Legends have it that Lord Shiva made Manipur valley which once underwater by draining the water through a tunnel drilled by his trident through the southern hills. A similar legend traces the earliest centres of human settlements on top of higher peaks like the Nongmaijing Hill (Longmaiching) and the Koubru Hill etc. when the valley at the lower reaches remained a vast sheet of water. Downward human migrations into the valley started as the water receded. Some investigators are of the view that the valley was formed as a result of a lake being filled up by the riverborne sediments. The present Loktak and other lakes in the valley are said to be the remnants of the original lake. But the lacustrine origin of Manipur valley has been questioned by various other theories. Dun (1996) was of the opinion that the Manipur Plain was formed by the depositions of a stream that was blocked by some convulsions of earth movements. Rajkumar (1982) also supports the theory of the riverine origin of the valley. In his words, the Manipur River and its tributaries that at the same time drained the area of the valley may closely connect the formations of Manipur valley with the upliftment of South Manipur Hills and subsequent downcutting of the area. Lithologically, the valley represents the axial region of an anticlinorium, the weak crest of which have been eroded. The erosional environments of the past in the valley have been studied in geo-morphological and geo-archaeological perspectives by several workers (Joshi et al (1979), Rajkumar (1982), Thokchom, (1984)). Fluvio-lacustral sediments are encountered in many parts of the valley to a depth of 152 m below the ground level (b.g.l). And, at the same time black clay of lake formation is exposed upto 40 m above the modern water level of the Loktak Lake. A few C14 data on Carbonised samples from Lamphel (at a depth of 0.35 to 0.40 m) and the Loktak Hydel Project area (at a depth of 5.3 m to 12 m) indicates that the age of the central and southern parts of the valley ranges from 7,980±470 B.P. to 25,000±600 B.P. The above observations drive us to infer that a considerable vertical change in the lake level has occurred in the valley. The lake levels were conspicuously higher around 25 K.B.P. - 23 K.B.P. (Thokchom, 1984). Thus, the origin and evolution of the valley may be ascribed to a tectonic theory and neo-tectonism remarkably influenced by a long history of fluvio-lacustral system. The valley remained free from Pleistocene glaciation. There was not a singular existence of lacustrine basin in the valley during the Quaternary. Low energy, fluvo-lacustral system anastomosing drainage with a number of disconnected lentic waterbodies on aggraded land dominated the landscape of this intermontane valley in the Quaternary.