1. Lines on a map or diagram connecting points of equal time, especially in geology or geochronology to show the age of rock formations.
Usage: technical; geology
2. In radiometric dating, a line on a graph representing samples with the same age, used to determine the age of rocks and minerals.
Usage: technical; geochronology

Examples

• Geologists used isochrons to map the age progression of the mountain range.
• The isochrons on the diagram showed that the volcanic rocks were all formed during the same period.
• Radiometric isochrons help scientists determine the absolute age of mineral samples.
• By plotting the isotope ratios, researchers identified several isochrons across the geological formation.
• The isochrons revealed that different layers of the rock had crystallized at different times.