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Continental Groundwater Flow: Great Artesian Basin. Great Artesian Basin 2. Great Artesian Basin 3. Great Artesian Basin 4. Great Artesian Basin 5. (ages in ka). Western edge ~1.4Ma-old water. Cl-36 Isotope dating technique.
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Great Artesian Basin 5 (ages in ka) Western edge ~1.4Ma-old water
Cl-36 Isotope dating technique 36Cl made by interaction of cosmic rays with 40Ar in atmosphere (40Ar is ~1% of atmosphere). Nuclear Reaction: 40Ar + cosmic ray energy = 36Ar + 4He 36Cl decays to 36Ar 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 36Cl can be used to date time since rainfall at surface.
Great Artesian Basin 6 Water moves through basin at ~1-5m/yr, flow-through time of ~1Ma
Great Plains 4 Implication: water at Boon’s Lick came from Rockies…