Based on the study of Upper Precambrian rocks penetrated by the Pavlovskii Posad parametric borehole in the 1770–4780 m interval, the Riphean succession is underlain by quartzose sandstones. The aulacogen within the Moscow Syneclise was covered by sediments accumulated during the intense chemical weathering of a peneplain. Above the 3550 m level, Upper Precambrian rocks comprise arkoses with abundant garnet. The immature (in terms of lithology and mineralogy) arkosic sequence was probably accumulated in grabenshaped structures (aulacogens).