NEEP602 Course Notes (Fall 1996)
Resources from Space
TABLE 7. Geologic model for emplacement of Apollo 17 orange and black beads
1. Eruption of the mare basalt flows that partially filled the Valley of TaurusLittrow-3.8-3.7 eons (Wilhelms, 1987, Table 11.3).
2. Eruption of orange glass beads and compositionally identical but more slowly cooled black devitrified glass beads as part of a pattern of basin edge pyroclastic eruptions in the Serenitatis Basin-3.7-3.6 eons (Wilhelms, 1987, Table 11.3).
3. Immediate covering of the pyroclastic deposits by a basalt flow of suflicient thickness to protect the orange and black bead deposits from significant contamination by regolith related processes-3.7-3.6 eons (Wilhelms, 1987, Table 11.3).
4. Avalanche from the north side of the South Massif to form the light mantle-109 m.y. (Drozd et al., 1977).
5. Meteor impact that created Shorty Crater and penetrated below the Light Mantle and into or through the basalt flow overlying the pyroclastic deposits-19 m.y. (Eugster, 1977).
6. Instantaneous shock stimulated release and pressurization of adsorbed gases and the fluidization of pyroclastic deposits immediately beneath the protecting basalt flow.
7. Eruption of gas-bead mixtures along conduits in the radial and circumferential fractures around Shorty Crater.
8. Continuous sorting of the orange glass beads from their more dense black crystallized equivalent toward the top of the gas column to give the sharp separation of orange and black beads observed on and in the core tube (Schmitt and Cernan, 1972, and Heiken et al., 1974).**
9. Development of 12 cm of regolith on the exposed top of the orange bead deposit.
*Small areas of mare basalts younger than the orange pyroclastic deposits in the Sulpicius Gallus region of southwestern Serenitatis have been mapped by Carr (1966).
**Preservation of primary layering remains an alternative explanation for the sharp physical separation of orange and black beads. The purity of the separation as well as the evidence that the bead deposit was emplaced in the rim rather than ejected from the crater argues against this possibility, however.
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