ageOfBasement_approx_Ga

Given a predicate that represents a relationship or action between entities, generate a one-sentence description explaining its meaning.  
# Instructions
Focus on describing the relationship, not the entities themselves. 
# Response Format
Begin the description with \' Indicates...\'

Predicate: ageOfBasement_approx_Ga

Indicates an approximate age, measured in billions of years (giga-annum, Ga), assigned to the formation or origin of a basement rock unit.