Relative Age Dating Exercise Part A. Use Principle 1: Original Horizontality, Pr
ID: 290461 • Letter: R
Question
Relative Age Dating Exercise Part A. Use Principle 1: Original Horizontality, Principle 2: Superposition, Principle 3 Inclusions, Principle 4: Cross-Cutting Relationships and Principle 5: Baked Contacts to determine the relative ages of the various geological features. All the rock layers are sedimentary rocks, except for Unit I and J, which are igneous plutons intruding the Geologic Cross-SectionA K Unconformity 1. Which rock unit is older- Unit G or Unit H? 2. Which rock unit is older- Unit J (Pluton) or Unit F? 3. Which rock unit is older- Unit J (Pluton) or Unit C? 4. Which rock unit is older- Unit I (Dike) or Unit J (Pluton)? 5. Which is older- The River Valley or Unit B?Explanation / Answer
1. Older rock: Unit H , Principle: Superposition
The principle of superposition states that in a sequence of sedimentary rock layers, each layer must be younger than the one below,
2.Older rock: Unit J , Principle: Inclusions
The principle of inclusions states that a rock containing an inclusion must be younger than the inclusion.
3.Older rock: Unit J, Principle: Original horizontality
4.Older rock:Unit J , Principle: Backed Contacts
The principle of baked contacts states that an igneous intrusion bakes (metamorphoses) surrounding rocks, so the rock that has been baked must be older than the intrusion.
5. Older rock: Unit B , Principle: cross cutting Relationships
The principle of cross-cutting relations states that if one geologic feature cuts across another, the feature that has been cut is older.