Until the work of the NHM/Yale team in the Emirate of Abu Dhabi, the only Miocene/Pliocene unit described from eastern Arabia was the Kharj Formation (Powers et al., 1966: D92). No type locality exists for this unit.

Philby (1933:79) states "The Sahba is one of the great and long-dead rivers of ancient Arabia, having a total length of more than 500 miles from its head ... in the central highlands of Najd ... to its mouth in the Persian Gulf" Philby's map (1933) shows Wadi Sahba entering the Arabian Gulf at As Sila.

Powers et al. (1966:D98) state that some patches of "late Tertiary" sediments are associated with the Kharj Formation near Wadi Sahba and "These probable links strongly suggest that the channel gravels are remnants of a group of Tertiary rivers which brought down the great gravel flood incorporated in the lower part of the Hofuf Formation. The relationship of the channel gravels to freshwater deposits of the Kharj Formation is unknown even though they are in contact at one locality ... It is tempting to suggest that the channel gravels may be the result of streams that discharged overflow from lakes in which freshwater sediments were being deposited, but this suggestion is pure speculation".