1. Stratigraphy

2. What is Stratigraphy?
The branch of geology that studies rock layers (strata) and layering (stratification).
Primarily used in the study of sedimentary and layered volcanic (igneous) rocks.

3. Steno’s Law Nicholas Steno (1638-1686)
Danish-born pioneer of geology, “The Father of Stratigraphy”.
Observed rock layers and suggested that geology is not totally chaotic but instead preserves a chronological record of Earth’s history and past life.

4. Principles of Stratigraphy
Law of Original Horizontality
Sediments are deposited in water in horizontal layers due to gravitational settling.
Law of Superposition
In undisturbed rock layers, the oldest layer lies at the bottom and the youngest layer at the top.

5. Principles of Stratigraphy
Law of Cross-Cutting
An igneous intrusion that cuts through existing rock is always younger than that disturbed rock.

6. Principles of Stratigraphy
Law of Unconformity
A surface that has a significant gap, layers missing, from its rock record from erosion or non-deposition.
3 Types:
Disconformity
Angular Unconformity
Nonconformity

7. Unconformities
Disconformity – The eroded surface is between sedimentary layers that are parallel to each other.
All sedimentary rocks!
Disconformity

8. Unconformities Angular Unconformity – Younger strata
overlie an erosional surface on tilted or
folded rock layers.

9. Unconformities Nonconformity – When igneous or
metamorphic layers are eroded and covered
by younger sedimentary or volcanic rock.

10. Deformation Processes
Strata can become deformed when changes to its shape or volume occur.
Changes in shape and volume occur when stress and strain causes rock to fold and/or fracture.
most visible in rocks that contain layering
3 Types of Folds:
Monocline
Anticline
Syncline

11. Fold Types
Monocline - The simplest type of fold, involves a slight bend in otherwise parallel layers of rock.

12. Fold Types
2. Anticline - fold in rock that resembles an arch like structure with the rock beds

13. Fold Types
3. Syncline - rock layers are warped downward

14. Deformation Processes
Faults form in rocks when the stresses (friction) overcome the internal strength of the rock resulting in a fracture.
faults are named according to the type of stress that acts on the rock and by the nature of the movement of the rock blocks either side of the fault plane.

15. Characteristics of a Fault
Fault Plane- A break in Earth’s crust where slabs of rock slip past each other.
Hanging Wall - is the block positioned over the fault
Foot Wall - is the block positioned under the fault
Foot wall
Hanging wall

16. Fault Types
Normal Fault - occur when tensional forces act in opposite directions and cause one slab of the rock to be displaced up and the other slab down
Hanging wall
Foot wall

17. Fault Types
2. Reverse Fault - when compressional forces cause one block to be pushed up and over the other block.
Hanging wall
Foot wall

18. Fault Types
Graben Fault - produced when tensional stresses result in the sinking of a block of rock.
On a large scale these features are known as Rift Valleys
Foot wall
Foot wall
Hanging wall