Geology 12 Presents Hand out note helper WS 8.45 Hand out note helper WS 8.45.

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