Solved Unit 6 Relative Dating Worksheet Name: Period: 6 6 | Chegg.com - Free Printable

Problem Overview:

The task involves determining the relative ages of rock layers (beds) in three cross-section diagrams using the principles of superposition, inclusions, and cross-cutting relationships. The goal is to identify the oldest bed first for each diagram.

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Diagram 1:

#### Description:
- Layers are labeled as A, B, and C.
- Layer A is a rounded inclusion within layer B.
- Layer B is overlain by layer C.
- There is no evidence of folding or faulting.

#### Analysis:
1. Principle of Superposition: In undisturbed sequences, the oldest layers are at the bottom, and the youngest are at the top. Here, layer C is on top of layer B, so C is younger than B.
2. Inclusion Principle: Layer A is an inclusion (rounded object) within layer B. This indicates that layer A must have existed before layer B was deposited. Therefore, layer A is older than layer B.
3. Cross-Cutting Relationships: There are no visible cross-cutting features in this diagram.

#### Conclusion:
- The oldest bed is A.
- The order from oldest to youngest is: A > B > C.

#### Stratigraphic Principle Used:
- Superposition and Inclusion.

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Diagram 2:

#### Description:
- Layers are labeled as A, B, C, D, and E.
- Layer B cuts through layers C and D, indicating it is younger than both.
- Layer E is a fold that affects layers B and C but not D.
- Layer A is on top of layer D.

#### Analysis:
1. Principle of Superposition: Layer A is on top of layer D, so A is younger than D.
2. Cross-Cutting Relationships:
- Layer B cuts through layers C and D, meaning B is younger than both C and D.
- Layer E is a fold that deforms layers B and C but does not affect layer D. Folds are typically younger than the layers they deform, so E is younger than B and C but older than A (since A is on top).
3. Folding: The fold (E) occurred after layers B and C were deposited but before layer A was deposited.

#### Conclusion:
- The oldest bed is D.
- The order from oldest to youngest is: D > C > B > E > A.

#### Stratigraphic Principle Used:
- Superposition, Cross-Cutting Relationships, and Folding.

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Diagram 3:

#### Description:
- Layers are labeled as A, B, C, D, and F.
- Layer B cuts through layers A, C, and D, indicating it is younger than all of them.
- Layer F is a fold that affects layers A, C, and D but not B.
- Layer E is on top of layer F.

#### Analysis:
1. Principle of Superposition: Layer E is on top of layer F, so E is younger than F.
2. Cross-Cutting Relationships:
- Layer B cuts through layers A, C, and D, meaning B is younger than all of them.
- Layer F is a fold that deforms layers A, C, and D but does not affect layer B. Folds are typically younger than the layers they deform, so F is younger than A, C, and D but older than E (since E is on top).
3. Folding: The fold (F) occurred after layers A, C, and D were deposited but before layer E was deposited.
4. Relative Ages of A, C, and D: Since there is no clear indication of which of A, C, or D is oldest based on superposition alone, we assume they were deposited in sequence with A being the oldest (as it is at the bottom).

#### Conclusion:
- The oldest bed is A.
- The order from oldest to youngest is: A > C > D > F > B > E.

#### Stratigraphic Principle Used:
- Superposition, Cross-Cutting Relationships, and Folding.

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Final Answers:

1. Diagram 1:
- Oldest bed: A
- Order: A > B > C
- Stratigraphic Principle: Superposition and Inclusion

2. Diagram 2:
- Oldest bed: D
- Order: D > C > B > E > A
- Stratigraphic Principle: Superposition, Cross-Cutting Relationships, and Folding

3. Diagram 3:
- Oldest bed: A
- Order: A > C > D > F > B > E
- Stratigraphic Principle: Superposition, Cross-Cutting Relationships, and Folding

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Boxed Final Answer:

\[
\boxed{
\begin{array}{l}
\text{Diagram 1: Oldest bed = A, Order = A > B > C} \\
\text{Diagram 2: Oldest bed = D, Order = D > C > B > E > A} \\
\text{Diagram 3: Oldest bed = A, Order = A > C > D > F > B > E}
\end{array}
}
\]