CROSSCUTTING RELATIONS

Cross-cutting relations states that if a rock unit "A" cuts through (intrudes) another rock unit "B", rock unit unit "B" must have been there prior to rock  unit "A". Therefore, rock unit "B" is younger than rock unit "A". This law is typically used to determine the relative age of rocks that have been intruded by igneous bodies.Picture (671x436, 25.8Kb)

Photo by Kevin Hefferan. Scale provided by UWSP Geog/Geology 393 Winterim Class of 2001.

Ship Rock, New Mexico. Cross-cutting Oligocene age dike (20-30 Ma) intrudes the Cretaceous age (65-135 Ma) Mancos Shale. 

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