Apollo 16 core 60013/14 as a product of path 1 and path 2 regolith evolution processes
We have made a petrographic study of 12 samples along the 62 cm profile of Apollo 16 core 60013/14 taken at Station 10 near the lunar module. The basic core description and maturity variations have been discussed earlier. This core is important because it enables a stratigraphic comparison with nearby cores 60001-7 and 60009/10. These cores form a triangle with sides 35-40 m. FMR data show a maturity-match between 60009/10 and 60013/14. Unfortunately, segments of the core 60001-7 are too disturbed for any cm scale comparison. We present new data on the grain size distribution and the modal petrography for six samples from six levels of 60013 using the same approach and rationale used for 60014. We have combined the new data with our previous data on 60014 to plot the variations of grain size distributions and grain type abundances, in the 500-1000 m and 90-150 micrometers size fractions, with depth. Agglutinate abundances match the I sub s/FeO profile and both show a significant break at a depth of about 45 cm, with lower maturity material below that point. Grain size distributions show that for all analyzed samples, the mean grain size is below 90 micrometers. The two lowest samples are somewhat more coarse-grained than the rest of the core. The break at about 45 cm is the most prominent feature of the core and was described during the initial dissection as a pronounced change in color from dark to light. It now seems clear that this break is primarily one of maturity rather than of bulk chemical composition.