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The AAPG/Datapages Combined Publications Database

Journal of Sedimentary Research (SEPM)

Abstract


Journal of Sedimentary Petrology
Vol. 42 (1972)No. 4. (December), Pages 876-888

Development of Previous HitSoilNext Hit on the Lunar Surface

John F. Lindsay (2)

ABSTRACT

The meteorite flux at the lunar surface provides the primary energy source for the development of the lunar Previous HitsoilNext Hit. Size, shape and modal analyses of Previous HitsoilNext Hit returned by Apollo 11, 12, 14 and 15 and Luna 16 indicate that the two most important dynamic processes resulting from meteorite impact are vitrification and comminution of the detrital material. The effects of the two processes are mutually opposed such that, as the glass content of the Previous HitsoilNext Hit increases over an extended period of time, the statistical parameters of the mature Previous HitsoilNext Hit tends to stabilize. Comminution probably plays a dominant role early in the development of the Previous HitsoilNext Hit by reducing the median grain size and producing a logarithmic-normal grain-size distribution. Later the combined effects of vitrification and agglutination of he fines produces a bimodal distribution of glass particles such that the median grain size stabilizes at approximately 3.5^phgr and the standard deviation of size distribution is increased to about 2^phgr. Synchronously the graphic skewness of the Previous HitsoilNext Hit approaches zero and the graphic kurtosis probably decreases.

The shape of the lunar Previous HitsoilNext Hit particles evolves as the Previous HitsoilNext Hit matures. In immature soils rock and mineral fragments with simple shapes and high sphericities predominate and the relationship between sphericity and grain size is simple and linear. However, impact vitrification produces two morphologically distinct types of glass particles and superimposes a more complex sinusoidal pattern upon the distribution as the Previous HitsoilNext Hit matures such that the mean sphericity of the particles is reduced in the 2 to 3^phgr, size range and in the 6^phgr, and smaller size range.

The evolution of the Previous HitsoilNext Hit does trot necessarily progress in a regular manner. Both introduction of freshly comminuted bedrock material by small local impact events, as well as local topographic effects, influence the development of the Previous HitsoilNext Hit and reduce its maturity. Mixed soils produced by local events tend to be coarse grained, positively skewed and very poorly sorted whereas the soils formed on steep slopes have gain size parameters similar to mature soils except that they may be somewhat finer grained. The shape parameters are similarly modified.

The accumulation rate of the Previous HitsoilNext Hit is not constant nor is deposition a continuous process. The growth of the Previous HitsoilNext Hit probably proceeds in an exponential manner with a primary accumulation rate of approximately 1.2 ^times 10-6 yr-1 which is gradually decelerated at between -3.3 and -1.7 ^times 10-16 cm yr-2. This suggests that approximately 90 percent of the energy potentially available for comminuting bedrock is absorbed in the reworking of the Previous HitsoilTop


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