English: This is Figure 6-61 of the
Apollo 16 Preliminary Science Report (NASA SP-315): Geologic map of North Ray crater. Station 11. Edited slightly.
The text of the
Report referring to the figure follows:
The geology of the materials exposed in the walls of North Ray Crater, at this early stage of investigation, is interpreted to be a grossly layered sequence of breccias exposed only in the east wall and largely obscured elsewhere by recently active debris slides (figs. 6-60 and 6-61). Beneath 20 to 30 m of rim-flap debris, the "upper layer," which is approximately 70 m thick, is predominantly white-matrix breccias with some mixed dark rocks. The more coherent materials form discontinuous rows or benches, indicating sublayering at 5 to 10 m intervals. The absence of blocks on the west wall and the heavy concentration on the east wall and in the ejecta extending up Smoky Mountain are suggestive of a steeply dipping discontinuity between the east and west sides of the crater that separates two major units. These asymmetrical relations also can be explained as lenticular variations in induration within the same rock unit. A low-angle impact by the projectile that formed North Ray Crater is not likely because it would not explain the asymmetry of large-rock distribution in the crater walls nor the radial symmetry of the main ejecta blanket on the crater rim.
The next underlying unit is a light-colored slope of possibly unconsolidated material approximately 100 m thick. The rugged floor mound is a dark, rubbly material that may be represented by House and Shadow Rocks, which were sampled on the ejecta blanket. The large size (25 m) and the angularity of House Rock reflect the strength, or coherence, and the wide spacing of joints of the rock mass from which it was derived. In terrestrial analogs such as Meteor Crater, Arizona, the largest blocks on the crater rim reflect the more coherent and thicker-bedded rock units penetrated, regardless of depth. Therefore, because House Rock is similar both in size and appearance to the coarse, dark rubble forming the crater floor and because it and Shadow Rock are very similar in composition but represent the least abundant rock type on North Ray Crater rim, they are interpreted as coming from a stratigraphic horizon exposed in the deepest part of the crater.