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Obsidian hydration dates glacial loading?
Science (New York, N.Y.)
|May 18, 1973
Summary
Obsidian hydration rind analysis reveals distinct age groups, correlating with volcanic emplacement 176,000 years ago and glacial events. This method dates geological formations in Yellowstone National Park.
Area of Science:
- Geochemistry
- Geochronology
- Glacial Geology
Background:
- Obsidian Cliff, Yellowstone National Park, provides a valuable geological record.
- Hydration rind analysis is a method for dating volcanic glass and geological events.
Purpose of the Study:
- To analyze hydration rind thicknesses on obsidian from Obsidian Cliff.
- To correlate these measurements with known geological events, including volcanic emplacement and glaciation.
Main Methods:
- Measurement of hydration rind thicknesses on thin sections of obsidian.
- Comparison of rind thicknesses with established dates from potassium-argon dating and glacial moraines.
Main Results:
- Three distinct groups of hydration rinds were identified, with average thicknesses of 16.3, 14.5, and 7.9 micrometers.
- The oldest rind group (16.3 micrometers) corresponds to the obsidian flow's emplacement 176,000 years ago.
- The younger rind groups (14.5 and 7.9 micrometers) correlate with obsidian pebbles from the Bull Lake and Pinedale glacial moraines, respectively.
Conclusions:
- Hydration rind thickness provides a reliable proxy for dating geological events in Yellowstone.
- Cracks and surfaces with younger hydration rinds suggest formation due to glacial loading during the Bull Lake and Pinedale glaciations.
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