Field mapping and sedimentologic investigations of Paleogene basins in eastern Tibet suggest that the depositional characteristics of widespread thick-bedded, purplish red, coarse-grained clastic series of Paleogene basins in the setting of regional strike-slipping and thrusting indicate that the series is a proximal and rapid-accumulating sediment body in debris flows and a fan-surface braided river in a typical dry and hot subaerial alluvial fan environment. The sequences of basin filling and coarse clastic rocks, fauna and sporopollen associations and 40Ar/39Ar dating confirm that the coarse clastic rocks formed in Paleogene basins in the period of 38 ~ 29 Ma, nearly coeval with the formation of the Paleogene basins in the northern segment (Hengduanshan area) and the disintegration of large basins in the southern segment (Lanping - Simao area). The sedimentologic characteristics of the Paleogene coarse-grained clastic rocks, basin tectonics and magmatic activity indicate that a rapid wholesale tectonic uplift may have occurred in the Tibetan Plateau from the Late Eocene to Early Oligocene.