarbon dating method can be applied to dinosaurs. Regretfully, this highly effective technique can only be used to date organic (carbon-containing) materials on a routine basis over only the last 40,000-50,000 years.

My paleontological colleagues tell me that the last of the dinosaurs apparently disappeared rather quickly following the impact on Earth of an asteroid about 70 million years ago. Other isotopic dating methods--not radiocarbon--are used to assign ages to rocks of the time period of the dinosaurs.

ERVIN TAYLOR

Radiocarbon Laboratory

Department of Anthropology

UC Riverside