"地质学上的" can be translated as "geological" or "in geology" in English, depending on the context.
If you're referring to something that is characteristic of or related to geology, you might use "geological". For example, "geological features" (地质学特征).
If you're indicating a context or scope within geology, you might use "in geology". For example, "This phenomenon is well-documented in geology." （这种现象在地质学上有充分记载。）