1. Continental Groundwater Flow: Great Artesian Basin

2. Great Artesian Basin 2

3. Great Artesian Basin 3

4. Great Artesian Basin 4

5. Great Artesian Basin 5 Western edge ~1.4Ma-old water (ages in ka)

6. Cl-36 Isotope dating technique 36 Cl made by interaction of cosmic rays with 40 Ar in atmosphere ( 40 Ar is ~1% of atmosphere). Nuclear Reaction: 40 Ar + cosmic ray energy = 36 Ar + 4 He 36 Cl decays to 36 Ar with a halflife of 310,000yr 36Cl incorporated into rainwater, but not made by nuclear reactions in Earth’s interior. Rainwater seeps into ground, where 36Cl decays slowly away… Amount of remaining 36 Cl can be used to date time since rainfall at surface.

7. Great Artesian Basin 6 Water moves through basin at ~1- 5m/yr, flow-through time of ~1Ma

8. Great Artesian Basin 7=4

9. Great Plains (same type of tale)

10. Great Plains 2

11. Great Plains 3

12. Great Plains 4 Implication: water at Boon’s Lick came from Rockies…