Geology of Hadley Rille preliminary report

Hadley Rille generally trends in directions that are controlled by pre-mare structures. The southern half of the rille, south of the Apollo 15 site, follows a mare-filled graben that is concentric to the Imbrium basin; however, the zigs and zags in the course are mainly north and east-northeast, directions that do not reflect pre-mare structures in adjacent highlands. The northern half of the rille follows a general direction that is parallel to pre-mare Imbrium-radial faults, is less sinuous than farther south, and intersects several fault-like features, all of which suggest some structural control along this part of the course. At the Apollo 15 site, the east rim is 30-40 m higher than the west rim as if the rille were a normal fault. The rille cannot be a simple fault, however, because the two sides do not match; instead, at bends, the outside has less curvature than the inside, which is partly attributed to recession of the rims by mass-wasting.