Geology 12Geology 12

PresentsPresents

Hand out note helper WS 8.45Hand out note helper WS 8.45

Unit Outline

• A: Fossil Record & Geologic Time– WSs: 8.1, 8.2, 8.3, & 8.4– Labs: 8.1, 8.2 & 8.3 (bonus)

• B: Relative Dating– WS: 8.5, Lab 8.4

• C: Absolute Dating– WS 8.5, Lab 8.5– Unit 2 Review WS + Unit 2 Test

B: Relative Dating

• Order of events: write numbers on sheet.

5 =

4 =

12

3

6

7

8

9 tilting

erosion

Relative DatingRelative Dating

Relative Dating • Involves placing events in the correct

sequence or order

12

34

10

5

6

9

7 = tilt = mtn’ bldg’

8 = erosion

14

1311

=

faul

ting

15 = erosion

12 = erosion

• Absolute Dating is determining how long ago something happened (ma)– ie. Dinosaurs became extinct 65 ma ago.

• Using the principle of Uniformitarianism, six principles have been developed

1. Principle of Superposition: oldest rocks on bottom; youngest rocks on top.

2. Principle of Original Horizontality: sediments deposited in water in horizontal manner.

3. Principle of Lateral Continuity: sediments continue in all directions until they thin and are pinched out at the edge of the basin.

4. Principle of Cross-cutting Relationships: an igneous intrusion (or fault) is younger than the rock it intrudes (crosses).

1

432

1

2

3

4

5

6

7

89

8-erosion

27

6

4

5

3

1

10119

13

12

14

15

16

17-erosion

5. Principle of Inclusions: xenoliths/ inclusions are older than the rocks they’re in.

1

3

2

1

3

2

1

1

4

3

22

3

45

- ero

sion

5 - e

rosio

n

1

2

3

4

5

6

7

6. Principle of Fossil Succession: fossils on bottom are older than fossils on top.

Unconformities

• Break or portion of time (hiatus) is missing

• Cause: period of non-deposition, period of erosion or mountain building

• 3 types

1. Disconformity: surface of erosion or non-deposition (hard to detect)

weathering, oxidation, jointing, etc.

Sed’ RxSed’ Rx

2. Angular Unconformity: beds tilted then eroded before deposition

(most common on exam)

Angular Unconformity

3. Nonconformity: erosion surface is cut into metamorphic or igneous rocks. Use principle of inclusions to determine if it is an intrusion or a nonconformity.

Ign’ or met’ Rx

Sed’ Rx

Practice Relative Dating Examples

Do Lab 8-4 Relative DatingDo Lab 8-4 Relative DatingWork on WS 8-5Work on WS 8-5Work on Chp. 8 Review WSWork on Chp. 8 Review WS