Chapter 10 Notes - Deep Time: How Old Is Old?

Sedimentary Law Principles

  • Horizontal Deposition of Sediments

    • Sediments are deposited horizontally; this means that they settle in flat layers.

    • This process results from the force of gravity acting on particles.

1. Law of Superposition

  • Definition:

    • The Law of Superposition states that in any undeformed sequence of sedimentary rocks, the strata located at the top of the sequence are younger than those at the bottom.

  • Assumptions:

    • This principle assumes that no deformation has affected the layers.

  • Visual Task:

    • Draw a cross-section view of the Law of Superposition using Figure 10.1c as a reference.

    • Illustration Needs:

      • Young strata shown at the top.

      • Old strata shown at the bottom.

2. Law of Lateral Continuity

  • Definition:

    • The Law of Lateral Continuity states that sedimentary layers are originally deposited in continuous sheets in all directions.

  • Constraints:

    • Sediments will continue to spread out until they either run out, reach the edge of a basin, or change into another sediment type.

  • Visual Task:

    • Draw a cross-section view of the Law of Lateral Continuity using Figure 10.1d as a reference.

    • Illustration Needs:

      • Indicate sediment spreading laterally until it meets an edge or changes type.

3. Law of Cross-Cutting Relations

  • Definition:

    • According to the Law of Cross-Cutting Relations, any geological feature that cuts across another feature is younger than the feature it disrupts.

  • Common Cross-Cutting Features:

    • Faults

    • Dikes

  • Visual Task:

    • Draw a cross-section view of the Law of Cross-Cutting Relations using Figure 10.1e as a reference.

    • Illustration Needs:

      • Include examples of reverse dip-slip faults and dikes.

  • Review Questions:

    • What is a fault?

    • What is a dike?

4. Law of Baked Contacts

  • Definition:

    • The Law of Baked Contacts states that when an igneous intrusion occurs, it will heat (metamorphose) the surrounding rocks.

  • Implication:

    • Any surrounding rocks that have been "baked" must be older than the intrusive rock that created the effect.

  • Visual Task:

    • Draw a cross-section view of the Law of Baked Contacts using Figure 10.1f as a reference.

    • Illustration Needs:

      • Show the baked contacts between igneous intrusions and the surrounding metamorphosed rocks.