isochron

/ ˈaɪsəʊˌkrɒn /

noun

1. a line on an isotope ratio diagram denoting a suite of rock or mineral samples all formed at the same time. The slope of the line is related to the age of the rock or mineral suite
2. a line or curve on a geological map or cross section (esp of oceanic crust) connecting points of identical age

Example Sentences

Hartmann, W. K. Martian cratering 8: isochron refinement and the chronology of Mars.

From Nature