gravity

1. Principle of Original Horizontality Sedimentary rocks were deposited in primarily horizontal beds deposited last - youngest gravity deposited first - oldest Principle of Superposition In an undisturbed sedimentary sequence, the oldest rocks are on the bottom of the stack

2. Youngest gravity Oldest Principle of Superposition In an undisturbed sedimentary sequence, the oldest rocks are on the bottom of the stack

3. Inclusions - pieces of older rock incorporated into younger rock Principle of Inclusion When clasts of one rock are found in another, the rock from which the clasts were derived is the older rock, since it must have already existed in order to be included in the new rock igneous intrusion

4. Principle of Inclusion When clasts of one rock are found in another, the rock from which the clasts were derived is the older rock, since it must have already existed in order to be included in the new rock Inclusions - pieces of older rock (clasts) incorporated into younger rock

5. Principle of Cross-Cutting Relationships Older features are cut or crossed by younger features.

6. Contact – surface separating two formations Hermit Shale Supai Group Redwall Limestone Formation – bodies of rock with recognizable characteristic that are thick enough to map Muav Limestone Bright Angel Shale Tapeats Sandstone

7. Reconstructing Geologic History • Unconformities represent missing time in the geological sequence, either due to no rock being formed or rock being removed. • There are three kinds of unconformities: • disconformity– unconformity between parallel strata. Represents a time of non-deposition or erosion without deformation of strata. • angular unconformity – unconformity between non-parallel strata. Strata were deformed as well as eroded (not necessarily at the same time) • nonconformity – unconformity representing erosion of a non-sedimentary rock

8. Complex Subsurface Geology

9. Sedimentary Deposition

10. Marine Sequence

11. Intrusion

12. Tilting & Erosion

13. Subsidence and New Marine Deposition

14. Missing Formation

15. Dike Event

18. Fluvial Deposition

19. Complex Subsurface Geology

20. Radiometric Dating Absolute dating using radioactive decay data http://www.cotf.edu/ete/modules/msese/earthsysflr/geotime.html

21. Alpha Particle emits a particle from its nucleus called an alpha particle (2 protons + 2 neutrons).

22. Uranium - Thorium Decay U He + Th 4 234 238 92 90 2 spontaneous decay “parent” “daughter product” alpha particle = 2 protons + 2 neutrons = positively charged ion of Helium Thorium: 90 protons + 144 neutrons

23. Beta Particle Emission But, Th is also unstable, and it emits a beta particle… 234 90

24. Alpha Emission Beta Emission Electron Capture

25. Decay sequence for Uranium-238 http://www.asa3.org/ASA/resources/Wiens.html Half life– the time it takes for half of the original element to decay to the new element.

26. Hypothetical ElementParentium Half Life = 10,000 yrs Decays to Daughterium Starting with 1,000,0000 nuclei of Parentium

27. ½ * ½ = ¼ 1-¼= ¾ +20,000 250,000 750,000 25% 1/2 1 - ½ = ½ +10,000 500,000 500,000 50% 1,000,000 0 0 100% Time Parentium Daughterium

28. ½ * ½ * ½ * ½ * ½ = 1/32 1-1/32= 31/32 +50,000 31,250 968,750 3.125% ½ * ½ * ½ * ½ = 1/16 1-1/16= 15/16 +40,000 62,500 937,500 6.25% ½ * ½ * ½ = 1/8 1- 1/8 = 7/8 +30,000 125,000 825,000 12.5% Time Parentium Daughterium

29. Parentium 1,000,000 750,000 Nuclei Will Parentium reach 0%? 500,000 250,000 Daughterium 0 0 10 20 30 40 50 Time (thousands of years)