Stratigraphy of the Valley of Taurus-Littrow, Southeastern Serenitatis, Moon

The valley of Taurus-Littrow forms a graben, radial to the center of the 740 km diameter Serenitatis basin. The local stratigraphic sequence of pre-mare basalt units constituting the 2000m plus walls of the valley, approximate thicknesses and ages of its units, can be hypothesized with some confidence. Definition of this section arises from field investigations during Apollo 17, impact ages of samples taken from large talus blocks, the relative ages of other large impact basins in the region, and rough calculations of the probable thickness of ejecta from those basins. The oldest primordial, basement material consists of fragmental mega-regolith derived from original, 4.55 Gyr ferroan anorthosite crust. (10-20 km of ferroan anorthosite ejecta, probably containing clasts of lower crust Mg-suite and KREEP intrusives, would have been deposited on the basement if a very large impact formed the ~3200km diameter, 4.4? Gyr Procellarum basin of the western region of the lunar nearside.) Then, in sequence, the section would record brecciation and gardening from Pre-Tranquillitatis primary and secondary impacts; ~700m of older than 3.87 Gyr Tranquillitatis ejecta and debris flow deposits; <100m of Fecunditatis ejecta and debris flow deposits; <100m of older than 3.87 Gyr Crisium ejecta and debris flow deposits; ~700m of 3.87 Gyr Serenitatis ejecta and debris flow deposits containing fragments of lower crust Mg-suite intrusive rocks and slightly younger impact melt intrusions; <100m of the Serenitatis impact melt sheet; and ~100m of 3.85 Gyr, Imbrium ejecta and debris flow deposits probably containing clasts of lower crust Mg-suite and KREEP intrusive rocks. Regolith exists between each large basin ejecta unit. Titanium-rich, 3.82 Gyr mare basalt, about 1.2km thick, has partially filled the valley, lying stratigraphically above relatively unconsolidated Imbrium material. 3.5 Gyr orange and black pyroclastic glass deposits and younger basalt flows form thin, discontinuous units above the mare fill.