Reliable dating techniques for young (< 1 million year old) mid- ocean ridge basalts must be established to understand the space and time scales of magma supply, fractination and eruption, and tectonism along spreading ridges and within distinct segments. This is an application of step-wise heating 40Ar-39Ar dating methods to well located, fresh samples the Juan de Fuca, Gorda, and East Pacific Rise spreading ridges. Many of these samples have been dated by mass spectrometric 238U-230U disequilibrium, and the two techniques will be compared and intercalibrated.
