An Encyclopaedia of Indian Archaeology v1.c14.s2.16

v1.c14.s2.16

2. Probably by the middle of the Middle Pleistocene the plain was already considerably aggraded. The drainage from the Himalayas seems to have started getting disorganized. In addition to a decline in rainfall, tectonic rise of land in the upper reaches of the rivers played a role in this process. The unusual height (70 m) of the Jalal gravel ridge above the present-day plain can hardly be explained except by invoking neotectonics. By the early Upper Pleistocene the drainage system of n. Rajasthan seems to have become totally defunct. Much of the evidence of this ancient drainage system has been completely obliterated by subsequent widespread aeolian aggradation and localized fluvial erosion and aggradation. But traces of these palaeochannels are visible on air photographs and landsat imageries and have been traced in Dts Ganganagar, Bikaner, Jaisalmer, and Barmer by scientists of the Central Arid Zone Research Inst. The fragments of these palaeochannels survive in Dts Ajmer and Nagaur between Kuchaman city and Got-Manglod e. of Jayal. During years of unusual rainfall the flood waters flow through these otherwise dry channels.